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.

No offence, but if you have yet to play with the crossover, how do you know what it is able to do or not do?

Be sure to bypass the subwoofers crossover so that you are not doubly attenuating the same frequencies (huge suck-out).

You could also use it simply as a subwoofer crossover and take it completely out of the main speaker signal path. Simply use it to give you a more precise degree of adjustability on the sub.

You could also go back to the original setup.

Good luck!

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

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

Jafox...I beg to differ with you about running main speakers full range and letting their natural bass rolloff occur.
Of course the obvious reason not to do this is to keep the LF signal out of the main power amp. But it's good to keep the LF out of the speaker as well. Although the acoustic output may roll off, the woofer will still be trying, ineffectually, to reproduce those subwoofer frequencies. It doesn't help the upper bass and midrange to have the cone floping around unnecessarily.

Oh, I see now. Aggielaw must have multiple amps, and no passive crossovers in the speakers. I definately agree that you do not want to overlap the frequency range of the two woofers.

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

Have any of you played with the inexpensive outboadr crossover fron Velodyne? It looks to be quite powerful for figuring out what frequency and crossover slope works best with a given system. After figuring this out you could get the tweaky audiophile hardware to do the same job. Might be worth picking up a used one if it pops up.

Whew! This is getting complicated, but I appreciate the input. Let me give you guys more history, an update, and then we'll see what your thoughts are.

About 6 months ago I realized my system (http://forum.audiogon.com/cgi-bin/fr.pl?vdone&1107477492) badly outclassed my Velodyne CT-120 sub, so I started looking at alternates. I read about the REL approach to setup, and ran cables from my amp to the high-level imputs on the sub, then cable from the sub's high-level outputs to the monitors. The bass slam and overall bottom end was a HUGE improvement! The problem here, of course, is that the sub in my room sits 4' behind the speakers and a couple feet outside the right speaker, so I'd have to run long (read: expensive) runs of cable from the sub outs to the speakers. Next, I tried the ACI filters, which are 6db/octave slopes, but they didn't produce nearly the effect the high-level connections did. Mike at ACI told me two intersting things: the high-level filters on their subs aren't nearly the quality required for a high-end system (and I think this is true of almost all subs); and that if I wanted a good, steep slope I'd need an active crossover. Hence the XM9 purchase.

I did try bypassing the crossover for my mains and only routed the sub through crossover, and the "magic" returned to my system. It was even slightly superior to what it was without the crossover in line. I did try turning the sub's crossover all the way up to 250Hz, but it produced huge, boomy bass, which surprised me. The crossover should have prevented that. The crossover was a kit, assembled by an authorized dealer, so I suppose it could be improperly, but I'd like to save that as a last resort.

I ordered 2 sets of crossovers today; 65 and 85Hz. We'll see what happens.

As for my setup: one amp powering both monitors and the sub is internally powered. The speakers do have magnificent passive XO's, rebuilt by Jim Salk with the finest parts available in the Murphy-designed crossover.

Thanks for your continued ideas. I'll keep trying your ideas and reporting back on how well they work in my system.

Thanks again!
howard

Howard - anything new to mention?

Dbld,

I liked the system well enough as it was in my last post to leave it alone. Unfortunately, my new house in Kansas has all-shhetrock walls, which are presenting some acoustic issues that I need to figure out how to address. I've read enough negative things about both the REL and Velodyne DD series subs to prevent me from puchasing a new sub for awhile - which is good because it forces me to focus on the room acoustic issue. :)

In the new room I did have a "first-time" experience: I head sounds on a stereo recording behind me and to my right. It was so bizarre I had to replay the song to be sure I didn't imagine it! Very cool.

I'm going to try running the crossover in the path of the main speakers again and tweaking controls in the next week or two as unpacking will allow, and post a note about how the system settles in without room treatments.

Thanks for asking for the update.

Howard

So does that mean you are running an XM9 with a 65Hz or 85Hz cossover? Also, are you running your mains through the XM9? I am asking because I am thinking about trying an active crossover, but I fear losing the "magic" on the high-pass side.

Dbld,

I will have to look and see which XO module I installed. I'm pretty sure it was the 85Hz. I never went back to running my mains through the high pass. I'm fairly convinced I could tweak the controls all day long and it just wouldn't be the same. I'll try again running high-pass through the XO Sunday when I get to Kansas and report.

Howard

Thanks, it would be interesting to know if you can hear a difference. I am not sure about the differences between the xm9 and the xm44 other than the xm44 can input a balanced signal. The boards physically look a lot different. I have been kicking around the idea of an xm44 embedded solution.

Dbld,
The XM44 is certainly a higher-quality unit. I'm not dissing the XM9, because it's great for what it does, but after more listening in my new hom I'm convinced I just can't get my speakers to sound as open and airy with it in their line.

I have heard and read over-and-over that the best sounding high-pass crossover is simply a capacitor soldered at each input of the amplifier to the main speakers. Or, a little black-box, with 4 RCA jacks outside and 2 capacitors inside. Two pairs of interconnects must come out of the pre-amp: one pair to the subwoofer, the other pair to the black box. Then, a 3rd pair from the black-box to the main amp. As stated in an earlier answer, the value of this capacitor must be calculated for the input impedence of the amp and the frequency. It makes sense to use the same 65 Hz so that the 6dB filter will work perfectly in conjunction with the acoustic roll-off to give you a simple steep 65 Hz cut-off frequency. Then, you can use the 65 Hz Marchand for ONLY the subwoofer, and use its "Damping" adjustment to tweek the midbass sound. The question is: Will a capacitor sound better than the high-pass side of the Marchand crossover?