external crossover when bi amping?

i have jbl l-7s that i want to biamp but am a little confused.The jbl supplement for the l-7s say have your jbl dealer make a modification.i have 2 hafler dh 200s one to the lf and the other to the lf/mfs.this isa 4 way system.i guess the way i did it was a horizontal biamp and i believe it can be done vertically also.which one is better and am i screwing anything up with my hookup.i am using a rotel preamp with 2 outputs to the amps.appreciate any thoughts.i also have 2 hafler dh 500s that i would love to try but only with proper connections

Hmm...I responded to this yesterday, but it's not here, and that's not the 1st time that's happened. This wait-for-the-full-time-babysitter-and-sometimes-your-stuff-doesn't-show policy of A-goN is highly annoying.

1. I'd replace your stranded jumpers with SHORT pieces of solid 14g. copper household wiring.
2. One certainly can adjust the frequency balance using tools, but we all still end up tweaking it by ear.
3. "What would be the point of biwiring with 2 pairs of cables connected to 1 pair of full range (20hz to 20khz) binding posts on an amp? It seems that you would only be duplicating your existing connection." The point is to use the speaker's crossover to split the frequencies in the cables. The 2 cables may be connected to the same driving terminals, but each cable see hugely different impedances by frequency, so the, say, treble cable of a 2-way is carrying little midrange and virtually no bass, and the bass/MR cable of that 2-way carries very little treble. When I had 2-way speakers with high crossover (as the vast majority of 2-ways are), I used Audioquest KE-6, a 4-pairs-of-solid-silver DBS cable on the bass/MR, and KE-4, a 2-pairs-of-silver DBS cable on the treble. That double cable is now driving my full-range Quad 989s in parallel. (Had I started with the Quads, I would have used just the KE-6.) In a 3-way with low crossover, the bass cable carries little midrange and virtually no treble, so the conductors don't have to be as high in quality but there has to be a lots of them for good bass damping. The MR/treble cable carries the vast majority of the music and should be as high in quality as you can afford. On my center-channel 3-way, I use quite-inexpensive AQ Type 6 on the bass and that great KE-6 on the MR/treble. Biwiring, too, can be complicated, and what cable to use or even whether to do it is quite contentious here.

So with biamping, you get BOTH sets of issues montioned above, besides the possibly complicated issues of which amps to buy and use. Based on what I've read over the decades, I'd say that most audiofiles who STAY with bi- or triamping use amps specially suited to the frequency bands they amplify.
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Thanks for your input on this topic. I asked this question because I have an extra amp and wanted to try biamping. The speakers in question are 2 way monitors with 2 pairs of binding posts. I have replaced the metal jumpers between the binding posts with 14 gauge 65 strand OFC speaker wire. This resulted in a brighter sound, but a little to bright with some sources. Now on a rainy day I want to try biamping. The point of level matching of the woofer and tweeter is one that I overlooked. How do you get this right? Is it trial and error or can you use a sound level meter and test tones? I have read that some people only biwire (not biamp) their speakers to seperate the high and low frequencies in the cables feeding the speakers. If this is done it seems that you would have to use an external crossover and bypass the internal crossover. What would be the point of biwiring with 2 pairs of cables connected to 1 pair of full range (20hz to 20khz) binding posts on an amp? It seems that you would only be duplicating your existing connection. You would still have a full range signal going through both sets of cables. Am I missing something in this equasion?

Sonny: "If you have a two way (sic) speaker with one pair of binding posts and an internal crossover, of course, then I don't see any other way of biamping than to disconnect the tweeter and the woofer from the crossover and then connect each directly to an amp."

In order to biamp or biwire such a speaker, one 'merely' has to separate the inputs of the 2 sections of the crossover. Sometimes that's easy; sometimes it's not.

The goals of biamping are many but do not HAVE to include eliminating the speaker's crossover. As I said earlier, many crossovers have impedance-contouring and/or tonal-response-equalization networks in them that the speaker's designer may have worked very hard to perfect. Driving the drivers directly eliminates the benefits gained by these networks. Of course one can deliberately eliminate such networks, but one should realize that one is changing the sound of the speaker, perhaps dramatically. If there are no such networks in the crossover, then it's much easier to replicate the response of the passive crossover in an active crossover.

There are no easy answers in biamping. Still, the easiest way to effect it is to use the 4 channels of 2 identical amps to drive the biwire terminals of the speaker. The next-easiest way is to use 2 different types of amplifiers...say, a solidstate amp on the bass and a tubed amp on the MR/treble...but one almost always has to have a gain control on the more-sensitive amp to tonally balance the system.
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Perhaps some further explanation is needed here. If you have a two way speaker with one pair of binding posts and an internal crossover, of course, then I don't see any other way of biamping than to disconnect the tweeter and the woofer from the crossover and then connect each directly to an amp. How else can you get one channel to go directly to the tweeter and the other channel to the woofer if everything is still going through the original inputs? I have always thought that the purpose of biamping was two fold:
1. to place the crossover before the amps, and
2. to give each driver it's own power source.
Which means, you would need an external crossover.
Are we confusing biwiring with biamping?
Sonny

George: "If you biamp with different amps the internal x-over must be removed from the equasion (sic)."

Absolutely not correct. Biamping with the existing passsive crossovers--and 2 identical amps--is the easiest way to do it. Even if the amps aren't identical in gain/sensitivity, it's STILL the easiest way to biamp, as one merely needs a gain control on the more-sensitive amp. Using the passive crossovers also retains all the impedance-correction and other equalization networks the speaker designer worked perhaps very hard to perfect.

Ner...:
1. An external crossover is NOT needed when biamping.
2. Don't quite know how to answer this. Perhaps all the other info here will answer it for you.
3. The same way it works when you feed it with one amp and one or 2 cables.

Biamping can be very complex and difficult to perfect. SOMETIMES it brings fine results. I suggest you start with biwiring--you'll need it anyway if you decide to biamp.

BTW, it's 'biamplify' or 'biamp' and not 'bi amp' or 'bi-amp'.
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Most all speakers have a x-over within. It controls what goes to what and cut-off points.If you biamp with different amps the internal x-over must be removed from the equasion.-The output of the amps will be different. The volumes won't match.---Biamping with 2 of the same amps allows you to still use the internal x-over.