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Bass and subwoofers

Duke

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One has, in that case, screwed the pooch and eliminated what one wanted to capture, in my book.

Now, it *IS* possible to create something reasonably realistic, but you have to know, before you start, what you NEED for a particular space. So now you need metadata.

You can introduce decorrelation in any number of ways, the number of ways to introduce it is literally, um, well, literally infinite. But most of those ways sound really, really, um, ?odd? to say the least.

Can you give an example of what metadata we'd need and an approach we might use to introduce decorrelation in the bass region at the playback end of the chain (assuming the recording itself is summed to mono in the bass region)?

You don't want to support the modes in the listening room, you DO want to support the modes in the intended RECORDING space.

What approach(es) in the playback room would be conducive to "supporting the modes in the intended RECORDING space"?
 
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j_j

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Can you give an example of what metadata we'd need and an approach we might use to introduce decorrelation in the bass region at the playback end of the chain (assuming the recording itself is summed to mono in the bass region)?
Yeah, but that's bordering on proprietary at the minute. Maybe I'll be able to be more specific later.
If you have the opportunity to measure a good space with a set of mikes .9 microseconds apart, some light may turn on.

ETA: DAMNIT, JIM, more coffee! That's .9 MILLIseconds. Not microseconds.


What approach(es) in the playback room would be conducive to "supporting the modes in the intended RECORDING space"?

NOT having modes in the playback space. Yeah, simple, but not very.
Having at least 3, if not 4, bass radiators, not in a line in front of you,at minimum.
 
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Duke

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Yeah, but that's bordering on proprietary at the minute. Maybe I'll be able to be more specific later.
If you have the opportunity to measure a good space with a set of mikes .9 microseconds apart, some light may turn on.

Thank you!

Point nine microseconds?? That corresponds to a path length difference of about 12 thousandths of an inch, if I'm keeping track of the decimal place correctly.

Assuming that somehow I'm able to make this measurement, can you give me any non-propriety hints as to what I should be looking for? (I'm not the sharpest tool in the shed, and my experience with microphones is limited to making time-gated loudspeaker measurements for designing crossovers.)

NOT having modes in the playback space. Yeah, simple, but not very.

This happens to be within my comfort zone. I subscribe to the school of thought that says, "minimize the playback room's spatial signature in hopes of enabling the recording's spatial signature."

Having at least 3, if not 4, bass radiators, not in a line in front of you,at minimum.

I think I was the first subwoofer manufacturer to sell a dedicated four-piece subwoofer system intended to be asymmetrically distributed around the room, ideally with distribution in the vertical plane as well.

My experience has been that introducing a 90-degree phase differential between the subs on the left and right sides of the room seems to enhance the feeling of spaciousness.

Perhaps, rather than actually synthesizing spaciousness, this approach is disrupting the playback room's spatial signature in the bass region, which in turn makes it easier for the spatial signature on the recording to become perceptually dominant.

I gather that you think this approach is misguided, and I'm all ears. I'm more interested in learning how to do it better than I am in being "right".

Thank you very much for having this conversation with me.
 

Duke

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ERK. More coffee. MILLIseconds. 900 MICROSECONDS!

Ooops.

Okay, 900 microseconds corresponds to a path length difference of about 12 inches. Hmmm. In this context, does this 900 microsecond interval have anything to do with the onset of the precedence effect?
 
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youngho

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Okay, 900 microseconds corresponds to a path length difference of about 12 inches. Hmmm. In this context, does this 900 microsecond interval have anything to do with the onset of the precedence effect?
0.8-0.9 ms is the time delay around the human head, which likely correlates to the 0.63-1 ms transition from summing localization to the "law of the first wavefront."
 

j_j

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Okay, 900 microseconds corresponds to a path length difference of about 12 inches. Hmmm. In this context, does this 900 microsecond interval have anything to do with the onset of the precedence effect?

Good question, that or the path length AROUND the human head. Or both? This is "learned by observation".

It seems very short for bass frequencies. In a small room, yes, it is. More I can not presently say.
 

Duke

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0.8-0.9 ms is the time delay around the human head, which likely correlates to the 0.63-1 ms transition from summing localization to the "law of the first wavefront."
Good question, that or the path length AROUND the human head. Or both? This is "learned by observation".

My understanding is that the onset of the precedence effect corresponds to the around-the-head path length distance from one ear to the other.

It seems very short for bass frequencies.

Yes it does, but evidently we have SOME mechanism for hearing spaciousness at bass frequencies, and my understanding is that it is related to the ear's ability to detect a pressure differential between the left and right ears, which implies sufficient resolution in the time domain for the ear to do so.

In a small room, yes, it is. More I can not presently say.

Thank you for saying this much.
 

audiofooled

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Yes it does, but evidently we have SOME mechanism for hearing spaciousness at bass frequencies, and my understanding is that it is related to the ear's ability to detect a pressure differential between the left and right ears, which implies sufficient resolution in the time domain for the ear to do so.

Just plain curious and probably shooting in the dark but can there be some correlation with peak energy time here?

wavelet.jpg
 

Duke

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ernestcarl

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Just plain curious and probably shooting in the dark but can there be some correlation with peak energy time here?

View attachment 344739

I don't know, but I'm guessing there must be some relationship to it and the phase... "peak energy time" in this graph is just more or less what you'd see in the more one dimensional group delay plot view.

1706134705688.png


1706134710987.png
 

ernestcarl

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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.
 

audiofooled

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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.
 

Sokel

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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.

This thread has some more,here's how it looks in REW:

1706136938638.png

R-red,L-blue.


@goat76 also made a files for testing,in the same thread:

 
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ernestcarl

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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?
 

ernestcarl

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This thread has some more,here's how it looks in REW:

View attachment 344756

R-red,L-blue.


@goat76 also made a files for testing,in the same thread:


The shift in the horizontal imaging in the linked track for download is quite obvious to me. However, not really a type of test track that one can hear more subtle bass "spatialization" effects.
 

ernestcarl

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How about "The World's Greatest Audiophile Vocal Recordings" (Chesky) ? These contain many tracks that have much more sparser mixes with a very clear bass line. Not sure which one would be a prime test track candidate, yet, I think I'm hearing some more obvious changes in the size of the width and (perhaps a little more or less) depth besides the usual horizontal imaging.
 

Kvalsvoll

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When I investigated perception of low frequency sound field properties (p and velocity vector), I found direction of sound p can be heard starting around 60Hz, I found direction of velocity for tactile perception to be undetectable (feels the same regardless of direction), BUT: level of velocity relative to pressure is indeed perceivable, and makes a huge difference in how low bass is experienced.

Having 2 channels, and feeding those individually to different sound radiators in the bass-system, it is also possible to change the properties of the sound field, so that a out-of-phase signal can create low frequency sound with a higher velocity and low pressure. This induces some quite special requirements for the system, to make it work. It can be done. Measurements from one of the tests shows a very significant difference in horizontal velocity comparing 1 radiator in one front corner to 2 radiators l and r.

Stereo bass does nothing for placement of low freq instruments, but there may still be a difference in perception of bass and thus "space", due to differences in sound field properties.
 

j_j

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How about "The World's Greatest Audiophile Vocal Recordings" (Chesky) ? These contain many tracks that have much more sparser mixes with a very clear bass line. Not sure which one would be a prime test track candidate, yet, I think I'm hearing some more obvious changes in the size of the width and (perhaps a little more or less) depth besides the usual horizontal imaging.
Some of his most recent tracks have interesting feeling to them, I'd say, too.
 

Sokel

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The shift in the horizontal imaging in the linked track for download is quite obvious to me. However, not really a type of test track that one can hear more subtle bass "spatialization" effects.
To tell the truth I don't test them with subs,I just lower and sum the x-over (at 80Hz) of my 3-way (it's easy,there actives and go down to 30's) and tested them dual mono vs stereo.The sense of space changes in favor of stereo in my room and the strange thing is that the proportions of instruments change too.
With their usual x-over at 240Hz the difference is more evident but probably there are lots more at play there.
 
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