Getting minimum acoustic sense into this mishmash of false dogma...

Posted by Thorsten (M) on July 14, 2012 at 08:15:57

In Reply to: Straightening out the mess Thorsten leaves behind... posted by villastrangiato on July 14, 2012 at 07:04:28:

Hi,

Okay, lets clear up some more confusion.

There is much woffle that is completely meaningless and empty verbiage which I cut...

> I've read various papers from Toole and distinctly remember
> him using the words "carbon copy " to describe frequency response
> measured far off axis in comparison to that measured on axis or
> close to on axis.

Then it should be trivial to supply the reference. BTW, I have ALSO read the papers AND retained copies on my hard drive for reference...

> http://www.harmanaudio.com/all_about_audio/loudspeakers_rooms.pdf

Does not contain "carbon copy"...

> But since you challenged me on this very basic concept -
> I'll direct your attention to figure 25 on page 14 here:

This is labelled "design objective for a room friendly loudspeaker"...

It does not show either a constant directivity or a controlled directivity system. It does show what Dr. Toole recommends and many others (if you had cared to peruse some of the references I provided you with) would disagree, though all would generally agree that figure 25 is a better choice than figure 24.

However, many would submit that this here is an even better choice than figure 25:

And even though this speaker (the Geddes "Summa") has a large variation in directivity below 1KHz, it is generally nevertheless considered "constant directivity", both by it's designer and audio professionals in general.

AND if you had paid any attention, you would have noticed that the Speaker system using D130 and 075 crossed over at around 5KHz will actually exhibit a SIMILAR off axis response, though not with as smooth curves.

> Once again, I'll reiterate for other potential readers here - constant
> direcitivity in the context of a loudspeaker indicates response lines
> off axis that are essentially the same as the on axis response only
> shifted down a few db in sensitivity. One should see what looks like
> a number of parallel lines that extend out to about 60 degrees. This
> is a speaker that possesses constant directivity - NOT TO BE CONFUSED
> WITH CONTROLLED DIRECTIVITY WHICH THORSTEN CLEARLY HAS DONE.

Nope, what you claim to be a "constant directivity" speaker, namely the typical design following Dr. Toole's recommendation are precisely NOT Constant directivity, becuase they show a rising directivity index with frequency. What is important with designs that follow this principle that rise in directivity is smooth and continous.

Again, had you perused the references I gave you you would know that...

To take something from Siegfried Linkwitz's site about a good example of what Dr. Toole advocates:

This loudspeaker exemplifies Floyd Toole's loudspeaker directivity requirements. They are the result of extensive listening tests where different box loudspeakers were ranked according to preference. The directivity index increases smoothly from 0 dB to 10 dB, without signs of the two crossovers in its frequency response. Moderately wide dispersion horizontally. (SL)

So, if anyone is confused about constant directivity, controlled directivity and what Dr. Toole advocates it appears that this person is you. Further, you ascribe to Dr. Toole claims you cannot back up (and which I doubt he would have made like that) and misrepresent your misunderstanding as his intentions and recommendations, when nothing could be further from the truth.

> The 075 bullet tweeter is a narrow directivity(+/- 20 degree)
> high output tweeter capable of 110 db at 1 meter and 1 watt. It
> was never intended to be used in people's living rooms and anyone
> who suggests it for such an application is totally clueless.

Are you SO SURE about that?

So if JBL had domestic styling 2-Way systems using the 075 marketed as HiFi Speakers these where "never intended to be used in people's living rooms" that would make you a boldfaced liar and actually the one who is "totally clueless"...

Now, let's look at the 1957 Catalog JBL issued for home customers (they had different ones for pro audio)...

Wow... I spy with my little eye the 075, so clearly JBL intended it for home use...

Even further, JBL's Systems/Pricing Page from this catalog shows many 2-Way systems using the 075...

Even worse, the 1976 Home Components catalog still has the 2-Way D130 and 075 in the list of recommendations.

Quel Domage, either everyone at JBL from AT LEAST 1957 to 1976 (or later - I still remember seeing this Combo in the 80's) according to you was totally clueless.

> The poor, uneven off axis response at frequencies it was intended
> by JBL to be crossed up to the D130 at are precisely the problems
> Toole has focused on in his papers - such as the one linked to above.

Now we come to the crux of the matter. And I agree, the original JBL system with a 2.4KHz 2nd order Crossover network created quite a few problems, not just in directivity but also in the frequency response, as I found out in the mid-80's when such systems came my way (long story how).

As we had a fair few of these available and as they had some interesting characteristics to their sound quality we did a fairly comprehensive job of characterising them and the re-engineering them.

Now this was over two decades ago, so I am not 100% on specific values (and the papers are long lost), however we used two LCR Equaliser on the D130, but no lowpass, to get the frequency response pretty flat, a short "Hornreflex" for the Bass which gave a boost in the 100-500Hz range that was a bit low and a 3rd order highpass somewhere around 5KHz for the Tweeters.

As I commented also before, this system measured pretty flat on axis and had a very CONSTANT DIRECTIVITY Response off axis. As Constant Directivity was one of the big buzzwords of the time and one needed to buy very expensive new horns to get this "Constant Directivity" we where pretty pleased that we achieved the same using very different means.

It may surprise you, but I have been dealing with such things like speaker directivity for the better part of three decades, in practice.

> The internet is a great place to gather and share information.

Yes, it be a good ting if you did that a bit more. You would perhaps come across a little less clueless if you did.

> Unfortunately, any idiot can link to someone's website or paper
> and claim that they know what is being said. In the process, it
> is not unusual for the idiot to twist or misinterpret what is
> being said and then disseminate that misinterpretation widely
> on forums such as this.

That sounds like an excellent description of what you have been doing, if I may say so.

> Most living rooms, based on the wavelengths generated in audio systems,
> constitute the near field zone.

Really? Now, exactly what is the definition of "near field" in the context of acoustics?

Do you even know? Here a good (but not exclusive) definition...

The near/far field transition is typically defined at a distance of d^2/l, where d is the effective diameter of the driver, and l is the wavelength of sound. Note that means that as you either increase the diameter OR play a higher frequency, the near/far field transition occurs at a further distance.

Taking for example a 4" radiating diameter and 1KHz we get what distance as near/farfield transtition?

Are you really suggesting that anyone lives in a shoecarton?

Honestly, your total lack of understanding acoustics makes it again time for a double-facepalm for you, honestly, I would think your face should smart something fierce by now...

Now, I would really suggest you actually apply yourself to the subject and gain some basic understanding, if you wish to debate the merits or not of my original recommendation, which send you on this thread of perfect and utter tomfoolery. As the old sages used to say, a little knowledge is a dangerous thing.

Ciao T

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

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Follow Ups Full Thread

Topic - Best Mid-Bass of All Times! - Belgarchi 18:51:03 07/08/12 (80)

RE: Best Mid-Bass of All Times! - Tom Brennan 13:46:13 07/10/12 (0)

A well known DIYer used that one... - Presto 09:00:34 07/10/12 (1)

RE: A well known DIYer used that one... - Belgarchi 16:50:29 07/11/12 (0)

RE: Best Mid-Bass of All Times! - rkeman 07:43:20 07/10/12 (0)

The old Dynaudio 15W-75 and 17W were known to do some of the best mid-bass in a dynamic driver - cfb 06:11:53 07/10/12 (0)

One of my favorites... - mkuller 19:47:37 07/09/12 (0)

Dare I include the big Acoustats? - Ozzie 12:44:30 07/09/12 (1)

RE: Dare I include the big Acoustats? - DKL 18:52:37 07/09/12 (0)

Ahh...semantics. I thought you were going to discuss one octave of bass. - jeffreybehr 11:02:36 07/09/12 (1)

Thanks, you are right... - Belgarchi 16:55:53 07/11/12 (0)

RE: Best Mid-Bass of All Times! - Presto 08:59:53 07/09/12 (0)

I'm sure it's quite good - badman 07:45:54 07/09/12 (0)

RE: Best Mid-Bass of All Times! - villastrangiato 05:00:58 07/09/12 (47)

AE woofers - Scholl 18:16:34 07/13/12 (1)

RE: AE woofers - huynguy.enlatoi1988@gmail.com 20:34:16 07/13/12 (0)

RE: Best Mid-Bass of All Times! - Belgarchi 10:30:08 07/09/12 (44)

RE: Best Mid-Bass of All Times! - Thorsten 04:51:21 07/10/12 (40)

RE: Best Mid-Bass of All Times! - Belgarchi 05:32:40 07/11/12 (39)

RE: Best Mid-Bass of All Times! - Thorsten 06:47:36 07/11/12 (38)

,,,and the enclosure size needed for large woofers... - Belgarchi 10:21:45 07/11/12 (1)

RE: ,,,and the enclosure size needed for large woofers... - Thorsten 10:57:03 07/11/12 (0)

You forget the response in the mids..... - Belgarchi 09:58:04 07/11/12 (34)

RE: You forget the response in the mids..... - Thorsten 10:42:54 07/11/12 (21)

That would most likely deliver... - E-Stat 17:59:10 07/11/12 (20)

RE: That would most likely deliver... - Thorsten 05:23:44 07/12/12 (19)

Do you find that - E-Stat 06:12:10 07/12/12 (18)

RE: Do you find that - Thorsten 08:43:51 07/12/12 (17)

To set the record straight on this antique JBL stuff... - villastrangiato 13:00:15 07/12/12 (8)

RE: To set the record straight on this antique JBL stuff... - Thorsten 22:52:45 07/12/12 (7)

RE: To set the record straight on this antique JBL stuff... - villastrangiato 05:11:37 07/13/12 (6)

RE: To set the record straight on this antique JBL stuff... - Thorsten 07:57:57 07/13/12 (5)

Straightening out the mess Thorsten leaves behind... - villastrangiato 07:04:28 07/14/12 (4)

Getting minimum acoustic sense into this mishmash of false dogma... - Thorsten 08:15:57 07/14/12 (3)

ugh - villastrangiato 10:06:05 07/14/12 (2)

RE: ugh - Thorsten 10:46:17 07/14/12 (1)

double ugh - villastrangiato 11:48:57 07/14/12 (0)

Ah, narrow directivity tweeter - E-Stat 09:06:57 07/12/12 (7)

RE: Ah, narrow directivity tweeter - Ozzie 11:31:31 07/15/12 (3)

RE: Ah, narrow directivity tweeter - Thorsten 00:01:45 07/16/12 (0)

RE: Ah, narrow directivity tweeter - villastrangiato 13:21:58 07/15/12 (1)

RE: Ah, narrow directivity tweeter - Thorsten 00:20:05 07/16/12 (0)

RE: Ah, narrow directivity tweeter - Thorsten 09:17:45 07/12/12 (2)

RE: Ah, narrow directivity tweeter - E-Stat 09:27:05 07/12/12 (1)

RE: Ah, narrow directivity tweeter - Thorsten 10:04:55 07/12/12 (0)

6 - 7 octaves if you're into low fi... - villastrangiato 10:35:18 07/11/12 (11)

RE: 6 - 7 octaves if you're into low fi... - Thorsten 11:16:34 07/11/12 (10)

RE: 6 - 7 octaves if you're into low fi... - villastrangiato 13:01:50 07/11/12 (9)

RE: 6 - 7 octaves if you're into low fi... - Thorsten 13:30:22 07/11/12 (8)

Double face palm time, yet again... - villastrangiato 18:00:23 07/11/12 (3)

RE: Double face palm time, yet again... - Thorsten 05:34:47 07/12/12 (2)

Are you as deranged as your posts suggest? - villastrangiato 08:19:59 07/12/12 (1)

RE: Are you as deranged as your posts suggest? - Thorsten 09:43:54 07/12/12 (0)

Never saw measurements proving your 'point.' - Belgarchi 16:34:50 07/11/12 (3)

RE: Never saw measurements proving your 'point.' - Thorsten 05:22:30 07/12/12 (2)

I think - Presto 11:28:05 07/12/12 (1)

RE: I think - Thorsten 11:44:45 07/12/12 (0)

Actual measurements "small vs. big midbass"... - Thorsten 06:56:46 07/11/12 (0)

RE: Best Mid-Bass of All Times! - John Elison 23:45:51 07/09/12 (2)

RE: Best Mid-Bass of All Times! - Belgarchi 10:14:33 07/11/12 (1)

RE: Best Mid-Bass of All Times! - John Elison 07:51:20 07/14/12 (0)

JBL D130 - Thorsten 01:54:36 07/09/12 (5)

Do you know of any plans for the JBL D130 as a 2-way with a wave-guide tweeter? - Frihed89 21:54:48 07/10/12 (1)

RE: Do you know of any plans for the JBL D130 as a 2-way with a wave-guide tweeter? - Thorsten 22:09:53 07/10/12 (0)

RE: JBL D130 - Ozzie 12:40:16 07/09/12 (2)

RE: JBL D130 - Thorsten 20:35:45 07/09/12 (1)

RE: JBL D130 - Ozzie 07:32:05 07/10/12 (0)

RE: Best Mid-Bass of All Times! - hahax@verizon.net 23:07:53 07/08/12 (7)

RE: Best Mid-Bass of All Times! - Disbeliever 23:43:01 07/13/12 (0)

RE: Best Mid-Bass of All Times! - Belgarchi 10:33:10 07/09/12 (5)

How are you using it? - caspian@peak.org 12:10:30 07/09/12 (4)

RE: How are you using it? - Belgarchi 16:45:23 07/11/12 (0)

RE: How are you using it? - Belgarchi 16:53:51 07/09/12 (2)

Everybody has their "best" for certain reasons... - villastrangiato 18:09:12 07/09/12 (1)

RE: Everybody has their "best" for certain reasons... - Belgarchi 18:24:22 07/09/12 (0)

RE: Best Mid-Bass of All Times! - DanWilson 19:35:26 07/08/12 (5)

RE: Best Mid-Bass of All Times! - Inmate51 12:38:32 07/09/12 (1)

Well, "bass" is the "base" of music - caspian@peak.org 11:01:55 07/10/12 (0)

...and now it's 'midbase'! :-) Dan, that should be 'midbass'. (NT) - jeffreybehr 11:06:08 07/09/12 (2)

RE: ...and now it's 'midbase'! :-) Dan, that should be 'midbass'. (NT) - Wojciech 19:55:06 07/10/12 (1)

RE: ...and now it's 'midbase'! :-) Dan, that should be 'midbass'. (NT) - Scott L 12:53:55 07/12/12 (0)

Follow Ups

Getting minimum acoustic sense into this mishmash of false dogma... - Thorsten 08:15:57 07/14/12 (3)

ugh - villastrangiato 10:06:05 07/14/12 (2)

RE: ugh - Thorsten 10:46:17 07/14/12 (1)

double ugh - villastrangiato 11:48:57 07/14/12 (0)

Getting minimum acoustic sense into this mishmash of false dogma...

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