Two Subs?

Hello.

What would you be trying to achieve by getting a second sub? Your REL probably has enough output for your room size, for music. I used a Storm III in a 30x18x9 for music and it was ok. But I grew interested in acoustics and got myself a measuring mic and card, and realized how much the room was effecting the response. I now have two 12" Rythmik subs, each set up differently, and placed asymetrically, and it sounds so much better than with the single REL. My goal was to smooth the room response, and I did.

But bottom line, depends on what you are trying to solve. 1 sub is better than none, 2 is better, 3 would be even better. Note that when using multiple subs, each sub doesn't need to be as powerful/expensive as when you are using a single sub.

I hope this helps.

I suppose he means the REL recommended approach of getting the signal to the sub from the speaker terminals, then the main speaker amp and the speakers themselves are still reproducing the whole bandwidth.

An alternative approach places a crossover between the pre and amp to filter the frequencies the sub is going to reproduce so that the main speakers only reproduce above the sub. Most speakers increase distortion at lower frequencies, so that's one benefit pursued by this approach. Same for the amp: you save headroom for the "higher" frequencies.

Of course the approach also has a downside: an additional circuit in the signal chain (the crossover itself), plus interconnects, etc. Another downside is the main speaker woofers are yet another source for low frequencies, helping to smooth the room response in line with what additional subs do. So a tradeoff, like we usually find not only in audio. Pick your poison, I guess! :-)

Back when I had the REL Storm I was getting much better bass response than when I didn't have the sub connected. No question it sounded, and measured better with the sub on. But there was no way around certain room modes, despite trying several diferent locations within the room.

With the two Rythmik subs well placed and dialed in I get much better sound than with the REL, at least for my taste. It took many iterations of placement and dialing in all the variables in the sub's amps, but well worth it for me. Frequency response is much smoother as well, and I was able to significantly reduce the impact from those room modes that were affecting the response so much. To me, this configuration sounds much better than the one with one REL.

But I don't have experience with active crossovers, although I've been toying with the idea of actively tri-amping.
Bob, what crossover do you use? Conceptually, having one amp for mid/highs, one amp for the bass drivers, and then the two subs running in mono makes sense to me, but trying it at home would be expensive.

"If I could I would place a sub in the front Left or Right corner and a sub in the opposite corner on the rear wall."

That would very likely be a bad choice as both subs would be exciting the same room modes. One sub in one corner is good, but the second one should not be in the symmetrical corner. Moreover, about midway of a wall would be more advisable.

The best configuration in my room has been one sub in between the main speakers and the second sub in a corner, with the front or back corners showing almost the same results (albeit with different settings/adjustments).

BTW, just like there is no substitute for good speaker placement, the same goes for sub placement. Sure, room correction will make it better, but the least correction you need to apply, the better.

Cheers!