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Critical subwoofer tip

I assume that everyone already knows the importance of phase matching a sub to the main speakers but it’s a little more complicated than simple 90 degrees or 180. The B&W sub that I have has four choices. In every case there has been a definite correct position that can be non standard. My current setup shined at 270 degrees vs the std positions. It’s completely obvious and the other choices would not have been satisfying. 
From my lengthy experience I would want a subwoofer with several phase choices. I personally don’t see how one could seamlessly integrate the mains and the sub without this flexibility. No one asked but i thought this info might be useful to anyone purchasing a subwoofer. YMMV
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rwbadley's avatar
rwbadley
143 posts
 
In my experience adjusting subwoofer phase matching to the mains using a fixed sine wave/null points was vexing. 
It was much too room and location dependent. 
I found a better result in my system by playing a repetitive kick drum and trying to match the beat sharper than softer. It seems more likely to result in a phase structure that is consistent from ‘the other room’. If you have inaccurate phasing, when you go elsewhere in the house it seems much more apparent. 
If you get this kick drum right, it seems more correct. Not just from the listening position that has room issues effecting it, but from a broader area of the structure. 
mapman's avatar
mapman
22,198 posts
 
kick drum or many modern pop recordings with synthesized percussion will do nicely. You want to maximize the “kick”.

there I said something positive about modern pop recordings. 👏👏👏
dvalverde
1 posts
 
Anyone familiar with phase cancellation technology used in headphones should appreciate the importance of optimizing phase relationships. The problem is that if you have a two position phase switch on your sub, you can only reverse the phase 180 degrees, and if your phase is only off by 90 degrees, you won’t hear a difference either way. I have two subs, and I accidentally had the phase switches in opposite positions from each other because like a lot of you, I didn’t think it made much difference. When I put both subs in phase with each other, the difference was obvious—I got louder, punchier bass. Golfnutz got it right—if your subs are out of phase with the mains, they’re literally working against the mains bass output, and the overall bass will be reduced. So setting the phase is simple—just use the position where the bass sounds the loudest. Just keep in mind that with a 2 position phase switch, you may not hear a difference.
mapman's avatar
mapman
22,198 posts
 
Worth noting that when choosing source material to tune phase with that is where a sound meter is crucial.  You have to be sure there is bass down in the frequency range the sub is covering.  Many recordings with good bass will not do much below 40 hz or so. So Adjusting phase on a sub with music containing little or nothing in the range the sub is covering will do little or nothing.  Details matter!  🏆
golfnutz
231 posts
 
I won't criticize anyone who sets theirs subs up by ear. Everyone has their own way to do things. That's all part of the fun.
However, I think it's kind of like watching a car drive past and guessing how fast it's going w/out using a radar gun.
I spent a couple more hours today tweaking my subwoofer(s) setting to try and improve the frequency response. There's no way I could have gotten to where I am without the aid of REW.
I'm pretty happy with the first image, as it's only out by a couple of dB (in one place) from what's acceptable using EQ/DSP (5dB).
Second image shows my previous setup compared to today's changes. It also includes how the 'Mains Only - without Subs' measure.
https://imgur.com/a/aXlCoXh
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