Hi,
You don't need multiple subs if they are working below your lowest room mode, in your case
your lowest 2 room modes, which are identical due to the 12' x12' room dimensions @ 47Hz.
Constructive room modes cause peaks in the response, and generally they are only considered,
but destructive modes also exist which cause dips, but they are generally ignored in analysis.
There are 3 types of room modes, axial (a path between two opposite walls), tangential
(a path between 4 parallel walls) and oblique (a path between all 6 walls).
http://amroc.andymel.eu/?l=12&w=12&h=9&ft=true&r60=0.6
Consider a room of AxBxC dimensions :
1,0,0 = the first (lowest mode) of dimension A (axial)
0,1,0 = the first (lowest mode) of dimension B (axial)
0,0,1 = the first (lowest mode) of dimension C (axial)
2,0,0 = the second (lowest mode) of dimension A (axial)
0,2,0 = the second (lowest mode) of dimension B (axial)
0,0,2 = the second (lowest mode) of dimension C (axial)
etc, you can go as high as you like but > 3 is not useful
1,1,0 = the first (lowest mode) of A and B (tangential)
1,0,1 = the first (lowest mode) of A and C (tangential)
0,1,1 = the first (lowest mode) of A and C (tangential)
etc but there are loads more combinations up to 3.
1,1,1 = the first (lowest mode) of A, B and C (oblique)
etc but there are even more combinations up to 3.
Fact your two lowest axial modes are identical,and
so are your two lowest tangential modes,you get
pairs all over the place due to a square room.
What this all tells us is you will have significant bass
boost at 47Hz, and with a decent sealed speaker the
bass would extend to 47Hz and then die, pretty much.
With the SR71 its likely you'd get an excess of bass
at 47Hz, on its own it would probably be fine, but you
want to add a sub, and the best way to do that it roll
it off before it hits 47Hz to be flat as possible.
Note the 47Hz boost will also apply to the sub, so
you want to roll that off lower than the high pass,
e.g. high pass might be ~ 55Hz, low pass ~ 40Hz.
rgds, sreten.
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