Stereo Sub Vs Dual Mono

[sarumbear]

Some other member has a question as to how spatial sensation can be measured, and I provided an answer. You have a problem with that?

Yes. You have just posted a non-peer reviewed paper. How do we know the author's premise is correct? Where is the tool that measures his metric? Scientific paper is not gospel.

 

[sarumbear]

Here (in the middle of the post)

Stereo Sub Vs Dual Mono

I'm pretty sure I will find none, so I will spend my time elsewhere. Understood, some will always prefer to not be guided by all the research on AES, etc. It's always a choice.

www.audiosciencereview.com

Her is the analysis of @goat76’s test file. There is a lot of information way above the subwoofer frequency range. At 200Hz signal is just 20dB down. Naturally you will hear the stereo effect of a signal that has less than a 2m wave. How far apart your speakers are?

 

[Sokel]

How far apart your speakers are?

2.8 meters symmetrically put to LP and I had my mains deactivated.
So,isn't that test signal what a sub would reproduced normally?
Say,crossover-ed at 80Hz with a 24db LR filter?

 

[sarumbear]

2.8 meters symmetrically put to LP and I had my mains deactivated.

That doesn’t effect your subs producing sound above the crossover frequency.

So,isn't that test signal what a sub would reproduced normally?
Say,crossover-ed at 80Hz with a 24db LR filter?

Correct but we are debating if you can hear bass, not testing a LR4 filter. Use a brick-wall filter (>100dB/octave) and try again.

 

[Sokel]

Correct but we are debating if you can hear bass, not testing a LR4 filter. Use a brick-wall filter (>100dB/octave) and try again.

Or I could just use a 50Hz tone.
But that's not how normal listening works,it much more resembles pink noise like that.
As you say,real life,just deactivate the mains and listen,that's what you also hear with music.

 

[sarumbear]

Or I could just use a 50Hz tone.

A single tone won’t work as each subs will activate different room modes. You can use pink noise with a brick-wall filter.

But that's not how normal listening works,it much more resembles pink noise like that.
As you say,real life,just deactivate the mains and listen,that's what you also hear with music.

You hit the nail on the head. In real life there are no bass instruments that emit only bass frequencies. All instruments produce harmonics. What you are hearing is the effect of mono/stereo switching of those harmonics, the higher frequencies that exist in bass instruments, similar to this test tone.

There had been many tests done early to mid last century in anechoic rooms using single tones and proved beyond doubt that localisation of sound is lost when the emitters are nearer to each other than the half wavelength of the signal used. As you sit at the centre of your speakers at 2.8m wide you shouldn’t hear any localisation from around 120Hz.

 

[NTK]

Yes. You have just posted a non-peer reviewed paper. How do we know the author's premise is correct? Where is the tool that measures his metric? Scientific paper is not gospel.

AES saw it fit for this paper to be presented at their conference, and this forum has a higher standard?
Then, should all posts be peer reviewed before they allow to appear in this forum?

 

[sarumbear]

AES saw it fit for this paper to be presented at their conference, and this forum has a higher standard?
Then, should all posts be peer reviewed before they allow to appear in this forum?

I’m an AES member. All interesting papers are presented at our symposiums. That is an editorial decision, not a peer review. We publish those papers so that it is out there for other scientists and engineers to read it, test the idea and refer it on their own research.

A published paper is not gospel. It’s not proven to be correct either. Here I am telling you what I see wrong about it.

 

[Sokel]

As you sit at the centre of your speakers at 2.8m wide you shouldn’t hear any localisation from around 120Hz.

I have no reason to disagree but seems that subs at 80Hz 24db LR also reproduce that harmonics (remember,my mains are off).
So it doesn't surprise me that I can hear that effect clearly.
The thread is about dual-mono vs stereo subs WHATEVER they reproduce.

 

[NTK]

Or I could just use a 50Hz tone.
But that's not how normal listening works,it much more resembles pink noise like that.
As you say,real life,just deactivate the mains and listen,that's what you also hear with music.

We localize through the first wavefront (precedence effect), not the continuous tone. And "stereo bass" is not just about localizing the sound source. It is also for the spatial sensation and also to externalize the bass (not hearing it as it is from inside the head).



[Edit] Add the source of the above quote: http://www.davidgriesinger.com/asa05.pdf

 

[goat76]

That doesn’t effect your subs producing sound above the crossover frequency.


Correct but we are debating if you can hear bass, not testing a LR4 filter. Use a brick-wall filter (>100dB/octave) and try again.

No, the debate is what the title of the thread says.

Stereo Sub Vs Dual Mono​

We should therefore debate how a pair of normally set-up subwoofers in stereo vs dual mono affect the sound that we hear.

If the most common crossover settings for subwoofers are at 80 Hz with a roll-off slope of 24 dB/octave, I can easily provide you with that if you think that will make a significant difference than a crossover at 60 Hz with a roll-off slope of 12 dB/octave.

Dropbox

www.dropbox.com

 

[anotherhobby]

I fail to see how it matters if sound produced by subwoofers above the crossover frequency also help. Does that not still increase spacial qualities over mono? Which specific range of frequencies being produced by stereo subs to increase the spacial effect doesn't change the effectiveness, since either way the stereo subs are assisting to produce better spacial audio than the mono subs. I don't personally subscribe to the notion that it's only in the crossover region, but I wouldn't care if that was the only reason, because it's still an improvement. While I am indeed insterested in the reasons behind this, the specific reason matters less to me than the enjoyment and quality improvement.

 

[sigbergaudio]

Do we even agree on the question here? The way I understand it, we are debating if perceived stereo effects (channel separation) as well as perceived spatial information (feeling or sensation of space) is diminished if we switch from stereo to dual mono on two symmetrically placed subwoofers, typically crossed over at 80hz (24db/octave).

We cannot determine this by testing stereo subs alone, and say "Yes, I experience a spatial sensation."
We must also test dual mono and conclude "Now I no longer experience the same spatial sensation" if we are to get anywhere. Preferrably in an ABX test.

 

[goat76]

Do we even agree on the question here? The way I understand it, we are debating if perceived stereo effects (channel separation) as well as perceived spatial information (feeling or sensation of space) is diminished if we switch from stereo to dual mono on two symmetrically placed subwoofers, typically crossed over at 80hz (24db/octave).

We cannot determine this by testing stereo subs alone, and say "Yes, I experience a spatial sensation."
We must also test dual mono and conclude "Now I no longer experience the same spatial sensation" if we are to get anywhere. Preferrably in an ABX test.

But you already got that in the files I provided.

The signal is dual mono between 6 and 12 seconds, and again between 18 and 24 seconds in the sound file. The left and right subwoofers are receiving the exact same signal on those two occasions, and the end result of that is the same as if you summed them to mono in your system.

And in your case when you always sum the signal to dual mono to your subwoofers, no matter if the signal was indeed in stereo in the first place, you now have “killed off” all the possibility of hearing any spatial effects from that “summed to mono”-signal you now have. If any spatial effect will have a chance to even occur, there must be differences in the two signals that reproduce that specific sound object, otherwise, it will just create a phantom sound object that will end up right in the middle of the speakers (in this case your subwoofers).

 

[anotherhobby]

Do we even agree on the question here? The way I understand it, we are debating if perceived stereo effects (channel separation) as well as perceived spatial information (feeling or sensation of space) is diminished if we switch from stereo to dual mono on two symmetrically placed subwoofers, typically crossed over at 80hz (24db/octave).

We cannot determine this by testing stereo subs alone, and say "Yes, I experience a spatial sensation."
We must also test dual mono and conclude "Now I no longer experience the same spatial sensation" if we are to get anywhere. Preferrably in an ABX test.

Yes, that is what I have done personally and stated earlier, but that doesn't mean my results predict any others. The original paper cited even states "The results show that certain common room shapes yield low spatiality regardless of loudspeaker and listener positions," so I'd expect that not everybody who has a system that can even support it would hear it based on their room/speakers/position. The paper cites some examples where there will be no effect. That makes it a little tricky to compare across systems, which is unfortunate.

All that said, I mentioned earlier in the thread that I tested switching back and forth from stereo to mono subs, and yes I concluded that when switching from balanced mono to stereo subs "Now I no longer experience the same spatial sensation" as you say. However, when going from stereo to balanced mono, I would not say I experience no spacial sensation in the bass region (rather, there is plenty), but it is not the same, and it is diminished in mono. I don't believe I've stated the effect to be dramatic, just a noticeable improvement, and at least on my system I think it's very fair to call it subtle. Also, for clarity, I'm saying balanced mono because you are saying "dual mono," but I have 4 subs equally balanced in the sound field and not 2. The quad subs help the situation since I don't have any dips in either channel.

 

[sigbergaudio]

But you already got that in the files I provided.

The signal is dual mono between 6 and 12 seconds, and again between 18 and 24 seconds in the sound file. The left and right subwoofer are receiving the exact same signal at those two occasions, and the end result of that is same as if you summed them to mono in your system.

But they don't tell us anything we don't know? Pink noise low passed with 12db/octave at 60hz will as Sarumbear pointed out contain more than enough high frequency content to allow us to localize it. So this in itself proves nothing with regards to channel separation that we don't know. And it proves nothing about dual mono.

Then we have spatial sensation. I don't see how your files tell us anything about that either.

 

[anotherhobby]

But they don't tell us anything we don't know? Pink noise low passed with 12db/octave at 60hz will as Sarumbear pointed out contain more than enough high frequency content to allow us to localize it. So this in itself proves nothing with regards to channel separation that we don't know. And it proves nothing about dual mono.

Then we have spatial sensation. I don't see how your files tell us anything about that either.

I personally did not find the pink noise test to be demonstrative of the effect under A/B testing. When I listen to the pink noise file all the way thru on both my balanced mono and stereo sub setup, they sound the same to me. Even the last bit which sounds more "spacial" sounds more spacial in balanced mono as well. So, as somebody who is claiming to hear the effect easily in music, I don't hear it in the pink noise.

 

[goat76]

But they don't tell us anything we don't know? Pink noise low passed with 12db/octave at 60hz will as Sarumbear pointed out contain more than enough high frequency content to allow us to localize it. So this in itself proves nothing with regards to channel separation that we don't know. And it proves nothing about dual mono.

Then we have spatial sensation. I don't see how your files tell us anything about that either.

Sorry, I updated my last post with this information for you who seem to think that you will receive spatial information from dual mono sources:

And in your case when you always sum the signal to dual mono to your subwoofers, no matter if the signal was indeed in stereo in the first place, you now have “killed off” all the possibility of hearing any spatial effects from that “summed to mono”-signal you now have. If any spatial effect will have a chance to even occur, there must be differences in the two signals that reproduce that specific sound object, otherwise, it will just create a phantom sound object that will end up right in the middle of the speakers (in this case your subwoofers).

 

[sigbergaudio]

Sorry, I updated my last post with this information for you who seem to think that you will receive spatial information from dual mono sources:

And in your case when you always sum the signal to dual mono to your subwoofers, no matter if the signal was indeed in stereo in the first place, you now have “killed off” all the possibility of hearing any spatial effects from that “summed to mono”-signal you now have. If any spatial effect will have a chance to even occur, there must be differences in the two signals that reproduce that specific sound object, otherwise, it will just create a phantom sound object that will end up right in the middle of the speakers (in this case your subwoofers).

I feel like I am repeating myself, but I will have another go: Almost all sound sources will cover a frequency range and/or have harmonics that are high enough to also be played back by the speakers. Instruments do not produce isolated sinus tones. The speakers are also not brick walled at 80hz.

Due to this fact, there are indeed differences in the two signals, but it is reproduced by the speakers rather than the subwoofers. This is typically enough to maintain the spatial effect.

 

[theREALdotnet]

Her is the analysis of @goat76’s test file. There is a lot of information way above the subwoofer frequency range. At 200Hz signal is just 20dB down. Naturally you will hear the stereo effect of a signal that has less than a 2m wave.

Thank you for pointing this out, I was going to let it go (don’t want to be overly argumentative about something of relatively little importance). It is not easy to set up valid tests and test signals for this, if you want the subs to play at appreciable volume (around 60dB(A)). I used brickwalled pink noise from REW’s generator, but my microphones picked up clearly audible noise above the cut-off frequency, because it does get generated by the subwoofers themselves or their surroundings (or even the brickwall filter). This makes it seem as if you can pan sub-bass from one sub to the other, when in reality you can’t.