Afaik the brain makes sense of frequency response variations in both time and space and this affects imaging and coloration.
So whether you're dealing with "coloration" or early reflections or diffraction it all comes down to interpreting frequency response variations.
I've been wondering if there is an audio equivalent to the random-dot stereograms of Bela Julesz?
Random dot stereogram - Wikipedia
B.
Julesz (an acquaintance at Bell Labs) produced spatial localization without a visual object (at least in the usual sense). Can we produce at least azimuth localization using prepared random noise?
It would be a test paradigm a lot better than some of the remarkable hearing claims in this thread.
B.
Whatever you call it, one critical factor seems to go missing in this discussion: it isn't the performance of a speaker we are talking about, it is the difference between the speakers' outputs that creates location. If both have similar diffraction, then diffraction has no meaningful first-order effect on localization.
(I'm sure somebody will riff on some second-order differential wall reflections phantasy about why diffraction really is so important.)
B.
As opposed to what stereo ideally does? Stereo will pinpoint image (at the very least) and by that I mean without fatigue.
Some interesting approaches to minimizing baffle diffraction:
https://www.diyaudio.com/forums/ful...rmance-speaker-enclosures-36.html#post5572691
https://www.diyaudio.com/forums/ful...rmance-speaker-enclosures-36.html#post5572691
Well I'm not sure I agree with this simplification. In my book diffraction of the enclosure makes it easier to spot the speaker position itself, that doesn't mean it can't project or produce a phantom image.
Less diffraction seems to help a great deal to help make the speakers "disappear".
I think the valuable information I take away from this discussion is in what was said in reply to
Which was:
That part explains why diffraction points out the speaker position, while for instance an early side wall reflection can seem to widen the perceived imaging. Reduce both and imaging gets more defined.
Hi all, a graph from this thread haunts me.....
I think it's all wrong...
I think for any waveform origination, phase alignment is when initial rise times are in sync....not peak energies.
And if that understanding is true, and IF our hearing is in sync with true waveform origination, graph must be back-asswards....????
Please straighten my thinking....
I think it's all wrong...
I think for any waveform origination, phase alignment is when initial rise times are in sync....not peak energies.
And if that understanding is true, and IF our hearing is in sync with true waveform origination, graph must be back-asswards....????
Please straighten my thinking....
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I think you're talking about the difference between a minimum phase system and a linear phase system ?
I took these grabs from 'delay alignment a survey' pdf I found online.
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Would it be possible to investigate these virtual image sources by a microphone placed near to baffle edge line as shown in the attached photo? If yes, what is the interpretation of the plot shown, measured this way. Thank you.
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Questions about diffraction audibility.
Localisation.
I just did an experiment where I was blindfolded and my kid was standing in random places in the room making a noise, and I was able to pinpoint his location very accurately even when standing right next to a corner, cabinet or couch. Shouldn't it be more difficult to pinpoint the location of a sound when close to a corner? This didn't seem to happen, but I'm not sure. Maybe others can do something similar and post their results.
When listening to square boxes, sounds seem all to have the same size. A small speaker, everything sounds small. A big speaker, everything sounds big. Is this due to diffraction?
Localisation.
I just did an experiment where I was blindfolded and my kid was standing in random places in the room making a noise, and I was able to pinpoint his location very accurately even when standing right next to a corner, cabinet or couch. Shouldn't it be more difficult to pinpoint the location of a sound when close to a corner? This didn't seem to happen, but I'm not sure. Maybe others can do something similar and post their results.
When listening to square boxes, sounds seem all to have the same size. A small speaker, everything sounds small. A big speaker, everything sounds big. Is this due to diffraction?
Hey Mark,
Create a Dirac pulse in RePhase and import it in REW, on the IR tab it will look like a single peak.
Next go to the filtered IR tab and choose some different filters, like 63 Hz, at 1/3th. Switch back each time to the IR tab to see the wave shape at that point, it will show the initial rise times are in sync.
Example from a filtered 63 Hz signal:
Turn off all filters and create a wavelet and it will show this:
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I think that in principle it should work, but in practice it is going to be difficult. The reason is that what you are measuring is a composite of everything, some of which is the diffraction, but the diffraction is fairly low in level compared to the direct sound, and some are near field pressures which do not propagate. So sorting it out may be problematic.
This kind of reminds me of my attempts to measure sound radiated from the enclosure itself. Never could sort out anything of value.
There are techniques which fall under the general classification of Acoustic Holography, which again, can in principle do this problem. But they are know to be notoriously difficult at resolving secondary source locations better than 1/2 wavelength.
There are simple cases which are easy. Consider a circular piston centered in the end of a long circular tube. The difference in the radiation pattern from this configuration and that of a simple circular source in an infinite baffle is due to the edge diffraction. From this difference pattern we could work back to the source and find precisely what was being diffracted from the edge. But the general case is far more complicated.
Thank you, this makes sense, of course. Would it be more revealing to measure aside and behind the baffle, so that bending of waves around the corner and diffraction should be more emphasized?
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Data point:
I went to the quite large Toronto HiFi show today. Saw (and in some cases heard too) maybe 70 speaker models almost all demonstrated without grill cloths. Some very very expensive and complex. Some very good*.
I'd guess fewer than 10 models had anything suggesting fussing over diffraction and some (maybe most) of those were probably just coincidentally part of the box aesthetics.
B.
*OK, after hearing the Martin Logan 300 Hz xover ESLs, everything else just sounded like cone drivers in a box, some a bit better than others
I went to the quite large Toronto HiFi show today. Saw (and in some cases heard too) maybe 70 speaker models almost all demonstrated without grill cloths. Some very very expensive and complex. Some very good*.
I'd guess fewer than 10 models had anything suggesting fussing over diffraction and some (maybe most) of those were probably just coincidentally part of the box aesthetics.
B.
*OK, after hearing the Martin Logan 300 Hz xover ESLs, everything else just sounded like cone drivers in a box, some a bit better than others
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