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Reducing sub-bass seat to seat variation

abdo123

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So my setup is 2.2 (two subwoofers) crossed at 100Hz (LR 48dB/Oct). I'm trying to minimize seat to seat sub-bass variation in 4 seats in total (4 measurement points).

Room layout and current subwoofer locations (red rectangles are subwoofers, all of them are on the floor, blue oval shape is listening area)

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Amroc simulation of the room (Link: https://amcoustics.com/tools/amroc?l=354&w=481&h=244&r60=0.60)

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Frequency response showing the variation between the different seats, the mode @48Hz (0,1,0) is completely minimized as expected from the placement of the subwoofers. The mode @ 36Hz (1,0,0) still show a lot of variation although the subwoofers are placed in different poles of the mode. I expected the mode at 60Hz to be minimized as well since it's (1,1,0) but there is still ~13 dB of variation.

The biggest issue is in the 90Hz to 100Hz region (1,1,1 and 0,2,0), Is there anything I could do about that without putting the subwoofers further in the room? and why there is so much variation at (1,0,0)?

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Some useful reading for those that cannot keep up with the thread.

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RayDunzl

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Is it a "listening to music" problem or a "measures like this" problem?

I have a deep hole across the listening couch that I don't actually notice, except when measuring steady-state or swept tones.

I suppose the harmonics and the context of the note tricks me into hearing it during musical progams.

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In this case, the room is asymmetrical behind the listeners - the left and right individually are fine, but the waves are 180 degrees out of phase in that area, and combine to create a null.

Left and Right phase:

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Mono bass makes a hole, stereo bass - not the same signal from both speakers - can cause the dip to disappear entirely.
 
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sigbergaudio

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Also, have you tried listening at feet and gut level in the three seats? At these frequencies we listen with the whole body, and the response often varies in height as well. If you average across the seats with that in mind as well, the result might be better.
 
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abdo123

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Also, have you tried listening at feet and gut level in the three seats? At these frequencies we listen with the whole body, and the response often varies in height as well. If you average across the seats with that in mind as well, the result might be better.
All 4 seats are at the same height (or like ~10cm from each other) which is why i haven't explored a 3rd subwoofer on the ceiling yet. Minimizing the variation in (0,1,0) was revolutionary in terms of subjective sound quality, trying to achieve the same thing with (1,0,0), (0,2,0) and (1,1,0).
 

sigbergaudio

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All 4 seats are at the same height (or like ~10cm from each other) which is why i haven't explored a 3rd subwoofer on the ceiling yet. Minimizing the variation in (0,1,0) was revolutionary in terms of subjective sound quality, trying to achieve the same thing with (1,0,0), (0,2,0) and (1,1,0).

My point wasn't that you may be sitting at different height, rather that if you measure at the height of your stomach, you may see a very different response. And this is felt and "heard" as well. So a measured dip at ear height may not actually be as bad as it looks, as for all you know (until you measure) it may not be there at stomach level.
 

alex-z

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Having your listening area near a wall is going to exacerbate room modes, because that is where pressure is the highest. I find even with 4 subs that a 38% listening distance sounds best, because the subwoofers are really only managing the axial modes, all the ones near and above the crossover region are still prominent.

With 2 subwoofers and a single row of seats, it would usually make more sense to put 1 subwoofer on either side of the row, eliminating the width axial mode, and beating the length mode down with EQ. Moving up to a 3 or 4 sub setup will allow you to get more complete room mode reduction.

Do the 90-120Hz problems exist with the subwoofers disabled and speakers measured full-range? If so, you need different placement.
 
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abdo123

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Having your listening area near a wall is going to exacerbate room modes, because that is where pressure is the highest. I find even with 4 subs that a 38% listening distance sounds best, because the subwoofers are really only managing the axial modes, all the ones near and above the crossover region are still prominent.

With 2 subwoofers and a single row of seats, it would usually make more sense to put 1 subwoofer on either side of the row, eliminating the width axial mode, and beating the length mode down with EQ. Moving up to a 3 or 4 sub setup will allow you to get more complete room mode reduction.

Do the 90-120Hz problems exist with the subwoofers disabled and speakers measured full-range? If so, you need different placement.
38% of what exactly? How do you determine which axis is the most important?

Sure 48 Hz (0,1,0) here is the most severe, but it also shows the least seat to seat variation. So it’s basically free gain for me.

It’s interesting that you asked about the full range performance, when you say different placement, do you have an idea of what might work?
 

Jdunk54nl

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Have you tried multi sub optimizer? I’ve heard good results with it. I’m going to be trying it out soon.


 
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