I thought long and hard about adding a second sub to my system.  But a good deal came on a SW 450, so I got it to go along with my 15 in sub and Icon V system.  All I could think about were the problems that could come from using two different subs:, different woofer size, different frequency respones, phase issues, cancelation issues and standing wave problems.  The first thing I did was use a Y connector to hook the subs up to the avr with only a .1 outlet.  Next I turned the gain up 1/2 way on each sub.  Then I used and spl meter to set each sub at 75 db.  Turning one off while I set the other one.  Next, came the autocalibration to re-set the whole system and checked it with the spl meter.  Both subs are on the front wall, but not the same distance from the corner to help with standing wave issues.

Results:  Great!  The system was tested with music and movies.  Nice balance sound  and no ablility to locate one sub over the next one.  Both subs are not able to be localizes.  More bang from the 30 Hz range due to the 10 in. sub and good 21 Hz response from the 15 in sub.  There is also a better frequency overall response in the bass region with using the two different subs.  The use of Identical subs is always suggested but not necessary always.  What are other members experience using 2,3, or 4 subs.

Derrickdj1,

Glad you patience has paid off and you are having good success with non matching subs.  It is tough to do but can be done as you now know.

A short while back I was using a Paradigm Servo 15a with my Klipsch RSW-10d and after much trial and error(countless hours and weeks) I was able to get them blended pretty well.   I changed the crossovers, gains, phase, placement many times to get it "right".

I now have a Revel B15 with a built in adjustable 3-band parametric equalizer and it was much easier to blend it seamlessly with the RSW-10d.  I am using the NAD receiver's crossover set at 80Hz for the RSW-10d and the B15's low pass filter set at 50Hz.  The subs are placed up front right/left next to my RF-63's and they really do disappear in the room.  I am more than pleased with the results.

Bill

Thanks Willand.  I  never thought about different subs, possibly making the bass coverage better because  of their different freqency responses.  I know it can also be a nightmare.  I just learned this gain matching method and find it make things much easier.  The room is the opponent when it come to good bass.  I seen pic's of your Revel B 15 in Jan., very sweet acqusition!