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In Reply to: RE: update on the Al Sekela tweak posted by Green Lantern on January 28, 2015 at 06:27:25
It looks like them. It's just a resistor and cap in series that is wired across the speaker terminals. Values are not critical but reasonable numbers would be 10 ohm and 0.22uF (calculated frequency ~72Khz).
Follow Ups:
Cap.resistor in series - Its a Zobel network? Correct?
I VOID WARRANTIES
Yes, placed across the speaker terminals....but optimized for high frequencies and not the typical usage you might see in a speaker crossover that impedance levels driver inductance.This RC network has a different purpose than the "choke tweak".....although Al Sekela didn't understand the distinction.
Dave.
Edits: 01/30/15
Davey, you may want to see someone about your compulsion to bash Al Sekela. Really, you could have repeated your own technical point of view without the need to mention HIM in this manner, at all.
We know it bothers you that Al was right, after all. At a practical and audiophile level -- regardless of the "known" technical reasons -- he was right. IF " Al Sekela didn't understand the distinction ", that's just a problem that you have. He certainly knew how things should sound.
It bothers me that some people are ignorant of the engineering involved and refuse to attempt to understand it. I had no problem with Al personally. He just had a simple misunderstanding regarding this. No big deal.Some users have noted the chokes didn't work well for them. How do you explain that? Can you consider the possibility there's a technical reason responsible in those cases too? I certainly can.
If a "tweak" is not universal, is it really a tweak?Cheers,
Dave.
Edits: 01/31/15 01/31/15
Davey, it works for many people. Trying it is cheap. Why should we hide this from many potential beneficiaries? Of course we should not. After all, many pharmaceutical things out there do not work on everyone either...and they are way more expensive and risky.
It is fine if you need to understand the engineering behind everything. For the majority, however, there is not always a need to understand that which basic PERCEPTION may demonstrate. Most folks get in a car, start it and ZOOM...who cares how it works!
There is, potentially, real added joy to be had via the chokes. It pains me greatly that a person like Al, who enjoyed sharing this kind of joy, keeps being treated this way by you.
You say "No big deal" and yet your reaction to this thread is, once again, suggesting otherwise.
Well I know it definitely worked for me...I just recently read another inmate's (I believe Dawnrazor) impression posted a few years back in which he also noted (among other things) a distinct 'blackness' in the background. This was also my first impression; in fact my brain immediately drew a comparison of the sound to that of a amazingly lit docking station floating in deep space against a black-ink backdrop.But then again Neolith also raises a good point: "was the improvement due to the choke, or due to the loss of that steel jumper" ... I'm inclined to think a little bit of both.
But for the sake of argument and for less than the cost of a cup of coffee per panel, it doesn't really matter to me ;)
I'll probably spring for another pair for the bass panels in the near future.
Edits: 02/01/15 02/02/15 02/02/15
GL, I am very glad that you may keep exploring the tweak's potential.Before I discovered Al's chokes, Dawnrazor had been bugging me to try Taz's capless tweak (archives in MUG). At that stage early in 2009, I was about to build my first PLLXO bi-amp. However, I had not yet decided on xover points and slopes. So, I figured, what the hell, let's try the darn capless tweeter thing while I decide other things. Who knows what else I'll learn.
Well, the whole exploratory exercise was an eye opener. For all its disadvantages, the capless tweak did show two great things. One was that the QR tweeter in my MMGs could sound almost like a ribbon tweeter (it is different from later MMGs).
The other discovery was as significant. When in "capless tweeter" mode, I had imaging improvements which vanished with any other type of xover mode. [Yet, I could not keep "capless tweeter" much longer. ]
That's when I bumped into postings describing what Al Sekela's chokes delivered for ribbon tweeter Maggies. I recognized these descriptions as if they were MY OWN! It made sense. In "capless tweeter" mode, there is an inductor in the tweeter's circuit...and the choke is an inductor. The rest is history.
So, a decision to explore further led me to unsuspected good discoveries, which often happens to many of us. Furthermore, the basic descriptions provided by several folks about the chokes were tremendously useful. I could relate to their experience. I'd encourage that we all read the stuff contributed by others, now in the archives. There are gold nuggets hidden in there.
Edits: 02/02/15
Who's hiding it? Certainly not me. I'm only highlighting the technical aspects of it. Find me a post where I told anyone not to try it.
Now it's pharmaceuticals and cars that are the analogy? More analogies, more straw men. You HAVE to get away from that. :)
And you seem to be implying that I'm dissing Al personally in some way. I suggest to read my posts again, and re-read them two or three times if you need to. This silly knee-jerking defensive reaction is tiresome. As I mentioned before, I chatted with Al offline a number of times. He was a nice guy. This forum misses him.
You didn't answer my question regarding why the "choke tweak" has not been working for some users. Do you have an opinion on that, or is "just try it, it's cheap" your standard answer for everything? I have a possible explanation.......are you interested in hearing it?
There is almost always a bona fide technical explanation for differences we hear when changing components/aspects of our systems. I know that it's fun to talk about the subjective aspects of audio. A synergistic component combination.....the magic quality to the midrange of speaker X.....the musicalness of valve amp Y....the improved 3D layering....etc, etc. But most of that is just nebulous nonsense that has a simple explanation.
It really is no big deal. This is trivial when you think about it. We're not abusing animals here......nobody's dying or being stricken with a horrible disease.....your house hasn't caught on fire......great amounts of money are not being spent on a crazy hobby...oh wait.
In case you haven't figured this out yet.....this choke tweak back/forth is just a very small example of an inherent issue that exists in much of the customer base of the "high-end" audio industry. It's very easy for folks to get side-tracked with their thinking on certain aspects of this crazy business. You HAVE to remain objective and get yourself back on course if you get deflected. I know from experience....believe me! Feeding the audiophile ego is dangerous.....especially when it's your own. :)
Cheers,
Dave.
Well, Davey, here is one of many possibilities. You may be partially "blind". And, by the way, this statement is not related just to the effect of the chokes. Even without them, there are things that you seem to not perceive.
So, the real big issue may be a perceptual handicap that prevents you from "seeing" a much more ample scope of sound, and to derive the resulting extra music enjoyment. You can't even accept that this larger, sweeter ear-scape world exists. We all have some kind of limitation but yours may have driven you into denial. In the process, you mask it with your overstated display of engineering imperatives. Most of us believe in science, and enjoy the music.
Yes, you are dissing Al personally, or trying to. As veiled an attempt as it may be, it is not invisible. You are also implying that this thread is a false. In fact, you are saying that many of us may be deluded.
OTOH, I am saying that, more likely, you are somewhat hearing or perceptually impaired. If you can't hear some stuff, there is no shame in admitting it; unless hypocrisy comes into play. Pretending that just the rules of engineering must apply is, among other things, an attempt to reduce us all to your own limitations.
More silly rhetoric and inane straw man arguments.My ears are just as good as yours....but when I hear something that shouldn't be there.....or don't hear something that should be there.....I investigate. When I hear something I expected to hear I still investigate....to make sure I haven't been fooled.
Subjective evaluation doesn't trump everything else.
Dave.
Edits: 02/01/15
Davey, your "my ears are just as good as yours" sincerely would make me extremely happy for you, even if perception is more than just hearing. However, the sticking point in my mind for years has been that you never allude to core music attributes. I am talking many things that I miss from someone whose system must have been tweaked using great engineering.
Where's the resulting emotional delight about so many things, the moving intricacies, the textural flavors, the soundstage spread detail or the positioning of 3D items on it, and much more? Actually, you hardly ever mention how your system sounds, and then do so on rather dry terms. More to the point, you never mention this kind of thing about ANY music source.
Sure, it is easy to hide it with comments like "Subjective evaluation doesn't trump everything else." Well, you even fail to post an inkling of what your system really measures like acoustically. Imperfect as this would be, it would still be usefully indicative. For someone so averse to subjectivity, this could have provided a "good enough" reference point.
That said, subjectivity -- to me -- is still a very valid value for pragmatic degrees of evaluation. Even on a half-well setup system with Maggies, the perception of recording attributes can be a superb and emotionally moving experience. At times, one may even want to tell others about it. There's nothing wrong with its subjective source, however. By and large, it may be "repeatable subjectivity", shared by many people.
This is better observed in exactly the same place, with the same gear and program material. Yet, it is amazing how despite the universe of variability out there, it all still yields a core set of "enjoyable attributes", perceived in a similar fashion.
Oh, you can be sure I REALLY investigate beyond what I myself hear or perceive; and it is not just by measuring whenever I can.
It is a great experience to see how, for example, 3D imaging can be perceived by friends. You ask them "where is this located"? Most will point to a specific location in width and depth. The location in space will easily vary from person to person but not usually by much. Amusingly, they sometimes are shocked by pointing OUTSIDE the room. This actually happens often enough. It certainly is not my imagination. What would you call it, then? Mass delusion?
Well, additional proof of the validity of this 3D thing comes from other sources; those who DO NOT perceive any localized 3D aural experience. Invariably, so far, they have a lost significant hearing in one ear. [They do enjoy other aspects of the music but "imaging" of any kind and "soundstage" are concepts lost to them.]
This 3D imaging feature is usually enhanced by using the chokes. Since my MMGs have the PLLXO biamp, the bass driver has no xover inductor. Thus, long ago I added chokes to the bass drivers for a better effect. Perhaps, even hopefully, this could help you perceive a stronger effect. You may want to add the 2nd set of chokes, since you biamp as well.
Let me try and simplify this for you.
Here's a bit of Davey audio philosophy for you. "Just because something sounds good, doesn't mean it's working right." (Think about that for a while.) :)
Is that a concept you can wrap your head around?I'm actually laughing as I type this because on this forum fellas like Satie always accuse me of being the hard-nosed objectivist who won't consider off-the-wall ideas. Yet, in this instance, I'm the open-minded one (considering all aspects) and other members have their heads in the sand. How funny is that?
You have to turn loose of this romantic notion that you're placing on your equipment and think about it more objectively. Sure, you embrace the emotional aspect your audio system can evoke......and subjective evaluation certainly has its place too......but always keep real-world common sense operating in your mind as well.
You've heard me say this before, but I'll say it again. Subjective evaluation is, by definition, incontrovertible. You will never hear me say that you're not hearing what you're hearing. You've mentioned a couple of times that I've said that....I absolutely have not! You HAVE to stop with the straw man arguments. Or if not, consider venturing into politics. :)
Cheers,
Dave.
Edits: 02/01/15 02/01/15
Davey, Davey, you are forgetting things or conveniently ignoring them.
Being brought up in a music environment, "more enjoyable" and "sounding good" means "more correct" for me. So, when I get emotional about what's playing, it is largely because the beauty comes from a more real reproduction of acoustic instruments and voices. Even some MMGs can also convey a whole world of additional, delightful, real musical information. This includes gorgeously realistic imaging and a convincingly ample soundstage, if in the recording.
Sharing with others the ideas that make this more real beauty possible, is what drives many of us here, including Al Sekela when he was around.
Yet, you can't do this; the words "beauty" and "beautiful" are simply not in your vocabulary about the music itself, much less "delight". It is clear that you can't get these concepts tied to music. If you did, we would have "heard" you saying it loudly. OTOH, you might be inclined to call a circuit "beautiful", I suspect. They are different things, though.
Thus, you can't pass judgement on music correctness, at least not in its fuller scope, whether subjective, objective or otherwise.
But, yes sir, you can do conventional circuits better than most of us, there's that.
I see them in Amplifiers all the time - on the speaker outs. Zobel circuits reduce chances of amp oscillating - improves stability....so what is its supposed to do here? What if you amp already has a Zobel circuit? Many do...
I VOID WARRANTIES
Zobel's on amplifier outputs are for most likely.....as you say....amplifier stability. The RC we're talking about here utilizes a much smaller value capacitor and is optimized for terminating the far end of speaker wires in the RF band. The theory is that speaker wires acting as antennas can source RFI back into an amplifier output where it might interact with the feedback configuration.
It's an unusual situation, but I have seen it firsthand on a few occasions.
The "choke tweak" is a different scheme and forms a real low-pass filter just above the audio band and obviously increases load impedance as frequency rises. Thus, you don't have the termination configuration an RC network provides. The reason the "choke tweak" is providing audible benefits in certain situations is because of this low-pass filtering effect and not an RFI-related operation
This has all been hashed and rehashed on this forum quite a few times during the years. :)
Dave.
I thought the idea was that the voice coils themselves in the Magnepans could act as antennas.
There's much longer exposed wire there than speaker cables.
Does that make any difference?
"I thought the idea was that the voice coils themselves in the Magnepans could act as antennas."
You bet they can. All possible sources of pick up should be considered. A listening room that's a Faraday cage might be fun. In fact, I know a fella who has done just that. (He built it for another purpose though.) :)
Dave.
Davey,
I do not have that deep understanding, technicly. Ljudtekniska Sällskapet (in english maybe the Swedish Audio Society), a non-commercial organisation, had an article in the member magazine running over 6 pages, later followed by a DIY description. Anders Eriksson, the guy who wrote most of it including presenting the graph, passed away last year at the age of just over 40. He is missed by the swedish audio scene!
Anders made a speaker cable with a characteristic impedance of just above 8 ohm. A Litz type with 40 insulated strands, connected as two cores with 20 each. A very common type of cable used for telecommunication! The capacitors: 2x150 nF/250V in parallel. The resistors: 12x100 ohm /2Win parallel (8.33 ohm).
For "normal" loudspeaker cables, 100 nF + 100 ohm could do the trick. I do not know the formula.
Tim Paravicini (Esoteric Audio Research) used to inject some signals "backwards" in his power amplifiers to test their stability.
Wiring geometry is certainly an aspect to consider. Even twisting existing wiring might have a beneficial effect with regard to RFI pickup.
Injecting signals into the output of a device is a common measuring technique. In fact, you can make a really good argument this is the ONLY way an audio power amplifiers output characteristics can truly measured. Most folks measuring an amplifiers output impedance would simply attach a dummy load and take maybe one or two measurements, perform a little arithmetic and presto!
Tim Paravicini's test procedure is an excellent way to test for stability.
We've been primarily talking about RFI here, but remember also that the drivers themselves are motors and generating EMF that is injected back into the power amplifier output. (Yet another thing to consider.) :) Not so much with Magnepan's because they are such weak motors, but certainly with conventional drivers.
Cheers,
Dave.
I find it strange that the Al Sekela tweak is only applied to the ribbon tweeter. It is no secreet that there is the possiblity of having HF/RF injected not only through the cables but also from the interaction speaker and cables. Power lines inside the amplifier may also pickup disturbancies. A Magneplanar driver looks very much a TV-antenna we use in Europe! The bass driver is very large, the push pull drivers may be better protected against RF. The power amplifier can see a brute impedance at very high frequencies.
The red curve in picture is what a power amplifier can "see" at its loudspeaker terminals with a conventional speaker. The blue curve is for a cable having a RC network at the speaker end (or inside the speaker).
http://forumbilder.se/EAC2G/karimp.gif
An RC network across the speaker terminals can help a lot for some combinations of power amplifier+speaker cable+speaker.
Al's theory (which I agree with in this aspect) was that it probably wasn't necessary for the bass driver since there is already a substantial low-pass network in operation on that driver. In that case you have one or two large value inductors already in series and possibly a shunting capacitor as well. It makes little sense to add a 10uH inductor in series with a multiple-millihenry inductor. The woofer is effectively disconnected from the power amplifier at high frequencies and the higher frequency driver(s) have the dominant connection.You are obviously correct about the drivers themselves being (possibly) antennas. HAM radio operators and engineers who specialize in RF issues have a lot of appreciation for these types of situations since they've been dealing with them for years. Audio and RF have many similarities that most don't fully appreciate. Shunting RF with an appropriate filter is a technique that has been used for decades.
That impedance trace is an interesting one and I'd like to know a bit more about how it was generated. However, if realistic, it does show the issue with a speaker/wires picking up transient RFI and presenting it to the amplifier output.
Al's initial premise (a perfectly viable one) was that RFI pickup by the speaker/wires needed to be prevented from making its way back into the power amplifier output. A simple series inductor attacks that issue directly. However, he didn't consider the other direction......where the real low-pass filter formed by the inductor alters operation of the tweeter, relative to what it was. Intuitively, you would think that low-passing the tweeter right above the audio band would also be a beneficial effect. It seems to be a win/win configuration, but think about it a bit further, and think about all the environmental issues and different types of power amps that are employed. In fact, the Gilmore Raptors that Al used are a very interesting case.......as are all switching amplifiers that have high-frequencies present on their outputs. When those high-frequencies are applied to the materials of a Maggie ribbon tweeter, what will happen? Will it be beneficial...subjectively? What will happen to the amplifier operation when you remove the high-frequency load from its output LC filter network? I don't think some of the posters here are appreciating what a potentially complicated interface this really is.
Cheers,
Dave.
Edits: 02/01/15 02/01/15 02/01/15
I also have switching amp which uses a similar chipset as Al''s.
I personally did not hear any big change with the tweak but kept it in as it couldn't hurt I thought. Would your proposed tweak also work on blocking RF picked up by the tweet into the amp?
There are other interactions possible as well, like the tweeter broadcasting RF to be picked up and modulated by other components.
I did find an improvement with a power cleaner (PS Audio Quintet). Not obvious but I found that over time the sound was relaxing and liquid, whereas before it was mostly so only at night.
Other benefits may be reducing noise generated from one component from being injected into others via the power circuit, I.e. Back from one through the power supply into the other.
These things could be very site dependent, how much RF and power line noise you have.
It wouldn't "block" it.....it would shunt it.
A tweeter "broadcasting" RF is a remote possibility. The switching frequency on some of these amplifiers is up close to the standard AM radio band.
The drivers are all laid out with multiple adjacent runs. A quasi-folded-dipole planar antenna? Good fun. :)
Dave.
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