Holy Crap What have I done?

TO FAST. Work with the crossover. I added a subwoofer for lower end and the additional reinforcement of the lower tones smoothed out the upper mid band of my system without equalization, "a trick of the ear". Have you tried treating your room for better acoustics? Patience is everything in this hobby however so go slow and listen to the changes.

What is the crossover frequency? I think the Marchand XM9 uses a plug in module.

Marchand X/O are fine sounding units, so you must have some setup thing wrong.

I just read about the XM9 from the mfr's web site. The crossover frequency of XM9L Electronic Crossover Network can easily be set by replacing the set of 2 frequency modules, located inside the cabinet. They can supply any frequency from 10Hz to 20,000Hz. If not specified they will shipped the XM9 with a crossover frequency of 100Hz.
First check what is your crossover frequency. Then we go from there.

Thanks, guys. This unit has the standard 100Hz crossover frequency. Originally I thought this was the best place for it, given the slope diagrams on Marchand's website. It occurs to me, though, that asking my down-firing sub to reproduce frequenies over 100Hz - against the maker (ACI) recommendations - is foolish. I plan to order an 85Hz module today and see how that goes.

Right now I have the sub's crossover set 10Hz higher than the crossover, but I'm not sure that's where it should be. Is there a standard relationship I should be looking for between the electronic crossover frequency and the sub's crossover frequency? Big, I don't think my ACI Titan will allow me to truly bypass its LP filter altogether, but I'll check. That would certainly be best.

Stephenson, I'm delaying room treatments because I'm moving in 3-4 months. I'll certainly look at treatments in the new place, though.

Eldartford, I always enjoy your posts. Thanks for helping me out. I look forward to whatever other thoughts you guys have on this!!

Howard

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