How do I go about bi-amping Martin Logan Ascents


I am way new to this topic, and have no idea what I need, but would like to try this experiment. I am curently running the Logans with a Threshold 300 Stasis II. I also own a Mac? I believe 150 power amp I would like to work in the system. I am also using now MIT 4 9.9 Enhanced Image Bi-wire. If the experiment didn't cost me much I would like to throw the Mac. in I hear this could make a real positive difference.
*Do I need a external x-over?
*Do I need new ICs?
*Do I need new Speaker Cable?
*Is this whole thing just dumb?
I'm new here be gentle. Take a look at my system in "Ever Evolving"
trumpetdoug

*Do I need a external x-over?
*Do I need new ICs?
*Do I need new Speaker Cable?
*Is this whole thing just dumb?
1. Yes. This will require extra i/cs
2. If your pre has dual outputs you will need a second set. If your pre does not, you will need Y cables.
3. You will need 2 sets of single-wire speaker cables.
4. Dunno. Add up the cost of 1-3 plus the value of the 2 amps. Maybe could be better put to use buying a single better amp OR sell one of the amps, get a second to match the one you kept. Then you could eliminate the cost of a cross-over.
Any time two amps of different power outputs and/or sensitivities are used to bi-amp a speaker system, a matching x-over must be used to retain a correct freq. response. Anyone that tells you differently simply doesn't know what they're talking about. The outputs of the amps must be matched somehow, or one part of the system will have a higher output level than the other(either the mids/highs or the lows). One of the best high/low pass filters ever designed for home audio is the Dahlquist DQ-LP1. It has a passive high pass section(very simple and transparent), and an active low pass filter with level, frequency, and EQ controls. They are generally available on the used market(since they're no longer manufactured), easily updated(IE- by Frank Van Alstine or DIY), still supported(by Ragnar) and still used in recently manufactured high-end systems(see this review: http://www.nolaspeakers.com/reviews/tas/exoticaGR_part1.pdf ) Not to hard to find on eBay or on this site. Well worth the effort if you really want to bi-amp correctly.
No a crossover is not required. The issue is that the amps will probably have differing amounts of gain and you'll have to match the voltage output of the two amps. All you need is to place an attenuator inline with the amp having the larger gain. An NHT PVC (~$150) will work just fine.
An Attenuator would match the sensitivity/gain which is one of the main issues of bi-amping with two amps that I mentioned. What about the overlap in frequency that he WILL have without a crossover or filter? Some of the greatest audible gains inherent with bi-amping come from being able to by-pass the passive crossover of the speaker system. Was I wrong in assuming that this is part of your goal Trumpetdoug?
Trumpetdoug- This thread contains discourse that you may find helpful: ( http://www.martinloganowners.com/~tdacquis/forum/archive/index.php?t-460.html ) Especially the last five posts to the thread. If it IS your intention to retain the internal passover: Yes- matching the power outputs of the amps would be your only issue, AND: My bad for making assumptions otherwise.
Rodman,
Thanks so much for the help No bad on your part whatsoever. I will check out the thread you mentioned. Any other advice would be greatly appreciated.
Doug - out
(http://sound.westhost.com/biamp-vs-passive.htm)(http://www.gcaudio.com/resources/howtos/biamping.html)(http://members.djcafe.com/djmapy/Biamp.html) Some pros & cons in those.(http://www.avahifi.com/root/audio_basics/ab_pdf/ab1989.pdf) Page 13 of Audio Basics download= some info on the DQ-LP1. If I were to bi-amp the M/L's personally: I'd feed the ES panel using it's existing passive network to take advantage of the EQ circuitry, but the amp through a DQ-LP1 to relieve it of the bass freqs. I'd open the bass cabinet and bypass the passive x-over(a simple task), wiring the woofer directly to the terminals with a short, high grade speaker cable(Audioquest Bedrock is cheap now days and excellent for bass in a short run). Easily undone should you not appreciate the results. If you can find a DQ-LP1, and decide not to continue bi-amping: You'll have no trouble regaining the $$ spent, as they are VERY popular. If you choose to pursue this course: don't hesitate to e-mail me for assistance of any kind.