So I was thinking of looking at a two way tube(Marchand?)active crossover in addition to adding an active sub to the system. It would look like >> CD player then Foreplay then Paramours then active crossover then 4 Pi's with one out of the active X-over going to the active sub.

Is this be the correct order? or is it active-x-over then amps then speaker & sub? I would still use the passive theater 4 pi crossover? No? Yes? Any suggestions for an active sub that would blend well with the above system? Parts Express DIY? And FINALLY the last question, does an active crossover increase the depth of image (or 3 D soundscape if you will)?

I have to say that I could easily live with the way the system is right now with no changes, but half of the fun for me is seeing what tweaks I can do to change this and that & see what happens as a result. These speakers are truely awesome.

Thanks all!!

Good to see you completed the Theatre-4 and you're enjoying it. They don't go all the way down to shake your walls, but low enough for most music.

I'm assuming what you want to do is keep the passive crossover in your Theatre-4 and use a 2-way active crossover to integrate a sub. There's a couple of options:

1) Active X0/Biamp. In this option, you'll need a 2-way active crossover with a summing function for the low freq, and a monoblock amp in addition to your Paramours. Sequence will be CDP -> Foreplay -> Active XO. One output from the XO will go to Paramours than Theatre-4. The second output from the XO will go to your new amp than sub.

2) Plate-amp/subwoofer amp. While the first option is technically the "best", it doesn't have to be that complicated nor expensive. A lot of us that received great results from a simple plate amp. All plate amp and subwoofer amps have an active low pass filter built in, so you don't need a separate active crossover. Just build your sub, slap a plate-amp on it and connect it to the output of your Foreplay. You'll have to split the output of your Foreplay so one goes to the plate-amp while the other connects to the Param's.

If you're looking for something a little different in a sub, Bill Fitz has a couple of interesting options on his site.

Gar.

Thanks

If you're using an active XO to divide the signal between your Theatre-4 and sub, there's no need for a passive XO in your sub.

I re-read your original post again and you mentioned "active-sub" a few times. An "active-sub" usually has a plate amp (active low-pass and amp) built in, so you don't want to use one if you're using an external active XO and amp for the sub.

Again, the second option of just using a plate-amp is very respectable and economical. Perhaps Bill Epstein can say a few words about his Titanic and Theatre-4 combo.

Gar.

Chris

I'd only use the high-pass filter in a plate amp as a last resort. I think it's much better to use the natural rolloff of the main speakers and adjust the low-pass freq on the plate amp accordingly to integrate. My Theatre-3's go pretty low by themselves and I'd assume the 4's go even lower. You'd have to bring the low-pass freq on the plate amp down to the 40Hz range for good integration.

Gar.

Chris