Holy Crap What have I done?


Ya know that scene in "Aladdin" where Abu the monkey touches the huge ruby of the forbidden treasure and everything goes to hell around them? Well, *that's* kinda what happened to me tonight.

I finally found a Marchand XM9 crossover at the right price from an honest seller, and it arrived tonight. I put it in line between my preamp and amp, and it did both what I wanted it to do and what I didn't want it to do: it improved the "slam" of the bottom end, but sucked all the air out of the music and my system went from a pretty high degree of "you are there" factor to realizing you're listening to music on a good stereo.

Admittedly, I haven't played with the crossover controls yet, but I'll be quite surprised if they can "bring the life back" to my system.

Any thoughts on how to get my system to give me that "I'm in the room with the musicians" feeling again with the crossover still in line? Maybe I need to go to an XM44, or some other brand of crossover?

I should mention I tried the crossover because my nOrh mini 9.0's only go down to about 65Hz -3dB with a really quick downturn to -10dB (around 55Hz at -10dB, if I remember my measurements correctly.) I was happy with my ACI Titan crossoved over at 85Hz, but had read that using a crossover to cut the lowest octave from the monitors would improve the midrange and imaging. In this case, it didn't, interstingly.

I'd sure appreciate whatever thoughts you all have on where to go next.

Howard
Ag insider logo xs@2xaggielaw
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
Set Lowpass Filters A & B to 250Hz.
You want the filter frequencies to be as far apart as not to interfere with the filter that is upstream (first) in the chain that is actually doing the work.

You have 2 different choices for the input

Left & Right Line Level Inputs: Use either or both of these inputs. You will need to set the Input Level and Lowpass Filters A & B. The (input level) volume needs to be set at the same volume as your main speakers to get a seamless blend.
When using the Theater input, the volume on the subwoofer is bypassed and will be controlled by your processor/receiver and maybe your crossover level controls.

Theater Input: Connect to this input from your sub output on your receiver, preamp or processor. Set Lowpass Filters A & B to 250Hz. Input Level is bypassed and volume is controlled from your system's subwoofer volume control or maybe the crossover level controls.

Hope this helps.
Man is this confusing! How can you put a crossover between the amp and preamp? Is this only in the subwoofer circuit? Seems to me that the inline filter would affect both the sub and the monitors, which would be the effect of more bass slam at the expense of mids and highs. This is what I think, and you guys tell me if I'm wrong. What Aggielaw originally had was a pair of speakers with a two-way internal passive crossover inside the box, and an ACI sub with a low-pass passive filter inside the box. If he adds a crossover in front of those crossovers, especially if it is a two way, he will really mess up the passive crossovers in the speakers. Unless I'm just not getting it, I would believe this setup is not good. And again, just my opinion, but I see no problem with the monitors rolling off naturally at 65Hz. I guess I don't agree with that article you read, Aggielaw.
"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