Subwoofer Set up Question

I use Super Eclipse III's with an ACI Force XL sub. The Coincidents are great speakers that already go pretty damn low without a sub. I do what you describe and run a line-out from my pre to the sub, and a second line out to my amp. This arrangement took quite a bit of fiddling to get to work seamlessly, but trial and error with some help from ACI and various posts here have helped get it right for me. It really is a subtle effect with speakers that go this low, but it works quite well once sorted out. It is a matter of getting the combination of the low-cut, phase and volume just right. Room position also is quite important, but in my case I was very limited. With only a single sub I wonder if my soundstaging abilities are compromised slightly. Ultimately the presence of the sub should not be readily apparent in 90% or more of what you are listening to (at least that's the case with the music I listen to). I only notice the presence of the sub at the very deepest of passages and I do prefer it this way. I do not like when it intrudes too much into the bass range of the speakers, or if the volume is set too high.

Good luck.

I do not want to run the second line out to my amps as this takes away from running the system via balanced from my preamp and amps. I am thinking of what Marty just described.

You lost me there. You said you had two line-outs at your pre. I'm using the two outputs on my preamp, one going to the sub, the other going to my amp which goes to my Coincidents. I prefer this to running the signal through the X-over components in the sub. So both components are getting a full range signal to deal with. The sub deals with it via the high-pass, phase and volume. I'm not sure what what approach you're considering, but it sounds like the one Marty describes is the same as what I'm using. It is also recommended by ACI. My room is 12X24 with cathedral ceilings (sloped 7 to 11 feet) and getting wider (16 feet), and taller (14 feet) at one end. So perhaps about 1/2+ the volume of your room.

No sweat, CK. It's a good method of going and bypasses running the signal to the main speakers through the crossover circuit. I think it's the best way to go for that reason, but does require some careful setup. An SPL meter or better yet, a computer with a mike and software to plot a response graph can be very helpful.

What frequency do you have the sub set for?

Since my sub and room are entirely different from yours I don't think it will matter, but mine has ended up at around 40hz (corrected when I checked) so there is definitely some crossover frequency.

For a system without a 2 output preamp, is the only way to hook up a sub by plugging the preamp outputs into the sub via long RCA interconnects, then connect speaker wires from the sub outs to the main speakers? Does the signal coming out from the sub to the mains get processed by the sub's amp as well? If so, this does not sound like a good approach. Is there any other way to do a sub in a 2 channel system without molesting the main speaker's signal with the sub amp? Hope someone can help, thanks.

Bob - No; you can get a Y-adapter for your preamp which will yield an extra set of outputs if you want to try running your setup differently. As you have it set up the signal goes through the crossover circuit in the sub and is fed back to the amp with the frequency limited at whatever the Xover is set at. Yes, this does put the signal through a path that has the potential to degrade it...or "molest" it as you put it.