I've been reading in a couple threads here about some of you with HT/Audio systems (where the two systems are one and the same) who are working on integrating your subs.
Some time ago, when I had my systems together, I used a set up that worked pretty well.
For this system to work you need:
1) a seperate preamp
2) a receiver or pre/pro with good bass management
Now the main focus here is 2 channel sub integration since the receiver-pre/pro already takes care of that for the HT,
The 2 channel wiring set up looks like this:
cd/dvd player analog out > 2 channel preamp > L&R amp channels > L&R speakers
then to get the ability to use the bass management of the receiver PrePro:
cd/dvd player "digital out" > receiver pre/pro input > LFE output > Sub or Sub amp
With this set up all you do is have your receiver or pre/pros L&R outs go to the 2 channel pre amp's "aux" input, rather than directly to the amp. Then when listening to HT, simply set the 2 channel preamp to "aux" and adjust the volume to a "pre selected" level that you determined during HT set up.
Now with this set up you have the ability to use the bass managment "only" for the sub when you are using the 2 channel only system, since the 2 channel system uses the cd/dvd players "analog" outputs and the HT system uses the cd/dvd players "digital" outs.
This allows you to not only select any x-over frequency available to "ramp" the sub in, but also the volume control to "adjust" the exact bass level for each CD.
It "does not" offer "high pass" for the L&R, only allows for the HT receiver/prepro to be used as a bass filter and volume control.
While a good, high quality X-over is always the best choice, this offers a "workaround" with pretty good results.