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Two subwoofers to counter an interference room mode

bachatero

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I have a specific 30Hz room mode that completely eliminates that frequency where the subwoofer is (and where I'm listening), and I believe this is due to the waves bouncing off the front wall, then the back wall, then canceling out the negative amplitude the subwoofer has reached by the time it gets back. I've also read how two subwoofers on each side of a room can help with modes, but I'm not sure if it would help in this case, either if both were in phase, one inverted, or one slightly delayed. Would it here? I would love to be able to hear low-bass without standing on the other side.
 

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I'm NOT an expert, every room is different, and some experimentation (after you have the 2nd sub) is likely required. But here's something from Floyd Toole's book that I've posted a couple of times.
 

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You may be able to do better simply by moving your sub around. IME multiple subs does make it somewhat easier.
 
Ever try modeling your sub/room with REW's room sim feature?
 
I'm NOT an expert, every room is different, and some experimentation (after you have the 2nd sub) is likely required. But here's something from Floyd Toole's book that I've posted a couple of times.
What does the text on the right say?
 
I have a specific 30Hz room mode that completely eliminates that frequency where the subwoofer is (and where I'm listening), and I believe this is due to the waves bouncing off the front wall, then the back wall, then canceling out the negative amplitude the subwoofer has reached by the time it gets back. I've also read how two subwoofers on each side of a room can help with modes, but I'm not sure if it would help in this case, either if both were in phase, one inverted, or one slightly delayed. Would it here? I would love to be able to hear low-bass without standing on the other side.
I've had this issue in the past. Very little bass in the listening area but plenty of bass off to the side in the dining room. Solved it by having one sub in phase and one out of phase. Brought the bass back into the listening area. Could be different in your set up, but worked for me.
 
I've had this issue in the past. Very little bass in the listening area but plenty of bass off to the side in the dining room. Solved it by having one sub in phase and one out of phase. Brought the bass back into the listening area. Could be different in your set up, but worked for me.
I'll give this a go once I have two subwoofers. In the meantime, it turns out that putting one of my 4 inch fiberglass panels right behind my seat increases the SPL by a whopping 2 dBA, a pretty good improvement for costing nothing. You can literally feel it shaking when the bass plays and that's moving air getting turned into heat.
 
As noted, moving the sub around the room might fix the issue (but could potentially create null in a different band).

If you keep the measurements of various positions that will give you insight how sub sounds at MLP and where are the nulls for these various positions. If a single sub can't provide smooth response and that is what you are looking at, you would have an idea if the other sub could fill in the null. Very simplified, you find a position where the sub fills the 30hz null, but e.g. has 50hz null, which in turn would be filled by the sub at the original location.

Ultimately the nulls will depend on the proportions of your room (if regularly shaped) and location of MLP. If MLP can be moved, then you have even more options to fix the problem either with one or two subs.
 
Put your sub at your MLP. Then make measurements at the possible sub locations. Use MultiSub Optimizer and see which location gives you the best response at your MLP. You can repeat the process using combinations of the measurements you made to see if a second sub would help.
 
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