Holy Crap What have I done?

If you have not already ordered the 85Hz modules, it might be beneficial to order a pair of 65Hz modules also. Why? Two reasons:

1) With the 65Hz modules in place, run your speakers first straight from your pre. Then run the signal through the Marchand. There should be little to no difference between the sound you hear (excluding bass, remember the Marchand has a 24db/octive slope vs. your nOrh's natural rolloff). This will tell you if the Marchand is altering your signal in any way. (BTW, do you know if this unit was preassembled and tested vs. a kit?)

2) 65Hz is just under 2 octives below middle C (65.41Hz). Using the Marchand at this crossover point will allow your nOrhs to work their magic to this frequency. Since they normally start their rolloff at this point you can use the Marchand to "bump" the frequency response (+ or-) to smooth out the transition.

Try it with both speakers through the Marchand and see if you can get the sound you want. (be sure to set the crossover on your sub to the highest setting as suggested above (250Hz?). Then try it with just the sub signal going through the Marchand as others have suggested. Be sure to watch your cables as John suggested!

I understand the reasoning behind wanting to eliminate the bottom octive of the main speakers but in your case, the crossover would need to be at 130Hz!

At least you will be able to experiment more if you have at least two crossover points.

Keep us informed of your progress.

Eldartford: I know from reading many of your posts here, you and I take a different approach to our systems. I do understand the benefits of these "corrective" electronic components. In fact, I have been playing with the Rives PARC for over a month now. And it helps a ton to clean up the mids because the bass peaks have been brought back into balance. There is great clarity in piano and voice that before was masked by the over-abundance of bass energy. This is immediately evident when toggling the bypass switch on the front panel. But I am also aware of dynamic contrast compression caused by the PARC and the additional IC (Purist Dominus). The minute I remove the PARC and this cable from the chain, the performance has much more life. Yes, tonal coherency is not as good but it does show me some problems caused by the PARC and the extra IC. And because of this, the ultimate solution would be to address this as much as I can through room design/treatments, speaker location and other system tweaks.

No matter how much I like what the PARC does, in the context of my system, I would like to find another solution. Even though the PARC is a high-end piece, it adds a level of sutraction to the chain. From this experience alone, I am incredibly cautious about inserting anything like this or an active crossover into the chain.

Concerning the main speakers' woofers flapping around from lower frequencies, rather than use the active crossover for this, I would simply put a high-quality (Black Gate, V-Cap, etc.) capacitor on the input of the amp. Knowing the amp's input impedance, the capacitor calculation is easy to determine. This would give me a nice and smooth first-order high-pass filter, strategically set for 65hz. And this would be enough to reduce the lowest frequencies in the main amp and any flapping in the main speakers.

There are simply far too many options that I would try before I put that crossover in my signal path. Use one preamp output to the main amp and the other preamp output to the crossover for the sub. Keep the main path as gadget-free and cable-free as possible.

John

Aggie- What John is suggesting is essentially the same approach as the Vandersteen 2WQ. i.e, roll off the bass signal to the main amp with a capacitor/filter and let the main amp and main speakers cover a smaller range. The subwoofer is fed from the speaker outputs of your amp. It works incredibly well, provides all the benefits you are looking for, integrates seamlessly, and you can adjust the filter frequency/crossover point with the W-2 before you get permanent filters. Since you already have the sub which runs off the line level signal, I imagine, maybe you can filter the lows out of the signal as John has suggested, and then run the sub with its own crossover. It would just take making up different filters with diff value caps. Easy for me to say, I can't solder worth a damn, but if you can and have the formula for calculating the values, you could easily experiment. I would use cheapy caps til you find the right crossover and then make up your keepers.

The capacitor input to the main amp is just a line level passive crossover. (Marchand sells those too). With only 6 dB (gradual) roll off it will not provide solid bass in the range above the 65 Hz that you propose.

I would suggest that people try every alternative and pick what they like. That's what I have done, and I ended up with 24dB/oct, HI and LO, with the X/O frequency easily adjustable to suit the music being played.

I want to clarify what was covered by Swampwalker: If you put a capacitor on the input of the amp to give it a first-order high-pass at 65 hz or so, you can NOT run the sub's crossover from the main amp's speaker terminals. This is because this amp no longer accurately covers the range below the crossover point. So you MUST either use a second pair of outputs off the preamp or use a Y adaptor off the preamp output to drive the amp and the crossover ICs.

And yes, this is just a line level passive crossover as Eldartford states. And "just" is the keyword.....nothing less, nothing more.

John