Charles, if you have any way to do so, I'd recommend you set up the REW software so that you can use it in your room to find the best positions for the new subs. The sub crawl is a good start, but since you're generally just estimating bass response of a single frequency while doing this, it's hard to know whether a given location provides the smoothest response or just the loudest response at the frequency you happen to be using for the sub crawl.
My (unconventional?) advice would be to start with placing both subs where they are most conveniently-placed in the room. In theory, with two subs, placement is going to be less important than with just one since the idea behind two is that they work to attenuate the effects of room peaks and nulls.
Based on that, I'd start where you want them and run a frequency response (FR) curve using REW from your main listening position and measure the results. Then without moving the subs, experiment by changing the phase on one, then the other, then both subs, and determine which combination gives you the smoothest response at your main listening position. This should be your benchmark against which you test any other placement options. (i.e. since this is the most convenient placement for your room, to move the subs to other locations which would look awkward or be less ideal than where they are, another position would have to have FAR better FR to justify making that move and dealing with subs sitting in the middle of the room, weirdly placed on sidewalls, etc.)
Once you've done this much, experiment with a couple of other options. Try the middle of two opposite walls if your room allows, or try opposite corners of the room (my current setup).
If/when my 800 arrives, I'm planning on moving both subs to the front corners outside of the M80s. That will be the "ideal" setup from which I create my benchmark readings. This choice is mainly for looks & balance. i.e. I think it'll look extremely odd to have an M80 and an 800 on one side of the room and just an M80 on the other side of the screen.
If I can't achieve the results I want from there (and using the BFD equalizer), I'll try going back to opposite corners or some other combination that produces flatter response than the way I'd prefer them to be set up in the front corners.
Just resign yourself to the fact that it's going to take some time to get right, and try to have fun in the process (it shouldn't be hard to have fun with it!). We'll look forward to hearing/seeing your results as you experiment.
Jason
Last edited by myrison; 12/13/08 01:50 PM.
