Crossovers, why so few options?

01-27-10: Rrolack
Does anyone here use an active crossover with a tube preamp? It seems like the input impedance on most active crossovers is pretty low as compared to tube/SS amps; has this been an issue for you in matching the preamp to the crossover?

This is a requirement in my system, the Megaline operates only with an outboard active crossover. The benefit is the amp is looking directly at the driver, no volume control, no inductors, no caps and no resistors. Accomplishing crossover at line level (1 volt or so) is much easier and cleaner than at amp level.

I have tube preamp, tube phono, tube crossover and tube amps. The input impedance of my amps are 150K, so no problem with the tube crossover driving them. The output of several preamps I've auditioned (Ypsilon, Einstein, Aesthetix, Allnic, Audio Research) had no problem operating into my tube crossover.

Some speakers are a natural for outboard crossovers and some would be a nightmare. Which applies to which depends on what the crossover must achieve to make the speaker linear.

The Maggie 20.1 is another speaker that works superb with tube outboard crossover. A friend of mine has this combo and it goes against anything in high end audio, even the kilo buck speakers he's tried it against.

Short answer, with the right speaker and outboard electronic crossover the combo can work miracles.

The down side is the crossover design must absolutely and PRECISELY match the requirement of the speakers drivers and a minimum of four to six mono amps (or two to four stereo amps) to function. The benefit is astonishingly low distortion, ultra high speed and control of drivers and wide dynamic range without compression.

Required sound pressure level is not as critical as with a passive crossover. Some speakers have a threshold that must be breached before dynamics and realism come into play and frequently that window is shallow, with high sound pressure levels becoming blurred as you push the envelope.

These issues are greatly reduced by direct drive to the speaker elements and upper limit if SPL is astonishing. There are benefits from active outboard crossover but it is a LOT of work to get it perfect.

Rrolack,

Another alternative is the Bryston 10B sub. It has fairly flexible xo frequency and slope settings. Maybe a little expensive for a sub crossover, but a very solid and good sounding piece (I use the full range version). By adding a crossover at line level for the sub you will achieve many of the benefits Albert Porter has described.

Mr. Porter,

Amen brother. I also think Shadorne would agree as he has had active speakers for quite awhile.

In an attempt to get the most out of my modest system of Magnepan 1.6's and older Arcam electronics I gutted the 1.6's of the passive crossovers, rewired them, and inserted a Bryston 10B. The change was truly transformational in all the ways you describe. A lot of hard work (and apprehension for someone who had no experience in this kind of thing), but worth it.

Jim S.

Jim S,

In an attempt to get the most out of my modest system of Magneplanar 1.6's and older Arcam electronics I gutted the 1.6's of the passive crossovers, rewired them, and inserted a Bryston 10B. The change was truly transformational in all the ways you describe. A lot of hard work (and apprehension for someone who had no experience in this kind of thing), but worth it.

A good friend who is a reviewer for Absolute Sound owns Maggies and like you, went all active on crossover. He hears very well and I respect his opinion.

Several well respected, super expensive speakers have passed through his listening room and the Maggie held their ground. I don't doubt you are getting the results you claim, active done right solves problems we didn't know we had, until after the fact.

AP,

It is still a modest system, and not "perfect" by any stretch, but it is amazing the difference going active made. More control, more transparency, more headroom for the little amps.

You said one thing that I think especially pertains to Magnepans;

"Some speakers have a threshold that must be breached before dynamics and realism come into play and frequently that window is shallow, with high sound pressure levels becoming blurred as you push the envelope."

The speakers are in a large room (30' x 60' irregular) and you could hear the strain as I would try to push the SPL's to the point where the music came to life with passive speaker level crossovers. Night and day difference going line-level active.

I need to give credit to the guys over on the "Planar Assylum" for documenting how to go about it. It is not a plug and play thing with the 1.6's. Your descriptions as you went through the development of the crossover for the Mega Lines was also an inspiration.

Jim S.