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In Reply to: Re: Whats the low-frequency slope of BASSMAXX One's? posted by Tom Dawson on August 23, 2003 at 14:19:56:
So why are you posting this here, if I didn't say it? Further, why don't you quote directly instead of how you did so people will know exactly what you're talking about?In any case, if a direct radiating point source with flat response and no digital eq has approximately a negative 90 degree phase response over a significant portion of its response, then it will not correctly reproduce a waveshape without some fancy allpass eq. If it has a constant time delay (ie, changing phase wrt frequency), then yeah, it can reproduce a complex waveshape.
John
Follow Ups:
Actually, a system exhibiting a constant N x +/-90 degree phase characteristic also will exhibit zero group delay, as well as complementary shelving responses sharing that characteristic, which is, for instance, why RIAA and NAB record and playback equalization together will pass arbitrary waveshapes including square waves correctly.
Just for fun, here are two plots I did about 6 months ago. The first is a 200hz square wave passed through a system with a constant delay. The ringing is from the finite bandwidth.
This next one is a 200hz square wave with a different phase response - not a constant Nx -90, but actually representative of a real speaker.
I'm not sure why you keep bringing up things like the RIAA curve as that is a different situation, and you're right - as a system, it should pass a waveshape correctly. Its phase should be related to its magnitude response, so when you apply the inverse filter, everything is back to a linear system. However, a speaker with flat response but phase response that is not flat (and is not simply a result of a constant time delay) does not behave like this, at least in such a simple manner. Of course you can use DSP and make it all work nicely.
John
Sounds like the best way to settle this argument is beer and female mud wrestling
I use it as a real world example that integration and differentiation, whether its due to an acoustical or electrical system results in zero group delay, a necessary result of the fact that the group delay is the negative of the phase differential, thus if the phase is constant with frequency, then the group delay is zero.I presume you agree with the above. JBL also, on their website describes how some of their direct bass radiator monitor systems using the 2344 HF horn can reproduce square waves and includes a photograph of an approx 350 hz example reproduced by said monitor that has the clearly rectangular outline to prove it.
I do not find any of that necessary to think about this issue. If you have a constant phase delay wrt frequency, that corresponds to a changing time delay wrt frequency. If this accompanies a flat frequency response and no correction in some form is applied, the system will not correctly reproduce a waveshape.This doesn't mean that no direct radiator system can correctly reproduce a complex wave. It's just not a given that it will happen.
Hi John!I got into this conversation late, but I think what Dawson was saying in this part of the thread is essentially that if the loudspeaker were to cause a constant -90 o phase shift, then the use of a simple +90 o filter would work. Essentially, one would have 6dB/octave low-pass rolloff from the hypothetical speaker, which would then be corrected by 6dB/octave high-pass compensation.
But I think we're all in agreement that this doesn't happen, because the system isn't minimum-phase. Some components of the system are, and others are not.
Wayne
Regarding the mass controled phase shift of the acoustically small direct rdiator Wayne says"But I think we're all in agreement that this doesn't happen"
Who do you mean when you say "we" are all in agreement?
Of that group "we", I wonder, does anyone there have the ability to measure actual acoustic phase? I bet not.
Tom
Tom -As is typical of you, you misrepresent the facts.
So let's see if we can't bring some honesty into the discussion, shall we?
I said that if a loudspeaker were to act as as a filter that presented a pure -90 o phase shift, then a corresponding filter of +90 o would act as a correction mechanism. The speaker would be an integrator, so a differentiator would fix its response, both phase and amplitude.
That would also mean that the loudspeaker alone would have amplitude response curve with a negative slope, and the correction circuit would have positive slope. The speaker would rolloff at a constant 6dB/octave, and the correction circuit would rise correspondingly at 6dB/octave.
The reason this doesn't work is that there are other electro-mechanico-acoustic filters in the system. It is not a pure filter, and so it cannot be corrected with a pure filter. There are several system solutions that address specific problems and optimize certain performance parameters. But there is no "magic bullet" solution that addresses them all.
Regarding your comment about phase, it isn't all that difficult to measure or to model. About my use of the term "we," it is a collective noun that referred to the people discussing this matter on this thread. And about agreement, well, the thing I suggested we probably agreed upon was that if am integrator/differentiator pair were combined, the result would be neutral amplitude and phase response. So if this doesn't occur when the differentiator (compensation circuit filter) is a pure minimum-phase filter, then the integrator (loudspeaker filter function) must be a complex filter that doesn't match the differentiator. Perhaps I was wrong to include you in my assumption of collective agreement.
Wayne
Firstly, I do want to differentiate my self from your “we” view of loudspeaker operation.I would also have replied to the “spoor post” too but Rod has apparently cut off any possibility of reply.
I will ask Pat to forward me your e-mails you sent to the office incase you still can’t remember who threatened legal action to who.You are still suffering from a misconception about the basics here and my explaining it yet another time to you will make no difference to you as your various position on things always seems set in 9 bag concrete.
On the other hand, while you rarely reply to any of my technical points, I know others are reading this too and would encourage anyone who is curious to root around and find out themselves.While my words have never persuaded you about anything I know of in the past, perhaps some words from a few of the all time great’s in the loudspeaker engineering area would.
For example, in the book “Theory and Design of loudspeaker enclosures” by J.E.Benson he describes the basic woofer this way on page 77. Benson’s work is used in Thiel and Small’s papers in the AES loudspeaker anthology fwiw .
Snipped > “but the frequency is sufficiently high in practical cases for the motional impedance to behave substantially like pure capacitance, or in other words, for the diaphragm motion to be mass controlled”Or how about this one from “Electroacoustics, The analysis of Transduction and its historical background”
Published by the American Institute of Physics for the Acoustical Society of America”
In the Chapter called Electrodynaic Transducers, page 145 it says;
“The effective mass is correspondingly defined so as to yield a total inertial reaction force which lags Velocity by 90 degrees in phase.”
A further explanation of how this happens is found on page 153
While knowledge of the “mass controlled” was known in some circles from the development of the Rice Kellog transducer and the reason why it this way is on page 81
Given I have had a TDS system which can measure real acoustic phase at my disposal for about 20 years and have very publicly presented measurements to both AES and ASA, why in the wide world of sports would I say something so openly and blatantly that you say is obviously not true?On the other hand, you do not take acoustic measurements (or at least you didn’t the last time this came up) that would reveal the facts about acoustic phase to you first hand. You ignore the “uncomfortable” parts of how things are. I would encourage you to look but I will be surprised if you can find any hard technical references which support the “we” view of driver operation.
It is a fact that the acoustically small point source (like a woofer) must have an acceleration response if its amplitude is to be flat.
That acceleration response is caused by the drivers mass dominating the system and when above Fb and below Rmin, it’s acoustic phase lags by a nominal - 90 degrees.
Because acceleration is force against mass and current is force and sound is proportional to acceleration, one can look at the current waveform’s phase with respect to input voltage and see the general shape of a drivers acoustic phase curve.
I would ask you to consider the following thought experiment.
You have two loudspeakers, one is a small direct radiator, the other is an efficient bass horn
You measure the response and they are essentially the same from say 40 Hz to say 200Hz with the horn being more efficient.One is a resistively controlled device, one is a mass controlled device (the direct radiator).
They have the same response curve but is the acoustic phase the same?
Remember, one is resistive dominated, the other is reactance dominated.
Think hard, reactance does what to phase and resistance does what to phase.A clue, the flat part of the response is actually the falling slope of the mass filter corner and phase (for a 1 pole low pass filter) reaches what well above the corner ? ans ~ -90 degrees
The part your not seeing is that the reason for the need for such a slope is because the radiation resistance change with frequency BUT there is no phase shift associated with it, it is just a changing resistance.
The acoustically small point source speaker on the other hand is a mass controlled filter with a corner F at the low cutoff. Anywhere its flat above Fb and below Rmin , you are on the slope of the filter response and getting the resulting phase nominal –90 degree shift.
A highly loaded horn on the other hand does not have the nominal –90 degree phase shift being resistively controlled.TD
Tom Danley wrote:[about the issue discussed here ]
> > I will ask Pat to forward me your e-mails you sent to the office
> > in case you still can't remember who threatened legal action to who.This statement seems terribly childish to me. It's like a little boy trying to tattle that someone called them names and wanting them to go to bed without supper.
If I had threatened litigation, it seems imprudent to discuss the matter publically - Even to say that you shouldn't discuss it. That is if you really thought you were going to court. The only reason you might mention it is to attempt to gain some pity from those who read your posts.
Beyond this, you cannot claim to have misunderstood the letter and also say that your attorney read it. This would mean that not only you misunderstood, but also your legal counsel, boss and co-workers. That can leave only one reason for your position, and that is to deceive the public.
No one that has read the letter has interpreted it as you have claimed. So I do not believe that your boss, co-workers and attorney misinterpreted the letter as a legal threat either.
There was a threat made by one of your friends though. John Hancock was making some threats, and I replied to him encouraging him to do whatever he wanted to do. But this is not something that you could have possibly misinterpreted, because others have seen this exchange and would have undoubtedly corrected you if you misunderstood.
Again, I do not believe that your boss, co-workers and attorney could have misrepresented these letters. No one else had a hard time understanding what was being said, or who it was being said to. I do think you have a relationship with John Hancock, but that is a different matter entirely.
> > You are still suffering from a misconception about the basics here
> > and my explaining it yet another time to you will make no difference
> > to you as your various position on things always seems set in 9 bag
> > concrete.No, Tom. It is not I that has a misconception and it is not for you to do any explaining. I think that the only reason you go to such lengths is to promote your agenda.
> > On the other hand, while you rarely reply to any of my technical
> > points, I know others are reading this too and would encourage
> > anyone who is curious to root around and find out themselves.On the contrary, your complaint with me is that I have frequently replied to your technical points. I don't agree with them, and you can't accept that.
People are not automatons, and they do not need you to encourage them to "root around and find out for themselves." If they are reading this, then they are already looking.
In the interest of brevity, I'll point you to my recent reply about this same pseudo-technical rant you've made. You go over and over the same points, but always make the same mistakes of oversimplifying a direct radiator as pure quadrature and a horn as purely resistive. Both assertions are inaccurate, and both lead you down the same flawed path to the same self-serving but incorrect conclusions.
You can't possibly be so arrogant as to think you are the only person that understands these kinds of systems so completely. Then again, it appears that is exactly what you think.
But Tom, you're boring me with this stuff. I've got more important things to do, and this just isn't all that tough. Deal with it; Perhaps you might try something a little more intellectually stimulating to give yourself a new challenge.
Wayne
Hi Wayne> > I will ask Pat to forward me your e-mails you sent to the office
> > in case you still can't remember who threatened legal action to who.> This statement seems terribly childish to me. It's like a little boy trying to tattle that someone called them names and wanting them to go to bed without supper.
> If I had threatened litigation, it seems imprudent to discuss the matter publically - Even to say that you shouldn't discuss it. That is if you really thought you were going to court. The only reason you might mention it is to attempt to gain some pity from those who read your posts.
Wayne, you re-opened this “can of worms” by in several posts attempting to give the readers the impression that it wasn’t you that threatened legal action. Perhaps your uncomfortable with your actions I don’t know but your evasive posture here is still one which side steps the fact that it WAS YOU that sent the e-mails to our office, got Pat upset and who’s e-mails were forwarded to the corporate lawyer.
Why not be honest and just admit to it, or should I post the letters here?
So far as legal advice, the lawyer recently said (when asking about this issue) “let him sue and see what happens”.> Again, I do not believe that your boss, co-workers and attorney could have misrepresented these letters. No one else had a hard time understanding what was being said, or who it was being said to. I do think you have a relationship with John Hancock, but that is a different matter entirely.
So now you admit there was more than the one letter I posted, that is progress.
Pat called me and said “who is this Wayne guy and why is he so mad and threatening legal action”
Pat gave them to Brad, Brad forwarded them to the Lawyer for examination, simple as that.John H on the other hand, lives in another country and I have never met him.
I did write answering some of his Unity questions and was surprised how quickly he picked up on how they work. Other than wishing he lived in the USA so I could offer him a job, there is no relationship like you suggest, he is just a very sharp fellow.
> You can't possibly be so arrogant as to think you are the only person that understands these kinds of systems so completely. Then again, it appears that is exactly what you think.No Wayne, In fact you missed a key point here, I am not the “only one”, in fact the technical references I gave you are from others who also are intimately aware of how loudspeaker drivers actually work.
References from the Acoustic Society of America and AES, references which have stood, unchallenged for ages at least until you came along.
Further, if I (and they) are wrong as you insist, it won’t be long before some one publishes something in a technical journal to dispute it.
You think your right? I would urge you to write the ASA and AES and give them your explanation about where they were wrong.While I can (and did) supply technical references and have measurements that back up what I say, I challenge you to find any similar technical references that support your “we” position ( I mean other than the self serving blather you wrote).
> But Tom, you're boring me with this stuff. I've got more important things to do, and this just isn't all that tough. Deal with it; Perhaps you might try something a little more intellectually stimulating to give yourself a new challenge.
Bored is it Wayne? or have you run out of ways to side step the issue.
More challenging, yes that sounds good, having a discussion with anyone with a fully closed mind is too similar to arguing with a TV set, it may be fun for a little bit but it goes no where.
Like you say “this just isn't all that tough. Deal with it” or at least show where the others and I are wrong since you seem to feel you have divine intelligence on the subject.
Cheers,Tom
Tom -Please do post the E-Mail that John Hancock wrote. Post my reply to him. You've already posted the letter I wrote to you, but then again, I had posted it two months earlier.
You're just trying to re-write history just like you try to re-write physics.
I don't think I've ever seen a technical person that was so willing to bend the facts to promote an agenda. I've seen this kind of behaviour in salesmen, but you've always tried to give the impression of being accurate and thorough. From what I've seen, you are neither. You state one fact, then repeat it ad-nauseum, so that you can throw in three fabrications on top and say, "see the fact proves it."
Please do post the correspondence between John Hancock and I. They were copied to you, so I know you have them. That will show the world how willing you are to bend the truth. I wanted everyone to see the nonsense that you and your buddies were doing, but didn't feel posting these things publically was in good taste. But you go ahead and post it here, please. I'd like everyone to see.
Wayne
> Wayne wrote> Please do post the E-Mail that John Hancock wrote. Post my reply to him. You've already posted the letter I wrote to you, but then again, I had posted it two months earlier.
Wayne, you will have to ask John to post it, I don’t have it nor do I have your reply to him you mentioned. AS I have explained to you ad-nauseum, I have not met John H., he is not part of the company in any way but I do know he is very sharp fellow technically.
Fwiw, your e-mail, the one you claim was sent two months before (what ever it is your referring to) arrived on 7-14-03, only days before your threats of taking legal action arrived at the shop.> You're just trying to re-write history just like you try to re-write physics.
I was suggesting that an acoustically small point source was mass controlled AND cited historical engineering references that show that (to some folks anyway) the mass controlled behavior was know since the Rice Kellogg transducer.
To YOU in Waynes world, this means that “I” am somehow re-writing history?
Do you also think I went "back in time" to "plant" the references too?
Has it not occurred to you that anyone with proper test equipment can measure it and see for himself or herself and that many of our customers DO have such test equipment?
On your Pi forum, you take the trouble to cite the Synaudcon article on horn arrays, you fail to mention that when one goes to a Synaudcon class to learn about such things, they use an SPL td-1 to teach with and publically measure in each class.Oh that’s right, you don’t believe in measuring loudspeakers yourself..
> I don't think I've ever seen a technical person that was so willing to bend the facts to promote an agenda. I've seen this kind of behaviour in salesmen, but you've always tried to give the impression of being accurate and thorough. From what I've seen, you are neither. You state one fact, then repeat it ad-nauseum, so that you can throw in three fabrications on top and say, "see the fact proves it."
I have run into people who’s approach has like yours been “don’t confuse me with the facts I know what I know” attitude, just never in engineering before.
So far as trying to paint a false or inverted image of reality, you take the cake, right up there with some politicians..
Also, speaking of a salesman's agenda, YOU are the one trying to sell to the DIY market, not me, we have nothing for the DIY’r and I would doubt anyone here is buying any of our products..
You start by accusing me of slamming you and your products (something I have not done), send an e-mail to me and then others to the shop threatening legal action if I don’t stop.
Threatening someone to stop doing what there not doing is humorous.This last week you jumped into several threads trying to give people the impression that I made up the threats of legal action when in fact YOU were 100% the source of those threats and the trouble it caused at work.
I guess I can understand why you would try to slime out of it, I’m surprised you would try so hard, I guess it is embarrassing being caught standing eyeball deep in the outhouse pit huh?.You accuse me of re-writing loudspeaker engineering too (by citing examples from respected sources in loudspeaker engineering) and yet you can cite nothing relevant to support your position.
So yes, I am comfortable letting the historical texts and measurements form my position and for me it really is a case of “the facts prove it”.
And your facts are what now?> Please do post the correspondence between John Hancock and I. They were copied to you, so I know you have them. That will show the world how willing you are to bend the truth. I wanted everyone to see the nonsense that you and your buddies were doing, but didn't feel posting these things publically was in good taste. But you go ahead and post it here, please. I'd like everyone to see.
.
Like a number of things you claim to “know”, this assumption is also wrong.
Wayne, I do not have any correspondence you sent to John, but if you think it will make things clearer, by all means you should post them or perhaps he will. I will post your threats sent to the office too to complete the picture.
I don’t see how having all your e-mails on this exposed publicly will hurt my position here though, the plain fact is regardless of you attempts of re-direction and innuendo you are the one who started the threats of legal action that got me in hot water briefly..
At this point, I would like people to see clearly the identity of the "worm in the can".Cheers,
Tom
Tom -There's no need for me to restate the facts because we discussed all this just a few posts back in this thread.
The only letter that was addressed to you was the one you posted already, which is also what I posted in response to your little pity ploy back in July. The only other things I sent to you were copies of the correspondence with your buddy Hancock. He wrote a letter, and I replied. I suspected you put him up to it, or that you two had at least discussed it. So I felt it would be good to let you know what was said by both parties.
There is no misunderstanding here. This is a full description of the communications between us and your attempts to make it appear any other way are intentional fabrications. You've been pulling this kind of thing as long as I've known you, and your credibility is nil.
Wayne
WayneI see that you have gone back and pulled your post already to re-edit it.
Here is the reply to the original, which still addresses what you left in this post.
> The only letter that was sent to you was the one you posted already, which is also what I posted in response to your little pity ploy back in July.More selective truth eh ?
Yes and there was never a dispute about that post either, the one I posted is the one you sent ME, the ones that caused the problems were the ones you sent to the shop, which were the ones threatening legal action, the ones my Boss saw and forwarded to the Attorney.
Do you remember those e-mails too, or, are you pretending you didn’t send them?
Maybe it wasn’t you that penned them and sent them under your name from “Pi” but one of your alter ego’s, what did you call them a “sock puppet” or something.
> The only other things I sent to you were copies of the correspondence between your buddy Hancock. He wrote a letter, and I replied. I suspected you put him up to it, or that you two had at least discussed it.Another set of incorrect assumptions, Wayne.
Again, so it is crystal clear to even you, it was NOT the post you sent me but the ones to the shop which caused the issue at work and my absence from the list.
Also, I had NO discussion with John H. about anything relative to you or this and do not have any of your correspondence with him, stop being so darn conspiratorial.> So let me make this clear. This is a full description of the communications between us.
Yes Wayne, but the point yet again is that it wasn’t the one to me that caused the problem, it was the one my Boss read that you sent to the shop.
> Your attempts to make it appear any other way are fabrications. You've been pulling this kind of thing as long as I've known you, and your credibility is nil.
Well Wayne, I guess at this point knowing my “credibility is nil” with you is somewhat reassuring at this point. To be sure, watching you do a “weasel dance” now trying to cover your butt (and now totally evade addressing the “mass controlled” issue) is sad but somewhat entertaining too.
Cheers,Tom
There's no way for you to put spin on this and make it appear any different than it is.First, I'll reply about the mechanical mass/suspension loading issue that you keep saying I'm "evading." I've responded to you several times, with two of the more succinct explainations, here and here . This isn't about my being "evasive." It's about you trying to say that I am, which is one of your manipulative tactics. I have not avoided the issue at all and , in fact, it was my choice to enter into the conversation and challenge your oversimplifications.
I just don't keep repeating myself as you have been. What I have to say has already been said.
Second, I'll say a few more things about your false claims of "threatening letters."
You and John Hancock are the guilty ones here. You both had repeatedly insulted me, accusing me of spoofing IP's and writing under an alias, even when the administrator of the forum told you he had proof in the system logs that this wasn't the case. Still, you and John continued to attack me, even when I did not participate in the conversation at all.
Your comments had begun to take the tone of harassment and "cyber-stalking," which is why I wrote you the letter asking you to refrain . Shortly thereafter, I received a letter from John, which I forwarded to you. I've included a copy of his letter, and of my reply to him below.
You then proceeded to pretend as though you had been a victim of lawsuit threats , hoping to sway public opinion and gain sympathy. You made misleading comments intending to make yourself look like the faultless victim of intimidation and frivolous litigation. And it did appear to have an impact at that time, because you got a lot of "support."
You can't claim to have misunderstood the issue; The only reasonable explaination is that you wanted to stage a scene and to manipulate public opinion. If you honestly felt you had been threatened with libel suit, you would never have come here and acted this way. And it's not the first time you've acted like this. From what I've seen from you, it's your normal mode of behavior.
Anyway, below you'll find a copy of the letter that Hancock sent, followed by my response. It is easy to see that it is not addressed to you, and I am certain that neither you nor your counsel or co-workers misunderstood this fact. You simply wanted to fabricate a story to manipulate public opinion.
----- Original Message -----
From: "Monica Melo"
To: "Pi Speakers"
Sent: Thursday, July 17, 2003 5:38 PM
Subject: sock puppets>
>
> Alright Wayne, I've just about had it with your sock puppeting.
> Keep it up and you'll see a very thorough and very public analysis
> of your speakers with detailed measurements. You and I both know
> your speaker "designs" can't stand up to scrutiny. In the interests
> of peace, I've been keeping quiet while you foist those travesties
> off on suckers who don't know any better, but if you're going to
> behave like this, people are going to know exactly what they have
> been buying. One more sockpuppet and my order goes out to eminence.
>
> John
>
> _________________________________________________________________
> The new MSN 8: advanced junk mail protection and 2 months FREE*
> http://join.msn.com/?page=features/junkmail
>This is my reply to John later that same day, which was copied to you, Rod Morris, Mike Baker and Bill Martinelli. Several other people have seen these letters as well, and not a single person has misunderstood the issues or confused the recipients.
----- Original Message -----
From: "Pi Speakers"
To: "Monica Melo"
Cc: "Mike Baker"; "Tom Danley"; "Rod Morris"; "Bill Martinelli"
Sent: Thursday, July 17, 2003 9:46 PM
Subject: Correspondence between John Hancock and Wayne Parham> Hello John,
>
> Please feel free to do whatever you want, including building
> speakers from my designs and measuring them. I've been pleased
> with them, and so have many others. They are academically sound
> designs, both from a mathematical perspective and also as measured.
> So please do feel free to build them. I sent you the plans a long
> time ago, when you requested them under a bogus name. You didn't
> need to do that. I would have sent them to you anyway.
>
> But as for your rudeness in public, I've spoken to Rod Morris about
> your misconduct on the Audio Asylum. This letter is forwarded to
> him as well. I should probably consider speaking to my attorney
> about taking this matter to court about the things you've said.
> Without having measurements made by someone less biased than yourself,
> the comments you've made are things I could probably get damage
> awards for. Same for the personal attacks.
>
> You speak of doing something in the interest of peace. That's
> ridiculous. There is little I can see from you that has been
> peaceful. If you really wanted to be "peaceful," it would be
> fairly easy to do. A simple absense of malice is peaceful. What
> you do has not ever been in the interest of peace.
>
> My designs are well considered designs, and I don't deserve your
> disrespectful comments. So please do build them and measure them.
> But have your measurements verified by someone that is qualified
> and impartial.
>
> Wayne Parham
Hi WayneYou sound sincere so I will explain again about acoustic phase, please read this all carefully before rejecting it.
Several data points:
For anything traveling in a sine wave motion, the velocity and acceleration are always 90 degrees apart.
Sound power radiated from a small point source is proportional to its Volume Velocity (Ud)
For a radiator, which is less than about ¼ wl in diameter, it feels a radiation resistance which changes with frequency. That is when the frequency increases, it radiates increasing sound power with a fixed radiator Velocity.
In this case, a constant velocity radiator produces a +6 dB /oct rising frequency response.A highly loaded horn on the other hand presents the radiator with a constant resistance, which is a significant magnitude. Being a resistance, the power radiated is proportional to radiator velocity (voltage). In this case, a constant velocity produces a constant power.
This need for a constant velocity is why horn drivers typically have so much more motor strength per radiator area than a direct radiator hasUnlike electrical analogues used in equivalent circuit models (and the reason they may not be “exactly” right modeling a loudspeaker) , this “frequency variable” radiation resistance is a changing resistance without the corresponding phase shift that reactive components provide when an amplitude is changing. Hence, electrical models which are used to approximate this action can include a phase shift which the real acoustic property does not have.
To make the output of a small point source flat, the changing radiation resistance must be compensated for, so the acoustic pressure is constant.
An alternative way of saying this is that the radiator velocity must fall with increasing frequency in order to deliver a constant power into a changing resistance.
For an electrodynamic motor such as a VC motor in a loudspeaker or even a DC servomotor, the force per amp and back EMF are always exactly related.
In the rotary motor, the force factor is Kt or torque per amp with Kv being the voltage constant, in the VC motor is it BL (Newtons of force per Amp) and Voltage constant is un specified in the loudspeaker case.In order for the acoustically small radiator to have flat frequency response (in the face of a changing radiation resistance), it must have a Velocity which FALLS at a rate which compliments the change in radiation resistance as above..
This fall off or slope is produced by the drivers moving mass which is reflected through the motor as a capacitance which is in series with the Rdc.
This part is what the technical references I gave you in a previous post are talking about and is what they mean by “mass controlled”.
This R / C forms a 1 pole low pass filter who’s corner F is the low cutoff of the speaker.
The speaker operates on the sloped part of the velocity curve not on the flat part.
A real speaker:
Taking the simplest case, a sealed box, one can follow how the speaker works and why.
Starting way below box resonance, one has a spring dominated system, it is the compliance which governs the motion and when a fixed voltage is presented, the motion of the radiator is constant with frequency.
This is because a fixed voltage produces a fixed current across the Rdc, the fixed current produces a fixed radiator force on the spring and so a fixed displacement results.
This produces an acoustic output, which decreases at 12 dB per octave with decreasing F.
Looking at the drive current’s phase, one can see that is leads the voltage.
Measuring or modeling a sealed box below cutoff, one can see the output falls 12 dB /oct AND the excursion or displacement is constant with decreasing F.At a higher F, at Fb, the spring and mass are equal but opposite reactance’s. , they form a parallel tank L/C/R tank circuit which at resonance, one see’s is a resistive impedance which represents the Rdc in series with the acoustic load paralleled with the mechanical losses, L and C.
For a direct radiaor, this is a high value as the acoustic load is insignificant and mechanical losses typically are fairly low (a high parallel R).
Those quantities are factored by the motor strength with a more sensitive motor (force per amp) producing a higher impedance value with a broader curve for a given set of physical properties..Above Fb, the spring has a decreasing influence and the mass becomes the dominant controlling element (the effect described in the technical references a few posts back).
In this range the radiator Velocity is falling 6 dB per octave due to the Rdc / mass (R / C) filter needed to off set the radiation resistance.
If one plotted radiator velocity (its “Voltage”) vs frequency, one would see that at say 1 Hz the impedance is Rdc, then it increases at about 6 dB per octave to a maximum at Fb, then above Fb, it decreases at 6 dB per octave.
Remember that it is the range when the velocity is falling 6 dB per octave that the acoustic output is flat.
This falling velocity is the result of being now an R / C (Rdc / reflected moving mass) and that filter which causes the fall off HAS a nominal –90 degree phase shift above Fb.AS the frequency in increase further, the secondary element begins to play a part, this is the series inductance.
This L is in series with the mass “C” and as the frequency increases the phase is shifted towards 0, at some frequency, these are equal but opposite reactance’s and cancel out.
Now the impedance is at resistive minimum being the Rdc in series with the acoustic load which is a small R.
Above Rmin, the impedance goes positive again, well above Rmin, it is nominally +90 degrees.Above this point, radiator geometry and a host of other effects begin to show up adding more phase shift.
Because back EMF and force per AMP are precisely linked, it has been possible to derive the radiator motion from the impedance by electronically removing the component of it proportional to the voltage across the Rdc which is proportional to current.
Once the Rdc drop is removed, one can determine the motor Velocity (as it is exactly proportional to Voltage through its Voltage constant) and / or the force or current through the Force constant (BL in the speaker).
In motor control it is common to use a negative output impedance to produce a much better velocity control than open loop because by electronically removing the Rdc, one has a direct connection to the part who’s velocity is exactly proportional to Voltage.
Conversely, when torque control is required, then the current is what is controlled.Alternatively, since a mass controlled system is also a constant acceleration system (constant force against constant mass equals constant acceleration), one can use an accelerometer on the radiator and use its output as a feed back signal for an amplifier to correct from.
This feedback can pertly overcome the compliance corner, pushing the response downward and since it is acceleration, also can partly correct for motor nonlinearities.
Please before rejecting all this, look into it further, while it may not be the way your used to seeing it, it is the way they work and I’m not pulling your leg..
So far as your e-mails, the only one I got was the one I posted, the ones that Pat got at work were the ones, which caused the issue.
I had received a call from her saying “who is Wayne and why is he so mad and threatening us with legal action ?”.
Then I got one from Brad saying to stay off A.A until Mike has a chance to look at the letters, it took him a couple days to get to it I guess. His assessment ultimately was there was no real threat and Brad said it was OK to go back on A.A.. The Lawyer however also suggested it might make better business sense to be more secretive about how things work etc.You do sound genuine here as well, I left a message with Pat to find the e-mails she sent to Mike to look at.
Depending which comes first (the mail server being up and running again today or not) I have to go to the shop Monday or Tuesday anyway, I will get the e-mails from Pat and post them.Tom
Tom -You are really a piece of work. You've restated the same things in every post. You've tried to make it sound like you didn't fabricate the whole E-Mail issue. And you've also tried to make it sound like you've got something technical to explain. But both are just "spin" - You have nothing new to say.
The point is that the speaker's motor/diaphragm system does not exhibit a constant 90 o shift. It is able to move above and below resonance, so the phase angle isn't a constant. There are also other things that modify phase, some consistently and some eradically. But the point is that you cannot expect the system to have a consistent 90 o phase shift.
For you to have taken issue with this statement is ludicrous. It's a fact, plain and simple. You even restate this fact, several paragraphs down in your diatribes. So it appears that your posts aren't meant to be informative, but rather just argumentative.
As for your comments about E-Mails, everything you've said about that issue was lie, a fabrication designed to sway public opinion.
Wayne
Hi WayneWell it is nice that my explanation sounded familiar, this suggests that you may have read and remembered some of my other explanations to you on this subject..
This time I did take a bit more time to lay it out in plain English without depending on the technical references in the other post.
I figured maybe historical, technical references were what turned you off to the concept.
The expression “you can lead a horse to water but you can’t make them drink” is particularly fitting here it seems to me.
Until YOU are able to measure speakers for yourself and see what I’m talking about or find someone else who is a loudspeaker engineer to explain it to you, you will likely not be persuaded by my words.I know there are a few such engineers on this list though and would welcome input from them here if they are familiar with what I described in the last post.
So far as the E-mails, in several recent posts here on AA you alluded to the E-mails to the shop and the fuss it caused being “made up”.
I then posted the one you sent me where you falsly accuse me of bashing you and your products and accuse John H. and I being “in league” and out to get you somehow. Then you posted your e-mail to John H. where you do in fact suggest that perhaps you should speak to a lawyer about it..
It was nice you eventually fessed up to actually sending those e-mails.I have not seen the ones you sent to the shop yet but I do know that first Pat (office mgr) called saying “who is this Wayne guy and why is he so mad, threatening legal action” which was followed by my boss calling saying “stay off AA until there is a reading on this by Mike”.
Our lawyers read was that you were not a legitimate threat.
I was then told I can go back on AA.
That is it in a nutshell, plain and simple.Like the other discussions where your posture is set in stone, I would be similarly surprised if sworn statements from Brad, Pat and the Lawyer outlining what I have said would effect your public persona either.
Never the less I will ask them all if they would consider posting here to that effect when I pick up your e-mails from the shop.The fact is, it was your e-mails to the shop that caused the problem, no amount of your whirling dervish will change that.
Fact two is horns and direct radiators have a different acoustic phase according to the reasons I explained.
The stuff I design for a living depends on knowing about / being able to measure acoustic phase. I forgot, you don’t think any of that stuff works either and don’t believe in taking your own measurements.
There are none as blind as those who choose not to see.
Cheers,Tom
Tom -Here we go with more of your double-speak. If you can't make an argument work to buttress your ego, you'll try misdirection instead.
I have been the person that has consistently stated that loudspeaker phase moves throughout its passband. You, on the other hand, claim it to be consistent, using the oversimplifications that you have said many times before. You claim horns have phase of zero, by generalizing them to be perfectly resistive. And you claim direct radiators have phase of ninety degrees, by oversimplifying them to be uniformly reactive. Neither case is accurate, and so both statements are false.
As for the the nonsense you've said about E-Mail's, I'll say it again: Your purpose was to sensationalize and exaggerate, and you've manipulated the issue in order to sway public opinion.
You could claim that everyone in your company was completely stupid if you wish, and that no one there could read the addresses. Or maybe reading your poor grammer and spelling has caused their reading skills to regress. But it is highly unlikely that everyone in your shop misunderstood these letters, when everyone else that has read them did not.
Wayne
Wayne, I composed this reply to the post you just removed (must be nice to be able to take back your words like that).
I am posting it here as it addresses many of the same pointsPerhaps if you carefully re-read what I have explained you will come away with more of the gist of what I was saying and the context it is in, instead of the simplistic view you cite.
If anything, one constant message has been “measure them and find out for yourself”.
I have in fact measured horns where the acoustic phase WAS around zero degrees over its operating band and similarly, countless direct radiators that behave as described.
The detailed explanation was to help you finally understand why it is this way (the way outlined in the technical references that seems so hard for you to accept.)
Not only that but I have been involved in several active sound cancellation projects, one with Penn State (that has a good acoustics program) so the idea of producing a specific waveshape and what is needed to do that is not a new concept to me.
Wayne, it was a bad idea for you to have sent the e-mails to the shop.
No one there knew of our discussions and to them it apparently sounded like some "emotional nut case" threatening legal action.
Surely even you can understand there reason for getting a lawyer to look at them and give his “read” (ever heard the expression “better safe than sorry”?) , on the other hand maybe your back to suggesting you didn’t send them?Wayne also wrote:
I'm not the only person that considers you to be a charletan, so you can give up on this crusade you've had for the last few years.Yes, I imagine you do have some friends who think just like you, but I would be surprised if you can find many actual technical people who dispute the operation of what we make and what I do or the argument I made here.
I figure AES and ASA would not have asked me to speak (as an invited speaker) on loudspeakers and transducers etc if they agreed with you on technical grounds. What have they asked you to speak about btw?
On the other hand, largely as a result of side by side demo’s, we are taking away business from a number of larger companies and I don’t imagine they are too happy about that, sour grapes.Also, In your e-mail to me, you accuse me of bashing your products, if your willing to lie about something like that (something where anyone curious can simply go back and look to see what I actually said) , how much of what else you say is also fiction (lies) to
forward Your image in Your market here.
We on the other hand sell NOTHING at all to this market, I am here because I like DIY.
Yes, it did piss me off that you would jeopardize my involvement in DIY here by taking your supposed “problems” to the company I work for.
I did post an explanation here as to why I had to be absent and since it was a 100% a direct result of your e-mails, I told it like it was (without actually saying your name you will notice).
Now that you have tried to slime out of it, it seemed appropriate to fill in the blanks with the missing name, Wayne.
Face it, you farted in Church and now you have to sit in your own pew.
No amount of your arm waving changes what happened as a result of your e-mails.Fwiw, I would also doubt that regardless of your own self image, that you think you can actually speak for everyone else on this as you suggest.
Cheers,
Tom
Tom -Doesn't this kind of thing ever get old to you? Do you enjoy acting like this?
In my first reply to you on this thread, I said "The mass/spring system forms a filter that changes phase with frequency." You, on the other hand, initially described it only partially - inaccurately - speaking only of the mass and disregarding the suspension. You said nothing of cone geometry and the other things that modify system behavior and prevent it from acting as a pure single pole.
So you merely invented an argument, as you had nothing useful to say. Your comments were out of place because my first post on this thread was a reply to Tom Dawson. It was about quadrature and DSP, and my reply referenced the subject and included links to DSP information. So you simpy derailed the thread and nothing more. You were combative because you wanted the attention, and that's all.
It is this very sort of action that has illustrated your real intentions. Your motives are clearly self-promotional, and you engage in all forms of deception towards that aim. You are manipulative, by inventing arguments and derailing useful conversations to promote yourself or your agenda. You are divisive, by misrepresenting issues such as the one about the E-mails. But the thing that is probably most unattractive is your arrogance, which shows in practically everything you write.
And speaking of the E-Mails, you keep talking about my "sending E-mails to the shop," as if I had sent something to people other than yourself within your little company. The fact is that this comment is another piece of spin - The address used was "tom@servodrive.com" and where this goes is your affair alone.
I pulled my last post and re-submitted it to remove the last sentence, which was "I'm not the only person that considers you to be a charletan, so you can give up on this crusade you've had for the last few years." It's another issue entirely, but I can't help but to wonder how you feel about your peers and suppliers beginning to distance themselves from you. I wonder what happened to Intersonics, and if it is happening again. With your behaviour patterns, you certainly can't be gaining any friends.
Wayne
Hi Wayne,In the time it took to reply , you withdrew your post again.
Here was my reply to it> Doesn't this kind of thing ever get old to you? Do you enjoy acting like this?
Rebutting your feeble nonsense is getting old but the kids are at Gramma’s, Mark has the TEF machine and I am bored.
> You, on the other hand, initially described it only partially - inaccurately - speaking only of the mass and disregarding the suspension. You said nothing of cone geometry and the other things that modify system behavior and prevent it from acting as a pure single pole.
Wayne, go back and read what I said, I describe the spring-controlled region as well as touch on the other effects which come into play well above low cutoff.
What we were discussing was the mass controlled response and the phase shift that goes along with it and what causes it and what you see when you measure it.> So you merely invented an argument, as you had nothing useful to say. My first post on this thread was to Tom Dawson, and it was a list of links to DSP information. You simpy derailed the thread and nothing more. You were combative because you wanted the attention, and that's all.
The post you were replying to was one that included the very things I continued to press with you.
Why in fact did you insert your self in it if it wasn’t for self puffery?> It is this very sort of action that has illustrated your real intentions. Your motives are clearly self-promotional, and you engage in all forms of deception towards that aim. You are manipulative, by inventing arguments and derailing useful conversations to promote yourself or your agenda. You are divisive, by misrepresenting issues such as the one about the E-mails. But the thing that is probably most unattractive is your arrogance, which shows in practically everything you write.
My gosh if that isn’t the pot calling the kettle black, you could probably have a bright future in politics if you want.
Deception, heck I am the one saying measure it for your self and see, some deception sheesh.
Hey Wayne, with all your talk about promotion, perhaps it didn’t occur to you that I don’t sell anything here, I have no DIY products, no one here is likely to buy the companies stuff and we already have a good reputation in our industry. What the heck do you think I am promoting here?
You on the other hand obviously have a great deal of interest protecting your image in your own market so why do you engage in these arguments? Why accuse me of bashing you and your products anyway?> And speaking of the E-Mails, you keep talking about my "sending E-mails to the shop," as if I had sent something to people other than yourself within your little company. The fact is that this comment is another piece of spin - The address used was "tom@servodrive.com" and where this goes is your affair alone.
Spin you say, I would say spin was you trying to make it sound like you didn’t send the e-mails that caused my absence from here.
When you sent your e-mail to me at home, you were sending it to me.
My DIY involvement is not an official part of my job understand, nor do I work at the shop, when you sent them to Tom@servodrive.com, instead, that is at the shop.
Pat at the shop checks all the e-mail and deals with it accordingly, in the process, she read yours and did what she thought was right.
I will get those e-mails Monday fwiw.> I pulled my last post and re-submitted it to remove the last sentence, which was "I'm not the only person that considers you to be a charletan, so you can give up on this crusade you've had for the last few years."
Name calling, calling me a Charlatan, teasing about spelling and grammar, real nice, it highlights what a “very special” person you are.
Makes me feel like cutting you some slack, you know what I mean?.> It's another issue entirely, but I can't help but to wonder how you feel about your peers and suppliers beginning to distance themselves from you.
I don’t know, I’ll let you know if it ever happens.
> I wonder what happened to Intersonics,
The focus of the company was on the NASA flight hardware and material sciences.
When NASA hq gave contract authority over our area (containerless processing) to JPL (who was our only competitor) it wasn’t long before the 4.5 M a year flight hardware / research budget went to zero.
The materials side spun off under a new name called Containerless Research Inc, the speaker side was spun off into the hands of a crook from south Africa by the president of Intersonics, then after that disaster Brad took it over and since then we have continued to grow steadily.> and if it is happening again.
No, Servodrive and Sound Physics Labs are a speaker company first and if I do any more gov’t work, it will be on our terms.
> With your behavior patterns, you certainly can't be gaining any friends.
If you were a problem in our market area, I would have to deal with you differently than here it is true.
Here I can saw what I think and not mince words if I choose.
As long as you and the sock puppets that were around here in your absence, are the only antagonistic people that have to deal with, I am not concerned.Cheers,
Tom
OK, Tom, so let me see if I get this straight:You say the letter from John Hancock that was forwarded to you, and my reply that was also copied to you, were misunderstood by you and everyone else in your shop. Copies of the exchange between John and I are here . You say you believed they were written to you, even though one was addressed to "Wayne" and the other to "John."
That's what you're saying? I mean, that is really pretty stupid. Then again, I suppose it might be better than to admit that you intentionally misled the public.
Now let's see; What other nonsense have you written for me to dissect?
You wrote:
> > I describe the spring-controlled region as well as touch on the
> > other effects which come into play well above low cutoff.You didn't mention that for several posts. In fact, you argued against this when I described the behavior of the system in regions of resonance and below-resonance, and the transition from being acoustically small to being acoustically large. That's just a few posts up , and it's all here in black and white, showing your tendency to be combative and invent arguments where none should exist.
Your first posts suggested that the system creates purely a 90 degree lagging phase shift. And frankly, you were quite rude in your demeanor, which gave me the inclination to treat you in kind. Especially since you took the tone of disagreement when I mentioned regions where this was not true. So it was obvious to me that you just wanted to be argumentative.
This is a common strategy that I've seen from you. You will equivocate, using only the part of the truth that you think justifies your position. It's like telling half-truths and choosing which half suits you best. I've even watched you change sides in order to make a different point. But when you buttress an argument with equivocation, the omission makes your statement false.
And speaking of equivocation, lets talk about your usual description of the impedance of horns. They act to increase radiating resistance, but they do have a reactive component. You have minimized this in your discussions of them - just as you did in the link above - and you consistently characterize them as being purely resistive. But even the best horns are nowhere near this ideal.
So how about you commit to something here, and make a definite statement. Tell us how you would describe the real and imaginary impedance of a horn. Tell us how near or how far from cutoff they can be expected to become resistive rather than partially reactive.
Something like this would be acceptable. This shows the acoustic impedance of the horn, with reactive and resistive components clearly visible. Notice that this horn is intended to be used from 40Hz-400Hz, and pay attention to the resistive/reactive impedance in this region:
Horn response and acoustic impedance
Clearly, there is significant reactance in the passband.
-and-
This means that acoustic phase cannot be zero.
Pressure and velocity are not in phase and are instead periodically changing like a series of resonances. That's also why the amplitude response has slight ripples, just like the phase response does.
You might prefer to see this demonstrated with data provided by an unbiased source, perhaps using a real-world horn that can be duplicated. Measurements can be made with the two-microphone method or models can be used instead, I don't care. But there is no denying this fact - No matter what horn is used, this is their very nature so they will all show this type of response.
Or maybe you will show the impedance chart for some of your horn products, to demonstrate their impedance curve and indicate their acoustic phase. It would not be acceptable to see data that was generalized or "doctored." So be careful now, because just about anyone can find this out for themselves.
> > What the heck do you think I am promoting here?
Yourself.
> > Why accuse me of bashing you and your products anyway?
Because you are, and have been for a long time. That's what this thread is about, and that's what the nature of our relationship has been about from the start. You are so arrogant and self-righteous that you believe you can attack everyone and that they should not argue their points in response.
I see where Mark Seaton got his example, and the things he said in the past were heavily influenced by you. You are the one that drives this thing, and you are solely responsible for the public image of your company.
> > I would say spin was you trying to make it sound like you didn't
> > send the e-mails that caused my absence from here. When you sent
> > your e-mail to me at home, you were sending it to me. My DIY
> > involvement is not an official part of my job understand, nor do
> > I work at the shop, when you sent them to Tom@servodrive.com,
> > instead, that is at the shop.So you don't read your own E-mail's? Try having someone write your E-Mail's then too. Someone who has taken a little bit of remedial English perhaps. Your grammer makes me feel like I'm reading something written with a crayon.
> > Name calling, calling me a Charlatan, teasing about spelling and
> > grammar, real nice, it highlights what a "very special" person you
> > are. Makes me feel like cutting you some slack, you know what I
> > mean?.That's right, Tom. You've always been so kind that it saddens me to see our relationship sour this way.
I noticed that you called yourself a Charletan with a capital "C". I didn't capitalize the word, but your use is fitting and appropriate. I've grown to recognize you as the "P.T. Barnum of the industry."
Wayne
> OK, Tom, so let me see if I get this straight:By gosh, that would be a refreshing and long over due but I will be surprised if you can pull it off.
> You say the letter from John Hancock that was forwarded to you, and my reply that was also copied to you, were misunderstood by you and everyone else in your shop. Copies of the exchange between John and I are here. You say you believed they were written to you, even though one was addressed to "Wayne" and the other to "John."
Wayne, I received ONE e-mail, the one I posted, then my isp was down and I could not receive any e-mail here.
You sent e-mails to the shop (probably because I didn’t respond to yours I would guess) , e-mails which so far I have not seen.
Pat at the office read them and called me about you.
Pat also gave Brad the e-mails and it was decided that “to be safe” the lawyer should see them and I should be absent from here until he makes a call on it.
I have explained this a number of times, get it yet? Probably not.> That's what you're saying? I mean, that is really pretty stupid. Then again, I suppose it might be better than to admit that you intentionally misled the public.
Mislead them about what?
What I described is what happened and while it is true I could have just signed off without explanation, I was angry that you would be the cause of it and did post “why” I was leaving.
Perhaps that made you feel uncomfortable, perhaps people thought you were responsible (as you were) but that is what happened.
Going back and reading the post you sent me, I again ask you to find examples of the bashing of your products you claimed I was doing at the time, you know, the reason you sent me the e-mail in the first place.So far as what I see, misleading the public is what you tried to do by suggesting that you didn’t write the e-mails or that the incident was made up by me.
> Now let's see; What other nonsense have you written for me to dissect?Yes Wayne dissect away, that way you never have to deal with the context or big picture, things that lead to understanding...
You wrote:
> > I describe the spring-controlled region as well as touch on the
> > other effects which come into play well above low cutoff.> You didn't mention that for several posts. In fact, you argued against this when I described the behavior of the system in regions of resonance and below-resonance, and the transition from being acoustically small to being acoustically large. That's just a few posts up, and it's all here in black and white, showing your tendency to be combative and invent arguments where none should exist.
Wayne, you see the combative side because your approach brings that out in me, it is hard to deal with some one like you who, if you could only do some measurements on the real thing would see what I was talking about.
Also, if the discussion was just starting here, I could understand your not being “up to speed” technically but there have been many many past discussion with you about the Unity horn and how the phase of everything matters etc. While you have stopped your “it can’t work” campaign on the Unity, I doubt that you have forgotten all the posts.Acknowledging this argument or that phase / time matters would also make you have to consider the acoustic phase of your designs as well, something you have seemed reluctant to do in the past. I guess this is a “window” that you can’t afford to open psychologically.
> Your first posts suggested that the system creates purely a 90 degree lagging phase shift. And frankly, you were quite rude in your demeanor, which gave me the inclination to treat you in kind. Especially since you took the tone of disagreement when I mentioned regions where this was not true. So it was obvious to me that you just wanted to be argumentative.
Wayne, again your dissecting approach prevents you from seeing the big picture.
For example, when I say nominal 90 degree shift, that is not the same as you saying purely a 90 degree shift. So you understand better, “nominal” in this use means approximate or “averages around” and not “is exactly” or “is purely”.I “Want you to be argumentative”, that’s funny, I wonder, can you even “turn it off” when someone disagrees with you? Actually quite the opposite was true, it was nice when you were gone.
> This is a common strategy that I've seen from you. You will equivocate, using only the part of the truth that you think justifies your position. It's like telling half-truths and choosing which half suits you best. I've even watched you change sides in order to make a different point. But when you buttress an argument with equivocation, the omission makes your statement false.
Fine Wayne, normally when I explain something technical to someone, I assume I do not have to explain every thing. Normally I deal with technical people who want to understand something new, not one whose mind has been made up and is unwilling to even consider something different.
> And speaking of equivocation, lets talk about your usual description of the impedance of horns. They act to increase radiating resistance, but they do have a reactive component. You have minimized this in your discussions of them - just as you did in the link above - and you consistently characterize them as being purely resistive. But even the best horns are nowhere near this ideal.
Wayne, the fact is I have measured a number of horns who’s acoustic phase WAS around zero degrees through out a considerable bw.
I have also dealt with systems that HAD TO preserve waveshape so I do have a grasp of what is going on.
Clearly I am unable to put these points into words (that you understand) and without the common ground of measurement, I don’t know how else to fill you in.
I guess if anything I would say that you seem to have a good grasp of the elements in involved but do not have much of an idea where or how much various things come into play.
Your approach reminds me of some one who has read a lot, knows the terms but has never actually built drivers or measured them first hand, that would be my guess anyway.> So how about you commit to something here, and make a definite statement. Tell us how you would describe the real and imaginary impedance of a horn. Tell us how near or how far from cutoff they can be expected to become resistive rather than partially reactive.
> Something like this would be acceptable. This shows the acoustic impedance of the horn, with reactive and resistive components clearly visible. Notice that this horn is intended to be used from 40Hz-400Hz, and pay attention to the resistive/reactive impedance in this region:> Horn response and acoustic impedance
> Clearly, there is significant reactance in the passband.
-and-
> This means that acoustic phase cannot be zero.
Yes Wayne, you are right in the strictest sense, no horn I have seen will have say
a + - .0001 degree acoustic phase around zero.
I have seen horns which were say + - 5 degrees and more that were say + - 10 degrees around zero.
However, to put this in your dreaded concept “context”, in all the discussions so far we have been talking about the difference between direct radiators and horns, direct radiators generally have an acoustic phase which goes from +90 well below cutoff to ~ –90 mid band to ~ +90 well into inductive roll off, with the possibility of hundreds more degrees if operated into cone breakup or non piston behavior. While I didn’t explicitly say so, this also means they traverse zero degrees.One thing you perhaps don’t realize is that by matching the impedance of the acoustic source to the horn’s average Z, the effect of the acoustic impedance variations is minimized so far its effect on acoustic output. This is because when the impedance’s are matched, one has maximum power transfer and shifting one of the two to one side or the other has little impact, one is siting on the top of a curve here..
This is the principal on which antenna power transfer is based and is different than the case when a low impedance voltage source is driving a changing impedance load.
For example in the Bdeap’s (measurements will be on the web site shortly), there is no visible low end ripple in the acoustic output and so, no ripple in the acoustic phase.> Pressure and velocity are not in phase and are instead periodically changing like a series of resonances. That's also why the amplitude response has slight ripples, just like the phase response does.
> You might prefer to see this demonstrated with data provided by an unbiased source, perhaps using a real-world horn that can be duplicated. Measurements can be made with the two-microphone method or models can be used instead, I don't care. But there is no denying this fact - No matter what horn is used, this is their very nature so they will all show this type of response.
> Or maybe you will show the impedance chart for some of your horn products, to demonstrate their impedance curve and indicate their acoustic phase. It would not be acceptable to see data that was generalized or "doctored." So be careful now, because just about anyone can find this out for themselves.Just as nothing I say to you will ever persuade you of anything (so far as the technical argument) , no measurements YOU come up with would convince me that the measurements I have taken and the stuff I have built based on them are based on fiction.
You caution about “being careful”, is humorously ironic both coming from one who doesn’t measure and as the measurement savvy part of the sound industry has embraced us most readily.
I am counting on the fact that real acoustic measurements ARE the language that our customers deal with. Some have the same measuring equipment I do.
Soon there will be a button on the web site where customers with a tef can download the actual measurement files on our products so they can compare with our products they have if they wish or other people’s products they measured.Further, Heyser’s view of acoustic phase is not a “LAW”, companies that sell MLS based systems often claim their technique shows “true acoustic phase” so there can be a difference in measured results on the same speaker in the same conditions.
Personally, I believe TDS is the way to go and agree with the manual for LSP cad which explains why the MLS systems do not show true acoustic phase ( page 117).
That explanation includes the Hilbert transform, which was in the thread you jumped into.
Such systems would show a horn and direct radiator with identical frequency response as also having identical phase response, which they do not normally have.
This was also part of the thread you inserted yourself into btw.
> > What the heck do you think I am promoting here?Yourself.
Sorry, I’m not for sale
> > Why accuse me of bashing you and your products anyway?
> Because you are, and have been for a long time.
Lets see some examples of me bashing your products, put up or shut up!!.
> That's what this thread is about, and that's what the nature of our relationship has been about from the start. You are so arrogant and self-righteous that you believe you can attack everyone and that they should not argue their points in response.
I see where Mark Seaton got his example, and the things he said in the past were heavily influenced by you. You are the one that drives this thing, and you are solely responsible for the public image of your company.Attack everyone?????, no Wayne, just responding to you..
You say “You are the one that drives this thing, and you are solely responsible for the public image of your company.”
In a way this is true, I do design everything we sell and the performance of our stuff is what we are known for.
> > I would say spin was you trying to make it sound like you didn't
> > send the e-mails that caused my absence from here. When you sent
> > your e-mail to me at home, you were sending it to me. My DIY
> > involvement is not an official part of my job understand, nor do
> > I work at the shop, when you sent them to Tom@servodrive.com,
> > instead, that is at the shop.> So you don't read your own E-mail's? Try having someone write your E-Mail's then too. Someone who has taken a little bit of remedial English perhaps. Your grammer makes me feel like I'm reading something written with a crayon.
I didn’t read my e-mails when they couldn’t be forwarded to me at least this sliver of what you said IS true.
Gee Wayne, I am hurt, your slander and insults make such a powerful argument, such a powerful intellect at work here, clearly, I am out of my league with you (Thank God)..
> > Name calling, calling me a Charlatan, teasing about spelling and
> > grammar, real nice, it highlights what a "very special" person you
> > are. Makes me feel like cutting you some slack, you know what I
> > mean?.That's right, Tom. You've always been so kind that it saddens me to see our relationship sour this way.
I noticed that you called yourself a Charletan with a capital "C". I didn't capitalize the word, but your use is fitting and appropriate. I've grown to recognize you as the "P.T. Barnum of the industry."You caught that, huh, I figured that was too subtle for you to notice.
I used caps because you misspelled charlatan in your post and I thought it was funny that you would harp on spelling and grammar as if it meant anything relevant to the discussion.You say . I've grown to recognize you as the "P.T. Barnum of the industry."
So... that would make you what, either Bozo the Clown or John Wayne Gacey, I suppose..
Cheers,
Tom,
Well, Tom, I see you'd rather talk around the subject than respond to it directly.The E-Mail issue was a fabrication of yours.
And the phase issue is an equivocation of yours.
You rightly discuss that having a resistive load is a requirement for zero phase. That's your argument why horns are better in phase than direct radiators. But when the issue is illustrated - and the reactive component is actually quantified - you backpeddle and use a different argument instead.
So rather than just admitting it and discussing the matter honestly, you go into one of your long diatribes, in an attempt to talk your way around the issue.
You're really a piece of work.
Wayne
Hi Wayne> Well, Tom, I see you'd rather talk around the subject than respond to it directly.
If it were anyone else, what I have said in many posts would have been considered responding directly. There are speaker designers on this list that have picked up technical things from my posts to you, or at least that’s what they say.
Unfortunately, I apparently don’t speak “Wayne speak” I guess, so I doubt I could even convince YOU the Sun would rise in the morning..The E-Mail issue was a fabrication of yours.
This is rich, you could choose to admit that it was your e-mails that caused me to be absent rather than try to make it sound like there was no issue, that I made them up or you didn’t send them.
This is pretty funny watching you try to slime out of it though.
> And the phase issue is an equivocation of yours.Ok Wayne, maybe things ARE different in Wayne’s world, maybe phase and physics are different too in your special “land without measurements”, clearly we are on different pages here.
Maybe the references I cited are wrong in your special place too.
If I were you, I would proceed at maximum magnitude in whatever vector you think is best. You are entitled to your own view of things after all as am I and I am perfectly content to know you’re off designing your boxes in your own special way.> You rightly discuss that having a resistive load is a requirement for zero phase. That's your argument why horns are better in phase than direct radiators. But when the issue is illustrated - and the reactive component is actually quantified - you backpeddle and use a different argument instead.
No, not a different argument at all, if you were paying attention or “wanted” to understand you might have at many points on this journey. You choose “not to see” which is different than ignorance, you are simply one very stubborn / proud fellow who desperately wants to be in the speaker business (my take)..
> So rather than just admitting it and discussing the matter honestly, you go into one of your long diatribes, in an attempt to talk your way around the issue.Yes, the posts are longer than you deserve, I keep having this glimmer of a suspicion that you really do want to understand rather than just be the root of a technical Monty Python argument sketch.
If you were interested though, you would have already done enough homework to know how drivers and horns work at this level. Sadly, if I were to waste more time and words trying to clarify it, you would simply call it more diatribes or pick one or two words to focus on.
I see you also carefully avoid mention of the “product bashing” you insist I was doing after I asked you to “put up or shut up”
This was the issue you wrote me and the shop about wasn’t it?, the e-mails that were the problem remember.
Again “put up or shut up”, you accused me of bashing your products a number of times (read your e-mail) show the examples of what you wrote about and stop lying.> You're really a piece of work.
Thanks Wayne, coming from you that is re-assuring.
Just as I am willing to let my posts stand on there own, I hope the readers of your posts here also gain an added appreciation for the “depth” of your personality, I know I have.
TaTa.Tom
Honestly, Tom, I'm expecting an apology.You need to acknowledge the manipulative tactics you used in this E-Mail thing . It was entirely a fabrication of yours, and you need to be held accountable for it.
You also need to be taken to task for the spin you've placed on technical matters . Especially when you become combative and argumentative just for the sake of self-promotion.
You've badgered me this way for years, and you've always been wrong to do so. Sometimes I've reacted to you and responded similarly. Sometimes not. But in general, I think this kind of thing is bad and don't care for it at all.
When disparate results are obtained using different measurement systems, one must consider the possibility of ambiguity. But there is no ambiguity in the correlation between phase and the ratios of real and imaginery impedance. You can easily find phase when resistance and reactance are known.The relationship between phase and impedance is determined by the following formula:
θ = ArcTan i / r
where,θ is the phase angle
i is the imaginary or reactive impedance, and
r is the real or resistive impedanceConsidering this, you can easily find the phase where impedance is known.
So let's look again at the response chart for a horn:
You can see that the horn is intended to be used from 40Hz to 400Hz, so that's the region of interest. You'll notice that the device is quite reactive, meaning that it has non-zero phase. And it isn't trivial - It is a significant amount. For example, phase θ = 65 o at 55Hz, 45 o at 110Hz, 30 o at 200Hz and 20 o at 400Hz, where the horn has reached upper cutoff. Phase isn't consistent either, but instead is a series of ripples representing large closely-spaced changes in phase.
Wayne
Hi WayneI don’t know the dimension of the horn you have modeled but there are a few things one can tell about it from the curves.
It would appear to be a horn that is 1 / 2 wl or longer vs the minimum 1 / 4 wl length (a guess based on the spacing of the ripples).
Based on the frequency response ripples, I would guess the driver is not a good match and / or the mouth is not large enough. This would not be a high efficiency horn.
Response ripples in the output can be caused by a mis-match at either end of the horn IE: mouth too small or driver not suitable. The latter is where the M.L. math is useful.
Fwiw, simpler models (like spice models or the transmission line model I use) also tend to over state the “Q” of such ripples compared to measured results (suggesting there are un-accounted acoustic losses).While this model show ripples in the output up to the high cutoff, it is not necessary to have them when everything is right.
The thing is, whatever the horns impedance is, it is not the definition of what comes out the mouth of the horn.
The horn has an acoustic “impedance” curve, which changes most rapidly in the range near the lf cutoff. Driving that horn is a driver that also has an acoustic impedance and reactance.
When the source and load (driver and horn) are matched, there can be a considerable change in either with a minimum effect on the output.
For example with a nominally matched source and load, one can change the load to 2X or 1 / 2 the original and see less than a 2 dB change in output power. Contrast that to the 6 dB spread when a voltage source is used on a changing load.
Since the driver’s impedance is in series, the effects of phase shift are also reduced (like any reactance in series with an R compared to just the reactance).
The driver also has reactance, however it is customary to make this a conjugating quantity, either by proper sizing of the driver properties and rear volume and / or adjusting the horn flare hyperbolic constant which shapes the rate of change of resistance and reactance (reactance annulling)Anyway, I have to help with some homework so I have to keep this short.
Since you have a way to model horns, how about if I see if I can find parameters which result in little or no ripple in the response. I will post the specifics (since I can’t post images) and you take your program or Mc Beans and see how it looks. Conversely, if this is a real horn you have, let me know the specifics and I will see if I can find a driver which is a better fit.40 to 400 Hz is wider bandwidth than most of the single horns I do but I think flat response in that range would be possible.
Without ripples in the output, there will be no ripples in the output phase as well.
With a horn that is more resistively dominated, the phase will be around zero at the output (after all the fixed delays are removed ala Heyser) and the result is also a more efficient horn
Remember it is only the efficient horn which is resistively dominated and having an acoustic phase around zero degrees.Shortly at the new web site there will be measurements for the Bdeap, while narrower BW than your example, acoustic phase is around zero from somewhat above low cutoff through its operating band.
Also if I recall, the BT-7 response curve also has the acoustic phase plotted.
Got to runTom
Perhaps you will post some examples of horns that have zero phase throughout their passbands. You have promoted time alignment as one of your main marketing strategies, so I can see that you are zealous about it. But I don't find it to be particularly accurate to state the generalization that horns are resistive and therefore phase is zero. Frankly, I always considered your "zero-phase" assertion to be a generalization at best.Horns do become more resistive at higher frequencies, and so there is some reason to mention this general trend. But the fact is that they are not purely resistive, and really aren't even predominantly resistive. So for you to say "horns are resistive" in an argument about phase or acoustic impedance is an overgeneralization that leads people to an inaccurate conclusion.
So I suggest that you back up this assertion with some demonstratable facts; Even when modeling hypothetical infinite horns there is a large reactive component, so it will suprise me to see evidence to the contrary, particularly on a finite horn. But you'll excuse me if I won't accept your measurements as evidence.
Dimensions and specifications would be acceptable, so that they can be used for modeling purposes. Or independent measurements from an impartial lab would be fine. But I think you can understand why I might be a bit skeptical of data coming from you after the comments you've made on this thread and others.
You might not accept my measurements either. I typically don't publish measurements for this very reason, and would prefer that anything we use as evidence come from an independent and impartial source. But anyone interested can use these discussions as "seeds for thought" and do their own analysis. Below are measurements of several horns connected directly to an amplifier without any crossover or electronic reactive components in the circuit, not even a protective capacitor.
Amplitude response is shown in black, phase is gray.
Altec 811
Edgar 650
Eminence H290
JBL 2370
Martinelli 17"
Peavey CH-3
Hi
If one passes a square wave through a Hilbert transform (producing a constant 90 degree phase regardless of frequency, like a direct radiating woofer midband), what comes out looks nothing like a square wave.
All harmonics are shifted ¼ cycle (which is a different time delay for each F) which is reassembling the waveshape and while it still has the same FFT amplitudes for the harmonics, it is not a square wave.
John is correct in his assertion and you can see the shape of the acoustic phase in a direct radiator by looking at the phase of the electrical current, that is the “moving force” which the radiator / motor system responds to.
While the scale is not the same (because of the series R in the motor), where the electrical phase is capacitive, so is the acoustic phase, where inductive (below box fb and above R-min), so is the acoustic phase.Tom
If one passes a square wave through a Hilbert transform (producing a constant 90 degree phase regardless of frequency, like a direct radiating woofer midband), what comes out looks nothing like a square wave.Such a constant amplitude quadrature filter is nonrealizable in real time, according to the following url:
http://sepwww.stanford.edu/sep/prof/pvi/spec/paper_html/node4.html#SECTION00112000000000000000.
...although it can be approximated by DSP, but that is not what is being discussed here.
Whatever a reasonably flat direct radiating speaker does to the input signal, it does not perform a Hilbert transform on it while converting it to sound. Discounting external reflections, if a given speaker is measured at a constant distance whether directly radiating or through a horn creating an equivalent group delay for either, if the frequency response is normalized for both (presuming both are being operated within their nominally minimaum phase frequency ranges, which means no dispersion narrowing for the horn, etc.), their passband waveshape responses will also be similar.
Hi Tom!I just came across this post from you. Good call. You might like some of the links contained in the post called " Holism and Reductionism - Fourier Series ." There's lots of great stuff there, and I think you'll find it interesting and useful.
Wayne
Hi WayneYou seem somewhat skeptical of the “mass controlled” acceleration response and its accompanying phase shift of small point source discussed in this thread. Why?
Cheers,
Tom
Tom -Are you kidding me? Remember that I am skeptical of claims of perfect acoustic phase by loudspeaker manufacturers. I'm agreeing with Dawson's assertion that the perfect quadrature is non-realizable, at least in the approximated form you've likened it to as a direct radiator.
The mass/spring system forms a filter that changes phase with frequency. Reactive components used in the circuit also form filters that modify phase. The phase of the current through the circuit is relatively easy to find with reactive formulas, and it is non-zero over much of the audio bandwidth for every speaker motor and/or crossover discussed here. For that matter, it is also not a constant quadrature at 90 o .
Beyond this, the speaker's diaphragm is not a point source, but rather a planar source. It approximates a point source at frequencies where wavelength is large compared to diaphragm size and acts as a radiating plane above that. This creates a filter system too. And finally, we have cone flex to consider, which also creates a filter that isn't minimum phase.
Horn's are not exempt either - They suffer from all the same causes of phase shift as direct radiators, and they have some additional ones as well, such as path length, diffraction and other dispersion modifiers and additional resonances such as those caused by panel vibrations and those from 1/4 wave peaking. Sure you can limit those, and that's the hope of every designer. And sure a "perfect load" would be perfectly resistive, having no phase shift. But we're not talking about hypothetical perfect loads here, and to design with such an assumption is absolutely foolish.
So there's good reason to question claims of perfect acoustic phase from a design based on components using these technologies. Then again, there are a lot of good design choices and solutions that will work well. Dawson has given you some examples of those he has found. But academically speaking, there are complications that prevent optimizations of all criteria simultaneously. If this weren't so, we'd probably not be building such a variety of machines.
Wayne
Wayne, you are free to believe what ever you wish.
So long as you continue to avoid / deny the complications of real acoustic measurements or real loudspeaker theory, your speaker world will continue to be comfortably simple.
Have a good dayTom
Tom -By protesting to my last post, it only goes to show how you would rather sensationalize the issues than to honestly discuss them. Thus, it appears that your participation on these forums is purely self-promotional.
Wayne
Hi TomIt’s a good thing Ham’s and others didn’t know it was “impossible” to make them as they (passive hilbert transforms) have been used for ages in producing SSB conversion in radio communication as well as being in the TEF 10, TEF 12 and TEF 12+ (while the TEF 20 is in software) for generating the quadrature test signal.
If you have a friend with Japan Radio 535 or TEF machine, you can see the schematic for one.So far as what a simple case driver (acoustically small, flat response, piston behavior) does, one has to choose what the books say or what the mfr's say.
If one buys into the mass controlled acceleration response to offset the changing radiation resistance, well then one has to buy the 90 degree shift thing.
Similarly, if one carefully measures a real low frequency driver with a suitable test (TDS) one also finds the phase shift.
Alternately, should one try to pass a specific signal for a waveshape critical application like active sound cancellation, well then one also finds the phase shift IS the main reason one can’t just use a microphone and invert the signal.
The speaker DOES NOT preserve the waveshape and so an adaptive algorithm is used instead (which does not work well on random noise cancelation).Understand too that a small acoustic point source like a woofer and a bass horn with the same frequency response will have a very different acoustic phase response because the horn is resistance controlled and the direct radiator is reactance controlled.
If one has a “perfect” example of each, the acoustic phase would be 90 degrees different from each other with the horn being at zero degree and direct radiator at ~ -90.
On the other hand, I have been able to find a room location and frequency where speakers that didn’t even sound good, made a decent square wave.
For a manufacturer to come out and say that “fundamentally our speaker cannot preserve a signal’s wave shape” would not sell many speakers.
Rather the argument made by speaker companies is that phase shifts and non zero phase are largely inaudible.Having heard many systems getting closer to ideal, I would have to say it is the other way around, that to a significant degree it IS the “time problems” and driver location issues which makes speakers sound more like a recording and less like the real thing.
These time problems occur AT the location of the speakers and your ear can identify then spatially (location and depth).
Eliminate the time issues to the point where one can preserve waveshape over a significant bandwidth and it makes a BIG difference in clarity and makes it much more difficult to tell how far away the speaker is or even where it is in a good stereo recording.
I have heard countless old recordings come alive, hearing stuff I could never make out previously and some good recording sound phenomenal with amazing depth of image.Tom, if are you in the midwest or near Chicago, I can demonstrate something I am working on related to all this, bring your best test recordings.
Cheers,Tom Danley
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