Using Two Subwoofers with Two 2-Channel Amplifiers.

+1 wolf_garcia regarding a monaural or summed below an approximate crossover point depending on the speakers and the room.

With the exception of subwoofers by REL manufactures include the convenience high level connectivity for those who lack source RCA outputs, experimentation should be seriously considered.

Review the subwoofers manufacture instructions when using high/amplifier level connections. Connecting both amplifiers Left channel outputs to one subwoofer seems unusually redundant.

With an honest respect to zipost's experiences. My only sub installation with very small mains that began their in room measured falling off at 97Hz stereo high level connectivity did sound subjectively better to the owner.

With main speakers falling off below 50Hz monaural has always produced a more desirable effect in my experience. It also liberates subwoofers for the always unique crawl test sub locating and an overall improved performance in speed and room node control.   

I am using two stereo JL Audio F-113 subs and I feel that 2 subs fill the room much more than one does. I have mine located close to the mains.

ozzy

Great input everyone, thank you very much.

@wolf_garcia  So if I am understanding you correctly, you have both Left and Right channels wired to both of your Subs?

@m-db  Your "unusually redundant" comment kind of hit home.  It makes sense that If I am dedicating a Sub to L/R channels, it should not matter if a Sub has either one or two Amplifiers connected to it.

Sorry, but just to be clear, when to say "Mono" or "Monaural" you are referring to connecting Left & Right channels to each Sub correct?  My initial thought was that this might confuse the Sub, but it sounds like you guys are saying that this is not necessarily the case (".. canceling standing waves..")

FYI, Mains are two sets of Klipsch Kg-4s.  38 Hz - 20 kHz +/- 3dB at 94 dB SPL.  Room is HUGE (finished basement).

I have both subs (they're different models from the same era, a Q150e and a Q108II...10" front firing and 8" down firing respectively) taking both channels just like when I used only one sub (which worked fine for years). I am fine with this, and the bass is coherent and stereo (except the low bass which isn't but seems like it is for the reasons previously described). Besides, one of the RELs sometimes is used in a nearby window to add bass to the smallish monitors I use for outdoor deck speakers (also in the windows for that purpose), and if it was hooked up to only one channel it wouldn't work like I prefer. I play bass, I'm a sound engineer, and the benefit of 2 subs taking all the low bass equally does have nice results overall as sort of a "mini storm" rig.

Sorry, but just to be clear, when to say "Mono" or "Monaural" you are referring to connecting Left & Right channels to each Sub correct? My initial thought was that this might confuse the Sub, but it sounds like you guys are saying that this is not necessarily the case (".. canceling standing waves..")

Depends on the connectivity options your subwoofers offer. My only high/amplifier level experience was with a REL Studio III using its proprietary cable. Maybe someone else here can answer your question.

By "standing waves" if you're referring those unusually bass heavy locations in your room they can be addressed by experimenting with subwoofer locations and feeding the subs a summed, mono, or monaural signal.

Eventually your setup will be as unique as your room and the system being used.