Stereo Bass using subwoofers

[Soundmixer]

Those who deny localization of LF have a much bigger hurdle to jump over then just quoting someone else's study or statement, and until they have a good enough DSP or enough data to form an opinion based on actual testing then their opinion while important isn't in the same category.

Okay, you don't seem to understand this at all. This is not about DSP's, this is how our hearing functions. Todd Welti of Harman has already conducted tests on this (so did Martens both published on it in 2004), and the statistical data pointed to our ears being able to detect stereo beginning at MID-BASS frequencies, or 80hz and up. That also happens to be the threshold of localization for subwoofers as well. So this my friend, is not opinion, it is research and data.

Those who hear a difference must not be "shouted down" to say they're wrong. I started this 7 week journey believing all the statements against localization and my mind was changed when every single set up had unique qualities and feel of localization effecting the whole sound stage.

People hear what they want. When you objectively blind test what they hear, most if not all differences disappear. Having participated in enough sighted and double-blind testing, I can personally attest to that. On this particular subject matter, double-blind testing was used to erase any subjectivity from the test, and the results do not agree with your assertions. Now if you have some published work gleaned from your 7 weeks of study, tests, and data gleaned from it, please present it here. What you are presenting here so far is an opinion not supported by science.

If running stereo subs the closer they are to mains will give a tighter sound stage

Correction, two subs. The subs have little to do with the soundstage, but putting them closer to the mains does make it easier to integrate them.

Stereo subwoofers to the sides creates an immersive experience like being on the stage of a concert instead of looking to the stage.

Two subs to the sides do increase the immersive experience, but the feeling of being on the stage of concerts comes from localization cues far above subwoofer territory.

Mono subs for more energy
Stereo subs for realism

This is opinion....untested opinion. This is not science either way.

Stereo subs if you can achieve balanced response in room
Mono subs if you can't (this will smooth out any stereo/panned content)

Two spaced subs will reduce seat to seat variations across one row of seats. Since there is no detectable stereo at bass frequencies, the rest of your comment is an air sandwich.

 

[Soundmixer]

I might add that with the specific type of music I listen to and record a lot, large pipe organs in large churches, there can be plenty of random phase information down to below 20Hz, and this can include low frequency 'room tone'. This is particularly true with the microphone setups I use with antiphonal organ ranks. This is usually 3 spaced omni microphones in front and 2 or 3 spaced omnis near the rear of the chruch with the spacing from the front mics to the rear mics usually 50 feet or so. This can introduce lots of random low frequency time/phase information which is preserved in the listening room (especially mine which is quite large) when using stereo subwoofers, but would be totally lost with mono subwoofers.

I understand the effect you are talking about, it has the effect of adding spaciousness to these particular types of recordings. The real issue here is if you can hear the difference between this out-of-phase information in two separate channels and the same information summed to a single sub at a low crossover point? Double-blind, I doubt it because of the lack of sensitivity our ears have at low frequencies. As you drop from the mid-bass downwards, our hearing system becomes less and less sensitive to phase and frequency.

 

[MakeMineVinyl]

I understand the effect you are talking about, it has the effect of adding spaciousness to these particular types of recordings. The real issue here is if you can hear the difference between this out-of-phase information in two separate channels and the same information summed to a single sub at a low crossover point? Double-blind, I doubt it because of the lack of sensitivity our ears have at low frequencies. As you drop from the mid-bass downwards, our hearing system becomes less and less sensitive to phase and frequency.

I don't know what your goal is here or what you are trying to 'prove', or you own experience level for that matter. I am far far from a novice, and frankly if you don't believe what I am saying, I don't care. Sorry to be blunt, but that's the way it is.

 

[Pdxwayne]

Okay, you don't seem to understand this at all. This is not about DSP's, this is how our hearing functions. Todd Welti of Harman has already conducted tests on this (so did Martens both published on it in 2004), and the statistical data pointed to our ears being able to detect stereo beginning at MID-BASS frequencies, or 80hz and up. That also happens to be the threshold of localization for subwoofers as well. So this my friend, is not opinion, it is research and data.


People hear what they want. When you objectively blind test what they hear, most if not all differences disappear. Having participated in enough sighted and double-blind testing, I can personally attest to that. On this particular subject matter, double-blind testing was used to erase any subjectivity from the test, and the results do not agree with your assertions. Now if you have some published work gleaned from your 7 weeks of study, tests, and data gleaned from it, please present it here. What you are presenting here so far is an opinion not supported by science.

Correction, two subs. The subs have little to do with the soundstage, but putting them closer to the mains does make it easier to integrate them.



Two subs to the sides do increase the immersive experience, but the feeling of being on the stage of concerts comes from localization cues far above subwoofer territory.


This is opinion....untested opinion. This is not science either way.


Two spaced subs will reduce seat to seat variations across one row of seats. Since there is no detectable stereo at bass frequencies, the rest of your comment is an air sandwich.

Are there links for the studies you mentioned?
Quote:
"Todd Welti of Harman has already conducted tests on this (so did Martens both published on it in 2004)"

 

[GimeDsp]

Are there links for the studies you mentioned?
Quote:
"Todd Welti of Harman has already conducted tests on this (so did Martens both published on it in 2004)"

The only study i found doe todd wenti DID NOT look at stereo subs and all his claims of non localization have no references, strange considering other claims have references.

Welti disnt test stereo bass and has makes weakly supported claims as proof.

https://www.harman.com/documents/multsubs_0.pdf

 

[MakeMineVinyl]

The only study i found doe todd wenti DID NOT look at stereo subs and all his claims of non localization have no references, strange considering other claims have references.

Welti disnt test stereo bass and has makes weakly supported claims as proof.

https://www.harman.com/documents/multsubs_0.pdf

As is usual with a lot of these types of studies, the authors make no attempt to dig as deeply as necessary, and instead rely on 'well this doesn't matter' and call it a day. That's just sloppy research. More specifically, did any of them even try to replicate the kind of recordings I make, or did they even consider that exceptions might exist to the conventional wisdom? My suspicion is 'of course not'.

 

[GimeDsp]

The only study i found doe todd wenti DID NOT look at stereo subs and all his claims of non localization have no references, strange considering other claims have references.

Welti disnt test stereo bass and has makes weakly supported claims as proof.

https://www.harman.com/documents/multsubs_0.pdf

Since Welti DIDN'T test ANY stereo sub config, makes a majority of unsabstationated claims, and only supplies 1 reference to his claims I am hunting them down for all our benifit.

I have found the article but it is not in orignal pub. so Weltis page reference may not point us to his sources.

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

I WILL BE ADDING to this post so refer back to it.
It seems all of Welti's claims HAVE NO references, are unsabstationated, and his ONLY REFERENCE IS IN FAVOR of localization!

I will post excerpts from the paper Welti referenced about localization

"Figure 11: The Normalized Average Pressure in a 12’x15’x9’ room in the 63Hz octave band from a single driver in the top left corner. Figure 12: Lateral AITD in a 12’x15’x9’ room, surface reflectivity 0.8, single driver in the top left corner, 63Hz octave band. This band has the largest AITD for this speaker position in this room. The next figure is more typical. Figure 13:

The Lateral AITD over a range of 20Hz to 90Hz in a 12’x15’x9’ room from a single driver in the front left corner. Surface reflectivity is 0.8. The medial AITD for the 12’x15’ rooms is plotted in figure 14. Unlike the room of figure 7, this room shows a substantial forward localization. The difference is significant. The medial AITD represents the lateral AITD for a listener who is facing the long wall of the room. If we decided to set our stereo system along the long wall rather than along the short wall, the lateral AITD would be much higher. The difference shown here has some historical significance.
​

So to sum up, Welti DIDN'T do any tests and the only reference he has to stereo bass is from an author who supports localiztion.

 

[GimeDsp]

More from Source: His main claim

"In audio as in life there is no free lunch, but it is possible that by moving the driver to the side of the room we could increase the lateral AITD at the expense of the medial AITD. Figures 15 – 19 show that this works rather well. Putting the LF driver to the side causes much the same type of increase we saw in the 12’x15’ room when the listener faced the long wall. The low frequencies become external, and tend to localize in the direction of the driver. In practice this means the low frequencies shift from inside the head to the side of the room. Whether this perception will be preferred depends on your expectations. In practice, the sense of externalization is much stronger than the sense that the low frequencies are coming from the side. One is not particularly aware of where the low frequencies are coming from, but at least they are external."

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

Now please lets all leave the TEXT walls behind and instead of shouting down people's opinions, lets just agree our perception matters, and that there is a great body of evidence and proof supporting localization.

"One is not particularly aware of where the low frequencies are coming from, but at least they are external."

As stated, an accurate system will convey the spatial data recorded or encoded. Localization will be as accurate as in real life. In real life a bass drum, floor tom, or bass amp is NEVER as localizable as a screeching electric guitar lead or hi hat cymbal. Also as stated the contents panned/stereo LF content must be taken into consideration for ANY claims and if it is not then the outcome and opinions carry much less weight.

LF sounds are almost always complex (CLint eastwood has a 40hz sign wave on the course, but that's rare)

Vague LF localizing
More precise 80-120hz spatial info
combined with very prices12-250hz data

All combine with bone conduction and structure born vibration tell use wear a kick drum, floor tom, and bass guitar is located.

 

[MakeMineVinyl]

More from Source: His main claim

"In audio as in life there is no free lunch, but it is possible that by moving the driver to the side of the room we could increase the lateral AITD at the expense of the medial AITD. Figures 15 – 19 show that this works rather well. Putting the LF driver to the side causes much the same type of increase we saw in the 12’x15’ room when the listener faced the long wall. The low frequencies become external, and tend to localize in the direction of the driver. In practice this means the low frequencies shift from inside the head to the side of the room. Whether this perception will be preferred depends on your expectations. In practice, the sense of externalization is much stronger than the sense that the low frequencies are coming from the side. One is not particularly aware of where the low frequencies are coming from, but at least they are external."

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

Now please leave the TEXT walls behind and instead of shouting down people opinions, lets just agree our perception matters, and that there is a great body of evidence and proof supporting localization.

"One is not particularly aware of where the low frequencies are coming from, but at least they are external."

As stated, an accurate system will convey the spatial data recorded or encoded. Localization will be as accurate as in real life. In real life a bass drum, floor tom, or bass amp is NEVER as localizable as a screeching electric guitar lead or hi hat cymbal. Also as stated the contents panned/stereo LF content must be taken into consideration for ANY claims and if it is not then the outcome and opinions carry much less weight.

Not to mention that at very low frequencies and relatively high amplitudes, your body can bloody well feel where these low frequencies are coming from even as the ears become less sensitive to localization.

 

[Pdxwayne]

Not to mention that at very low frequencies and relatively high amplitudes, your body can bloody well feel where these low frequencies are coming from even as the ears become less sensitive to localization.

Yeah, I call this butt feels.

: )

 

[GimeDsp]

https://audioroundtable.com/misc/Welti_Multisub.pdf

 

[GimeDsp]

edited-to remove commentary and focus on facts.


Welti's logical position has flaws. He discounts a study that showed localization because it was done in an anechoic chamber and thats not "real life scenario, then he touts a study showing no localization under 80hz that uses pink noise.

Just as an anechoic chamber doesn't represent real World so do tests using non music material have no bearing.

Welti also promotes the incorrect generalization that "it doesn't matter because almost all popular music has mono bass"
this statement is inaccurate and its generality excludes it from supporting a specific claim.
"Majority of popular music is has LF summed to mono"
Popular like top 100 or popular within genre?
Broad claims require precise language.

Regardless, I can not find any example where welti actually tested stereo LF, and his summary even shows he didn't.

 

[DonH56]

Todd Welti has a number of papers, as do others, but most of the papers I found are on the AES site and are not free unless you are a member. There are bunch of them, some going either way. I have not been a member for years so can't see anything but the titles and some abstracts.

Whenever someone denigrates a(nother) researcher, right or wrong, it is nice to know the credentials of the naysayer.

 

[MakeMineVinyl]

Todd Welti has a number of papers, as do others, but most of the papers I found are on the AES site and are not free unless you are a member. There are bunch of them, some going either way. I have not been a member for years so can't see anything but the titles and some abstracts.

Whenever someone denigrates a(nother) researcher, right or wrong, it is nice to know the credentials of the naysayer.

Just real world experience is sometimes enough - there is nothing golden about 'researchers', and they are subject to the same biases all of us are, and can make the same mistakes. I've done enough research myself to know the fallacy in assuming that all research is beyond questioning.

 

[DonH56]

Just real world experience is sometimes enough - there is nothing golden about 'researchers', and they are subject to the same biases all of us are, and can make the same mistakes. I've done enough research myself to know the fallacy in assuming that all research is beyond questioning.

Agreed, but I like to know a little something about the questioner when going against established dogma. I admit to being biased and jaded from the trumpet forum I help moderate -- we get high school kids coming across as experts and running off players with decades of high-level experience because it isn't worth their time to debate kids (or armchair adults) with keyboards and lots of time.

 

[MakeMineVinyl]

Agreed, but I like to know a little something about the questioner when going against established dogma. I admit to being biased and jaded from the trumpet forum I help moderate -- we get high school kids coming across as experts and running off players with decades of high-level experience because it isn't worth their time to debate kids (or armchair adults) with keyboards and lots of time.

Just watch out for that one obnoxious kid who will go on to be the world's best trumpeter.

 

[andyc56]

Todd Welti has a number of papers, as do others, but most of the papers I found are on the AES site and are not free unless you are a member.

This file contains an AES paper by Welti called "Subjective Comparison of Single Channel versus Two Channel Subwoofer Reproduction."

 

[GimeDsp]

Todd Welti has a number of papers, as do others, but most of the papers I found are on the AES site and are not free unless you are a member. There are bunch of them, some going either way. I have not been a member for years so can't see anything but the titles and some abstracts.

Whenever someone denigrates a(nother) researcher, right or wrong, it is nice to know the credentials of the naysayer.

I do not believe there was any degradation, but since you may have thought I did I have hopefully removed it from the post.
The "fallacy of expertise"

People are using Welti as a source to disprove stereo LF/localization and Welti himself declares he did no investigate it. that is the most illogical position to take and anyone with the most basic understanding of logic knows that.

"Pizza tastes horrible because Bob says so."
"Has Bob tasted pizza"
"No, but he knows someone who has, and bobs an expert on food"

EDIT_ thankfully a Welti paper in regards to stereo subs has been provided.
"Subjective Comparison of Single Channel versus Two Channel Subwoofer Reproduction."

 

[GimeDsp]

This file contains an AES paper by Welti called "Subjective Comparison of Single Channel versus Two Channel Subwoofer Reproduction."

Thanks! I was looking for Martens and only found martinis.

 

[Pdxwayne]

This file contains an AES paper by Welti called "Subjective Comparison of Single Channel versus Two Channel Subwoofer Reproduction."

From the paper:
.....
Audible differences for music signals were found only for the comparison of single channel front center subwoofer vs. two channel subwoofers at +/- 90 degrees. This was not surprising, as it is hard to conceive of a more extreme comparison in terms of spatial information conveyed to the listener.
..........

Enough said, right? I was saying difference between a single sub on the front (a bit to the right) vs stereo subs is audible in my living room. Then someone keep arguing that it is not possible...... using the same researcher as his proof!

Not only that, the author said this:
.....
Significant results were found in all cases for the contrived stimulus. This suggests that for certain signals, differences between any of the subwoofer configurations are likely to be audible, however, signals such as modulated warble tones are unlikely to occur with any frequency in typical program material.
...........
Did he ever heard of electronica music?
Yes, I listen to lots of them.....