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Old 22nd August 2011, 05:08 AM   #2001
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Esperado,

Crikey! Earl would have to be the one least open to the charge of snake oil, or not providing measurements. I can't think of anyone further from being guilty of either. Even Genelec with their studio monitors only show off axis response at a couple of different angles. There is far more data contained in Earl's measurements than in those commonly seen.

I have compared various horn and waveguide profiles. In my opinion, the oblate spheroid is the best sounding of all of them so far and it also measures very well. I recall one that measured very well in the polar plots, but has a noticeable "horn honk." The oblate spheroid with the foam does not sound like a horn at all. It sounds like a good dome tweeter in terms of smoothness, but adds about 18 dB of output (at least) as well as a certain effortless quality and greater dynamics.
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Old 22nd August 2011, 07:48 AM   #2002
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Originally Posted by paulspencer View Post
Earl would have to be the one least open to the charge of snake oil, or not providing measurements.
Please, don't misunderstand my postings. I don't said that it is Snake oil, but it was presented like, in general, snake oil is presented .
I do not knew who was Earl, and that was my first feeling, looking at his site.
Smoothed curves like designed by hand, no responses curves at 30, and this method for presenting the polar is nice to have a good global idea in one sight, not to get a precise scale, on my point of view.
I know, for now what kind of work earl did those past years, but i still feel the style of his web site deserve-it. And i've read i'm not the only one in the audio business.
.
About "horn sound", it is the same kind of legend that the sound of cables. Just the bad designed horns or not well realized ones (resonant) presents that kind of color., reason why i build mine in plain wood. In fact, on my point of view, and when the size makes-it possible, compression drivers and horns are the best way to transform an electric signal in a faithful acoustic one. Thanks to the rigidity and little size of the diaphragm, and the gain of the horn. Efficiency is a very important part of a hifi enclosure. Only way to reduce dynamic distortions, to produce a realistic acoustic level etc....
.
Too, i do not agree with the choice of the motor in those loudspeakers. The motor makes a big difference. We tried TAD's one on the Aeria system with good results. But not so good than the JBL they (and i) use, despite the fact we where obliged to sort them, from some bad manufactured copies.
I, too, did not like Genelec at all, and avoided to mix with them. It was the old ones (coaxial, with those horrible and unbalanced trebles, i did not knows the last ones.

About smoothed curves, i know that, when working on an enclosure, it can help to gives a global idea of the energy. I know too it gives a glorious wrong image of linearity, so it looks like fake to me in a commercial data sheet. I'm very interested, looking in a response curve to can have an idea where the cone begin to fractionate, if a horn have huge resonances etc.

Last edited by Esperado; 22nd August 2011 at 07:56 AM.
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Old 22nd August 2011, 08:08 AM   #2003
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Quote:
Please, don't misunderstand my postings. I don't said that it is Snake oil, but it was presented like, in general, snake oil is presented .
I do not knew who was Earl, and that was my first feeling, looking at his site.
Smoothed curves like designed by hand, no responses curves at 30, and this method for presenting the polar is nice to have a good global idea in one sight, not to get a precise scale, on my point of view.
I understand but don't agree. Try running the application that is included and you can see the response at 30 degrees or any angle you choose. Who else provides that much data? Snake oil makers tend to provide no data at all and put in just enough pseudo science to convince those not really interested in it.

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About "horn sound", it is the same kind of legend that the sound of cables. Just the bad designed horns or not well realized ones (resonant) presents that kind of color., reason why i build mine in plain wood.
Again, I can't agree at all. Take the same driver and set it up in different waveguides and horns, you will hear a difference. Some of them can be close enough that it's not so easy to pick, but even the good ones will measure and sound different. You can take two of them with the same construction and they will sound different for reasons other than the material itself. In my opinion, the design of the horn itself is the dominant aspect, but it's easy enough to deal with any issues related to the unit itself.

Regarding compression drivers sounding different I would tend to agree, but the most obvious ones are between units like the B&C that Earl uses and the Selenium titanium unit often used in the Ewave. Huge difference. If you compare the B&C to more expensive TAD units, I can't comment as I haven't tried it.
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Old 22nd August 2011, 08:43 AM   #2004
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Originally Posted by Esperado View Post
Please, don't misunderstand my postings. I don't said that it is Snake oil, but it was presented like, in general, snake oil is presented .
Does this look like the typical snake oil presentation to you?

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I do not knew who was Earl
Then you have a lot of reading to do. If you're interested in horn theory then this is a good start.
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Old 22nd August 2011, 09:22 AM   #2005
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Originally Posted by paulspencer View Post
Again, I can't agree at all. Take the same driver and set it up in different waveguides and horns, you will hear a difference.
That's what i said: "Bad designed". My horn, by example, as other i knows, does not add accidents to the response curve of the driver, apart the low frequency roll off. And you can compare different diameters or depths, they all measure very close and sound the same. One thing is interesant is to compare the impedance curve of the motor in free air, and charged by the horn. If the horn is well designed, the impedance curve won't change. If your horn create resonances, you will see them in the impedance curve as well.
I would like to add that some other circular spherical waves horns with different designs give quite similar results, and no one present any "horn sound" at all. In fact, their response curves are very similar, some soo flat, like this one:
http://www.azurahorn.com/JA6681B%20o...%20%282%29.pdf
I can believe that earl have a directivity controlled nice horn, but he is not alone in the world. Which can ensure to have the absolute truth, if even this truth exists ?

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Old 22nd August 2011, 01:20 PM   #2006
gedlee is offline gedlee  United States
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Esperado

You make some good points, the typical ones.

The horizontal response of the system is by far the more important than the vertical one because this is the same as the plane of our ears. Our hearing is much more accute to horizontal aberations than vertical ones. Hence, I will sacrifice some vertical problems to alleviate horizontal ones. My horizontal response is as good as it gets.

The polar response data that I post are 1/24 th octave results, they are not "smoothed" as you suggest.

As to sharper slopes, sharper slopes have greater phase change per Hz than shallow ones. This means that while the overlap bandwidth is narrower, the phase change within this bandwidth and hence the depth of the problems at crossover are greater. There is no magic bullet when it comes to crossovers, its what works. There is nothing standard about my crossovers because they are designed to get the best response no matter how steep or shallow they are.

As to Zobel's, a flat impedance curve is irrelavent when the amp is a voltage source ( and I hope the ones that get used are). When the amp has a "highish" output impedance then the Zobel can be a benifit, but there are other, and less costly, ways to achieve the same result. All in all the use of a Zobel is a lot like using "magic caps" or foil inductors. A lot of hype for little to no real effect.

Regarding the drivers, we built a set of Summas with TADs and another set with B&C - both crossovers were optimized for the driver sets. In a blind test of some 16 listeners the results showed that there was no clear preference for the TADs over the B&C (the B7C were slightly prefered) but there was a clear preference for the design over other designs. The obvious conclusion here is that the drivers do not matter nearly as much as the system design. When you do sighted tests of the TADs everyone is overwhelmed by how gorgious they are - so they MUST sound great! Fact is that they don't sound or measure any better than any other drivers.

Perhaps you should read my book if you want to know the theory behind my waveguides. There is no more complete analysis of the theory than you will find in that text. But I warn you, it is not easy reading in any language.

Last edited by gedlee; 22nd August 2011 at 01:28 PM.
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Old 22nd August 2011, 02:49 PM   #2007
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Originally Posted by gedlee View Post
As to Zobel's, a flat impedance curve is irrelavent when the amp is a voltage source ( and I hope the ones that get used are). When the amp has a "highish" output impedance then the Zobel can be a benifit, but there are other, and less costly, ways to achieve the same result. All in all the use of a Zobel is a lot like using "magic caps" or foil inductors. A lot of hype for little to no real effect.
I am sorry, but Zobel and motional impedance compensation makes a noticeable difference you can measure and listen with evidence.

A pure voltage amp does not exist, that is the first reason.

The second one is that, delivering a constant tension/current, the amplifier will have less to ask to feedback's corrections, and phase swifts between A and V. Adding the fact that the response curve will be less altered with any serial wire Z.

The third one is it helps to calculate accurate filters.

One thing i like to insist on is the motional compensation. The change can be heard even with no amp, kicking the cone of the bass driver with the finger. The resonance is greatly reduced.
Here, too, and more than the Zobel, it helps to design accurate filters on the low pass side. Calculations applies with no tuning.
The result is visible a lot in the time domain, with some waterfall exploration. And audible with more controlled basses. Motional compensation has to be done for the loudspeaker in free air.. Accord tuning of the bass reflex has to be done with no compensation. When you add the two, it is amazing to look how it turns on the impedance curve. You just have to tune the serial resistance to get rid of too low z in the bottom.

The last thing i know fore sure id the way to position absorbent material in the enclosures:
instead of putting-it on the sides, to put in at all the centers of the volumes. Making a cross in all the dimensions. The difference is amazing, and you can see it again with waterfall, a reduced level in low medium on the response curve, no more bass reflex typical sound.

Just make the try, if not done yet.. On the bad side, I agree it add some cost in filter's components.

Btw: I don't believe in magic of any kind, like the sound of materials in the electric domain. I believe in their characteristics. I don't listen to cables's sound, never use audiophile caps or whatever, but appropriate less expensive caps as possible. IM distortions of some caps are measurable, like the ceramic ones, but i cannot understand the bad reputation of good electrolytic caps, as an example. I know the influence of too much R with coils, and the distortion they can add if their wires are not tightly glued. The only thing that is in the magic domain, on my side is, as far we are talking about passive filters, i like to design perfectly symetric ones.
At the end, my enclosures, at home, have a impedance curve less than +-1 Ohm around 6 Ohms on all the range. 5 only at the resonance of the Bass reflex. 6.5 at the cross over of the filter.

Last edited by Esperado; 22nd August 2011 at 03:09 PM.
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Old 22nd August 2011, 03:37 PM   #2008
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Originally Posted by gedlee View Post
The polar response data that I post are 1/24 th octave results, they are not "smoothed" as you suggest..
That is what i call smoothed. I prefer to use a Neutrik for that kind of exploring measurements, but, like you can feel, i'm kind of old scool. ;-)
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Old 22nd August 2011, 04:18 PM   #2009
gedlee is offline gedlee  United States
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No one would agree with you that smoothing to 1/24th octave is a problem. I suppose you are one of those guys who believes that every bin of an FFT is "perfect". Well that is simply not the case. Each FFT bin has an error associated with it and only when a few bins are averaged together does one get an accurate result. The more bins the more accurate the average, but of course the less resolution in frequency. So one has to pick an "optimum". The almost universally accepted optimum is 1/20th to 1/10th octave.

No matter what other technique you use (other than FFT) there is SOME averaging. SO don't kid yourself that there is some "magic" measurement box or technique that is error and averaging free, because it does not exist.
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Old 22nd August 2011, 04:23 PM   #2010
soongsc is offline soongsc  Taiwan
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I have had very good experience placing stuffing away from walls simply because that is here the high velocity is and thus more effective damping.
Impedance flattening proved to also audibly improve sound quality.
I quite agree with cap selection. There are many reasonably priced alternatives.
Interconnect impedance flattening is also important in my experience, which is also what has lead me to develop interconnects.
But let's face it, every engineer has his own thing about what is best combination for a design.
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Last edited by soongsc; 22nd August 2011 at 04:28 PM.
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