Phasing, locating, or stacking subwoofers?

[mfishmike]

I've finished up my second (identical) dual SS RLP-15 subwoofer with 4 side mount passive radiators. Tuning is 23 hz. Power is about 900 watts with each subwoofer driven by a separate QSC 1450 amp.

I got the newly finished sub in the house last night and even though I didn't corner load the new one like the first, when I powered them both up, the bass wasn't as good as with just the first one turned on. I really lost a lot of bass. When I turned the second amp off, the bass improved.

I've heard of co-locating them ie stacking one on top of the other, but that would put my subs at 6.5' tall. With the side firing passive radiators, I can't place them side by side. Using pro amps I don't have the ability to adjust the phasing and the Rotel amp doesn't have a delay built in for the subwoofers. I've got the WAF approval to stack and am wondering if this would be my best route to go. 18' x 24' ideal shoebox room with 9' ceilings.

I'm looking for any thoughts on how to get the most out of these two subs in the system. Links would be appreciated also.
Thanks, Mike

[DL86]

If your getting nothing with both subs and amps turned on. Try playing with the phase of your second sub. I am guessing this should fix the problem.

[mfishmike]

New avatar, problem solved, and super bass!

I was getting power and bass, but one was cancelling the other one out. There is no phase adjustment in my Rotel or pro amps. I've ended up stacking the subs as shown and am proud to have changed the avatar pic to show the end result.

I spent about 4 hours researching multiple sub locations and there was one extreme to the other on suggestions, but the most mentioned with good reason, was the co-locating of the two subwoofers. Reports indicate that there is a 6 db gain with this placement. THX recommends this type of installation as well. Joe Satriani has four bass guitar quads stacked on both sides of his sound stage for a reason. I just figured out why. I stacked them on top of each other and there is a tremendous gain resulting in this configuration with all of the drivers working together instead of cancellations from each other if they were to be located on different sides of the living room.

I now have 12-15" active and passive drivers working together in the same corner and I'm at the point to say I think I could have too much clean bass now. I have reduced the gains on my amps, reduced the db gains in the Rotel set up program, and the output is extremely more pronounced. I've bumped the crossover point up to 60 hz and the mains are producing cleaner sounds than I've ever heard. They are not having to carry the 40 to 60 hz range which is quite a load. The QSC amps are blowing out cold air meaning they aren't working as hard. I've cut them back by 30%. This will also save my drivers as they don't need as much power as before.

It's all a win win situation, but I'm going to have to live with a tall subwoofer. I'm leaving the grills off the lower one until the upholstery shop finishes the top one so it won't look funky in the mean time.

I now think I have the ultimate sub setup :T The WAF has not been affected. When I told her I was going stack it, she said get some help. When she got home, I reminded her of the don't ask, and don't tell policy. Each subwoofer weighs 235 lbs. each. It was a chore indeed to do by myself.

Mike