...when it comes to perception and preference in the quality of reproduction, certainly. Not when one is concerned with the physics. Ironic that you'd quote Olson, the quintessential objective researcher into the physics of audio in boxes and baffles. He did not use his ears when studying diffraction and baffle shapes. His results are as applicable today as they were then.
Let me ask some questions directly, not rhetorically. Bear with me, because I'd really like to know precisely what people believe to be true without side-stepping the issue as happens all too often.
Do you believe that the human ear, any human ear, can detect, at any level, that a driver can launch and in fact can reliably confirm the launch of a flat wavefront vs. non-flat? Assume, of course, that it is theoretically possible for a dynamic driver to actually launch a flat wave.
If yes, what must be done to provide acceptable evidence that this is true? Anything? Nothing?
Do you believe that the human ear can reliably detect phase shift due to crossover group delay with music, not a test signal? If the answer to the first question above was yes, then the answer to this must be yes If the answers are yes, on what basis have you come to this conclusion?. Has any serious scholarly study ever shown this to be the case with music and not special test signals through headphones? Remember, we're speaking of typical drivers, not headphones nor earphones.
I'd like to see direct answers.
Dave
Dave, I have no relevant training nor measurements relative to your question, but my intuition says yes to your second question. I don't think the ear can detect in the sense that it notices individual frequency shifts and the like. But I do believe, after listening to a few full range implementations, that there is, for lack of a better word, some "smearing" of the sound from crossover components which seems to me (again intuitively) could be related to timing and phase shifts. I can't say definitively that's the source of the "smearing" I hear - obviously - but it's strongly circumstantial.
And I don't believe microphones measure exactly what our brains INTERPRET from our ears. It'd be interesting to see someone do microphone measurements and correlate them with brain waves if that were even possible. There's an interpretation that's missing from the analytical approaches we currently use. Maybe that's one hint at why there is such controversy here.
FYI, I'm still a curious Enabl skeptic...haven't tried it yet but will someday when my bench clears.
Yes and I do think it is practical and possible. The sort of system that auplater has in his home should be capable of flat wave emission. I have certainly heard large format driven film systems provide a flat wave emission and the perceived illusion of palpable space that should arise from this. I have also heard EnABL'd drivers provide the exact same form of illusion. My definition of a flat wave signal would be that all signals that are recorded in a particular grouping in time are emitted in that same time order or grouping. This would be the definition that should give rise to a perception of space and time.
As for how to measure and confirm, it would have to be a group of objectively recognizable signals that could be distorted by their interaction in a non flat wave emission. I am not sure how these signals should be shaped because I do not have a reliable idea of what "group delay" means within the context of either music or discrete signals.
Bud
Perhaps my common sense has not changed, but that your perception biases do not allow you to accept that there may be somethng to this.
When i 1st encountered EnABL is was very skeptical, but i kept an open mind and took measures to be able to experience it. Have you?
dave
You "think" so. What objective evidence or proof do you have to offer?
Large format systems do not launch a flat wave, they are generally cylindrical. "Should be capable" and something that "should arise" doesn't offer us anything. It's a belief or assumption in the absence of some sort of proof.
This is your proof of flat wave emission? I suggest that you should provide a bit more clarity in making claims such as flat wave emission. What you are saying is a perception of the sound, but is in no way indicative of flat wave emission in the precise sense of the term, as in a planar wavefront, at least as I and I suspect most others think of the definition. There is no relationship to your definition and an actual wavefront because, again, there does not have to be a broad spectrum in the wavefront.
This is the problem. You're using your own definition that does not comport with what I suspect how most of us would define it. The wavefront could even be that of a single frequency, it does not have to have a broad spectrum. Even in the single frequency case, no dynamic driver, however modified, is capable of producing a flat wavefront. If someone shows me how I am wrong and can correct me on that, please do so, but not based on assumptions.
Group delay does not rely upon the content of the signal applied, it is the result of the time delays introduced by the driver to whatever signal is applied. It is an inherent characteristic of the transfer function of the driver. Group delay affects all signals equally, music or discrete, based upon the specific group delay of the driver/system. Being bandpass devices, group delay is unavoidable without using some form of DSP processing. Enabl does not alter that. The only thing it can do is alter the shape of the group delay as a result of changing the SPL response.
Dave
The human ear can detect nothing without interfacing with the brain, which does most of the work.
And any ear/brain may not, but just like any aquired skill, athletics, playing an instrument, whatever requires some 10,000 hrs of training (ref Levitin). It is certainly possible for a trained listener to hear things where an another listener has no clue.
A trained listener can certainly detect when the harmonics of a note are outside of the envelope. Phase shift is but a crude measurement of this.
As to flat vrs non-flat wavefronts, once one is in the far-field, the radius of any sphere is large enuff that it is essentially flat. This is an important distintion made with any experiment on spatial hearing.
dave
If one were to accept your premise as true ("radius of any sphere is large enuff that it is essentially flat"), Enabl is irrelevant with regard to this aspect. Yet Bud claimed dramatic change from non-flat to flat wave emission. I don't think it had anything to do with geometry. Does anyone else see contradiction here?
Dave
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Answering from 2 completely different premis as to the ill-defined term "flat".
From my premis of what you mean by flat, using the context of "Large format systems do not launch a flat wave, they are generally cylindrical", there is no premise. I am simply reiterating an expert in the field from one of his text books.
dave
Flat panels are attached for support, usually around the periphery. These attachment points do not move. There is a transition region to central area, movement of the diaphragm is not flat. More significantly, at frequencies with wavelength significantly short in relation to the surface dimensions, the polar response shows a wave that is anything but flat across the spectrum. This is simple geometry based on distance to each radiating point on the surface.
Now if you want to argue that it does emit a flat wave, then at any listening position other than the extreme far field, that flat wave will create a non-flat response at your ears due to geometry. But then one could claim that any driver or system is effectively a point source, since at the limit of distance, the dimensions of the driver become less important. It's a poor argument.
I do not see large format output as having a flat wavefront. But this is a divergence from the original issue, dynamic drivers, on which the claims were made. This still has nothing to do with Enabl on a dynamic driver that you claimed went from non-flat response to flat. You have yet to address this. Either one considers a dynamic driver to have non-flat wavefront response (which claim was made without regard to distance) or it is flat without Enabl, since at the limit, geometry becomes less important. Either way, there's a contradiction and no proof of the claim.
Dave
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so youze guys would rather prattle on back and forth rather than plunking some thing appropriate on the surface of some cheapo cones and listening and measuring them??
Forget who says what about it.
If this has been done, I'd appreciate it if someone would point me to the proper thread and post(s)?
It's just that it seems simple enough to do.
_-_-
PS. on the cymbals, the density and structure of the metal changes when it is hammered. Clearly this alters the wave that travels through the metal. If it changes the wave that travels along the surface, I don't know, and don't think anyone does. However cymbals that are made WITHOUT the hammering do not sound particularly good at all. Bottom line is that it changes the sound - for the better in the case of a cymbal. Is the equivalent good in the case of a speaker? Dunno, try it on some metal cones??
Forget who says what about it.
If this has been done, I'd appreciate it if someone would point me to the proper thread and post(s)?
It's just that it seems simple enough to do.
_-_-
PS. on the cymbals, the density and structure of the metal changes when it is hammered. Clearly this alters the wave that travels through the metal. If it changes the wave that travels along the surface, I don't know, and don't think anyone does. However cymbals that are made WITHOUT the hammering do not sound particularly good at all. Bottom line is that it changes the sound - for the better in the case of a cymbal. Is the equivalent good in the case of a speaker? Dunno, try it on some metal cones??
It has been done, though we have not seen the measurements. The basics of the changes were described a few pages back. They did not correlate at all to the claims made with regard to the changes that were said would occur.
The post is here.
Dave
The polar response is not the wavefront.
Your argument largely ignores the reality of the geometry. There will start to be combing somewhere above 7-10k, if the planar was a perfect picton, with output diminishing towards the clamped sides higher.
Some details:
1/ flat panel with 0.2mm excursion and 8" (203.2mm wide -- about the size of an acoustat panel). 0.2mm is a lot and except at loud volumes in the bass likely orders of magnitude larger than normally encountered.
2/ 3m listening distance. I never got that close to mine.
3/ average adult distance between ears of 150mm
4/ on axis analysis (mono)
5/ off axis analysis (2.5m separation of stereo pair)
6/ CAD program dimensional readout turned up to as high a precision as allowed.
dave
Attachments
Actually, it is. When considering polar response of a panel and a wavefront, it is 3-dimensional, not 2-dimensional. The horizontal polar response does not come close to characterizing it. You would have to show the results of the full front hemisphere, the complete polar response, to do that.
I think that you would have to something similar to what Geddes is doing in his efforts to impute the response at the source by measuring a large number of points at a distance and do so on a plane in front of the panel system.
I had a ribbon, Apogee Centaur Majors. One single ribbon over a 10" woofer, not the full-range ribbons, it was a very narrow single ribbon. Extremely sensitive to tiltback due to the ribbon, even a few degreess unless one was at an extreme distance. The need to listen at a far distance simply reinforces my point. From what I recall, all Martin-Logans use curved panels. At least those that I recall seeing did. From what I see now on their web page, that is still the case. That alone would eliminate any possibility of those having a flat wavefront. Acoustats are closer to flat wave initially if they are perfectly uniform displacement (I'm not convinced of that, either), but the height of these requires little or a very specific limited range of tilt, just as my ribbon did. You still must listen at significant distance and within some limited vertical range. That "flat" wavefront does not sound the same at the extreme end vs. the center.
But again, this is still diverting the issue. No one here is adding Enabl to the moving diaphragm of a panel and I doubt that anyone in their right mind would do so.
I'm looking for responses related to the claims made to driver diaphragms actually modified and in this case, those have all been dynamic drivers exclusively. These are the ones on which essentially all claims have been based.
Dave
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I was pointing to flat wave emitters as a theoretical ideal in a two channel illusion of performance space. Since they emit in a hemispherical "launch" into the air there must be some ideal shape to that curved wave form that provides an intuitively correct recreation, as an illusion within the mind of the listener, of a performance space. Typical loudspeakers provide an illusion of this space caught between the two emitters. Some provide an illusion of space to either side and these seem to also have a depth to them. The large format ribbon/film drivers I am familiar with (Acoustat, Magneplaner 2.6, Red Rose large system) do not provide any lateral extension beyond the speakers but are capable of a reasonable illusion of depth between the speakers.
EnABL'd speakers, regardless of how many drivers are involved, provide a portrayal of an illusion of performance space that is obviously from behind the actual speakers, with typically intuitively correct width, depth and height. Including wall to wall and floor to ceiling and very great radial depth from the listener. In addition this illusion is available from outside the on axis width, at either on axis position or at the typical center position without any serious degradation of the spatial illusion. I am just trying to understand what a wave front that will do this is actually shaped like. Is it tightly curved, is it flat or is it shallow bowl shaped? My assumption had been that an actual flat wave front would be the ideal form for these illusions to arise from.
Bud
You know, I don't see much of anything to take issue with above, it would all be fine in the other thread. Well, you might have to put the last few lines here, since that goes to the objective and is supposed to be verboten over there. You perceive things your way, it's all fine subjectively. Your descriptions would suit a review publication on the subjective part.
The only thing that keeps getting in the way is trying to make technical claims without any objective support. It's usually as you say in your last sentence above, you make an assumption. That's fine as far as it goes. To go beyond that and resolve your questions requires something more rigorous.
I see nothing to make me think that a truly flat wave front is the holy grail of audio reproduction. That's not going to come from dynamic drivers in any case.
Dave
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