Hi Bud,
Concerning what you are seeing - If it were me it could be a flashback to some of my encounters at the Fillmore Auditorium back in the '60's (peace - love - far out).
There are some interesting videos on cymatics at YouTube.
http://youtube.com/watch?v=1iXY2BE1S8Q
http://youtube.com/watch?v=6sonpvUxGL8
Be careful at what you start looking at because things can get rather weird rather fast!
This link pretty much stopped me in tracks
http://youtube.com/watch?v=cy2Dg-ncWoY
Then there is always Hutchison and Tesla stuff to look at
http://youtube.com/watch?v=xeUgDJc6AWE -
but this is getting away from tweaking speakers.
The cymatics videos deal with frequency and resonance and the standing waves created by them. I don't believe that you will make marked progress there until you deal with the pulse rebound response reflected from the speaker surround first and I think the best way to deal with that reflection is with your EnABL blocks placed in something resembling your current pattern of 18 pairs (the math works for even harmonics but I would use math based on odd harmonics). I would suggest that you consider an arrowhead type of "block" instead of the square block - but this would need some study and debate on just what is trying to be accomplished.
The cymatics videos deal with resonance on a flat piece of material (that might work to look at baffle design) but not on conical or dome speaker surfaces. You might be able to see what is going on there (speaker cones) if a low mass powder (talc?) can be thinly applied to the cone surface (electrostatic charge?) and strobe lit in slow motion with the speaker cone facing straight up (or down) to counter the effects of gravity.
I've been busy working on my design for my 2 foot (perhaps 1 meter) plasma tweeter
but the spouse has used her veto power to ban it's indoor use (my dachshund Manfred would most likely destroy it anyway as he can destroy almost anything). I did read an article about the "Dragon Horn" speaker used at Stanford during the '60's which used methane gas and belched flames as a result. The wife doesn't seemed thrilled about a speaker that would smell like a horse barn and belches flame either - but I think it would make for a great show up at Dave's (planet10) place for his next fest!
And that leads me to this conclusion - John can honestly say, with a clear conscience, that I am full of horse**** and I won't mind it a bit.
BTW - back in the day when I was repairing stereo's with "Papa Nelson" I always liked the Yamaha equipment for their design and quality. That stuff was (and is) well made and will get you most of the way to audio bliss. It can be beat by the audiophile gear but then what can't? Heck - I'm using Onkyo for my HT and it's 90% good stuff for day to day!
Concerning what you are seeing - If it were me it could be a flashback to some of my encounters at the Fillmore Auditorium back in the '60's (peace - love - far out).
There are some interesting videos on cymatics at YouTube.
http://youtube.com/watch?v=1iXY2BE1S8Q
http://youtube.com/watch?v=6sonpvUxGL8
Be careful at what you start looking at because things can get rather weird rather fast!
This link pretty much stopped me in tracks
http://youtube.com/watch?v=cy2Dg-ncWoY Then there is always Hutchison and Tesla stuff to look at
http://youtube.com/watch?v=xeUgDJc6AWE - but this is getting away from tweaking speakers.
The cymatics videos deal with frequency and resonance and the standing waves created by them. I don't believe that you will make marked progress there until you deal with the pulse rebound response reflected from the speaker surround first and I think the best way to deal with that reflection is with your EnABL blocks placed in something resembling your current pattern of 18 pairs (the math works for even harmonics but I would use math based on odd harmonics). I would suggest that you consider an arrowhead type of "block" instead of the square block - but this would need some study and debate on just what is trying to be accomplished.
The cymatics videos deal with resonance on a flat piece of material (that might work to look at baffle design) but not on conical or dome speaker surfaces. You might be able to see what is going on there (speaker cones) if a low mass powder (talc?) can be thinly applied to the cone surface (electrostatic charge?) and strobe lit in slow motion with the speaker cone facing straight up (or down) to counter the effects of gravity.
I've been busy working on my design for my 2 foot (perhaps 1 meter) plasma tweeter
but the spouse has used her veto power to ban it's indoor use (my dachshund Manfred would most likely destroy it anyway as he can destroy almost anything). I did read an article about the "Dragon Horn" speaker used at Stanford during the '60's which used methane gas and belched flames as a result. The wife doesn't seemed thrilled about a speaker that would smell like a horse barn and belches flame either - but I think it would make for a great show up at Dave's (planet10) place for his next fest! And that leads me to this conclusion - John can honestly say, with a clear conscience, that I am full of horse**** and I won't mind it a bit.
BTW - back in the day when I was repairing stereo's with "Papa Nelson" I always liked the Yamaha equipment for their design and quality. That stuff was (and is) well made and will get you most of the way to audio bliss. It can be beat by the audiophile gear but then what can't? Heck - I'm using Onkyo for my HT and it's 90% good stuff for day to day!
c2cthomas said:Hi Bud,
The wife doesn't seemed thrilled about a speaker that would smell like a horse barn and belches flame either - but I think it would make for a great show up at Dave's (planet10) place for his next fest!
And that leads me to this conclusion - John can honestly say, with a clear conscience, that I am full of horse**** and I won't mind it a bit.
c2c :
1) Dave's events are usually held during the dry season, and after the frivolity of the boys playing with a propane powered tiger torch on the driveway, I think Ruth would have something to say about any flame belching apparatus
2) sooner or later, we are all full of methane producing semi/solid waste, some of us more than others - especially after snacking on the salsa, beer and BBQ beefsteaks at these get togethers (in other words, don't pull Cal's finger)
chrisb said:2) sooner or later, we are all full of methane producing semi/solid waste, some of us more than others - especially after snacking on the salsa, beer and BBQ beefsteaks at these get togethers (in other words, don't pull Cal's finger)
What was that famous quote of his again...? "It's only a 1 inch speaker, but it sure has good bass!"
Geek said:
What was that famous quote of his again...? "It's only a 1 inch speaker, but it sure has good bass!"
my dad used to say - "a lot of volume for a.... " - and maximum amplitude is not gender specific
this thread page sponsored by Mel Brooks - if you loved the Broadway musical version of "The Producers", and "Young FronkenSteen" - don't miss the traveling road tour of "Blazing Saddles" coming to a select list of outdoor venues soon. Order your tickets early, as the view is better from the windward side.
can we get back to the EnAbl subject - I'm sure there's enough pre-adolescent in all of us to continue this recent diversion for pages
Bud,
I'm going about this ENaBL thing very,very slowly and with deliberation. Thats why I first put the driver into an OB so as to give a reasonable insight into the EX3. I only ever use your classic patterning. What I've experiment with,is where the rings are positioned (inspired by Soongsc) - low tack masking tape is great for this as the process is reversible and also it does to some extent take on the character of the substratum (as does paint!).After every block pair I put down I listen and listen; a slow but happy process.
The position for the outer ring for the Lowther you have just inside the cone end where it meets the surround. For my experiment I straddled the pattern across the cone and surround ( Mamboni), to facilitate this meant I had to make each block slightly deeper.The next inner ring was put on to "meet" the outer as per classic positioning.
The whizzer roll has, so far ,only four block pairs applied - each in their classic positions.For some fancy or other I decided to "load" the roll asymmetrically. Roughly the positions are: 12, 12.15, 12.35 and 12.45 o-clock. Boy oh boy ! by fluke I seemed to have touched the lowthers 'G' spot! (blush).
I don't have easy access to a digi-cam but hopefully you can picture a little more clearly
what I've been doing.
Cilla
I'm going about this ENaBL thing very,very slowly and with deliberation. Thats why I first put the driver into an OB so as to give a reasonable insight into the EX3. I only ever use your classic patterning. What I've experiment with,is where the rings are positioned (inspired by Soongsc) - low tack masking tape is great for this as the process is reversible and also it does to some extent take on the character of the substratum (as does paint!).After every block pair I put down I listen and listen; a slow but happy process.
The position for the outer ring for the Lowther you have just inside the cone end where it meets the surround. For my experiment I straddled the pattern across the cone and surround ( Mamboni), to facilitate this meant I had to make each block slightly deeper.The next inner ring was put on to "meet" the outer as per classic positioning.
The whizzer roll has, so far ,only four block pairs applied - each in their classic positions.For some fancy or other I decided to "load" the roll asymmetrically. Roughly the positions are: 12, 12.15, 12.35 and 12.45 o-clock. Boy oh boy ! by fluke I seemed to have touched the lowthers 'G' spot! (blush).
I don't have easy access to a digi-cam but hopefully you can picture a little more clearly
what I've been doing.
Cilla
Opps - my bad!
Just trying to lighten things up a bit.
As to the discussion of EnABL and wave reflection - Lynn O mentioned something of interest a while back. He wrote about the odd angled facets used on the F-117 aircraft to reflect and or trap radar signals. I have a bit of experience with this bird as we were the repair depot that maintained them back in the day - but I wasn't anywhere around 'em. I was around a lot of radar transmitters tho and I do know how well the facets of the 117 worked in terms of not reflecting RF.
Point being that odd angled facets used at the edge of the speaker surround where it meets the speaker cone might be a concept to consider.
Just trying to lighten things up a bit.
As to the discussion of EnABL and wave reflection - Lynn O mentioned something of interest a while back. He wrote about the odd angled facets used on the F-117 aircraft to reflect and or trap radar signals. I have a bit of experience with this bird as we were the repair depot that maintained them back in the day - but I wasn't anywhere around 'em. I was around a lot of radar transmitters tho and I do know how well the facets of the 117 worked in terms of not reflecting RF.
Point being that odd angled facets used at the edge of the speaker surround where it meets the speaker cone might be a concept to consider.
Are not exotic materials also part of the radar stealth technology?
Further, as the wavelengths of even the highest audio frequencies generally considered audible to the average human are considerably longer than those for which radar stealth is designed, and the mechanism of energy propagation of the two are quite different, would not also the physics of dealing with controlling diffracted / reflected energy require different approaches?
Further, as the wavelengths of even the highest audio frequencies generally considered audible to the average human are considerably longer than those for which radar stealth is designed, and the mechanism of energy propagation of the two are quite different, would not also the physics of dealing with controlling diffracted / reflected energy require different approaches?
Hey BudP,
Thanks for the videos. Very cool! I am certainly not qualified to judge what's going on there, it's a realm beyond my ken. Some of the visuals are shocking, like the spinning propeller patterns. What might that be doing the the sound?
Though it should not be hard to do the power tests on EnABL'd and stock drivers, how would you interpret the results? What patterns would sound better than others?
The end of video 3 is great. Looks like they generated an EnABL pattern in the dust!
See you at RMAF.
Thanks for the videos. Very cool! I am certainly not qualified to judge what's going on there, it's a realm beyond my ken. Some of the visuals are shocking, like the spinning propeller patterns. What might that be doing the the sound?
Though it should not be hard to do the power tests on EnABL'd and stock drivers, how would you interpret the results? What patterns would sound better than others?
The end of video 3 is great. Looks like they generated an EnABL pattern in the dust!
See you at RMAF.
Stealth: The black colour is a carbon compund, converts sone radio energy into heat.
Imagine the aircraft as a mirror, the idea of the flat panels is to send any reflections off in different directions, anywhere but back at the radar.
Ideally the speaker should be put together differently. The straight (actually circular) lines where surround and the cone join should be feathered together with an acute angle zig zag. Look around the bottom edge of the cockpit windows on a stealth fighter, they avoid anything that is strongly perpendicular to the radar source. the edge is zig zagged to send any reflections off to the side.
In a driver this feathering together would blur the density transition between the materials. Reducing the clarity of the reflector is better than applying materials near it to disrupt the coherence of the wave before and after the reflections. I think this is what AER are doing if you look at the white paper zig zag near the centre of their drivers.
Imagine the aircraft as a mirror, the idea of the flat panels is to send any reflections off in different directions, anywhere but back at the radar.
Ideally the speaker should be put together differently. The straight (actually circular) lines where surround and the cone join should be feathered together with an acute angle zig zag. Look around the bottom edge of the cockpit windows on a stealth fighter, they avoid anything that is strongly perpendicular to the radar source. the edge is zig zagged to send any reflections off to the side.
In a driver this feathering together would blur the density transition between the materials. Reducing the clarity of the reflector is better than applying materials near it to disrupt the coherence of the wave before and after the reflections. I think this is what AER are doing if you look at the white paper zig zag near the centre of their drivers.
Panomaniac,
Those waves marching around are similar to and may actually be Raleigh waves. The Hemp Cone driver I recently treated had that occurring at the over tall ring, mounted where the surround was attached to the frame. At very specific frequencies, mostly in alto trumpet range, the sound would suddenly blare out and there was a definite twisting sensation to the blare. This is quite different from a normal horn fan fare, as it just suddenly erupts and just as suddenly is back to the volume level of the surrounding notes from the same horn.
This can of course also be a sharp peak of resonance, not related to a spinning wave, but the twist given the sound is a pretty sure indication you have to look for and treat a vertical wall. Once patterned as shown, this artifact completely disappeared and normal performance was the rule.
These video's are of course somewhat dramatized in scale and the moderators voice over is just horror show perfect. We get to thank tireless C2C for tracking these delights down the first time they were posted, back on page 3 or 4 of this migrated thread, so almost six months ago.
If I am to be found at RMAF, Jon Ver Halen from Lowther America's room will know. Not where exactly, but that I exist and he did see my face. Financial strength of a failing industry will determine my presence.
Bud
Those waves marching around are similar to and may actually be Raleigh waves. The Hemp Cone driver I recently treated had that occurring at the over tall ring, mounted where the surround was attached to the frame. At very specific frequencies, mostly in alto trumpet range, the sound would suddenly blare out and there was a definite twisting sensation to the blare. This is quite different from a normal horn fan fare, as it just suddenly erupts and just as suddenly is back to the volume level of the surrounding notes from the same horn.
This can of course also be a sharp peak of resonance, not related to a spinning wave, but the twist given the sound is a pretty sure indication you have to look for and treat a vertical wall. Once patterned as shown, this artifact completely disappeared and normal performance was the rule.
These video's are of course somewhat dramatized in scale and the moderators voice over is just horror show perfect. We get to thank tireless C2C for tracking these delights down the first time they were posted, back on page 3 or 4 of this migrated thread, so almost six months ago.
If I am to be found at RMAF, Jon Ver Halen from Lowther America's room will know. Not where exactly, but that I exist and he did see my face. Financial strength of a failing industry will determine my presence.
Bud
OzMikeH,
I wonder if the tall diamonds found on the AER drivers aren't for the same purpose as those found on Lowther drivers with a whizzer cone.
I have not seen an AER nor heard two in performance, but in the Lowther, these are the actual emitter surfaces for high frequencies. I am a little confused as to whether or not there is an actual separate voice coil attached to the base of these triangular fingers or not. I can tell you that the DX 4 version of these is quite a bit more active and powerful than the PM6A's. After EnABL rings were drawn just beyond the tips of the fingers, the high frequencies from both were much more apparent.
When the final whizzer cone patterns and gloss coat were applied, the DX 4 just took off. Far more energy available than I was expecting, just like the rest of the driver actually, now that I think about it. The PM6A was much more predictable and actually clearer in presentation.
I applied no materials to these fingers, per Jon Ver Halen's warnings, so things could actually have gotten even more extreme than they did.
Perhaps AER would tell us?
Bud
I wonder if the tall diamonds found on the AER drivers aren't for the same purpose as those found on Lowther drivers with a whizzer cone.
I have not seen an AER nor heard two in performance, but in the Lowther, these are the actual emitter surfaces for high frequencies. I am a little confused as to whether or not there is an actual separate voice coil attached to the base of these triangular fingers or not. I can tell you that the DX 4 version of these is quite a bit more active and powerful than the PM6A's. After EnABL rings were drawn just beyond the tips of the fingers, the high frequencies from both were much more apparent.
When the final whizzer cone patterns and gloss coat were applied, the DX 4 just took off. Far more energy available than I was expecting, just like the rest of the driver actually, now that I think about it. The PM6A was much more predictable and actually clearer in presentation.
I applied no materials to these fingers, per Jon Ver Halen's warnings, so things could actually have gotten even more extreme than they did.
Perhaps AER would tell us?
Bud
BudP said:
I'm sure there have been plenty of blind tests on amps over there in Dave's stronghold on the tenth planet (BC). Anyhow, that's a whole other argument, the differences between amps.
I didn't actually buy the receiver - it was a gift from my very generous and well intentioned girlfriend, who was offended by the chipped faux walnut end panels on my vintage Pioneer SA-6800.
I have enjoyed it since day one.
Dave's been ribbing me every chance he gets about it but you're right, I don't care.
c2cthomas said:
Is this the reason for your peculiar choice of protective headgear as depicted in your avatar?
Ionic plasma tweeter:
http://www.plasmatweeter.de/eng_plasma.htm
Is it worth the fire hazard? I, for one, can't hear tones above about 13K anymore so I'll settle for a silk dome.
Great conversation piece though (follows the oblique questions concerning your hat)
Hi Chris - wavelengths gets us involved with frequency and resonance and that's fine if we were attempting to "selectively tune" the speaker cone to pass or reject certain frequencies. You are indeed correct about the wavelength of the frequencies involved in audio - anywhere from around 0.6 inches (15mm for our intelligent friends that use a base 10 measurement system) to around 56 feet (1,422 mm) depending on atmospheric pressure and temperature (I'm not including considerations for phase of the moon, personal karma levels, or the amount of methane gas produced by pulling on Cal's finger). BUT you can use harmonics of the base frequencies (as you know that from your 1/4 wave work) with which to form a pattern. OxMileH (Ta Mate!) pointed out the triangles around the windows of the F-117 versus the "facets" used on the fuselage and the story there is that one design is used to trap signals and one is used to deflect signals - and for those of you that know a bit about RF will realize that I'm not talking out of class here - it's fairly common stuff and the RF theory has been around for years.
But my point is that the testing performed to date has dealt with frequency measurement tools in order to determine if BudP's EnABL pattern makes an audible difference when used with speaker cones. It has been stated thrat using Fr plots and phase plots do not seem to show what is really going on in many respects - perhaps because the information to be seen is buried to deep down in the plots or is masked by the overlying primary signal (which is what these tools are designed to measure in the first place). My suggestion is to use a "pulse response" test as this will result in readings that are not masked by the audio frequency. This is a bit like a "clap" (echo response) test used when sitting up sound in a large hall or outdoor arena. In a "live" area one can hear someone clap there hands together while standing front center on stage quite clearly - but without any echo being present. If the surrounding area is very "live" and large you will get an echo effect when you clap your hands. If you are standing in an anechoic chamber things are might sound like you are wearing gloves! Now when the crowd arrives and takes their seats (hopefully a full house) then the echo response of things will change dramatically but there may still be some "hot spots" of echo reflection to deal with (that's a discussion for a different thread). Until the reflections are dealt with you will have a difficult time sitting up your volume levels for LMHFr (Low-Mid-High) Frequency response. Deal with the pulse reflected energy 1st - it will give you a base from which to measure improvements in frequency and phase IMHO.
Just trying to clarify my position on things so please do not take offense if your point of view should differ. I do recognize the frequency response train of thought - but I don't see that working well until reflections are tamed.
BTW OzMikeH - the father of the math behind "stealth" using deflection is a chap named Prof. Pyotr Ya. Ufimtsev and you can find some interesting papers of his at http://care.eng.uci.edu/ufimtsev.htm
John - in regards to the head gear - it's related to two things 1) the movie "Signs" where the kids put on aluminum hats to keep the aliens from reading their thoughts and 2) a thread by "Carlos" the destroyer who is able to "read" me like a book (he states that I am a very strong transmitter of thoughts). He stated in his thread that I was a "missile expert" even though I had never discussed this with him and had been a missile tech 30 years ago when I was in the Navy. I put the hat on as a joke and told Carlos that it was to block him from reading my thoughts. Didn't work tho!
The 2 foot plasma tweeters are a standing joke of mine - just for the reason you mention about heat (4000f). You may not be able to hear frequency above 13k - but I'll bet that you can still sense dynamics and phase changes pretty well (most of us with hearing in two ears can) and thus these aspects of things can improve one's enjoyment of well reproduced surround sound when watching movies or HD NASCAR!!! (Darn right I watch it!)
Now would MJL21193 have anything to do with power transistors that use perforated emitter technology - hmmm?
My Best to All !!
But my point is that the testing performed to date has dealt with frequency measurement tools in order to determine if BudP's EnABL pattern makes an audible difference when used with speaker cones. It has been stated thrat using Fr plots and phase plots do not seem to show what is really going on in many respects - perhaps because the information to be seen is buried to deep down in the plots or is masked by the overlying primary signal (which is what these tools are designed to measure in the first place). My suggestion is to use a "pulse response" test as this will result in readings that are not masked by the audio frequency. This is a bit like a "clap" (echo response) test used when sitting up sound in a large hall or outdoor arena. In a "live" area one can hear someone clap there hands together while standing front center on stage quite clearly - but without any echo being present. If the surrounding area is very "live" and large you will get an echo effect when you clap your hands. If you are standing in an anechoic chamber things are might sound like you are wearing gloves! Now when the crowd arrives and takes their seats (hopefully a full house) then the echo response of things will change dramatically but there may still be some "hot spots" of echo reflection to deal with (that's a discussion for a different thread). Until the reflections are dealt with you will have a difficult time sitting up your volume levels for LMHFr (Low-Mid-High) Frequency response. Deal with the pulse reflected energy 1st - it will give you a base from which to measure improvements in frequency and phase IMHO.
Just trying to clarify my position on things so please do not take offense if your point of view should differ. I do recognize the frequency response train of thought - but I don't see that working well until reflections are tamed.
BTW OzMikeH - the father of the math behind "stealth" using deflection is a chap named Prof. Pyotr Ya. Ufimtsev and you can find some interesting papers of his at http://care.eng.uci.edu/ufimtsev.htm
John - in regards to the head gear - it's related to two things 1) the movie "Signs" where the kids put on aluminum hats to keep the aliens from reading their thoughts and 2) a thread by "Carlos" the destroyer who is able to "read" me like a book (he states that I am a very strong transmitter of thoughts). He stated in his thread that I was a "missile expert" even though I had never discussed this with him and had been a missile tech 30 years ago when I was in the Navy. I put the hat on as a joke and told Carlos that it was to block him from reading my thoughts. Didn't work tho!
The 2 foot plasma tweeters are a standing joke of mine - just for the reason you mention about heat (4000f). You may not be able to hear frequency above 13k - but I'll bet that you can still sense dynamics and phase changes pretty well (most of us with hearing in two ears can) and thus these aspects of things can improve one's enjoyment of well reproduced surround sound when watching movies or HD NASCAR!!! (Darn right I watch it!)
Now would MJL21193 have anything to do with power transistors that use perforated emitter technology - hmmm?
My Best to All !!
Regarding tests of ENABL'd speakers.
If you are going to do blind tests of listening experience, then make sure you do include SPL as a variable.
There was a very interesting post on (I think) the Beyond Ariel thread by Earl Geddes about his research of diffraction effects in wave guides indicating our hearing of diffraction is level dependent that is - the physical phenomenon arriving at our ears is linear, but our hearing is not.
He said his Summa would suddenly "crash" and become unlistenable at about (I think) 110 dB due to HOMs, which are a diffraction affect, but in fact these phenomena become increasingly more audible over 80 dB in more ordinary designs.
The Ariel thread is a monster but someone may have those posts to hand.
Hah! Googled DIY audio. Page 145 post 1444
And Page 46 post 1134:
The difference between a reflection and an HOM - which is a form of diffraction - is that the reflection is minimum phase while the diffraction is non-minimum phase. This means that the peak energy of a reflection arrives at the same time as the main signal (there will be a tail), but the peak energy of the HOM and/or diffraction arrives delayed in time (plus a tail). This is a small but very distinct difference, especially when subjective aspects are taken into account. The ear is far less sensitive to the minimum phase aberation than the nonminimum phase one, but more significantly, the minimum phase one is mostly level independent while the nonminimum phase one is highly level dependent. The ear masks the diffraction (HOM) more at lower SPL levels than at higher ones. This makes diffraction sound like nonlinear distortion in that it "distorts" (subjectively) higher SPL waveforms while not affecting lower level ones.
This has a profound impact to our understanding of "distortion" in that a linear system that has diffraction will sound like a nonlinear system. Its the ear that is nonlinear here, not the system.
Your data on the perception of delays is consistant with typical understanding, but is contradicted (more like refined actually) by several studies, one of which is my own. We dealt with delays on the order of .2 ms and found substantial subjective effects, but typically only at higher SPLs. What you need to factor in here is that most studies of delay perception are done at a single SPL (usually fairly low in fact) and it is well know from Toole and Moore that these effects are level dependent. .2 ms is quite audible on a loud passage, but inaudible on a softer one. This aspect has been overlooked in virtually all studies of the perception of reflections and diffraction. Moore noted the effect, but never went further in his investigation. Toole noted it also, but only for non-musical signals and never followed up with a study of level as a principle variable. Our recent paper did three variables - SPL level, delay time, and delayed signal level. Our results were completely consistant with all previous results where they overlaped, but we found the strongest effect with SPL, the variable which others have virtually always held constant.
http://www.google.com/search?q=geddes+diffraction+"diy+audio"&num=30&hl=en&lr=&as_qdr=all&filter=0
If you are going to do blind tests of listening experience, then make sure you do include SPL as a variable.
There was a very interesting post on (I think) the Beyond Ariel thread by Earl Geddes about his research of diffraction effects in wave guides indicating our hearing of diffraction is level dependent that is - the physical phenomenon arriving at our ears is linear, but our hearing is not.
He said his Summa would suddenly "crash" and become unlistenable at about (I think) 110 dB due to HOMs, which are a diffraction affect, but in fact these phenomena become increasingly more audible over 80 dB in more ordinary designs.
The Ariel thread is a monster but someone may have those posts to hand.
Hah! Googled DIY audio. Page 145 post 1444
And Page 46 post 1134:
The difference between a reflection and an HOM - which is a form of diffraction - is that the reflection is minimum phase while the diffraction is non-minimum phase. This means that the peak energy of a reflection arrives at the same time as the main signal (there will be a tail), but the peak energy of the HOM and/or diffraction arrives delayed in time (plus a tail). This is a small but very distinct difference, especially when subjective aspects are taken into account. The ear is far less sensitive to the minimum phase aberation than the nonminimum phase one, but more significantly, the minimum phase one is mostly level independent while the nonminimum phase one is highly level dependent. The ear masks the diffraction (HOM) more at lower SPL levels than at higher ones. This makes diffraction sound like nonlinear distortion in that it "distorts" (subjectively) higher SPL waveforms while not affecting lower level ones.
This has a profound impact to our understanding of "distortion" in that a linear system that has diffraction will sound like a nonlinear system. Its the ear that is nonlinear here, not the system.
Your data on the perception of delays is consistant with typical understanding, but is contradicted (more like refined actually) by several studies, one of which is my own. We dealt with delays on the order of .2 ms and found substantial subjective effects, but typically only at higher SPLs. What you need to factor in here is that most studies of delay perception are done at a single SPL (usually fairly low in fact) and it is well know from Toole and Moore that these effects are level dependent. .2 ms is quite audible on a loud passage, but inaudible on a softer one. This aspect has been overlooked in virtually all studies of the perception of reflections and diffraction. Moore noted the effect, but never went further in his investigation. Toole noted it also, but only for non-musical signals and never followed up with a study of level as a principle variable. Our recent paper did three variables - SPL level, delay time, and delayed signal level. Our results were completely consistant with all previous results where they overlaped, but we found the strongest effect with SPL, the variable which others have virtually always held constant.
http://www.google.com/search?q=geddes+diffraction+"diy+audio"&num=30&hl=en&lr=&as_qdr=all&filter=0
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