Active Crossover Recommendations

I want to experiment with using an Active Crossover to seperate high frequencies (going to my Quad 988's through Cary EL34 triode amps) from low frequencies (going to self powered subs by TBI or an ACI Titan). Can anyone recommend a good active crossover with a steep slope for this application. I would like the Xover frequency to be somewhere between 80-120 hz, best case around 100 hz.

Thanks very much for your suggestions.
Look at Marchand Electronics for their tube crossovers.
Look at the Bryston10b Sub or 10b LR
If you want the best:

Get the Krell KBX
marchand crossover doesn't work. I wasted time and money on those (still waiting for refund). Be careful!
Linkoping...Please provide some detail about your problem with the Marchand X/O. They have a reputation of excellent performance at reasonable cost, although my experience has only been with the SS units.
It may seem cheap, but there are a lot of positve reports on using Behringer DCX2496.
It's not the price of the Berhinger that puts me off, but the fact that it appears to digitally upsample and then downsample to do its crossing over. I can't imagine that would be good for the signal, even at 24/96. Kenn39 - what have you heard about its application?

I purchased a used Bryston 10b-sub, and will give that a shot. The distribution of frequencies that they chose is not all that suitable to my desired 120hz Xover frequency: they use:

50, 60, 70, 80, 90, 100, 200, 250, 300, 400, 500.

Bryston will change out the resistors at a cost. I will play around with the available frequencies, but think I may modify it to:

70, 80, 90, 100, 110, 115, 120, 130, 140, 160, 200, 250

The rolloff slopes are choosable b/t 6, 12 an 18 db/octave. It may be worthwhile to leave a gap between high pass and low pass, and I'm not sure how big of a gap, that's why I'm thinking of using high resolution around 115 hz, my target area. Any thoughts or suggestions?

Thanks, Peter S.
wouldn't ever do that to my signal, although it is probably very effective frequency wise.
Peter, I first read about the Behringer on the Newform Research Speakers website:

There are many posts on various forums by people who use it to do bi-amping.

The Behringer does not resample. It does A/D and D/A to do the processing in digital domain. The conversions may be a concern. The digital domain processing provides a vast array of options though.
Peter, I've fooled around a bit with active crossovers altho with no CURRENT products. I believe:
1. You'll find virtually no difference between any 3 adjacent frequencies in your string beginning at 70; they're just too close together. IOW, there's simply not enough difference between/among 100, 115, and 120, to pick just 3. The only 3 with enough split are the last 3.
2. I strongly recommend you use a single-order slope on the hi-pass filter to the Carys and that it be a 'passive active' filter, meaning no more than a series capacitor, and a VERY-high-quality one at that. Your Cary/988 backend is probably VERY resolving, and probably you'll hear the circuitry AND the additional cables AND all the additional connections if you use an active filter. Think about how many mechanical and solder connections you'd add to the signal path with an electronic crossover!
3. I suggest you use the lo-pass filter(s) in your powered subwoofer(s).
4. I suggest you use stereo subwoofers. There is indeed directionality to bass frequencies.

IMO what you need is a soldering iron, knowledge of your amp's input impedance, and a few hi-quality caps. I suggest you experiment with crossover frequencies (=cap values) using SoniCaps. When you've decided on a frequency/capacitance, replace the SoniCap with a SoniCap Platinum or AT LEAST a Cardas Golden Ratio, the 2 finest caps I've ever heard. your money by NOT buying an electronic crossover, experiment with cap values, and enjoy superior sound thru your system. BTW I think you'll end up with a LOTS-lower hi-pass crossover frequency than 100 and above.
Jeffreybehr's suggestion is a good one if a 6dB high pass is OK, and for this application it is. However, I believe that a good electronics X/O would do the job without audible degradation.

My only caution is that this fixed capacitor approach does not give you flexibility to easily change the X/O frequency. I have recently concluded, after years of seeking the "right" frequency, that there is no "right" frequency for all music. So I have a X/O that is easily changed with the twist of a knob.
I am presently running a B&K PT-5, it has an 80hz low pass output, and a 100hz high pass output, and dual mono outputs, it works very well. However, certain amplifiers can tax this units power supply, and hence, it's output abilities, the sound however, is very good.

Wednsday I will recieve my Van Alstien Super Pas 3 tube preamp, it will be interesting to "hear" how tubes compare. I am running a pair of Cerwin Vega 15's for the low end, and Dynaudio/Vifa for the upper registers in a 14x28 room- spl has been mesured at over 140db at full power (given the source). Presently, amplification is two Proton D1200's, and an Audio refinement CD player.

I have experimented with a Crown 3-way active and it was very good, but the more you add the less you get (so to speak) this is why I chose the B&K, simple and yet, good sound for not much money.
Peter, I didn't go quite far enough in my comments. I believe that in a subwoofered system, one needs to run the main system as full-range as it and you can stand. With your 988s, I believe you'd increase their power-handling capacity substantially merely by removing most of the low bass from their signal. That can be done with a 40- or 50Hz hi-pass filter point; I'd start with a 50. Then set the woofers' crossover points and levels wherever you want that SOUNDS good. The point is to keep your fine-sounding main system doing about 90% of the work, and sounding GREAT at it, of course, while increasing power-handling a bit AND adding lo-bass capability. The trick will be to find PLACES for the woofers to blend well with the main system.

I've done something similar in biamping my Eminent Technology 8s. Initially I duplicated ET's c. 40Hz MR hi-pass filter point with an active filter in the amps. I then eliminated the hi-pass filter and have been running the MR panels wide open. I THINK it sounds better. At least I've eliminated the sound of one cap and its inherent phase errors.

If those 'Cary EL34 triode amps' are Rocket 88s, their 150K-Ohm input impedance would create a 48Hz filter with a 0.022µF cap.

Good luck. Pls let us know what you do.

Try Bryston 10B sub ccrossover with following settings..
High Pass 100 - 110Hz 18 DB slope
Low Pass 50Hz 18DB slope
+3 DB sub volume


just run quads full range and use crossover to roll off sub only around 40hz....volume maybe down 1-2db
Go to the ACI website they have some passive filters in 2 flavors ($30-40) that I am going to try 1st. before I start on the electronic path. I am trying to bi-amp w/ ML-9s.
Whoops - I guess I've been offline for a couple of days. Jeffreybehr - thanks for your suggestions. In about a month I'll have a preamp that has 2 sets of RCA outputs: 1 with caps that are selected to roll off at 80hz into my 100kohm Cary SLM70 monoblocks, and one without any filters. I will try it both ways: 1) passive filter on the high frequencies and active filter built into the subs, and 2) active filter (Bryston) on both. For now, I can only work with the Bryston, until I get my other preamp.

The sub options include: 1) a pair of TBI Magellan VII's, and 2) a single ACI Titan. The TBI's only have phase reverse whereas the Titan has fully adjustable phase. I'm not looking forward to moving the subs around, but it has to happen! The TBI is very fast, which is why I bought them (to keep up with the Quads). I needed 2 because they aren't that powerful, plus I believe in stereo subs. If the single ACI works, I would likely buy a second.

Thanks all for your comments. Check back on this thread in about a month for a summary of my results (I hope).
By the way Jeff, what is the equation for calculating the capacitance for a passive crossover frequency based on the input impedence of the amp?

Thanks, Peter
does anyone have the equation for calculating required capacitance for use in a crossover (given amplifier input impedance)? this thread stalled just when it got handy...

Rhyno, I assume you;re referring to a passive line level low-pass? If so, 1st order Butterworth is C= 1/2pi(F)(Ramp)(1+a). F= xover frequency, Ramp is the amp's impedance, a is the relation between amps' gain.
I.e. if a=1, the amps to be used have identical gain. If not, give a the appropriate value to balance the gain. For a much better take on this, check out Art Ludwig's site (sorry don't have it handy).
hi greg, so if i understand correctly, this is 6db per octave, yes?

and, if the high freqency amp had a gain of 20db, and the subwoofer amp had a gain of 10db, then "a" would be 2, and pi would be 3.1417, correct?

the cap would of course go in series w/ the high freq amp, while the low freq amp (the sub) you could simply rely on its own internal crossover to filter out higher freq info?

the cap would of course go in series w/ the high freq amp, while the low freq amp (the sub) you could simply rely on its own internal crossover to filter out higher freq info
For hi pass, cap in series, correct.

Matching the two xovers, however, may take some experimentation: if the sub's xover is not 1st order (6dB/octave) electrical -- which it probably isn't -- you may just get away with playing w/ the low pass frequency. This worked for me once, where the powered woofers part of the speaker system was detachable from the rest of the speaker; the cut off for the woof (12dB/electrical) was set ~1 octave lower than the main; then we used placement of powered woofs to compensate for the phase differences between the two.
Energy makes a nice subcrossover.I have one if your interested was going to list fri.I liked these much so far have bought 3 over the years much better than paradigm x30 its very useful and well built.

I disagree with your blanket statement about the Marchand xovers. I am using the XM126 in my system with excellent results. Additionally, the company provides very good support for its products. The Marchand tube xovers are excellent performers at a reasonable price. Check my review of the XM126 at the url below:
Accuphase F-25 active xover