Bass and subwoofers

[Thomas Lund]

Considering auditory envelopment (AE), don't focus on loudspeaker group delay. The main contributor of LF inter-aural distortion is the listening room.

In recreational sound, especially with stereo, such distortion may be considered benign, but it also limits the envelopment-range the room+system is able to convey; and limitations may be from both sides. Even pop recordings now include joyful AE contrasts that cannot be appreciated unless the listening room+system offers some degree of transparency.

 

[audiofooled]

In my upmixed bass managed desk setup I'm not really sure I hear anything obvious that jumps out to me. Bass is still centered and mono (sub is in middle of front wall) -- though, maybe ever so audibly shifted for me to the left... yeah, well, I'm not so very sure if it's just the room. Also, there seems to be more sense of width -- but how do I even isolate that from the rest of the mix?

I recommended this track because to me it is brilliant in harmonic richness and hardly anything is mono in those bass lines. There are all kinds of modulation effects. You may see for yourself that there are all sorts of waves more or less square, so what comes to mind is that it's very system, room and setup dependent on how it would be reproduced. Try listening to it on your headphones and compare.

 

[Duke]

The main contributor of LF inter-aural distortion is the listening room.

In recreational sound, especially with stereo, such distortion may be considered benign, but it also limits the envelopment-range the room+system is able to convey; and limitations may be from both sides.

Thanks for participating in this thread.

What are the "distortions" contributed by the room, which degrade auditory envelopment, in this context? Frequency response anomalies? Reflection arrival times? In-room decay characteristics?

And, what part of the spectrum are you referring to here - just the bass region, or further up the spectrum as well?

 

[goryu]

Quick question for the experts here-

If I was to say use stereo infinite baffle subs, one in the middle of the front wall and one in the middle of the rear wall of my rectangular listening room from say 20-50Hz, and ob stereo subs from 50-100Hz in the middle of each of the side walls, would I see the advantages of the 4 mid wall sub arrangement that seemed to be one of the optimal arrangements of the literature, or do all subs need to be the same driver, same freq range, and mono?

I have read through several of the papers, etc., linked in this thread but didn't really find an answer to my question...thanks!

 

[dualazmak]

Can someone suggest a stereo music track where low bass spatialization (40-90Hz?) may be more obviously experienced if one's system setup is capable?

My single sub and bass management xo is unlikely optimal for this at all, to be honest, but I'm quite curious.

I use L&R subwoofers, heavy and large YAMAHA YST-SW1000, and frequently/periodically check my system by listening to my consistent "Audio Reference/Sampler Music Playlist", and several of the track within my "Playlist", especially the red-underlined posts in the spoiler below would be of your reference and interest, I assume; all of them are shared with 3D color spectrum (Fq-Gain-Time) by Adobe audition 3.0.1 (and some also with analysis by MusicScope 2.1.0), as well as YouTube links if available, even though I do not know the sound quality of your YouTube listening in your listening environments.

I shared my brief comments for each of the tracks including how I use the reference music track for checking bass sound covered by sub-woofers for the several "bass oriented" music tracks.

Spoiler

"Excellent Recording Quality Music Albums/Tracks for Subjective (and Possibly Objective) Test/Check/Tuning of Multichannel Multi-Driver Multi-Amplifier Time-Aligned Active Stereo Audio System and Room Acoustics; at least a Portion and/or One Track being Analyzed by Color Spectrum of Adobe Audition in Common Parameters:"
[Part-00] Introduction: #587
[Part-01] Full Orchestral Music: #588
[Part-02] Solo Piano Music: #590
[Part-03] Typical(?) Smooth Jazz Music with Guitar: #591
[Part-04] Bimmel Bolle Antique Orgel; Extremely High-Energy High-Frequency Sharp Transient sound: #592
[Part-05] Color Spectrum of Tracks in CBS/Sony's "Super Audio Check CD": #593
[Part-06] Female Vocal in Jazz and Popular Music, and One Male Vocal Track for Comparison: #596
[Part-07] Female Vocal and Counter Tenor in Early Classical Music: #639
[Part-08] (Smooth?) Jazz Trio: #640
[Part-09] Organ Music: #641
[Part-10] Lute Music: #642
[Part-11] Violin Music: #643
[Part-12] Cello Music: #644
[Part-13] Harpsichord (Cembalo, Clavecin) Music: #645
[Part-14] Piano Concertos: #650
[Part-15] Again, CBS/Sony's "Super Audio Check CD": Analyzed by Adobe Audition 3.0.1 and MusicScope 2.1.0: #651
[Part-16] A Cappella Chorus and A Cappella Vocal Ensemble: #652
[Part-17] Excellent Quality Music Tracks, But Containing Unacceptably High Gain Low-Frequency Air Conditioning Noises; What Counter Measures Can We Have? #658
[Part-18] An Interlude or Provisional Finale of the Post Series: #669
and,
Updated, the latest, Audio Sampler Playlist as of October 20, 2022: #670

This post would be also of your reference, I think:
- Reproduction and listening/hearing/feeling sensations to 16 Hz (organ) sound with my DSP-based multichannel multi-SP-driver multi-amplifier fully active stereo audio system having big-heavy active L&R sub-woofers: #782

Edit: This one (YouTube clip uploaded by myself) also... (ref. here)

 

[dualazmak]

Sorry to be out of the scope of this thread, but I also host this thread entitled "Music for Testing Treble (High Frequency) Sound"; your interests and participation will be highly welcome!

 

[ernestcarl]

Considering auditory envelopment (AE), don't focus on loudspeaker group delay. The main contributor of LF inter-aural distortion is the listening room.

In recreational sound, especially with stereo, such distortion may be considered benign, but it also limits the envelopment-range the room+system is able to convey; and limitations may be from both sides. Even pop recordings now include joyful AE contrasts that cannot be appreciated unless the listening room+system offers some degree of transparency.

I agree. But, your room caused "inter-aural distortion" does still end up manifesting itself there, too:

FDW 35

Bass arriving out of phase at the listening position

So riddle me this: The above graph shows the response at my listening position from my left speaker (red), right speaker (green) as well as the response of both playing at the same time (blue). All graphs use 1/12 octave smoothing for readability. Ignore the large null on the right channel...

www.audiosciencereview.com

To contrast, the in-room LF performance of my speakers as measured at the couch MLP (~2.3m distance) have quite a bit of a magnitude level imbalance due to wall reflections, yet are overall more symmetrical in time:

FDW 35

 

[ernestcarl]

I agree. But, your room caused "inter-aural distortion" does still end up manifesting itself there, too:

FDW 35

Bass arriving out of phase at the listening position

So riddle me this: The above graph shows the response at my listening position from my left speaker (red), right speaker (green) as well as the response of both playing at the same time (blue). All graphs use 1/12 octave smoothing for readability. Ignore the large null on the right channel...

www.audiosciencereview.com

Relatively simple inverse phase filters (created with REW and rePhase) that might "correct" at least some of the visible time domain imbalance measured at the MLP above:

FDW 35 cycles


Filters created via REW calculated excess phase inversion using FDW 15 cycles range at 30 to ~300Hz -- rePhase only above that range:

*Not much fine user control available in REW -- either way, there's still a risk of audible artifacts from too much "correction"

 

[Thomas Lund]

What are the "distortions" contributed by the room, which degrade auditory envelopment, in this context? Frequency response anomalies? Reflection arrival times? In-room decay characteristics?

And, what part of the spectrum are you referring to here - just the bass region, or further up the spectrum as well?

Thanks. I am using Auditory Envelopment (AE) solely about the sensation elicited by low frequency inter-aural fluctuations, so it is an elementary, perceptual definition narrower than Listener Envelopment (LEV) used in acoustical engineering. Over decades of research into reverb and spatialisation, we found AE to be one of the most important percepts of audio production and reproduction; to an extent listening testers started craving that particular quality.

“Distortion” in this context is therefore any influence during distribution or reproduction that changes potential AE, i.e. prevents it from reaching a listener. Overall frequency response is not so important, if it is reasonably smooth, and it extends to 50 Hz, individually per channel. In a small room, LF stasis between 40 and 700 Hz because of room modes (see earlier comments on movement) is generally the main enemy. A large room, however, may blur or even replace potential AE with a certain time-domain signature of its own.

Considering reproduction, deliberate acoustical treatment can help reduce AE-destructive modes of a (small) room. It can also be effective when the listening room is imposing its own time-domain signature, washing out AE contrasts in the content. Control of loudspeaker directivity below 700 Hz, or moving closer to lhe loudspeakers when monitoring, may also help.

 

[sigbergaudio]

Quick question for the experts here-

If I was to say use stereo infinite baffle subs, one in the middle of the front wall and one in the middle of the rear wall of my rectangular listening room from say 20-50Hz, and ob stereo subs from 50-100Hz in the middle of each of the side walls, would I see the advantages of the 4 mid wall sub arrangement that seemed to be one of the optimal arrangements of the literature, or do all subs need to be the same driver, same freq range, and mono?

I have read through several of the papers, etc., linked in this thread but didn't really find an answer to my question...thanks!

Several subs give you two benefits, increased capacity, and more even response. When your subs don't overlap, you essentially don't get either. So not an ideal setup.

 

[youngho]

Several subs give you two benefits, increased capacity, and more even response. When your subs don't overlap, you essentially don't get either. So not an ideal setup.

@goryu 's situation is rather more complicated, so I replied to him directly, but in essence the front and rear wall IB subwoofers would not be really stereo but mono (though in theory could set up as bass array or souce-sink), so could potentially (depending on specifics such as room construction details like locations of doors and windows, listener position) get the benefits of two mid-wall subwoofers. The two side OB (open baffle) subwoofers would be more complicated, since would depend very much on orientation of drivers, also listener position (I included Linkwitz page on dipole bass, since I didn't really know much about this).

 

[goryu]

If I had mono IB subs in front and rear wall from 20Hz to 50Hz and had stereo subs (slot loaded bass ob or slot loaded TL) on the two side walls at 50-80Hz, I wouldn't get that tiny improvement that 4 subs operating over the same region would give but it seems that 2 subs placed front and back gives most of what 4 subs do, and having the side wall subs would add a bit more even though they don't operate over the same range. Seems I would still get about 90%+ of the benefits, no?

 

[sigbergaudio]

If I had mono IB subs in front and rear wall from 20Hz to 50Hz and had stereo subs (slot loaded bass ob or slot loaded TL) on the two side walls at 50-80Hz, I wouldn't get that tiny improvement that 4 subs operating over the same region would give but it seems that 2 subs placed front and back gives most of what 4 subs do, and having the side wall subs would add a bit more even though they don't operate over the same range. Seems I would still get about 90%+ of the benefits, no?

Are they different types of subs, or why don't you want all to operate 20-80hz?

 

[goryu]

They are different types. IB's are Acoustic Elegance 18" drivers which can handle that range. The drivers I want to use on the sides are 8" drivers in a slot loaded bass array, 10 per side. They won't play down to 20Hz. I might get mid 30's out of them. Originally I planned to place them next to a set of planar panels and run them up to 200Hz or so but now I am going to buy a set of electrostatic panels that play down to 50Hz or so, thus thought about using them on the sides of the room.

 

[Matthew J Poes]

Thanks! The article only references older material from even before 2012, and I still don't think that the discussion should be so binary as "To set up for stereo bass or to setup for proper bass management; that is the choice in front of us. Unfortunately, it is not possible to have both." Such statements are unnecessarily reductive.

For example, two mid-sidewall subwoofers are likely to provide good MSV for a variety of seating configurations as noted in the two Welti investigations. Looking at Figure 8.18 in the third edition of Sound Reproduction, where Toole discusses the Welti 2012 results, left-right midpoints or LRM performed almost identically with front-back midpoint or FBM setups in most seating configurations, barely worse in small centered SC and large center modified LCM setups, yet identically with 4 corner subwoofers in SC and better in LCM).

Stereo bass setups can still "provide proper bass management" for home theater and the majority of pop music, whenever mono bass content is present since all the benefits of mono subwoofers would accrue even with stereo subwoofers in such situations. Poes himself writes, "In general, low frequencies in most recordings are highly correlated, meaning monophonic," so setting up for stereo bass does not necessarily mean "improper" bass management as his first quoted sentence implies.

p.s. Poes: "[Bassiousness] creates a shift from sounding like it is in your head to arrival from all around you." This sounds suspiciously (or exactly) like the concept of envelopment and consistent with what was written by Griesinger, @j_j ("bass spread around a room"), and @Thomas Lund ("envelopment," "swirling LF patterns").

It is an older article so of course it references older material. It was inspired by a years worth of experimentation with David specifically to hear this effect, as I had been unfamiliar with the concept before talking with him. However, I walked away more unimpressed than anything.

It is not possible to place side subwoofers as you mention and still use Welti's approach. Welti's approach relies on a summed mono subwoofer signal. My point was you can't have both, because you can't. You could certainly have multiple setups and presets if your system allowed that.

But in my listening tests, I had the exact same experience the Harman guys did with David. He explaiend it as if it was extremly easy to hear and recreate. With headphones, that was true to a point (but I have to say, even after I learned to recognize it, I found it hard to hear with actual content much of the time). Once we moved to speakers, I could no longer hear it. Which is exactly what happened to Welti, Toole, and Olive. All three walked away completely unimpressed and feeling the effect was largely inaudible and unimportant. I walked away feeling that the effect was audible in the right circumstances, but too much of the music I listen to day to day did not have the recording style needed for it to be produced.

 

[Matthew J Poes]

First, the name you've given that is horrid.

Second, rather above, I've provided a simple experiment for you to try, and the effect will emerge. While there are better ways to do this, try just slowly turning the relative phase in headphones (either sine, or better narrowband noise) up from zero, slowly. (that at 50Hz for a decent example)

Just try it.

I'm sorry you dislike this term so much, but it was a term adopted by Welti and used widely at the time I was researching this. David expressed no similar concerns with the term, in fact he quite liked it as I recall.

 

[Matthew J Poes]

I'm afraid that that article does not really understand envelopment in any number of ways.

What's more, "either this OR that" is utterly wrong. Sometimes you want "this" and sometimes you want "that". It's a choice that can easily be done AT THE PRODUCTION END if the room is properly set up.

You don't want to support the modes in the listening room, you DO want to support the modes in the intended RECORDING space. There's so many things mixed together in that article I hardly know where to start.

The article was thoroughly peer reviewed by David, Todd, and Floyd. Some changes were made to my description of how we percieve envelopment based on feedback from Floyd and David, but overall they had no concerns with my description. I am not sure what I got wrong.

As for this or that, even David agreed, but mabye you aren't understanding the two bass management approaches being presented? Todd's approach (which Geddes also favors) and is the industry standard approach to bass management, sums the bass signal to mono. That is then distributed, as a mono signal, to all subwoofers. As such, any phase variation between channels in the bass is summed and lost. That is in fact necessary for Todd's approach to work. Maintaining a stereo bass signal is not possible in most bass management systems and recreating what David wanted me to recreate requried use of a customized setup to the bass management. Testing of the seat to seat consistency and bass smoothness showed that Welti's approach did a far better job than maintaining a stereo bass setup. So I concluded rightly that it is a choice of one or the other. You can argue that the seat to seat consistency is not important or that bass smoothness is not important, but that doesn't eliminate the conclusion I drew.

I tested this fairly thoroughly with David's help using both contrived test tracks and music. I also used a ton of music I had been listening to and both David and I analyzed a lot of those tracks. We found that virtually no current music had stereo bass of any kind meaning there is no phase variation in low frequencies. You can point to classical or live natural music, but that isn't what most people listen to and it is not the majority of music right now. So ultimately I found it not even useful for new music. With older music, it was a mixed bag. Sometimes it was there and sometimes it wasn't. With the music halls (which again, is a very small portion of the music people listen to now), it was only ever audible with music supplied to me by David and it was extremly subtle, easily disturbed, and not obviously better.

 

[youngho]

It is an older article so of course it references older material. It was inspired by a years worth of experimentation with David specifically to hear this effect, as I had been unfamiliar with the concept before talking with him. However, I walked away more unimpressed than anything.

Your article was dated 2020 on the Audioholics website. The referenced material was 2005-2008.

It is not possible to place side subwoofers as you mention and still use Welti's approach. Welti's approach relies on a summed mono subwoofer signal. My point was you can't have both, because you can't. You could certainly have multiple setups and presets if your system allowed that.

1. One mid-wall subwoofer on the left wall, one mid-wall subwoofer on the right wall. This is consistent with Welti's approach from both of his papers, as previously noted.
2. In the quote below, you write that "virtually no current music had stereo bass of any kind meaning there is no phase variation in low frequencies" (which may be a bit at odds with what a senior technologist at Genelec reported). Can you please explain the difference in the signal received by the left subwoofer and that by the right subwoofer in a situation where the subwoofers are set up for potential stereo but receive signal where there is no stereo bass "of any kind", or does each subwoofer receive the equivalent of mono even without summing to mono? I was assuming the latter, but please educate me.
3. There's also the situation of home theater, where presumably the LFE content sent to "stereo subwoofers" set up as I described ends up being dual mono in reproduction, so still gets the benefits a la Welti

lot of those tracks. We found that virtually no current music had stereo bass of any kind meaning there is no phase variation in low frequencies. You can point to classical or live natural music, but that isn't what most people listen to and it is not the majority of music right now. So ultimately I found it not even useful for new music. With older music, it was a mixed bag. Sometimes it was there and sometimes it wasn't. With the music halls (which again, is a very small portion of the music people listen to now), it was only ever audible with music supplied to me by David and it was extremly subtle, easily disturbed, and not obviously better.

I listen to classical music, and my very first post https://www.audiosciencereview.com/forum/index.php?threads/bass-and-subwoofers.51589/#post-1857133 indicated that my interest in this topic was relevant to concert hall acoustics. I also think it's possible that different people may have different sensitivity to this effect, in a similar way that different people can have different sensitivity to lateral reflections or even pitch.

 

[Matthew J Poes]

Your article was dated 2020 on the Audioholics website. The referenced material was 2005-2008.

1. One mid-wall subwoofer on the left wall, one mid-wall subwoofer on the right wall. This is consistent with Welti's approach from both of his papers, as previously noted.
2. In the quote below, you write that "virtually no current music had stereo bass of any kind meaning there is no phase variation in low frequencies" (which may be a bit at odds with what a senior technologist at Genelec reported). Can you please explain the difference in the signal received by the left subwoofer and that by the right subwoofer in a situation where the subwoofers are set up for potential stereo but receive signal where there is no stereo bass "of any kind", or does each subwoofer receive the equivalent of mono even without summing to mono? I was assuming the latter, but please educate me.
3. There's also the situation of home theater, where presumably the LFE content sent to "stereo subwoofers" set up as I described ends up being dual mono in reproduction, so still gets the benefits a la Welti

I listen to classical music, and my very first post https://www.audiosciencereview.com/forum/index.php?threads/bass-and-subwoofers.51589/#post-1857133 indicated that my interest in this topic was relevant to concert hall acoustics. I also think it's possible that different people may have different sensitivity to this effect, in a similar way that different people can have different sensitivity to lateral reflections or even pitch.

1) Welti's approach requires sending a mono signal to all subwoofers. Yes a mid wall placement is consistent with one of his setups, but it must recieve a mono signal to work. Soundfield management is contingent on the input to the DSP being mono. Same for MSO. Same for Geddes approach. So they all take this stereo bass signal and sum it to mono.
2) My comment is specific to current as in pop music, not classical or audiophile music. When David and I went down this road, he was telling me that tons and tons of modern music could be used. But when he analyzed music tracks I sent him, none of them had stereo bass. They all summed to mono at some point, say 100 to 200hz. So he kept tellingme that those tracks wouldn't work. What he told me at the time was that he had developed at lexicon a reverb unit that produced the desired effect, but that when it had been ported to digital, that was left out. That he was very disappointed in that fact. Same for Logic7. He also mentioned that he thinks the workflow in modern studios had simply moved to summing bass to mono. So to your question, per my understanding, while the subs are setup to be able to receive a stereo bass signal, they will simply get a mono signal, each sub gets a fully coherent signal.
3) LFE is only one of the bass sources in a home theater. The mains are also bass managed and so for Welti's trick to work you need to sum all to mono and treat accordingly. The SFM and MSO approach takes the mono signal and then sends it as a discrete signal to each sub. Sub 1, 2, 3, and 4, for example. Each sub is given different EQ, delay, and level in order to create a more consistent LF soundfield across a larger spatial area. That summed signal isn't flat, so a final mono EQ profile is applied to all four subs to give a flat response (or whatever shape you desire). If you send that same setup a non-mono LF signal, what comes out would be a mess of any non-coherent LF signals.

I believe this is actually extremly important for classical or natural acoustic music. It could be very important for all music, but sadly, nobody who matters cares. The entire recording industry is not interested in this. They ruined David's beautiful Lexicon reverb unit and paid no attention to the effect. So my arguement really was that for people who listent to modern/current rock, rap, techno, and pop, this probably isn't useful. For those who listen to classical, jazz, etc. and who desire to accurately reproduce the sound you get in a concert hall, it's quite important and shouldn't be ignored (but then again, the type of recording of the concert hall is really important, David found that most of my classical recordings were not acceptable). I did this 7 years ago (the article was published long after I wrote it and even longer after I did the work, because my results were lack luster, I spent a lot of time with David and Todd trying to figure out a viable next step, before Gene asked me to just publish what I had). I don't even have the old data anymore, but I recall that I tested (and David similarly tested) dozens of albums. I think for classical alone, something like 20-30 seperate albums that I thought might be good were tested, and of those, only 5-6 turned out to be any good. David told me the problem was the microphone technique they used. If I were to provide a subjective impression of the sound of those recordings, the ones that turned out to be "good" were the ones that had the lowest direct to reflected sound and captured the revberberant sound of the space the most. One of those recordings I had heard when it was recorded, it was a saxaphone and Organ in a Church. What I heard in real life and what I heard in the final recording never jived. I would guess that our brains ability to ignore these reflections (the precedence effect) made it sound more "direct" in real life than in the recording, where such cues are obfuscated in the recording.

 

[youngho]

1) Welti's approach requires sending a mono signal to all subwoofers. Yes a mid wall placement is consistent with one of his setups, but it must recieve a mono signal to work. Soundfield management is contingent on the input to the DSP being mono. Same for MSO. Same for Geddes approach. So they all take this stereo bass signal and sum it to mono.
2) My comment is specific to current as in pop music, not classical or audiophile music. When David and I went down this road, he was telling me that tons and tons of modern music could be used. But when he analyzed music tracks I sent him, none of them had stereo bass. They all summed to mono at some point, say 100 to 200hz. So he kept tellingme that those tracks wouldn't work. What he told me at the time was that he had developed at lexicon a reverb unit that produced the desired effect, but that when it had been ported to digital, that was left out. That he was very disappointed in that fact. Same for Logic7. He also mentioned that he thinks the workflow in modern studios had simply moved to summing bass to mono. So to your question, per my understanding, while the subs are setup to be able to receive a stereo bass signal, they will simply get a mono signal, each sub gets a fully coherent signal.

Yes, this was my point I was trying to make. A stereo subwoofer setup along the lines of what I described will still get mono much of the time, as in pop music and home theater LFE, so one can set up stereo subwoofers but still get the benefits of Welti's approach whenever the bass content is mono. Welti's approach relies on a number of different phenomena, so the mid-wall positioning will presumably place the subwoofers in the node of the first-order length mode (odd-order length modes) , while the symmetry with respect to relatively central listening positions will result in so-called "mode cancellation" of the odd-order width modes when coherent signal (whether this occurred during production or is done in the bass management system) is supplied to each. Obviously, one would lose the benefits of "mode cancellation" when stereo bass content is present, but that's exactly the mechanism by which Griesinger proposed the lateral asymmetric (first-order width) mode (edit: odd-order width modes) creating a pressure gradient at the listening position, so the frequency response would be expected to show a relative null (and thus would lose SOME of the benefits of a Welti-style setup).

Griesinger did make a comment in the 2018 publication I linked that revisiting this topic since 2005 had been interesting and humbling.

3) LFE is only one of the bass sources in a home theater. The mains are also bass managed and so for Welti's trick to work you need to sum all to mono and treat accordingly. The SFM and MSO approach takes the mono signal and then sends it as a discrete signal to each sub. Sub 1, 2, 3, and 4, for example. Each sub is given different EQ, delay, and level in order to create a more consistent LF soundfield across a larger spatial area. That summed signal isn't flat, so a final mono EQ profile is applied to all four subs to give a flat response (or whatever shape you desire). If you send that same setup a non-mono LF signal, what comes out would be a mess of any non-coherent LF signals.

Yes, I wasn't really addressing MSO/SFM at all, only the specific setup I had described. Again, however, one would expect the subwoofers to receive a mono LF signal much of the time (all of the LFE content in home theater, pop music).

I believe this is actually extremly important for classical or natural acoustic music. It could be very important for all music, but sadly, nobody who matters cares. The entire recording industry is not interested in this. They ruined David's beautiful Lexicon reverb unit and paid no attention to the effect. So my arguement really was that for people who listent to modern/current rock, rap, techno, and pop, this probably isn't useful. For those who listen to classical, jazz, etc. and who desire to accurately reproduce the sound you get in a concert hall, it's quite important and shouldn't be ignored (but then again, the type of recording of the concert hall is really important, David found that most of my classical recordings were not acceptable). I did this 7 years ago (the article was published long after I wrote it and even longer after I did the work, because my results were lack luster, I spent a lot of time with David and Todd trying to figure out a viable next step, before Gene asked me to just publish what I had). I don't even have the old data anymore, but I recall that I tested (and David similarly tested) dozens of albums. I think for classical alone, something like 20-30 seperate albums that I thought might be good were tested, and of those, only 5-6 turned out to be any good. David told me the problem was the microphone technique they used. If I were to provide a subjective impression of the sound of those recordings, the ones that turned out to be "good" were the ones that had the lowest direct to reflected sound and captured the revberberant sound of the space the most. One of those recordings I had heard when it was recorded, it was a saxaphone and Organ in a Church. What I heard in real life and what I heard in the final recording never jived. I would guess that our brains ability to ignore these reflections (the precedence effect) made it sound more "direct" in real life than in the recording, where such cues are obfuscated in the recording.

Thanks for the details on history of publication--unfortunately, this wasn't evident on the Audioholics web page.

What programs were helpful in analyzing for stereo bass content? Thanks!