Originally Posted by Big-Pete
indeed it does.
OK, so what you have is two integrated amps, one is fed from the PC, the other is fed from RCA passthru from the first amp.
Here's what I'd recommend:
A decent soundcard, say a Xonar Essence STX, or a D2X. You then have two separate (stereo) runs of cable to the amps.
One goes from the "front left/right" output of the sound card to the Marantz amp, and that feeds the B&W front left/right speakers.
The second goes from the "Centre/Sub" output of the sound card - most sound cards combine centre and sub on a stereo jack plug here, so you just want to use whichever channel is to the sub, it's a mono channel and you just ignore/discard the other channel. This goes into the Rotel amplifier and feeds the subs. You can either split the mono channel and feed both the left and right channels of the Rotel (then connect one sub to each channel), or you can use only one channel of the Rotel amp and connect both subs to it, I'd favour the first option (splitting the sub feed and connecting it to both channels of the amp) since the second might give you impedance problems (if you connect the subs in series, you'll raise the impedance, in parallel and you'll lower it, lowering it can damage the amp, raising it won't hurt anything but the volume will be lower).
You select, in the sound card software, the crossover type option so that you are cutting off frequencies below the range that the main B&W speakers can reproduce, and sending them to the sub output (and _not_ sending them to the front L/R channels). That way, you are feeding only bass to the subs (and not asking them to attempt to reproduce mid-range and treble frequencies which they can't), and feeding only mid-range and treble to the B&Ws which is also correct.
You then set up the amps with the volume knobs set so that you can achieve anything from quiet to fully loud just by adjusting the volume on the PC. You tweak the volume knobs to achieve the correct balance between the subs and the full-range speakers, ideally you do that using test signals at different frequencies and using an SPL meter to get the volumes equal (to get as close to a flat response as you can), but you can just do it by ear to your personal taste if you want.
Then, the balance between the mid/treble and the bass is roughly correct, and you can just control volume from the PC. From then on, you leave the volume knobs on the amps alone - they are set and forget.
You then go through and tweak the EQ curve on the sound card software to flatten the response of the B&Ws (or adjust it to personal taste), either that or you just turn off the EQ to simplify and clean up the sound path, which of those sounds better to you depends on personal taste, the room and the speakers.Edited by BorisTheSpider - 11/14/12 at 12:08pm