I'd just like to add a couple of comments to my earlier posting on this topic.

My guess is that anyone who has gone from using a single sub to two or more has noticed a big difference - and hopefully an improvement. The question is whether you hear a difference between two subs in mono, and two subs in stereo. And I would argue that, as with all listening tests, unless you can keep everything else equal, and unless you can transition between the two states in a very short period of time, you might be giving your brain too much time to forget what it has just heard. "Time" is a serious factor when it comes to our ability to make comparisons. (Heck, our sense of hearing varies throughout the day depending on any number of factors - something that I proved to myself by taking a number of audiometry tests throughout a single day and seeing that my sense of hearing did indeed vary slightly from one test to the other.) In my case, by having to do nothing but switch between mono and stereo on my ICBM, I'm getting as close to an instantaneous switch in states as possible - and then only when I have someone standing behind the equipment racks to make the switch while I listen. (It's also important that the listener does not know the initial state (mono or stereo) and that a "switch" between states can be no switch at all, when conducting the tests.)

Since my first posting on this topic, I've given it a bit more thought and wonder if stereo subs might produce a noticeably different sound compared to a two-sub mono set up in the case where the front main speakers have less bass extension. I can't easily swap my large mains for less bass-capable speakers, however I CAN use the ICBM to simulate this by simply changing the crossover point. A series of listening tests with the ICBM on bypass, 40, 60, 80, 100, and 120 HZ should either prove or disprove the hypothesis.

When I can find the time I'll see if I can set something up and will report back on the results.

Regards.

Jeff Mackwood