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Large room, 4 subs, bass null - looking for rough placement ideas and principles.

1niltothe

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Here's a sketch of the room - it's not at all to scale. It's a loft style apartment in a converted mattress factory. The 4 subs are shown with the radial bursts.

It's a multi-use space, i.e. there's a bar / kitchen area, a big dinner table that we sometimes work at, and a sofa / screen area. It's quite a social flat. The intention is closer to nightclub sound, where one can wander freely and there's relatively balanced low end. Rather than a single sweet spot or listening position.

The coverage of the room is pretty good, with the exception of this null. I have only just set the speakers up, and haven't yet gone deep with REW - this is rough, heuristic - listening to music, there's a point in the room where you can't really hear the low end at all.

I've kept a lot of information out of the sketch - e.g. the position of the bar area, projector screen etc - as I want to see purely based on the rough dimensions of the room what people notice about the subs and the null.

One of the reasons the subs are currently where they are is because of cables I have - there's a nerve centre where DSP / amplification happens, and currently I don't have vastly long cables to put the subs very far away from it - although if need be I can order some long cables.

The subs can basically go anywhere. I can do timing and EQ on any of them.

It could also be a DSP thing, where the polarity / timing of the subs can be played with - I'm not that familiar with this, and haven't tested it.

Apologies if this is all too rough and heuristic for ASR, my intention is to learn a bit about fundamental principles before starting to lug these big subs around and spend ages doing frequency sweeps etc.

I forgot to put on the diagram - ceiling height is approx 4 - 5 meters.

Drawing (1).jpeg
 
Null at which frequency? You could switch of one by one to see what combination changes the null the most and play with the level/timing of that sub.
measurements!
 
Here's a sketch of the room - it's not at all to scale. It's a loft style apartment in a converted mattress factory. The 4 subs are shown with the radial bursts.

It's a multi-use space, i.e. there's a bar / kitchen area, a big dinner table that we sometimes work at, and a sofa / screen area. It's quite a social flat. The intention is closer to nightclub sound, where one can wander freely and there's relatively balanced low end. Rather than a single sweet spot or listening position.
well - “sound everywhere” can be a challenge.

The coverage of the room is pretty good, with the exception of this null. I have only just set the speakers up, and haven't yet gone deep with REW - this is rough, heuristic - listening to music, there's a point in the room where you can't really hear the low end at all.
.


Apologies if this is all too rough and heuristic for ASR, my intention is to learn a bit about fundamental principles before starting to lug these big subs around and spend ages doing frequency sweeps etc.
….

Why don’t you start with putting a single sub where the null is at.
Then drag around the lighter microphone and do measurements where the subs could be tolerated?
With reciprocity, it means that you can swap the sub and the microphone.
Once you have all that data, and maybe some extra sweet spot data, then you should have a better idea which sub placements are more optimal.

I’d try moving the sub from the 1 o’clock position to the 6 o’clock position along the 8M wall.
 
You might try moving one of the subs, perhaps the one in the bottom right corner, as close to the null zone as you can.

Assuming the null is the result of destructive interference, you might try reversing the polarity of one of the subs. I'm not sure which one would be the best to try. You'd probably need to re-EQ, assuming this helps with the null zone issue.

Would it be feasible to introduce some distribution of your bass sources into the vertical plane as well? Would it be feasible to raise one of the subs so that it's closer to the ceiling than to the floor?
 
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Null at which frequency?

Yes, get some measurments. If you have the problem frequency you can place a single sub in the null spot playing that frequency, then crawl around the room to find the places where not to put a sub.

EDIT If you don’t care to find the problem frequency, play subwoofer band limited noise in REW and do the crawl around. Where it sounds thin you don’t want to put a sub.
 
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You could try the Geddes multiple subwoofer method. Basically one sub goes into a corner, the others are in random places around the room but in non-corner positions. At least one of the subs should be elevated off the floor. If you google "Geddes multiple subwoofer method" you will find a lot of links and some videos.
 
Here's a sketch of the room - it's not at all to scale. It's a loft style apartment in a converted mattress factory. The 4 subs are shown with the radial bursts.

It's a multi-use space, i.e. there's a bar / kitchen area, a big dinner table that we sometimes work at, and a sofa / screen area. It's quite a social flat. The intention is closer to nightclub sound, where one can wander freely and there's relatively balanced low end. Rather than a single sweet spot or listening position.

The coverage of the room is pretty good, with the exception of this null. I have only just set the speakers up, and haven't yet gone deep with REW - this is rough, heuristic - listening to music, there's a point in the room where you can't really hear the low end at all.

I've kept a lot of information out of the sketch - e.g. the position of the bar area, projector screen etc - as I want to see purely based on the rough dimensions of the room what people notice about the subs and the null.

One of the reasons the subs are currently where they are is because of cables I have - there's a nerve centre where DSP / amplification happens, and currently I don't have vastly long cables to put the subs very far away from it - although if need be I can order some long cables.

The subs can basically go anywhere. I can do timing and EQ on any of them.

It could also be a DSP thing, where the polarity / timing of the subs can be played with - I'm not that familiar with this, and haven't tested it.

Apologies if this is all too rough and heuristic for ASR, my intention is to learn a bit about fundamental principles before starting to lug these big subs around and spend ages doing frequency sweeps etc.

I forgot to put on the diagram - ceiling height is approx 4 - 5 meters.

View attachment 372645
Is this an enclosed room?

Where is the bar? Large furniture can change the room modes of a subwoofer dramatically.

Even bass in a room like that you need to have one or 2 of your subs reinforcing the nulls of your other subs. For that null it's likely a delay issue with the nearest subwoofer. That may fix the null in that area. Maybe not. You'll need to test with rew and possibly eq if you have a mini dsp or the like.

What subs are we talking about?
 
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