BIAMPING

I run a tri-amp system using an electronic crossover. I have found that the tweeter gets by nicely with 50 watts per channel but the midrange improved dramatically when it was replaced with a 250 wpc amp from a 100 wpc amp. The mid range runs from 90 to 4000 Hz. My subwoofer uses another 250 wpc amp but it may be more conservatively rated. My impression is that my ears are very sensitive to any clipping in the midrange but not in the low bass and tweeters being more efficent don't need much power to be driven. If the led readouts can be believed, at very loud levels, the tweeter amp is putting out 5 watts while the peak meters on the midrange amp say 50 to 100 watts. I have no meters on the bass amp but I find myself attenuating my bass levels to placate the spouse and neighbours. So go stereo mode and triamp!

Sfrounds: Njonker has raised the most important question for
you to answer. Are your speakers truely biamp-capable to
begin with? Check with the dealer/manufacturer. The speaker inputs MUST allow you to connect to (typically) the
woofer independently, and the midrange+tweeter units
independently (usually there is a passive crossover inside
the speaker to split between mid and high). If so, then
separate amps can drive the two "halves" of the speaker, each amp delivering a restricted frequency range specific
for that driver(s). This is done by putting an active
crossover device between your preamp and the amps, to "feed"
each amp a limited Hz range. This active device should at
least approximate the crossover frequency/slopes that the
manufacturer originally built into the speakers (i.e., the
original internal division of bass from mid/hi signal). In
my opinion, the resulting "vertical biamping", which uses 2
stereo amps, gives a much more open sonic presentation. The
speaker/amps are less stressed too. And as Sean has nicely
outlined above, you can choose different "styles" of amps
for bass and mid/hi. If the 2 amps have different GAIN, then
your active crossover will need level controls to match the
loudness resulting from the separate amplification. Active
crossovers can be obtained from Bryston, Marchand, and some
other companies. You may want to consider a 3-way crossover
which would do all the above, but also route the lowest Hz
to an active subwoofer, to relieve your main woofers of having to produce the lowest octave; this in a sense would
be tri-amping.
Good luck... it's a lot of work/money but worth it.

In my last post, I should have said that the use of 2 stereo
amps with an active crossover gives "horizontal" biamping.
Anyway, there is a detailed disussion of this type of
biamping at www.sound.au.com/bi-amp.htm

sfrounds,

if yer speaks are truly bi-ampable, and ya *do* have two identical amps, the best ting to do is yust try the 3 different methods - bridged, wertical, or horizontal bi-amping. it's easy to tell if yer speeks w/two sets of binding-posts are *really* biamp-able: yust hook one amp to only one set of binding-posts w/o the yumper in place, and only that driver should play - the other should be silent. (but, it's hard for me to imagine why a speaker mfr wood have two sets of binding-posts, if all drivers play when only one is used, w/o a yumper).

i have had good luck horizontally biamping w/an electrocompaniet aw100 driving the woofs & an aw75 driving the tweets of my monitors. but, yust this week, i sent my aw100 to a guy who wanted to trade his aw75 for a bit more power. his aw75, w/serial # only 5 digits away from my aw75, should give me the perfect opportunity to try bridging & wertical bi-amping, as well as horizontal bi-amping. i also have a pair of gnu aw60's, bought from europe, waiting for me to conwert from 220 to 120v. (i had given up on finding an aw75, & the trade offer happened shortly after i bought the aw60's!). so, i may also try bridging all 4, so each driver has a mono amp. but, this may really be over-kill in my system, so i may end up using 'em in another system, trying to sell 'em & use the money for a pair of melos mono-toob amps, or...??? ;~)

re: ral's suggestion of using an active x-over, i'd recommend this *only* if ewe can completely bypass the speakers' internal passive x-over - i wood *not* use an active x-over *and* the the speek's passive x-over - this is sure to muck-up the signal, imho. and, an amp run to one set of binding-posts of a bi-amped speaker only sees the the load above or below the speakers' passive x-over point, anyways...

good luck, doug s.

There are some speakers which actually sound better if you use an active xover to externally separate the bass from the mid/hi (prior to the amps), then let the speaker's internal passive
xover split the mid and hi's within the remaining signal. E.g. the larger Magnepan speakers (I
own and biamp the MG3.6 in just this manner). Also, you certainly don't want to run a full-range
amp signal into each individual driver of a biamp-ready speaker; this would send high-freq. info.
to the woofer, and bass info. to the midrange/tweeter, which could cause distortion or
damage the drivers.