Lasher:

Yes you are reading the graph correctly

I guess my graph could be a testament to the theory you've heard - this is a graph of all four of my 18" subs playing at once. Individually the response, while still extremely good, is not quite as flat.

I couldn't say however that more than one sub will automatically give you flatter response in all rooms. Sometimes a single sub will be better in an ideal location in a less-than-ideal room. My room is perfectly symetrical and built from the ground up for this purpose, so that makes a lot of difference.

The best thing to do is to invest in some RTA software, a calibrated microphone and experiment. An RTA is really the only way to sort out all the possibilities since you can see the effects of positioning and such at once and all across the band.

[This message has been edited by soundhound (edited January 03, 2004).]