ZDL

[soongsc]

System phase is certainly not audible as many studies have shown.

For vertically aligned drivers, in the horizontal plane what you say is true, the lobing is only vertical, but it can still have a significant effect on the power response. Olive has shown that the power response is audible even if the axial response is flat and smooth.

It's much easier to not hear something, because it most likely would take efforts equal to legal debates to prove that the listener truly did not hear it. But to hear it and describe what is heard, is a different issue. By describing what is hear, and matching it to descriptions of what others have heard then becomes evidence that it is truly heard.

Since my polarity tests have been demonstrated on many people's systems, their own systems, more than 80% hear the difference in about 1 minute, 10% probably takes longer. Whenever I play music, it take me on an average of 10~30 seconds to decide to flip the polarity.

I agree that power response is important.

 

[ThorstenL]

Hi Joachim,

One listener out of maybe 20 was slightly better to identify the phase linear version. He picked the phase linear version significant more often as the one he prefered.

This listeners name perchance was not Tony Faulkner, was it?

I find phase, groupdelay and polarity are audible under some conditions, but audibility varies with frequency and SPL, it is hard to get anything significant.

Ciao T

 

[soongsc]

We could do the same and did the same 20 years ago with the Essex equalizer. We did a double blind test in a dark chamber. A digitally equalized speaker with LR4 and the phase linear version compared at a flip of a switch. The outcome was not statiscally significant different with music material of average complexity. With artificial signals like a dirac impulse there where small audible differences. The phase linear version sounded "tick" on that signal, the conventional LR4 sounded "tock". One listener out of maybe 20 was slightly better to identify the phase linear version. He picked the phase linear version significant more often as the one he prefered. In an open discussion afterwards he claimed that the phase linear version had better image focus. I concluded after that experiment that flattness of frequency- and power-response is much more important when the crossover is a LR4 type then the phase distortion that it introduces. Still it is "good to have" the phase linear option. Maybe some day comes a musically meaningfull signal along that needs a phase linear speaker to cary the message across.

This is actually very interesting. I can also confirm that equalizing to near field measurement data (0.5cm in fron of diaphragm) is actually much better improvement than equalizing far field (1M) data. However, one thing is critical. As the sound becomes cleaner and more focused, the resolution of the driver becomes critical.

 

[dantheman]

It's much easier to not hear something, because it most likely would take efforts equal to legal debates to prove that the listener truly did not hear it. But to hear it and describe what is heard, is a different issue. By describing what is hear, and matching it to descriptions of what others have heard then becomes evidence that it is truly heard.

You can't prove a negative, but you know that.

Read Wolf's Attitudes Cap Test it would seem the people perhaps better at describing a change heard than they are actually hearing the change.

Wolf, could you elaborate on why you think the group did so much worse than your family?

Thanks,

Dan

Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com - View Single Post - Alright, Cap-Results-Blog posted....

Well, Dan- becauuse it was not an ABX test. The test with my family and Matt at 2 different occasions were basically just: 'listening, and they tell me what they think.' Being that, their opinions of their own accord. That is why those little auditions cannot be admissable to the group of 'cap-ignorant/objective' persons. It doesn't hold as much water as the test I just recently did, and you see where that went. Being that my family was not 'guessing an X', there was no need for accuracy, but for returned opinions or thoughts.

Thanks for asking!
Wolf

If you remember that thread, the ABX, though not well controlled, gave a null result.

Hope that helps,

Dan

 

[Joachim Gerhard]

Even a carefully controlled ABX gives null results most of the time when it is about finer diffences in caps, amps, cables and the like. I know of no conclusive generally agreed test that proves that an LR4 crossover in the midrange is audible. I have my own subjective experience but i whould be hard pressed to "prove" anything. They only thing that will happen as sure as the sun rises each morning, is another endless and fruitless discussion when i air my "opinions".

 

[dantheman]

Yep.

Dan

 

[soongsc]

You can't prove a negative, but you know that.

Read Wolf's Attitudes Cap Test it would seem the people perhaps better at describing a change heard than they are actually hearing the change.


Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com - View Single Post - Alright, Cap-Results-Blog posted....


If you remember that thread, the ABX, though not well controlled, gave a null result.

Hope that helps,

Dan

Well, I'm not going to go into the "proving negative" issue. But Regarding description, I personally have learned a lot from description provided by other people, so there are some people whom provide useful description. They compare listening to specific passages in a piece of music. There was one case that I had difficulty deciding which interconnect design to use, and a friend pointed to vocals, and described clearly what he listens for. Of course, there will be people that provide descriptions that we cannot pinpoint or learn from. So we just have to be careful who and how they describe. Normally if the person can go to a specific passage as an example, then you have the opportunity to decide whether you agree or not. When only 1/1000 can tightrope, can it be done or not? It's only a matter of how long you stay on that rope. This is the same with listening.

 

[fntn]

I have my own subjective experience but i whould be hard pressed to "prove" anything. They only thing that will happen as sure as the sun rises each morning, is another endless and fruitless discussion when i air my "opinions".

I always thought those kinds of "debates" attracted fruitful discussion rather than "fruitless" ones. There never seems to be a shortage of "fruits" to keep those kinds of arguments alive.

As for Malcolm and the ARL gang, I think they are really onto something worthwhile with the last couple of papers on low frequency distribution. We've been doing a lot of experimenting with sub placement based on the modeling they've done. The equations aren't too complicated and it's been surprising how easy it is to reduce routine peaks and dips.

 

[Joachim Gerhard]

Yes, they do wounderfull work.

 

[fntn]

No references to any research by Bharitkar/Kyriakakis - makes me wonder.

Makes you wonder?

Bharitkar focuses too much on equalization from my perspective as far as effectively dealing with frequencies near and below the Schroeder is concerned. As a number of folks are finally starting to learn with poorly designed folded and tapped horns - it's difficult to effectively attenuate the first several harmonics of a fundamental resonance without filtering out the applied signal at resonance altogether or severely compromising spectral balance. Room resonances are no different. And I think the ARL approach is more thorough and well thought out. Equalization has been with us for a very long time (remember the Bose 901? ) and it should be clear by now for most folks in the audio industry what it can and can't do. Can it help tame room modes? Obviously, it can. Will it be effective in doing so without a full understanding of how acoustic energy is distributed in the space? Clearly, the answer for me is no. And I think the work of ARL puts more emphasis in that area - where it belongs.

 

[markus76]

No need to roll your eyes. Don't forget that you talk to a real person.
Found a reference in this paper but couldn't delete my post anymore.

Equalization has been with us for a very long time (remember the Bose 901? ) and it should be clear by now for most folks in the audio industry what it can and can't do.

I'm not so sure about that.

 

[fntn]

No need to roll your eyes. Don't forget that you talk to a real person.
Found a reference in this paper but couldn't delete my post anymore.




I'm not so sure about that.

As for "talking to a real person" - given the number of "unreal persons" running around in attack mode on forums these days, my policy is to assume they are "unreal" until they prove otherwise. Your "makes me wonder" comment was not a very good start but that's only strike one.

There are a great number of people doing great work in the field of acoustics. Perhaps you could forgive me for not mentioning all of them.

There are two other papers on the subject from ARL in the last several years. They are clearly sticking with the original concepts introduced here:

http://www.essex.ac.uk/csee/researc...ubdocs/C136 Visualization of 3-D acoutics.pdf

and here:

http://www.essex.ac.uk/csee/researc...ubdocs/C123 Modeling romm interaction DML.pdf

 

[gedlee]

Regarding the audibility of system phase, at best the data suggests that it is just audible under some unusual conditions. Thats fine, I have no problem with that conclusion. But I do not understand why we would be concerned with this problem in the least when compared to the other far more massive problems of directivity, diffraction, etc. that plague even the best loudspeakers. Its like the nonlinearity discussion, sure there are extreme cases where this is relavent, but its not a major issue for the vast majority of listening situations and sources. The best designs come from addressing the most pressing problems - these aren't those.

 

[soongsc]

Well, in a previous post, I have shown that EQ (with phase EQ) cleans up the sound as indicated in the CSD. If it truly does that for off axis response as well, then that not only effects direct sound, but also how the speaker reacts with the room as well, and even diffraction. Which means you kill a few birds with one stone.

 

[gedlee]

Well, in a previous post, I have shown that EQ (with phase EQ) cleans up the sound as indicated in the CSD. If it truly does that for off axis response as well, then that not only effects direct sound, but also how the speaker reacts with the room as well, and even diffraction. Which means you kill a few birds with one stone.

George

I am rather surprised that you don't know the problem with this statement. Sure EQ can clean up the CSD at any partiicular point in space, that is well known (how audible this is, is another question), but the problems off axis are not always the same as the ones on-axis, so what corrects the problem at one point can make a problem significantly worse at another point. So instead of "killing two birds with one stone", you just winged the first one and scared the other one away.

 

[dewardh]

The only real differences between active crossovers and passive are 1) with active the driver sees the output impedance of the amplifier as its driving point impedance. That might be an advantage, might not. 2) The transfer function of the filter is not dependent on the diver impedance, and possible variations thereof.

Indeed 1) is a mixed bag . . . most drivers benefit from low Z drive when used near their resonance, while some, used well above resonance, seem to benefit from a higher Z drive (which can, of course, be designed into the driving amplifier in active implementations). As for 2) . . . driver impedance *does* change, both statically (low level, with frequency) and dynamically (compression) overall. As a result the behavior of active and passive crossovers that look identical on paper will change in real implementations.

But "crossover" is only part of the picture. The “UE” thingie works quite well *as a crossover* and, crossovers being subtractive thingies, can be made to replicate “passive” crossovers very well, at least at low levels. But it’s not named “Ultimate Crossover” (which would be an almost acceptable exaggeration) . . . it’s named “Ultimate Equalizer”, and as an equalizer it is capable of doing misguided, and often bad, things. One such bad thing occurs when it attempts to correct response irregularities caused by cone breakup.

One common mode of “cone breakup” occurs when significant areas of the cone move in opposite directions (and whether one regards that as “non-linear” or “just a resonance” (and thus “linear”) hardly matters). The result is cancellation of radiated sound, and a dip (null) in the measured frequency response. An “equalizer” attempts to correct this null by pumping energy into it, and since the cancellation is rarely complete it has at least a chance of rendering a “flat” frequency response curve. What it has done, though, is make the breakup *worse*, and any secondary effects (intermodulation etc.) *worse*. And it has, at least potentially, added a *peak* in off-axis radiation, where the emissions of different parts of the cone sum rather than cancel. The “cure” may well be worse than the disease . . .

 

[fntn]

Indeed 1) is a mixed bag . . . most drivers benefit from low Z drive when used near their resonance, while some, used well above resonance, seem to benefit from a higher Z drive (which can, of course, be designed into the driving amplifier in active implementations). As for 2) . . . driver impedance *does* change, both statically (low level, with frequency) and dynamically (compression) overall. As a result the behavior of active and passive crossovers that look identical on paper will change in real implementations.

But "crossover" is only part of the picture. The “UE” thingie works quite well *as a crossover* and, crossovers being subtractive thingies, can be made to replicate “passive” crossovers very well, at least at low levels. But it’s not named “Ultimate Crossover” (which would be an almost acceptable exaggeration) . . . it’s named “Ultimate Equalizer”, and as an equalizer it is capable of doing misguided, and often bad, things. One such bad thing occurs when it attempts to correct response irregularities caused by cone breakup.

One common mode of “cone breakup” occurs when significant areas of the cone move in opposite directions (and whether one regards that as “non-linear” or “just a resonance” (and thus “linear”) hardly matters). The result is cancellation of radiated sound, and a dip (null) in the measured frequency response. An “equalizer” attempts to correct this null by pumping energy into it, and since the cancellation is rarely complete it has at least a chance of rendering a “flat” frequency response curve. What it has done, though, is make the breakup *worse*, and any secondary effects (intermodulation etc.) *worse*. And it has, at least potentially, added a *peak* in off-axis radiation, where the emissions of different parts of the cone sum rather than cancel. The “cure” may well be worse than the disease . . .

Oh no. There you go again Deward - trying to infuse a little reality into an engineering discussion here on DIY. You should know better


But....but...but...I thought the UE thingie made all the "breakup baddies" go away. I'm still waiting for a real non linear distortion plot and fr plot of a real driver in the break up region before the magic of UE and after. But more than likely, all I'll ever see is another simulation of a real driver whose response is being corrected by UE.

 

[fntn]

One common mode of “cone breakup” occurs when significant areas of the cone move in opposite directions (and whether one regards that as “non-linear” or “just a resonance” (and thus “linear”) hardly matters).

Actually, to be technically accurate (God forbid ), as I mentioned earlier in this thread , the essence of cone breakup is the transfer of energy at a given frequency (that of the applied signal or fundamental) into a higher order harmonic as a result of physical deformation of the diaphragm being excited. This completely satisfies the definition of non linear distortion. It is not a phase issue or some other linear time based process. The degree of deformation experienced by the diaphragm is related to the acceleration of said diaphragm. And we all know there are two fundamental forces involved in that acceleration - frequency and amplitude. The process of deformation, as noted earlier , is anything but a linear process. Perhaps this explains why a lot of the distortion plots that are called "Non Linear" tend to contain obvious signs of cone break up (especially woofers at the upper end of their passband). Ya think?

The notion that this type of distortion (non linear) is either inaudible, easily fixed, or seldom occurs - is absurd on its face. In fact, a good number of driver manufacturers such as Peerless have switched to metal cones as of late. Their trouble with harsh breakup is legendary. The issue of non linear distortion generated by cone breakup is an ever more important concern for those interested in building high performance speakers that possess a minimum of crossover points and minimal distortion using today's drivers.

 

[dlr]

I'm still waiting for a real non linear distortion plot and fr plot of a real driver in the break up region before the magic of UE and after. But more than likely, all I'll ever see is another simulation of a real driver whose response is being corrected by UE.

It was provided. You chose to equivocate after seeing it and continue now to deny. Here it is again.

Raw driver FR:

Driver equalized FR:

Raw driver distortion:

Distortion after UE equalization of the same driver:

Link to the page: A Brief Study of DSP Crossover and Equalization Linear and Nonlinear Distortion Effects

Once again you choose to ignore that which thoroughly contradicts your claims. You show nothing.

Dave

 

[gedlee]

Actually, to be technically accurate (God forbid ), as I mentioned earlier in this thread , the essence of cone breakup is the transfer of energy at a given frequency (that of the applied signal or fundamental) into a higher order harmonic as a result of physical deformation of the diaphragm being excited. This completely satisfies the definition of non linear distortion.

Yes, it does satisfy the deffinition of nonlinear distortion, except that is not what happens. For most cones, the breakup is high enough in frequency that the displacements from the breakup modes are miniscule and the materials are completely linear. As such there is no transfer of energy from the excitation frequency to any other frequency.