or Connect
AVS › AVS Forum › Display Devices › Ultra Hi-End HT Gear ($20,000+) › Burn-in: Real Or Imagined???
New Posts  All Forums:Forum Nav:

Burn-in: Real Or Imagined??? - Page 17

post #481 of 665
Well, well. Kevin, sounds like you remember the Freddy Funnel events back in 1978. As of a couple years ago, Telarc still had a big orange hanging around. (OTOH, I bet you already know that ... my connecting the dots.)

Quote:


I think the audio industry is in enough of a mess, without pigeonholing itself into an "assured lower quality" situation.

No kidding.

Todd...JJ...Sean .. you guys are having way too much fun with way too many toys.
post #482 of 665
JJ

I was refering to the ears not the recordings. Let's not get that confused. There certainly could be uncorrelated signals in the recordings, just as one could completely uncorrelate the signals to multiple subs. This is because there is nothing linking the completely independent electrical signals. But the pressures at the ears are not independent at all - they are tied together by the physics of sound around a sphere. At LF they are forced to be virtually the same and hence will always have a very high correlation no matter what kind or how many signals there are in the room. Basically, as far as LFs are concerned the head is simply not there.

Decorrelation of the LF signals only has an effect on the spectral and spatial frequency variances. It will have no effect on the LF correlation at the ears.

The issue with the velocity had to do with its having any effect on ear signals. At LFs I can't see this at all.
post #483 of 665
amen
post #484 of 665
Quote:
Originally Posted by gedlee View Post

JJ

I was refering to the ears not the recordings.

Yes, yes, I know that.
Quote:



Let's not get that confused. There certainly could be uncorrelated signals in the recordings, just as one could completely uncorrelate the signals to multiple subs.

However, you want a decorrelation like what you'd get in a room. This is why I don't think the "Hilbert" approach has any legs perceptionwise. It might help even out the playback room modes, but this is not what we want to have happen, see below.
Quote:



This is because there is nothing linking the completely independent electrical signals. But the pressures at the ears are not independent at all - they are tied together by the physics of sound around a sphere.

And with a whole body attached. The differences are not large, then, but what you need to do then is look at the ability of the ear to distinguish between leading edges in the lowest-frequency critical band. It's well established that we do not find directional cues, I hope nobody's arguing that. However, you'll find that you do sense "spaciousness" with some shifting of the leading edges. You can try this in headphones (with much less than a phase inversion, of course, the phase inversion is mentioned to show that there is indeed an effect).
Quote:



At LF they are forced to be virtually the same and hence will always have a very high correlation no matter what kind or how many signals there are in the room. Basically, as far as LFs are concerned the head is simply not there.

Unless it's attached to a body.

Furthermore, the decorrelation is going to happen if you have a zero between your ears, yes? And how many will there be in a big, complex, good venue?
Quote:



Decorrelation of the LF signals only has an effect on the spectral and spatial frequency variances. It will have no effect on the LF correlation at the ears.

That sounds like a perilously theoretical statement. If it was true, it's hard to explain, then, just how one does hear differences. If you put your head across a zero, you won't detect that, btw? Are you SURE?
Quote:



The issue with the velocity had to do with its having any effect on ear signals. At LFs I can't see this at all.

So, how much of a wavelength would it take to change your mind? Your body is very close to 1/4 wavelength at the lowest frequency this is argued to matter.

To the point about "smoothness", you're missing the point entirely. An actual, GOOD, PLEASANT venue doesn't have this "smoothness". As the measurements pointed out above show (and as other measurements also show, if you saw Beranek's Heyser Lecture, for instance) "smoothness" is not the characteristic one sees spatially, rather what one sees is a very complex node structure that mimics smoothness, but with a great deal of dispersion even at bass frequencies. You can't get that with acoustics in a small room, but you certainly can mimic it with multiple radiators.

And, head being only a sphere (forgetting the body) or not, if the soundfield in the room has a zero or three inside your head, the effect is going to happen, head-size regardless. And it does.

So, you can't actually sound like an actual, good, pleasant venue if you have this "smoothness". So, do you want to be "smooth" (which is a property of small venues) or do you want to be like a real, pleasant, good venue? Which is it now?

While there are certainly venues where there are problems (you did notice my qualification as "good", yes?), good venues provide a wide listening area.

And you, me, and most everyone else moves their head while they are listening, to sample the soundfield. So even if you would get this at one point (which is hardly what one wants to do, btw, and which is not what multiple subs give you), you'd move your head outside of it quickly enough.

This ties directly into the use of panpots in multichannel, but that's another debate for another time.

Oh, and Earl, the microphones used in the recording were .9 milliseconds apart,(which by most people's reasoning should put them well within a heavily correlated distance at bass) but pointing in different directions. That, alone, makes the point, simply and cleanly, that the decorrelation is coming about well within 1 wavelength. (and the .4 crosscorrelation mentioned is in fact including lags up to and beyond the distance between the farthest two mikes , and absolute value of correlation, there's no trick involved) So, that's an actual measurement, in an actual, good, acclaimed concert hall (that I am not free to name, for bizzare reasons), that shows bass decorrelation in much, much less than 1 wavelength. Just in case you didn't have a chance to check it out, I'll explain that. No, I didn't expect that, either. (Oh, and yes, there was bass content in the recording, from a pipe organ stomping around on its biggest pipes, where I expected gobs of correlation, in one of the test pieces. It wasn't even the one with the highest correlation. But there was lots of energy below 90Hz. The room tone had more correlation than anything else, basically, which is interesting, but perhaps not germane to this discussion.)
post #485 of 665
Quote:
Originally Posted by jj_0001 View Post

I refer you to the Johnston and Kuo paper cited above.

It measures crosscorrelation between channels, including lags larger than the microphone spacing, and shows rather a lack of cross-correlation with an appropriately spaced microphone array.

Velocity is very simple, really, it's maximum at a pressure zero, and minimum at a pressure peak. But I think you knew that, so I'm not sure what issue regarding velocity you're referring to.

But, in any case, it's quite clear that the human body is long enough to interact with a velocity field well below 100Hz. So perhaps we should examine that, yes?

Are you saying that we can feel if a subwoofer that is to one side or another? Because I find that if I do two subs on either side of the seating position, I can't tell where they are, but if there is only one, I can feel and/or hear that it's beside me rather than elsewhere in the room.
post #486 of 665
Quote:
Originally Posted by Alimentall View Post

Are you saying that we can feel if a subwoofer that is to one side or another? Because I find that if I do two subs on either side of the seating position, I can't tell where they are, but if there is only one, I can feel and/or hear that it's beside me rather than elsewhere in the room.

You can't get any directional sensation under about 90Hz.

And you get no remarkable change in any kind of sensation with most present recordings that use coincident or pseudo-coincident kinds of panning, etc.
post #487 of 665
I am talking about LFs in small rooms, nothing else. Smoothness is an important factor since the variations in a small room are considerably greater than a large room. I suspect that your results and comments only apply to larger rooms, because there they make sense. But small rooms are completely different.

But we don't "hear" with our bodies so the size of the body is irrelavent. It's the ears on either side of a sphere that governs the degree to which the two signals can differ, the body has very very little to do with it. And these differences in the modal region of a small room cannot be very different and must be highly correlated. Thats why we can't detect direction of bass in a small room (assuming no HF cues above Fs), but have no trouble at all in a larger room.

There may be some subtle connections fo perception to tactile feeling at bass frequencies, which would involve the whole body, this can be shown for cars, most certainly for car noise, but I suspect that effect is not great in a small HT.
post #488 of 665
Quote:
Originally Posted by gedlee View Post

I am talking about LFs in small rooms, nothing else. Smoothness is an important factor since the variations in a small room are considerably greater than a large room. I suspect that your results and comments only apply to larger rooms, because there they make sense. But small rooms are completely different.

***cough***

And you can get the high density of modes in a SMALL ROOM with MULTIPLE LOW FREQUENCY RADIATORS, using signals captured from a large room with a high density of modes. No, you don't get the same modes. This appears to be less important than having the high mode density.

And that's part of how you make a small room look and feel like a LARGE room.

As to "hear with your body" there's two problems. First, bass sensation in the chest and gut is not so weak, but that's not my point. My point is that YOUR BODY interferes with the velocity in a room. Your body is attached to your head. So what your body does to the soundfield affects your HEAD. Put your body in a velocity peak (i.e. pressure node) and it creates pressure. Some of which gets to your head. Try it. Measure it. Yes. Really.
post #489 of 665
Quote:
Originally Posted by jj_0001 View Post

***cough***

.

Damn, I am going to get a physical today too
post #490 of 665
Quote:
Originally Posted by jj_0001 View Post

You can't get any directional sensation under about 90Hz.

Well, how many subs put out no sound over 90Hz?
Quote:

And you get no remarkable change in any kind of sensation with most present recordings that use coincident or pseudo-coincident kinds of panning, etc.

Mmmmm, you're doing a lot of qualifying.

BTW, not talking about stereo cues, I'm saying that I can sense when a subwoofer is placed on one side or the other, but when there are two subs on either side, mono or stereo, I can't. I don't know whether this is because of distortion elements over 90Hz or if it's because of the pressure wave from the LF. I rejoined the part late, so I wasn't sure where the effect of your body comes in.

PS - could you get recording engineers to mix properly in DTS so I can buy and enjoy surround discs? (musicians up front, ambience/effects in the back, hard panned vocalists, etc, etc).
post #491 of 665
>decorrelation filter
>It looks to me like one could use the Behringer reverb unit

Earl, that seems like a very good idea, I may have to try that. It could have a lot of potential. Do you offhand know the model number of ther reverb unit you were thinking of? The "Ve-Verb" or maybe one of the other boxes (such as DSP10234) that have reverb? functions?
post #492 of 665
Quote:
Originally Posted by Randybes View Post

Damn, I am going to get a physical today too

lol...

Yep. You might want to have that checked out...
post #493 of 665
Bill

Berhinger only makes one. Just go to their web site and look for "Reverb Unit". I don't remember the model.
post #494 of 665
Earl,
It looks like they currently have several devices that include both reverb and delay (a "virtualizer" and a "minifex", categorized under "digital effects processors"). There was a (now discontinued) unit called "Ve-Verb" that had mainly reverb plus some other functions, and some other discontinued "virtualizer" or "effect" devices that also did reverb. It looks like about any of these might do what you were suggesting, though. Ebay lists several for quite little $$.
post #495 of 665
The Ve-Verb REV2496 was the one that I had looked at. I can't speak to the others.

I am working now on a project which s gong to produce a box which will allow 1 to 4 subs to be "optimally" setup in room using a PC for setup and download of the control parameters into a stand alone DSP box. This will have decorrelation filters in it also. Target street price is $500 - $700.
post #496 of 665
I may wait for your box to come out then. Is the plan for it to include parametric EQ as well? The sub bass decorrelation trick for dealing with the room interface issue would make for an interesting paper, have you published anything on it?

Seems ironic to be discussing something like this (a proposed solution for a known real and dramatic problem that probably anyone can hear) under a topic heading like this!
post #497 of 665
Bill

Yes, almost absurd - how did we get here.

The box will do all the EQ required as it will be part of the algorithm for each channels filter. You know that JBL already has a box lke this, although I don;t think that they attempt to decorrealte the signals.

This would be a great paper if I ever got the time to do anything scientific again. I've had this idea for almost four years now and have not done a single thing with it. At some point you just have to give up and say "I'm NOT going to do this and so I may as well let it out into the public domain so that at least I can prove that 'I thought of that!'".
post #498 of 665
I think it's great that it ended up here for a couple of reasons. For one thing, it shows that there are real issues that objectivists agree affect sound quality in significant ways. And for another, it shows that they don't reserve their aggressive argumentation just for subjectivists and tweakers
post #499 of 665
We objectivists are just as argumentative as everyone else. Its just that we know we are right so OUR arguments are valid!
post #500 of 665
Quote:
Originally Posted by gedlee View Post

The Ve-Verb REV2496 was the one that I had looked at. I can't speak to the others.

I am working now on a project which s gong to produce a box which will allow 1 to 4 subs to be "optimally" setup in room using a PC for setup and download of the control parameters into a stand alone DSP box. This will have decorrelation filters in it also. Target street price is $500 - $700.


Hmm. An interesting issue, that, both "optimal" and decorrelated.

Can you tell me what "optimal" means, in that context?
post #501 of 665
Optimal means the minimum spatial and spectral frequency variance through the measured seating positions.
post #502 of 665
To summarize one aspect of this disscusion, I think we could agree that in a small room, at the ears of a human subject, the left and right ear signals are correlated to a large degree. Of course, under the right circumstances, our auditory system can detect amazingly small phase differences even at low frequency. The question is whether or to what extent it is audible, and more importantly, if decorrelation is preferred - an assumption which sounds reasonable but that doesnt' make it a true, especially if all factors are taken into consideration. For example if in trying to get some subtle spatial effect you degrade the spatial uniformity, it's not a clear cut improvement. When people have a complaint about bass in a small room, it is almost always "it sounds boomy", or "it sounds thin", or "it sounds boomy here and thin over there", NOT "gee, the subwoofers don't sound spatial enough".


This thread reminds me of many discussions I had with David Greisinger, which were fascinating but theoretical. This is why I did the research I did on "stereo bass". You can theorize all you want, but it is just theory until you can back it up with real research. Bill Martens is one of the few who has done such research.

SUBJECTIVE EVALUATION OF AUDITORY SPATIAL IMAGERY
ASSOCIATED WITH DECORRELATED SUBWOOFER SIGNALS
Proceedings of ICAD 2002

He did find spatial effects at low frequencies by decorrlating the sub signals, but not below 80 Hz. For my paper, I did a literature review, and could not find much evidence for documented spatial effects below 80 Hz.

Give me some real research that shows people prefer the effect in question, or at least a demo I can sink my teeth into. We had several demos of "spatial bass" by Dave G. (who also has many interesting theories), which were not very robust to say the least. Despite a lot of work by Dave, and plausible sounding theories, IMHO, it hasn't happened yet.
post #503 of 665
Quote:
Originally Posted by cap'n View Post

To summarize one aspect of this disscusion, I think we could agree that in a small room, at the ears of a human subject, the left and right ear signals are correlated to a large degree.

True, but hardly relevant. After all, we're talking about how to create the sensation of a large room inside of a small room. So what we must do is FIX the problem you cite above. The correlation is a problem, and remains so.
Quote:



Of course, under the right circumstances, our auditory system can detect amazingly small phase differences even at low frequency. The question is whether or to what extent it is audible, and more importantly, if decorrelation is preferred - an assumption which sounds reasonable but that doesnt' make it a true, especially if all factors are taken into consideration. For example if in trying to get some subtle spatial effect you degrade the spatial uniformity, it's not a clear cut improvement. When people have a complaint about bass in a small room, it is almost always "it sounds boomy", or "it sounds thin", or "it sounds boomy here and thin over there", NOT "gee, the subwoofers don't sound spatial enough".

All of which testify exactly to the idea that you haven't broken up the LISTENING ROOM's modes enough. Damping them is great, breaking them up so that they behave (via multiple subs, not by attempting the impossible regarding walls, etc) more like a large venue, on the other hand, at least has a chance of sounding like a large venue. To that end, what you need is a lot of modes, a lot more than a small room will ever provide without some help from electronics. And, what's more, a lot more than you'll ever get with one subwoofer in any location.

Part of what makes large (good) venues smooth is the lack of hot spots, booms here or there, nulls, etc. The way this comes about is not by eliminating nodes, but by creating many, many nodes. Check out Beranek if you don't accept that, it's not my opinion. Measurement, certainly, does bear out the idea remarkably well, though.
Quote:



This thread reminds me of many discussions I had with David Greisinger, which were fascinating but theoretical. This is why I did the research I did on "stereo bass". You can theorize all you want, but it is just theory until you can back it up with real research. Bill Martens is one of the few who has done such research.

Do you accept the measurements shown in the paper I cited above. Yes or no? If yes, then what's with the 'theoretical' codswallop? If "no" what's your problem with them? They are simple measurements, simply made, and the results are plain as day. Measurements are measurements. As far as I know, that's about as down-to-earth practical as is humanly possible.

So, since when is measurement "theoretical"? By what mechanism do you dare to insinuate my argument here is "theoretical"? It is not, it is based on simple, clear, measurement. Unambiguous measurement, in fact.

I've published 1 paper, which, although it wasn't intended to address this issue, does so in a rather clear and startling manner, as regards the actual content in a large room. It shows, very clearly, that even at low frequencies, in a good large venue (or 3, I would have to go back to see how many, I know it's at least 4, it wasn't particular to any one venue, but I wouldn't call one of them "good" by any reasonable standard) that the soundfield in the bass region is much more highly decorrelated than you expect (or that I expected!), in fact the coherence length (meaning the point at which the correlation drops to 1/e) is remarkably well under 1 wavelength. (And none of that is even remotely true in a small venue, of course.)

To the perception of phase shifts, you have already stipulated. We have the evidence from large rooms, we have your stipulation. Ergo, we have an effect, unless your stipulation is unwarranted. (and it's not)

So, we have evidence that this is a real, not theoretical issue, and that it is audible in large rooms. So we can now abandon "theoretical" insinuations, insults, and name calling, please, and do so completely. So, no more "theoretical" now or ever, in this context. NONE. We are not talking theory, unless by some magic observation has now become theory.

Now, what are you still missing?

All of your arguments about a soundfield in a small room simply do not address any attempt to create a more complex node structure in the small room, by using multiple sources.

And no, artificial decorrelations are just not a useful thing to do, unless you really do the right kind of decorrelation. The "hilbert" idea, for instance, decorrelates two signals, but does little, if anything, for the node structure in the small listening room. N.B. Please don't presume that I know how to do the 'right kind' myself, other than by measurement, at this point. I might, I might not, and I don't know the answer to that myself.

Earl:
Now, as to "smoothness" in the room, allow me to point out that good, large venues are not "smooth" in any sense one would usually use the term. So, creating a "smooth" response in the usual sense is not, can not, sound like a large room.

Now, how do we create that kind of soundfield in a small room? That's the question, not "smoothness" or "decorrelation" of some particular fashion with some particular method.

And this is where the problem with "optimization" comes in. Do you wish to optimize to some particular standard of "smoothness" or do you wish to recreate something like a good, real venue? Do you want to do the same thing when such information is present (which is rare in the present day) as when it's not (for which I think you're doing the right thing)?

Now, suppose I give you a recording with the proper information. What is your system going to do with it?

And therein is my objection to enforcing monophonic bass. You can't use information when you get it, and information that even the uber-denier admits is most likely audible. So, what do you do when you get the information?

(I'm not presently in a position to offer you a germane recording. I doubt I have to explain the problems in being able to release material.)
post #504 of 665
We've had pretty good luck using dual mono small subs in small rooms. We've done quite a few PJ-based HT systems in spare bedrooms. But then, to be honest, it would ben nice to have a summary of the opposing arguments here as I'm not quite following what is being argued and why.
post #505 of 665
Quote:
Originally Posted by Alimentall View Post

We've had pretty good luck using dual mono small subs in small rooms. We've done quite a few PJ-based HT systems in spare bedrooms. But then, to be honest, it would ben nice to have a summary of the opposing arguments here as I'm not quite following what is being argued and why.

Indeed. While the discussion is interesting and well informed; something more digestable to the laymen would be most welcome!
post #506 of 665
I'm trying to figure out if 'decorrelation' in this context means 'stereo bass' or if it means varying the signal to each woofer with the sole intention of smoothing in room response or if it means 'independent of the associated speakers' and then what each person's 'side' of this is without wading through the entire thread!
post #507 of 665
Quote:
Originally Posted by gedlee View Post

The Ve-Verb REV2496 was the one that I had looked at. I can't speak to the others.

I am working now on a project which s gong to produce a box which will allow 1 to 4 subs to be "optimally" setup in room using a PC for setup and download of the control parameters into a stand alone DSP box. This will have decorrelation filters in it also. Target street price is $500 - $700.

I will take one
post #508 of 665
Quote:
Originally Posted by sierraalphahotel View Post

Indeed. While the discussion is interesting and well informed; something more digestable to the laymen would be most welcome!

If I understand correctly, the debate is about stereo bass and whether you really can hear it. I had a Lexicon that supposedly added or at least allowed you to hear this effect if set-up correctly. I never could hear it, but I can't say that I had it set-up correctly or listened to the correct music. I did have them set-up in stereo with them in the front balanced etc.
post #509 of 665
Quote:
Originally Posted by Randybes View Post

I never could hear it, but I can't say that I had it set-up correctly or listened to the correct music. I did have them set-up in stereo with them in the front balanced etc.

I have my subs directly to my sides and it's pretty easy to hear. You can hear a similar effect by adjusting the "Low Freq Width" parameter in the Panorama mode. Just in case people don't like the effect, Lex ships their processors with Bass Enhance processing set to Off by default.

Sanjay
post #510 of 665
Quote:
Originally Posted by jj_0001 View Post

All of which testify exactly to the idea that you haven't broken up the LISTENING ROOM's modes enough. Damping them is great, breaking them up so that they behave (via multiple subs, not by attempting the impossible regarding walls, etc) more like a large venue, on the other hand, at least has a chance of sounding like a large venue. To that end, what you need is a lot of modes, a lot more than a small room will ever provide without some help from electronics. And, what's more, a lot more than you'll ever get with one subwoofer in any location.

You can introduce a resonance electronically of course, and you can optimize the response at the seats - but: you CANNOT create room modes! Those are strictly a function of the room, not the sources, and certainly not the electronics.

Quote:
Originally Posted by jj_0001 View Post

Do you accept the measurements shown in the paper I cited above. Yes or no? If yes, then what's with the 'theoretical' codswallop? If "no" what's your problem with them? They are simple measurements, simply made, and the results are plain as day. Measurements are measurements. As far as I know, that's about as down-to-earth practical as is humanly possible.

Your measurements were made using a (i believe) a 7 mic array using hypercardioid and shotgun mics! Last time I checked, I dont have shotgun mics coming out of my ears. I was refering to the end result, at the ears of a human. Your measurement technique is NOT simple, and not relevent unless your point ist hat we can create decorrelated recordings using directional microhones. Measuring at the blocked ears of a human or dummy head is simple and as relevent as you can get.

Quote:
Originally Posted by jj_0001 View Post

So, since when is measurement "theoretical"? By what mechanism do you dare to insinuate my argument here is "theoretical"? It is not, it is based on simple, clear, measurement. Unambiguous measurement, in fact.

No, it's good that you have and refer to measurements. I just meant that if you are after results, a listening test or at least a demo is needed to prove your point.

Quote:
Originally Posted by jj_0001 View Post

So we can now abandon "theoretical" insinuations, insults, and name calling, please, and do so completely. So, no more "theoretical" now or ever, in this context. NONE.

"insults", "name calling"...? show me where please.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Ultra Hi-End HT Gear ($20,000+)
AVS › AVS Forum › Display Devices › Ultra Hi-End HT Gear ($20,000+) › Burn-in: Real Or Imagined???