Holy Crap What have I done?

Some different thoughts here: you said when you added the crossover to the system, it sucked all the air out of the music. Are you talking about the portrayal of space, harmonic richness, textures, etc.? If so, the crossover betwen your preamp and amp could ultimately do far more harm than good.

Time and time again, I have found the most critical cable in the system to be the preamp-to-amp link. I have achieved incredible musical magic with the sonic attributes described above. But I can so easily destroy all of this with a change in the IC in this link. And with a crossover here, you have two such ICs in the critical mids/highs.....not to mention all these extra active circuit stages driven by a rather wimpy power supply to boot.

Changing from 100hz to 85hz is just not gonna do anything if you have problems in the upper frequencies. Try the crossover out of the main link and have it drive only the subwoofer as a low-pass and let the main speakers run full range. You lose the benefit of taking the bottom octaves out of the main amp and thus bringing on more clarity in the mids/highs.....but you get the crossover and extra IC out of the loop and this alone can be a huge benefit.

I have found crossovers and equalizers to be fine up to a certain level of system refinement. And yes, they can be beneficial to compensate for low-frequency room nodes, but they can so quickly wipe out the dimensionality and dynamic contrasts that you may have worked so hard to achieve up to that point.

John

"How can you put a crossover between the amp and preamp?"

It's called an active crossover. Read this for further details.

Besides the Marchand products, Bryston makes the very nice 10B that comes in a version optimal for subwoofers. If you really want to go high-end, the Pass XVR1 is quite a statement product.

The last thing I would ever want to do is have a subwoofer (that is optimal in the 85hz and below range) handle the very critical upper bass/lower midrange of the 3rd and 4th octaves. You clearly do NOT want the sub AND the mains both running in the 65-250 hz region! That will be a disaster to the instruments in this range. Keep the lowpass as low as you can go, just a tad above the natural roll-off of the mains and let the mains run full signal. You will certainly get the bass extension you want. The only issues will be coherency between the sub and the mains and finding an optimal location for the sub.

Please let us know how things progress.

John

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

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