Stereo Bass using subwoofers

[MakeMineVinyl]

Other than me, there are at least 3 other people in this thread who can hear directivity with stereo subs. So, why not have the curiosity to say to yourself, maybe a certain artificial bass tones indeed can show directivity?

Are you able to try the same tests as mentioned in post above?

I wouldn't call the presence of low bass on one subwoofer channel only "artificial". In my pipe organ recordings using widely spaced microphones, the random phase mixing and cancellations due to the microphones at distances >25' can and certainly does cause dynamically changing nulls depending on the notes being played, causing some bass frequencies to almost entirely come from only one of the two subwoofer channels at various times. The fact that these phase relationships are not static and dynamically changing makes their ability to be sensed (NOTE THAT I DID NOT SAY "HEARD" IN THE TRADITIONAL SENSE!) easier.

Now my question to the esteemed experts here - did you perform this exact test, using this exact exact program material, and more to the point, on my system in my room? If you did, I sure didn't see you, and if you were in my room without my knowledge, I'm calling the police.

The point is, a phenomenon only has to occur once to prove that it can indeed happen.

If some people here don't buy into the stereo subwoofer thing, fine DON'T USE THEM! But it is inconsiderate to the extreme to insist that other people aren't sensing things that they clearly are. Enjoy your preferred setup, but please don't insult the intelligence of people (and very qualified people like me) and insist that we somehow have to "prove" our ability to sense something or it isn't valid. Frankly I don't give a damn if you believe me or not. I'm too old for this shit.

To each his own. Have a nice day.

 

[Pdxwayne]

I wouldn't call the presence of low bass on one subwoofer channel only "artificial". In my pipe organ recordings using widely spaced microphones, the random phase mixing and cancellations due to the microphones at distances >25' can and certainly does cause dynamically changing nulls depending on the notes being played, causing some bass frequencies to almost entirely come from only one of the two subwoofer channels at various times. The fact that these phase relationships are not static and dynamically changing makes their ability to be sensed (NOTE THAT I DID NOT SAY "HEARD" IN THE TRADITIONAL SENSE!) easier.

Now my question to the esteemed experts here - did you perform this exact test, using this exact exact program material, and more to the point, on my system in my room? If you did, I sure didn't see you, and if you were in my room without my knowledge, I'm calling the police.

The point is, a phenomenon only has to occur once to prove that it can indeed happen.

If some people here don't buy into the stereo subwoofer thing, fine DON'T USE THEM! But it is inconsiderate to the extreme to insist that other people aren't sensing things that they clearly are. Enjoy your preferred setup, but please don't insult the intelligence of people (and very qualified people like me) and insist that we somehow have to "prove" our ability to sense something or it isn't valid. Frankly I don't give a damn if you believe me or not. I'm too old for this shit.

To each his own. Have a nice day.

If you have time, would you please try ABX files 9 and 10? Link to download is mentioned in

Stereo Bass using subwoofers

OK. Just done with stereo subs ABX. Subs are Paradigm Seismic 110 (10 inch sealed subs with 800 Watts RMS capability). Both subs eq using multiple microphone position to handle room modes. Subs about 12 ft away from my seat. Subs on front wall ~10 ft apart. Room is living room, about 5000+...

www.audiosciencereview.com

I know that we have different subs and room, so I am curious if that makes any difference at all. For my setup and room, it was very easy. It would be nice to have another abx result here.

Thanks!

 

[MakeMineVinyl]

If you have time, would you please try ABX files 9 and 10? Link to download is mentioned in

Stereo Bass using subwoofers

OK. Just done with stereo subs ABX. Subs are Paradigm Seismic 110 (10 inch sealed subs with 800 Watts RMS capability). Both subs eq using multiple microphone position to handle room modes. Subs about 12 ft away from my seat. Subs on front wall ~10 ft apart. Room is living room, about 5000+...

www.audiosciencereview.com

I know that we have different subs and room, but it would be nice to have another abx result here.

Thanks!

Honestly, time is kind of tight these days, so I'm going to have to take a pass on that. Actually I haven't had time to fire up my system for over a week due to home maintenance crap.

 

[FrantzM]

Other than me, there are at least 3 other people in this thread who can hear directivity with stereo subs. So, why not have the curiosity to say to yourself, maybe a certain artificial bass tones indeed can show directivity?

Are you able to try the same tests as mentioned in post above?

From my vantage point...
I hope the following is not construed as condescending.

However artificial the bass tone is... it is made of a fundamental and harmonics... If it a pure tone and under 80 Hz, then it can't be localized by 99.9999% of the world population. The outliers have not yet been tested.
Now an artificial bass tone, is made of sinusoids. Localization is carried by the overtones, the harmonics that are superiors to 80 Hz, thus an artificial bass signals with a fundamental at 40 Hz is localized due to its higher harmonics content, the first being at 80 Hz, the second at 120 Hz, that you can localize the fundamental at 40 Hz? What allowed to localize the sound was the 120 Hz harmonic.
Oh Boy! You had me delve in to long forgotten notions in filter designs.. But bear with me.
A crossover is a filter. A filter is an approximation of a mathematical function. The behavior is often describerd as such dB per Octave.
let's analyze the terms:
Octave is a doubling of frequency.
dB is the amount of attenuation
And there is the notion of a cutoff frequency which the frequency at which the attenuation is -3 dB
Thus a 12 dB per octave filter at 80 Hz means the following.
At 80 Hz, the attenuation is -3 dB, this is called the cutoff frequency

For illustration purposes, the attenuation at an octave (160 Hz is -12 dB)...
A subwoofer with a 12 dB slope at 80 Hz fed a bass tone from a say a bass guitar at 160 Hz, will play it at -12 dB below what it would play a 40 Hz signal. Fact.
And that is where it becomes weird and complex. Our hearing apparatus is pretty poor in the lows...
Let's assume a noise floor of 30dB, a very quiet room. To hear a 20 Hz under such conditions requires that the tone be played at 90 dB at the listening position... Not too many subwoofer are so capable, but let's assume capable subwoofers... meanwhile under the exact same conditions a 100 Hz , only requires to be played at 65 dB... SPL at the LP.
Wait there is more. .
Any tone is made of a fundamental and of harmonics. They are integers multiples of the fundamental. Assuming a 40 Hz tone, that is not pure, then it is made of a signal at 40 Hz + various signals at various levels at (2 x 40 Hz), (3 x 40 Hz), (4 x40 Hz), (5 x 40 Hz), ( 6 x 40 Hz) +The levels of the harmonic can be zero... but any tone is made of a fundamental and a number of harmonics Any sound. The theory behind this, was discovered by a French mathematician named Fourier...
An artificial tone (any tone actually) is made of a combination of one fundamental and various harmonics...

it becomes more complicated.... Subwoofers distort.. a lot , depending on level, of course. Many subwoofers when tasked to reproduce 20 Hz at a perceivable level (90 dB for our noise floor) could distort upward of 20%... Such amount translates in the production of , yes, harmonics (why this is called harmonic distortion) that weren't part of the original signal: if you feed a pure 20 Hz to a subwoofer, it will produce 20 Hz but also 40 Hz, 60 Hz, 80 Hz and, yes 100 Hz..etc ... the latter are frequencies at which localization occurs and the sensitivity of the hearing apparatus is much better ...

All this to conclude. if you hear localization with artificial tones, it comes from the harmonics in the reproduction signal , not the fundamentals.

Peace

 

[pjug]

If you have time, would you please try ABX files 9 and 10? Link to download is mentioned in

Stereo Bass using subwoofers

OK. Just done with stereo subs ABX. Subs are Paradigm Seismic 110 (10 inch sealed subs with 800 Watts RMS capability). Both subs eq using multiple microphone position to handle room modes. Subs about 12 ft away from my seat. Subs on front wall ~10 ft apart. Room is living room, about 5000+...

www.audiosciencereview.com

I know that we have different subs and room, so I am curious if that makes any difference at all. For my setup and room, it was very easy. It would be nice to have another abx result here.

Thanks!

I am traveling this week but I will try it this weekend in a room that might give me pretty symmetrical L and R. I'll use different filtering and speeding up the tracks so I can use my mains speakers, as I mentioned previously.

One thought though: you mentioned that you heard distortion with the track when you initially tried an ABX with the subs. As part of your posted ABX tests, did you measure or hear distortion to make sure there was nothing significant being put out at higher frequencies? The distortion might help you to localize.

 

[Pdxwayne]

From my vantage point...
I hope the following is not construed as condescending.

However artificial the bass tone is... it is made of a fundamental and harmonics... If it a pure tone and under 80 Hz, then it can't be localized by 99.9999% of the world population. The outliers have not yet been tested.
Now an artificial bass tone, is made of sinusoids. Localization is carried by the overtones, the harmonics that are superiors to 80 Hz, thus an artificial bass signals with a fundamental at 40 Hz is localized due to its higher harmonics content, the first being at 80 Hz, the second at 120 Hz, that you can localize the fundamental at 40 Hz? What allowed to localize the sound was the 120 Hz harmonic.
Oh Boy! You had me delve in to long forgotten notions in filter designs.. But bear with me.
A crossover is a filter. A filter is an approximation of a mathematical function. The behavior is often describerd as such dB per Octave.
let's analyze the terms:
Octave is a doubling of frequency.
dB is the amount of attenuation
And there is the notion of a cutoff frequency which the frequency at which the attenuation is -3 dB
Thus a 12 dB per octave filter at 80 Hz means the following.
At 80 Hz, the attenuation is -3 dB, this is called the cutoff frequency

For illustration purposes, the attenuation at an octave (160 Hz is -12 dB)...
A subwoofer with a 12 dB slope at 80 Hz fed a bass tone from a say a bass guitar at 160 Hz, will play it at -12 dB below what it would play a 40 Hz signal. Fact.
And that is where it becomes weird and complex. Our hearing apparatus is pretty poor in the lows...
Let's assume a noise floor of 30dB, a very quiet room. To hear a 20 Hz under such conditions requires that the tone be played at 90 dB at the listening position... Not too many subwoofer are so capable, but let's assume capable subwoofers... meanwhile under the exact same conditions a 100 Hz , only requires to be played at 65 dB... SPL at the LP.
Wait there is more. .
Any tone is made of a fundamental and of harmonics. They are integers multiples of the fundamental. Assuming a 40 Hz tone, that is not pure, then it is made of a signal at 40 Hz + various signals at various levels at (2 x 40 Hz), (3 x 40 Hz), (4 x40 Hz), (5 x 40 Hz), ( 6 x 40 Hz) +The levels of the harmonic can be zero... but any tone is made of a fundamental and a number of harmonics Any sound. The theory behind this, was discovered by a French mathematician named Fourier...
An artificial tone (any tone actually) is made of a combination of one fundamental and various harmonics...

it becomes more complicated.... Subwoofers distort.. a lot , depending on level, of course. Many subwoofers when tasked to reproduce 20 Hz at a perceivable level (90 dB for our noise floor) could distort upward of 20%... Such amount translates in the production of , yes, harmonics (why this is called harmonic distortion) that weren't part of the original signal: if you feed a pure 20 Hz to a subwoofer, it will produce 20 Hz but also 40 Hz, 60 Hz, 80 Hz and, yes 100 Hz..etc ... the latter are frequencies at which localization occurs and the sensitivity of the hearing apparatus is much better ...

All this to conclude. if you hear localization with artificial tones, it comes from the harmonics in the reproduction signal , not the fundamentals.

Peace

I would say there are ways to reduce the audibility of harmonics.

Regarding subs harmonics:. Turn your subs volume down as much as you can so second, third, forth harmonics, etc, are too low to recognize. There is no need to use loud volume to hear a difference between file 9 and 10.

Regarding test files: Even if the files already filter @48db slope at 80hz, you can do double filter using your subs lowest crossover point. You can do triple filter using minidsp in the chain to make sure you are getting mostly 30hz tones and very little harmonics.

Would you please be a good peer and review file 9 and 10 with stereo subs and tell me what you hear?

 

[Pdxwayne]

I am traveling this week but I will try it this weekend in a room that might give me pretty symmetrical L and R. I'll use different filtering and speeding up the tracks so I can use my mains speakers, as I mentioned previously.

One thought though: you mentioned that you heard distortion with the track when you initially tried an ABX with the subs. As part of your posted ABX tests, did you measure or hear distortion to make sure there was nothing significant being put out at higher frequencies? The distortion might help you to localize.

I moved my left sub about 2ft to left and reran ARC. The graph shows less room null issue around 30hz region. I also made sure I turned down the volume of both subs equally and made sure I hear no rattle, before doing my ABX. So no, rattle was not an issue for me when I ran all 3 ABX.

I look forward to seeing your results.

Thanks for doing peer reviews!
: )

 

[NTK]

Dr. David Griesinger is one of the strongest advocate for stereo bass. Below is slide 2 of his presentation.

http://www.davidgriesinger.com/vancouver_asa.ppt

To Griesinger, localization at low frequency is not the goal. 99+% of the time the sound is localized by its higher frequency harmonics. What Griesinger after are the low frequency spatial effects of envelopment and externalization.

Whether a person values low frequency envelopment as much as Griesinger is a personal choice. However, I wouldn't so quickly dismiss Griesinger and assert that we can't hear any differences between mono and stereo bass below 80 Hz.

 

[Sancus]

From there we diverge.. entirely. A lot has been said about the so-called "stereo" bass in his thread. The argumentation is, to be charitable, lacking. We are left with vociferous claims of been able to hear what most people on the planet can't.

There is no such thing as stereo imaging in low bass, but some of the studies do indeed state you can hear something, including the article in the OP which iirc was based on the Griesinger one.

I just agree with the audioholics article that this difference isn't worth pursuing. Too subtle and too little support among recordings, especially since all my favourite recordings are multichannel many of which use the LFE.

I think there is enough evidence to state there is some kind of difference, but thst doesn't necessarily mean it's better either.

P.S. I will soon open a thread on my (and so many other people) ability to hear differences between audiophile Ethernet cables...

We've had cable threads with plenty of delusional posters so it would hardly be unprecedented. I wasn't arguing against discussion, more that shouting other people down in a condescending way isn't going to produce the results you wanted. Does it seem to have based on the contents of this thread???? This just makes people dig in their heels, get upset, and put you on ignore. Literally all of which have happened in this thread.

There's a way to have respectful, calm discussion and the posts I was replying to weren't it.

 

[dkinric]

OP here. If it helps, I respectfully withdraw the question.

 

[Pdxwayne]

There is no such thing as stereo imaging in low bass, but some of the studies do indeed state you can hear something, including the article in the OP which iirc was based on the Griesinger one.

I just agree with the audioholics article that this difference isn't worth pursuing. Too subtle and too little support among recordings, especially since all my favourite recordings are multichannel many of which use the LFE.

I think there is enough evidence to state there is some kind of difference, but thst doesn't necessarily mean it's better either.


We've had cable threads with plenty of delusional posters so it would hardly be unprecedented. I wasn't arguing against discussion, more that shouting other people down in a condescending way isn't going to produce the results you wanted. Does it seem to have based on the contents of this thread???? This just makes people dig in their heels, get upset, and put you on ignore. Literally all of which have happened in this thread.

There's a way to have respectful, calm discussion and the posts I was replying to weren't it.

Curious, what does "low bass stereo imaging" mean to you?

If one sub is 20db louder than the other, at around 30hz, and you sense the direction of the louder sub, is this considered stereo imaging?

 

[Pdxwayne]

OP here. If it helps, I respectfully withdraw the question.

I would prefer more people get involved and do peer review of my ABX results.

The more people run the tests, the more we learn.

 

[Sancus]

Curious, what does "low bass stereo imaging" mean to you?

It means I don't think you can produce the impression of an instrument location between two subs with only low frequency information. Not just pure directional sensing(though I am somewhat skeptical there as well, and do tend to agree with the posts that excising all harmonics and potential room resonances for a good test would be difficult).

In my pipe organ recordings using widely spaced microphones, the random phase mixing and cancellations due to the microphones at distances >25' can and certainly does cause dynamically changing nulls depending on the notes being played, causing some bass frequencies to almost entirely come from only one of the two subwoofer channels at various times.

I'm curious, since you seem to have a very specific workflow with your own recordings, why not multi-channel? I do enjoy pipe organ music myself from time to time, and the multi-channel recordings(eg E. Power Biggs Bach) are just sooooo much better than any stereo recording I've ever heard. I feel like the sound of a pipe organ is hard to separate from its venue/church and so you should probably attempt to record as much of the spatial information as possible 2L style with a big mic array.

 

[MakeMineVinyl]

I'm curious, since you seem to have a very specific workflow with your own recordings, why not multi-channel? I do enjoy pipe organ music myself from time to time, and the multi-channel recordings(eg E. Power Biggs Bach) are just sooooo much better than any stereo recording I've ever heard. I feel like the sound of a pipe organ is hard to separate from its venue/church and so you should probably attempt to record as much of the spatial information as possible 2L style with a big mic array.

Because stereo done right can produce an enveloping soundfield which is just as complete as multi channel. With a lot of multi channel I hear, I've been able to identify the locations of the speakers - that doesn't happen with enveloping stereo images (i.e. binaural over speakers which are capable of producing binaural). This localization is particularly bad with quad, which E. Power Biggs would have done in his lifetime.

Producing this envelopment is obviously easier to do with multi channel, but still the location of the surround and overhead speakers call attention to themselves to my ears.

Granted, my setup is highly atypical - I'll give you that.

 

[Pdxwayne]

It means I don't think you can produce the impression of an instrument location between two subs with only low frequency information. Not just pure directional sensing(though I am somewhat skeptical there as well, and do tend to agree with the posts that excising all harmonics and potential room resonances for a good test would be difficult).



I'm curious, since you seem to have a very specific workflow with your own recordings, why not multi-channel? I do enjoy pipe organ music myself from time to time, and the multi-channel recordings(eg E. Power Biggs Bach) are just sooooo much better than any stereo recording I've ever heard. I feel like the sound of a pipe organ is hard to separate from its venue/church and so you should probably attempt to record as much of the spatial information as possible 2L style with a big mic array.

I see, so you are talking about precise instrument placing.

My tests were more about stereo. For me, stereo means there are differences between channels. As long as I can sense differences between channels, then I consider I have sensed stereo bass. So it is a lot more lenient than your precise placement requirement.

 

[MakeMineVinyl]

I see, so you are talking about precise instrument placing.

My tests were more about stereo. For me, stereo means there are differences between channels. As long as I can sense differences between channels, then I consider I have sensed stereo bass. So it is a lot more lenient than your precise placement requirement.

Expecting any better imaging precision than identifying left and right is really not going to happen since the ear distance doesn't play that large a role at these low frequencies. But the point is, that level of imaging is enough to convey spatial enhancement.

 

[Sancus]

Because stereo done right can produce an enveloping soundfield which is just as complete as multi channel. With a lot of multi channel I hear, I've been able to identify the locations of the speakers - that doesn't happen with enveloping stereo images (i.e. binaural over speakers which are capable of producing binaural).

There are other problems as well though, such as channel interference producing a null in the presence region compared to a real center channel. I'm sure you're aware of all this stuff since it's in Toole's book though so I won't derail this thread further.

I'm glad your setup works very well for you, and I'd be curious to hear it since I've never heard any stereo setup that comes close to a good multi-channel one, so I'm definitely on the side of Toole's statements.

This localization is particularly bad with quad, which E. Power Biggs would have done in his lifetime.

This recording is a bit of a cheat example, as it's produced in a cathedral that has 4 organs in different locations all controlled at once. It wouldn't be possible to reproduce very well without surround channel information(or a binaural/modern spatial audio approach). The original recording was indeed probably for quad though the version I have is mixed for 5.1. I agree with you about quad recordings, I have several examples of both(eg Dark Side of the Moon) and I always prefer the 5.1 remixes where they typically blend channels significantly more. Some people in the surround music community seem to prefer the highly "discrete" quad mixing strategy though for some reason.

 

[MakeMineVinyl]

There are other problems as well though, such as channel interference producing a null in the presence region compared to a real center channel. I'm sure you're aware of all this stuff since it's in Toole's book though so I won't derail this thread further.

I'm glad your setup works very well for you, and I'd be curious to hear it since I've never heard any stereo setup that comes close to a good multi-channel one, so I'm definitely on the side of Toole's statements.


This recording is a bit of a cheat example, as it's produced in a cathedral that has 4 organs in different locations all controlled at once. It wouldn't be possible to reproduce very well without surround channel information(or a binaural/modern spatial audio approach). The original recording was indeed probably for quad though the version I have is mixed for 5.1. I agree with you about quad recordings, I have several examples of both(eg Dark Side of the Moon) and I always prefer the 5.1 remixes where they typically blend channels significantly more. Some people in the surround music community seem to prefer the highly "discrete" quad mixing strategy though for some reason.

Yes, antiphonal organ ranks can be captured binaurally, but some provision needs to be taken for very low frequencies since a dummy head's ear spacing is the same as a human, and subject to the same inability to hear directly the direction of low frequencies. Low passed and very widely spaced omni-directional mics can be used to capture the phase differences at these frequencies. With a mono sub, the random phase cancellations/reinforcements which took place in the recording locale relative to the microphone spacings are lost as 'directional' information - with stereo subs these frequencies mix acoustically in the listening room, mimicking what happened during recording.

Another complaint I have with discrete multi-channel is that under any sane conditions, the surround speakers are smaller than the mains (and the mains must be large to be convincing with organ music), so there is a front/back disconnect. If the total soundfield is coming from two stereo speakers, this problem does not exist. My mains are refrigerator-sized, so you can see the problem there. I do listen to all types of music, but I'm using organ music as an example.

True, this is all very-edge-case stuff and specific to a few nut-heads like myself, but I like exploring those dark corners of the sonic basement, because I can. Essentially all commercially released music has what is basically mono bass - movies certainly do - so its no surprise that stereo bass is so infrequently given any consideration or validity.

 

[Chromatischism]

There are other problems as well though, such as channel interference producing a null in the presence region compared to a real center channel. I'm sure you're aware of all this stuff since it's in Toole's book though so I won't derail this thread further.

Does this not show up with a moving mic average of both left and right speakers? I don't think I've seen it, but I could measure and look for it.

 

[Sancus]

Does this not show up with a moving mic average of both left and right speakers? I don't think I've seen it, but I could measure and look for it.

See figure 7.2 on pg161 in 3rd edition of Toole's book for more details. It was measured in a variety of ways and also confirmed by multiple studies and is pretty audible with pink noise comparisons as well. I don't think of it as new/interesting tbh. If you have music that is available and recorded very similarly in both stereo and mch formats, it's striking how much clearer a real center is.

Yes, antiphonal organ ranks can be captured binaurally, but some provision needs to be taken for very low frequencies since a dummy head's ear spacing is the same as a human, and subject to the same inability to hear directly the direction of low frequencies.

My main problem with the binaural approach is it only captures what someone would hear in a precise position. Once you're used to regular multi-channel, headphone-like audio destroys immersion because even if you only move your head a half inch or turn it slightly, there is no accompanying shift in the sound that should be there.

The modern 3D spatial audio work addresses this by using head tracking, which is a good solution, but has some way to go yet.

None of this has anything to do with Stereo Bass though so I don't wanna derail too much