Biamping Martin Logan ReQuest

[WVU ML Fan]

Hello all!

I finally have the second hand pair of ReQuests working perfectly thanks to Russ in Cleveland! Now I am debating on the best way to run them. I have a pair of Golden Tube SE 100 amplifiers that sound absolutely outstanding on the panels but have something to be desired for the lows. This being said, I would like to biamp the speakers with tubes on top and solid state on the lows. I have been told that without running an active crossover the highs and lows are being played full range just cutting off and there is a lot of wasted power. Is this true? If so, what is the common way of dealing with this? Also, anyone with experience biamping I will gladly hear it! This is my first time. Also willing to hear what you recommend putting on the lows! Lastly I heard of a crossover modification. I don't know if this is related to biamping but if so, I will gladly hear it! Thank you in advance!

Sincerely,
Stephen

 

[Spike]

My system involves ML ReQuests, bi-amped with tubes on the panels and solid-state on the woofers. I made a conscious decision to go this passive bi-amping route for simplicity sake. Theoretically, the ultimate bi-amping configuration involves active (electronic) crossover at the pre-amp stage to route the low-level signals to the amplifiers which drive the speakers directly, without speaker-level crossover. In practice, this is not easy to accomplish. You will have a linestage, connected to electronic crossover and then to the amplifiers. Moreover, in the case of Logans, you'll also have to remove the internal crossover to maintain the purity of this approach. In my opinion, you're doing lots of complex work moving the crossover components from the passive side to the electronic side in the Logan case. If I were to start from scratch, designing my own speakers, I will go this route, with a crossover circuitry built-into the linestage to keep things simple, but I am straying away from the main topic... Back to my system involving the Logans, since I could not find any preamp with built-in crossover, or crossover with preamp functionality of the ModWright or Cary SLP-98, I chose to go with the passive bi-amp approach. I like to keep the component count down to the minimum in order to maintain the purity of the signals. In my specific case, adding an electronic crossover into the mix will just double the electronic components at the linestage level and they will just degrade the original signal.

Here are the threads which have discussed this issue of bi-amping:

Biamping the older generation of ML
Question about biamping ReQuests
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Good Luck.

 

[Tosh]

You could use an electronic (active) xo for just the bass, as long as it's set to the correct xo frequency and slope, has a level adjust pot to match the two amps' gain, and you bypass the stock passive bass xo. You would leave the tube amp to drive the ESL portion and its stock passive XO and EQ only, and that would be an easy load for the tube amp.

 

[Rich]

Forget about active crossovers for now and go the passive route, which is what the majority of people in your situation do. Hook up your tube amp to the panels and a good 400 wpc or so amp on the woofers. I think you will be amazed at how good they sound and won't look back for a second. If, for some reason, you want more, then you can always explore the active crossover route later. But my guess is you will be in heaven and not look back. Please give us an update once you make your choice.

My experience is with Ascents. I passively biamped my ascents using a CJ Premier 140 tube amp on the panels (140 wpc) and some basic Outlaw Audio mono blocs (200 wpc) on the woofers. The sound was superb, and much better than running it all solely with the CJ tube amp. I can't recommend highly enough biamping these older ML speakers with tubes on the panel and SS on the woofers.

BTW, I am not an electronics guru so can't say for sure, but the whole "wasted power" argument against passive crossovers sounds like BS to me. I'm sure someone with more knowledge in this area will chime in with some insight on that.

Oh, and one more thing . . . you need to make sure that the voltage gain is the same or very close for both amps. Otherwise you will need to put an attenuator (basically, a volume control) in the mix in order to match voltage gains.