Burn-in: Real Or Imagined??? - Page 19 - AVS Forum
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post #541 of 665 Old 01-20-2009, 10:38 AM
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Originally Posted by Alimentall View Post

Just as I said to JJ, there's a WHOLE lotta qualification in that statement, enough so to make it useless.

Without the qualification, it would assume extreme arrogance in our sciences. We will forever look backwords at our previous coclusions and think how short sighted we were.

Research in our sciences is on-going. The possitions, opinions and assumptions we hold at the present time now may someday soon be completly irrelevant.

"Every great advance in science has issued from a new audacity of the imagination"
-John Dewey
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post #542 of 665 Old 01-20-2009, 11:14 AM
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Maybe what we need are great advances in recording capability. Based on some of the comments by posters, this does not seem immediately hopeful.

"I've found that when you want to know the truth about someone that someone is probably the last person you should ask." - Gregory House
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post #543 of 665 Old 01-20-2009, 11:20 AM
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Originally Posted by krabapple View Post

Maybe AudioGrasshopper should learn more about the careers of the participants in this thread's little symposium, before making a second vacuous post to AVSForum.

Curious? How much background information on AudioGrasshopper have you obtained krabapple? Would the comments be more valid if John Vanderkooy made them?
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post #544 of 665 Old 01-20-2009, 11:33 AM
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Originally Posted by jaxter View Post

Curious? How much background information on AudioGrasshopper have you obtained krabapple? Would the comments be more valid if John Vanderkooy made them?

The more pertinent question: is it likely that a Vanderkooy would make the comments AudioCaterpillar did?

(While the urge to express l'esprit de l'escalier is natural, do you really need to respond to the same post twice?)
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post #545 of 665 Old 01-20-2009, 11:42 AM
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Originally Posted by krabapple View Post

The more pertinent question: is it likely that a Vanderkooy would make the comments AudioCaterpillar did?

(While the urge to express l'esprit de l'escalier is natural, do you really need to respond to the same post twice?)

I do not need but as you say I desired too. I understand your passion in defending John, but in this process you ignore the questions and attack each persons character and challenge their intent.

In this, you digress from the actual discussion pertaing to the facts about audio. You should be catious in this manner, as some might consider you a mere shill for Mr Johnston and less a person with passion for the studies of sound reproduction.

I will of course give you the benefit of the doubt since I truly have no knowledge of your character or intent.
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post #546 of 665 Old 01-20-2009, 11:58 AM
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Originally Posted by Chu Gai View Post

Maybe what we need are great advances in recording capability. Based on some of the comments by posters, this does not seem immediately hopeful.

I would say that our recording capabilities are actually very good. Our microphones might use some bit of improvement. But it is our reproduction or playback systems that are in dire need of improvement.

The lack of standards in certain areas of the recording industry is incredibly lacking. The current lack of meaningful specifications for loudspeakers is another area for concern. If we could find a way to amke improvements in these areas as well as a few others, I believe great leaps in sound quality and reproduction could be achieved.
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post #547 of 665 Old 01-20-2009, 11:59 AM
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Originally Posted by jaxter View Post

I do not need but as you say I desired too. I understand your passion in defending John,

Gee, it's nice to be understood, but actually I'd have written the same thing had AudioCaterpillar's windy first post to AVSF been referring to any of the other notables, as well.

Are you done now, please?
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post #548 of 665 Old 01-20-2009, 12:16 PM
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Okay, so if we take away all the $10 words, we're really arguing over stereo bass with dual subs versus mono or dual mono bass? I thought we were beyond those arguments and into something deeper

John
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post #549 of 665 Old 01-20-2009, 01:16 PM
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Originally Posted by Alimentall View Post

Single source bass or mono multi-source bass? And when you say right in front, do you mean perpendicular to your ear axis? Does the effect only happen when there are no high frequencies?

Single-source bass is best. Multiple mono sources add in other issues. For example, the Lexicon setup guide for bass enhance recommends the highest crossover setting for the center channel so as much bass comes from the sides as possible.

Right in front meaning in front of your nose, ie. 0 degrees. Bass envelopment has the most effect directly to the sides: +-90 degrees. The effect doesn't really depend on high frequencies.

And yes, we are talking about stereo bass with multiple subs, but things that appear simple on the surface can be pretty complicated underneath.

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In a concert hall the acoustic instruments are all individual mono sources. The spaciousness comes from the reflections of the room or the reverberation time. The source is still mono.

A playback system seeks to reproduce the entire acoustic event, not just the instruments. Therefore the hall effects, including lateral-moving bass frequency waves, are important.

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Originally Posted by Chu Gai View Post

Count on more touchy/feely alternative science from the hordes on the left coast.

Hey! A whole bunch of us resemble that remark! JJ, Sean, Todd, and I are all left-coasters. We'll count John, too, if he behaves.

--Andre
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post #550 of 665 Old 01-20-2009, 01:24 PM
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Originally Posted by AndreYew View Post

Single-source bass is best. Multiple mono sources add in other issues. For example, the Lexicon setup guide for bass enhance recommends the highest crossover setting for the center channel so as much bass comes from the sides as possible.

Right in front meaning in front of your nose, ie. 0 degrees. Bass envelopment has the most effect directly to the sides: +-90 degrees. The effect doesn't really depend on high frequencies.

And yes, we are talking about stereo bass with multiple subs, but things that appear simple on the surface can be pretty complicated underneath.



A playback system seeks to reproduce the entire acoustic event, not just the instruments. Therefore the hall effects, including lateral-moving bass frequency waves, are important.



Hey! A whole bunch of us resemble that remark! JJ, Sean, Todd, and I are all left-coasters. We'll count John, too, if he behaves.

--Andre

So is there a so-called "sweet spot" for stereo bass and do you have to give up better bass at all seating positions to get "stereo bass".
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post #551 of 665 Old 01-20-2009, 01:26 PM
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"Left coast" is relative to how you hold the map...

"It is worse still to be ignorant of your ignorance."
-- Saint Jerome (374 AD - 419 AD)


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post #552 of 665 Old 01-20-2009, 01:32 PM
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Originally Posted by Randybes View Post

So is there a so-called "sweet spot" for stereo bass and do you have to give up better bass at all seating positions to get "stereo bass".

In my experience, it's better over a wider area.

But "stereo" is barely sufficient. Use all full-range radiators if you want my vote.

James D. (jj) Johnston
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post #553 of 665 Old 01-20-2009, 01:33 PM
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Originally Posted by AndreYew View Post

Single-source bass is best. Multiple mono sources add in other issues. For example, the Lexicon setup guide for bass enhance recommends the highest crossover setting for the center channel so as much bass comes from the sides as possible.

That sounds contradictory! So, you're saying that you should have only one subwoofer for all channels, right? (I can't agree with that), But then you don't want that sub in front of you because if the bass hits your ears at the same time, it comes across as mono? But if you can sense that it is off to one side or another, then you'd be off kilter. And if they bass should come from the sides, then you're really off kilter without dual subs. But now you have two sources for the same bass. Also, what other problems do the multiple mono subs add? I've known them to help cancel the lateral room mode but not cause other problems.
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And yes, we are talking about stereo bass with multiple subs, but things that appear simple on the surface can be pretty complicated underneath.


If it's stereo bass with multiple subs, how does this work with a 'single source'? Am I misunderstanding what you mean by a 'single source'? Could you mean that the bass of any channel should all come from a single full range speaker and therefore be as multi-channel as the rest of the frequencies?

John
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post #554 of 665 Old 01-20-2009, 01:39 PM
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Originally Posted by krabapple View Post

Maybe AudioGrasshopper should learn more about the careers of the participants in this thread's little symposium, before making a second vacuous post to AVSForum.

Dearest Krabapple ... I anticipate your response is correlated to growing pains, due in part to an difficulty in offering technical insight or question less than pertinent contributions such as those posted by jj_0001. Nevertheless, I have faith you shall grow into your own shoes, challenge what is imposed as opinion, and be less of a follower.

Credibility and respectm are earned, they do not fall from the heavens. We should expect to be challenged.
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post #555 of 665 Old 01-20-2009, 01:50 PM
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Originally Posted by jaxter View Post

Your rhetoric assumes that you must have stereo bass to maintain accurate representation subjectively in a listening room.

'Assumes' is incorrect. My observations are based on the measurement of real soundfields in real venues. While one might argue about the method of measurement, one can not argue about the sound of the resulting playback.
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In a concert hall the acoustic instruments are all individual mono sources. The spaciousness comes from the reflections of the room or the reverberation time. The source is still mono.

Wrong, but not at bass frequencies. At anything but bass frequencies, acoustic instruments are nothing like monopoles. However, we'll let that go for bass frequencies, except for Bodhrans and a few other implicitly dipole instruments.

So, at bass freuquencies, as I've pointed out already, the issue arises from the hall. Yes, good, fine, true. This has nothing to do with "mono bass" from multiple uncorrelated instruments in a hall that performs massive amounts of further decorrelation over a several-second period.
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I also do not know of very many stereo recordings that actually utilize stereo bass in the final mix, including multi-channel recordings which usually sum the bass into a single channel. Stereo is simply a psychoacoustic way of achieving multiple sources of sound with only two speakers.

We've already discussed this. It's very true that most recordings are in fact made wrong. I agree. As to what "stereo" is, well, you're kinda-sorta right. You don't achieve multiple sources, you achieve the perception of multiple sources, which is a very important distinction that will continue to arise.
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Admittedly this is a difficult area of acoustics to define clearly with the given research at this time. But I do believe that the possible benefits of stereo bass (if any are proven) would be overridden if any sacrifice was made to the timbre. Our sensitivity to tone (frequency response) is well researched and documented. The idea that we lose much detail in spaciousness from frequencies below say 100 Hz in small listening room belies the fundamental physics of acoustics and hthe crrent level of knowledge about human perception of sound.


Really? You say "belies ...", now I think you need to support that contention.

You are using an irrelevant point (mono sources), and an assumption "timbre problems" in order to justify a huge leap to a conclusion that is not, in my opinion, warranted.

What's more, your projected theory does not account for what actually happens in the original venue, and does not address how you can transport that to the playback venue.

You argue about "the fundamental physics of acoustics" but you don't bother to address the modal density in a large vs. a small venue. Perhaps you need to review your argument on that basis?

As to modes in small rooms, you certainly won't be creating an even, complex mode structure with ONE woofer. Right?

And you won't match the concert hall's if you do something involving lots of memory and DSP, either. Right? (Match even in a perceptual sense, let alone in any real measurable sense.)

Now, Todd said "you can not create ... in a small room". That's an interesting statement, I dare say, but I won't discuss it THEORETICALLY since I am previously accused of being an empty theorist.

James D. (jj) Johnston
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post #556 of 665 Old 01-20-2009, 01:53 PM
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Originally Posted by Alimentall View Post

Are we talking about electronically controlling the output of the subwoofers to better merge into the room or are we simply saying that there needs to be more musical differentiation in the low frequencies?

I'm talking about trying to create at least the illusion of the modal structure of the original venue in the playback venue. So neither of your choices, sorry.

James D. (jj) Johnston
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post #557 of 665 Old 01-20-2009, 01:59 PM
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Originally Posted by AudioGrasshopper View Post

Dearest Krabapple ... I anticipate your response is correlated to growing pains, due in part to an difficulty in offering technical insight or question less than pertinent contributions such as those posted by jj_0001. Nevertheless, I have faith you shall grow into your own shoes, challenge what is imposed as opinion, and be less of a follower.

Credibility and respectm are earned, they do not fall from the heavens. We should expect to be challenged.

Interesting, two posts, two personal attacks.

Do you have anything more to offer, perhaps something of a testable or verifiable nature? Oh, something like "measurements", say, or subjective test results?

James D. (jj) Johnston
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post #558 of 665 Old 01-20-2009, 02:00 PM
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Originally Posted by jj_0001 View Post

In my experience, it's better over a wider area.

But "stereo" is barely sufficient. Use all full-range radiators if you want my vote.

The challenge I see with stereo subwoofers is the thought of how recordings are captured. Consider the following ...

Many musicians start off with project studios in their homes, not uncommon to have a very simple setup in their bedrooms. Some grow into having more gear, expanding their studio, even dedicating an entire isolated room for their recording purpose. They become technically proficient along the way, incrementally understanding acoustics, in small portions. From what I have observed, the use of a subwoofer in many of these applications is almost an afterthought. That is, from what I have observed, the majority of musicians with their home studios have at most, one subwoofer that is usually tucked away in a horrible location. That's the reality, with some musicians who prefer having a switch to defeat the subwoofer, lets them hear their mix. Head over to a retail store with profesional audio gear and see the proportion of choices between many monitors and few subwoofers. This is the source of music content, it starts with a humble very simple technical footprint.

Large leap forward, if we wait and expect the majority of musicians with the balance of their industry to adapt to particular recording techniques, recording microphones, to capture stereo bass; I suspect we'll be waiting for some time. Perhaps in some instances with certain program material we remain convinced we perceive differences loosely correlated to "stereo" subwoofers. However, I would add that it shall be a while before this becomes mainstream; it just won't happen in the majority of content producers starting with home studios and expanding in what are considered profesisonal recording studios. As a result, it is difficult to believe that it shall become part of mainstream media. Hence, the concerns posted shall likely resonate most effectively with those who are technically savy, discerning audio enthusiasts in search of more audio fun.
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post #559 of 665 Old 01-20-2009, 02:06 PM
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Originally Posted by jj_0001 View Post

I'm talking about trying to create at least the illusion of the modal structure of the original venue in the playback venue. So neither of your choices, sorry.

Why would you want to do this? You mean replacing the existing one (Audyssey does a great job of killing bass) with a faked long wavelength bass structure? Would that not take the information recorded into the mix in multiple dimensions or at the very least some information about the room encoded into the disc for the processor? OR, IOW, just using proper recording methods and 5-7 full range speakers? You could easily put a delayed inverse into each full range speaker to cancel the rooms bass modes [almost] completely, then overlay the other bass *but* that also means that the recording would have to master in that environment or the sound would be incredibly lean.

John
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post #560 of 665 Old 01-20-2009, 02:30 PM
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Originally Posted by jj_0001 View Post

Interesting, two posts, two personal attacks.

Do you have anything more to offer, perhaps something of a testable or verifiable nature? Oh, something like "measurements", say, or subjective test results?

Certainly, much is available, let me first offer the following ... I would encourge you to please consider adjusting your radar, a challenge is quite different from an insult. Nobody has insulted anyone, this is what is considered as a challenge provided by post pubescent men. In the meantime, see the humor and accept another offer of warm milk, fresh cookies, followed by a belly rub intended to put you in a better mood.

On a relatively serious note ... I have read many papers from people who have made substantial contributions to the audio community. They offer insight but at the end ofthe day, do not enitrely map one to one with what's going on outside our tech world. Think about the source of content, the likelyhood people will effectively use or understand the utility of two subwoofers; we are far from having this adopted as mainstream. The recordings are not readily captured as such, the playback systems are in a similar state, and the majority of end users shall likley not hear the difference. Too many variables, very little audible correlation with stereo subwoofers remains as the challange to date. The variations of rooms and source content represent enough variables to reduce the lilkelyhood anyone to discern "stereo" bass. The 5.1/7.1 source media supporting Dolby/DTS is does not help when providing a "0.1" subwoofer signal.

It's tough to provide a compelling audbile experience when conducting sighted listening tests, lets not mention double blind listening tests of stereo subwoofers. The latter were performed by corporations who have determined and shared the same. In my view, this is a difficult nut to crack with neutral double blind listening tests. We shall continue to entertain a discussion, its seems this shall not readily become mainsteam.
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post #561 of 665 Old 01-20-2009, 02:34 PM
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Originally Posted by jj_0001 View Post

I'm talking about trying to create at least the illusion of the modal structure of the original venue in the playback venue. So neither of your choices, sorry.

When trying to recreate the modal structure of orignal venue, do you have rough estimates on the delay line(s) needed; the MIPs, the memory needed? What are your findings? I sense this would be taxing on the hardware although I have seen/heard versions that capture venues and large banks of effects in pro-audio...
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post #562 of 665 Old 01-20-2009, 02:54 PM
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Originally Posted by Randybes View Post

So is there a so-called "sweet spot" for stereo bass and do you have to give up better bass at all seating positions to get "stereo bass".

I don't know if you give up seat-to-seat consistency, but you do give up some bass slam. With Bass Enhance turned Off, I get the typical chest-thumping bass (what others call in-your-head bass). With BE decorrelation turned On, the bass doesn't hit as hard, but sounds like it's all around you. Some people like it (they say it sounds more like a live venue) while others don't (saying it's too phasey/swimmy for them). I turn it On for classical and Off when listening to heavy metal.

BTW, since Todd mentioned Dave Griesinger, you may want to check out one of his papers on stereo bass:

http://www.davidgriesinger.com/sfaes.pdf

First read his conclusion on page 27, then go back to the begining.

Sanjay

Sanjay
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post #563 of 665 Old 01-20-2009, 03:11 PM
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Originally Posted by AudioGrasshopper View Post

Dearest Krabapple ... I anticipate your response is correlated to growing pains, due in part to an difficulty in offering technical insight or question less than pertinent contributions such as those posted by jj_0001. Nevertheless, I have faith you shall grow into your own shoes, challenge what is imposed as opinion, and be less of a follower.

Credibility and respectm are earned, they do not fall from the heavens. We should expect to be challenged.

Gentle AudioG, I'll be happy to accord you the respect you seem to think you are owed...if you reveal yourself to be, say, Floyd Toole, who has received it already from me many-fold.

As things stand, I'm not seeing it...you are retailing an argument that common practice militates against something like 'stereo bass', both at the recording and home playback stage. Not so long ago, common practice also militated against five loudspeakers plus a subwoofer in the home...who would stand for that? It turns out: more than a few. You might retort that the realistic reproduction of a venue's bass is a relatively *small* effect in comparison to the impact of 5.0 vs. 2.0. Perhaps so, but I would note that the consumer audio industry (and high-end journals) have in the past happily hyped 'improvements' with less scientific foundation, less measurable impact, and less chance of making an perceptible audible improvement in the home ('high rez' audio, anyone? boutique cable, anyone?), than proper recording and playback of 'stereo bass'.

It appears to me, from my humble vantage of the back and forth, that it is JJ here who is doing the 'challenging' of conventional wisdom and practice. That is something I associate also with the writing of Dr. Toole, who challenges, for example, the conventional wisdom regarding attenuation of listening room reflections...and backs it up with measurements and listening tests.
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post #564 of 665 Old 01-20-2009, 03:14 PM
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Originally Posted by jaxter View Post

Actually there is no substantiated research that clearly indicates that you cannot achieve reasonably accurate reproduction with mono-bass sources that I am aware of.

Your rhetoric assumes that you must have stereo bass to maintain accurate representation subjectively in a listening room. In a concert hall the acoustic instruments are all individual mono sources. The spaciousness comes from the reflections of the room or the reverberation time. The source is still mono.

I also do not know of very many stereo recordings that actually utilize stereo bass in the final mix, including multi-channel recordings which usually sum the bass into a single channel. Stereo is simply a psychoacoustic way of achieving multiple sources of sound with only two speakers.

Admittedly this is a difficult area of acoustics to define clearly with the given research at this time. But I do believe that the possible benefits of stereo bass (if any are proven) would be overridden if any sacrifice was made to the timbre. Our sensitivity to tone (frequency response) is well researched and documented. The idea that we lose much detail in spaciousness from frequencies below say 100 Hz in small listening room belies the fundamental physics of acoustics and hthe crrent level of knowledge about human perception of sound.

Jaxter,

Are you saying that an acoustic instrument is a zero-dimension radiator?

rob r.

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post #565 of 665 Old 01-20-2009, 03:27 PM
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If you want to cut through the mumbo jumbo, theory and philosophy, and get to the hard science, read the work of those who have been around and contributed in a meaningful way with respect to room acoustics and psychoacoustics. That would be, among many others, Floyd Toole, Sean Olive, Earl Geddes, John Vankerkooy, .... and going a bit further back, Leo Beranek, Alton Everest, Philip Morse, Richard Bolt, and many more. These are the people who do real work, and publish it.

Some sources are more readable than others. Floyds book has minimal mathematics and very insightful. you can get a good understanding of room modes from reading that chapter. Enough to know that you can never create new room modes. ...and that talking about low frequency room modes in a large venue is like discussing room modes in a small room at 4 kHz, i.e. meaningless.
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post #566 of 665 Old 01-20-2009, 03:29 PM
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Originally Posted by krabapple View Post

Gentle AudioG, I'll be happy It appears to me, from my humble vantage of the back and forth, that it is JJ here who is doing the 'challenging' of conventional wisdom and practice. That is something I associate also with the writing of Dr. Toole, who challenges, for example, the conventional wisdom regarding attenuation of listening room reflections...and backs it up with measurements and listening tests.

Yes, but Floyd does not believe in "stereo bass"! so much for that theory.
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post #567 of 665 Old 01-20-2009, 03:42 PM
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Originally Posted by AudioGrasshopper View Post

When trying to recreate the modal structure of orignal venue, do you have rough estimates on the delay line(s) needed; the MIPs, the memory needed? What are your findings? I sense this would be taxing on the hardware although I have seen/heard versions that capture venues and large banks of effects in pro-audio...

To answer your questions:

1) yes.
2) they belong to someone
3) No.

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post #568 of 665 Old 01-20-2009, 03:44 PM
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Originally Posted by beezelbub123 View Post

Enough to know that you can never create new room modes. ...and that talking about low frequency room modes in a large venue is like discussing room modes in a small room at 4 kHz, i.e. meaningless.

Obviously, you can never create "new room modes" that are due to the physics of the playback room.

Why is this relevant, except to point out that mono bass has problems?

Or are you of the 'get rid of all room modes' persuasion, in which case how do you make a small room sound like a large room?

Or do you assert that at bass frequencies, large and small rooms already sound alike?

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post #569 of 665 Old 01-20-2009, 03:47 PM
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Originally Posted by sdurani View Post

I don't know if you give up seat-to-seat consistency, but you do give up some bass slam.

Perhaps so, with a particular system. Which system do you refer to, specifically? (Sorry, I don't know all present consumer systems, I tend to avoid them for straight amplification and rendering, and the bits come out of my computer.)

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post #570 of 665 Old 01-20-2009, 04:06 PM
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Originally Posted by jj_0001 View Post

Which system do you refer to, specifically?

Lexicon surround processors (consumer, not pro), from the mid-1990s to present. On the MC-12, for example, all the bass filtered from the left channels (front, side, rear) gets sent to the left subwoofer. Ditto the right side.

Their (optional) Bass Enhance processing keeps a 90 degree shift/lag between the two subs, which they recommend you place as far away from the centre line as possible (the listener's +/- 90 degree points) in order to maximize the effect. The reason for the low frequency decorrelation processing is because, as you and others have mentioned, there are very few recordings with true decorrelated bass.

There are valid reasons for keeping recorded bass mono. But it's nice to have a workaround (just as one would use Neural if their favourite recording is not available in multi-channel). And, like any processing, you always have the option to turn it Off if you don't like the 'bass externalization' effect.

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