Details for bi-amping

Magfan is right. If you're dealing with a 2-way with a 2K crossover we could have saved a lot of time and called you nuts to begin with. On the other hand, if you're talking about an Infinity Kappa9, that's another kettle of fish.

Some more thoughts/issues.

Yes, you do need to match gain; IMHO, the amps don't need to be of equal power but should be in the ballpark; and I would not use any Y-cable from a preamp.

Most people using a bi-amp setup will use an active crossover between the pre-amp and the 2 pairs of monoblock power amps (a la Pass Labs XVR1). This is so that each pair of monoblocks will be dedicated only to amplify a certain portion of the audio band - either the low freq's for the woofers or the mid/high freq's for the midrange/tweeters.

Contrastingly, if you bi-amp with a passive crossover (e.g., use the crossovers built into the speakers), then each pair of monoblocks will amplify the full audio band. For example, the monoblocks for the woofer will be amplifying the full audio band but at the passive crossover, the mid/high freq's will be filtered out and essentially lost (the same thing happens for the monoblocks for the midrange/tweeter, except that the low freq's. will be filtered out and essentially lost).

Passive is not very efficient. Active is more efficient because only the specific part of the audio band is being amplified. This latter method leads to what, to me, appears to be more headroom - that is bi-amping my 100W Aleph 2 monos and my 125W Threshold SA/6e monos sounds much more than `100W full bandwidth.

So, let's say you now want to use an active crossover. In doing that, you also need to remove the passive crossover from the signal path. Otherwise the signal will be going through 2 filtering networks - first the active and then the passive crossover. This should be a consideration if you ever want to sell your speakers. In some speakers, removal of the passive crossover can be reversible; others not.

Also note that a few passive crossovers not only filter the lows/mids/highs, but also act as an rudimentary equalizer. If you go the active crossover route, you will lose the equalization that was inherent in the passive crossover. Might be better, worse, the same, or just different.

Also, someone mentioned using XLRs and RCAs for the 2 pairs of monoblocks. You don't have that problem with an active crossover because it will split the signal from the pre-amp. Also, if you do use the XLRs and RCAs from the pre-amp, note that there usually will be a gain difference from these outputs from a fully differentially balanced pre-amp.

In sum, a lot of things really need to be looked into. But if you can get it set up correctly, the bi-amped active crossover method works real well.

FWIW, from time to time, I bi-amp with an active crossover my Aleph 2 (for mid/highs) and Threshold SA/6e (lows). When set up right, they sound amazing - the liquidity of the Alephs on top with the bass authority of the Thresholds.

Also, be forewarned, if you like to setup your system once and not touch it, the bi-amp & active crossover may not be for you. The level of adjustment and permutations available with such a set up leads to constant fiddling. =) Some like it, some don't.

YMMV

"Contrastingly, if you bi-amp (SIC) with a passive crossover (e.g., use the crossovers built into the speakers), then each pair of monoblocks will amplify the full audio band. For example, the monoblocks for the woofer will be amplifying the full audio band but at the passive crossover, the mid/high freq's will be filtered out and essentially lost (the same thing happens for the monoblocks for the midrange/tweeter, except that the low freq's. will be filtered out and essentially lost)."

A common misconception. Yes, the entire frequency band is presented to each poweramp, but the 2 ends of the frequency band are NOT amplified equally, because the crossover presents a rapidly rising impedance within the filter (rolled-off) band. That's why one 'saves' amp power when passively biamping.
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Either way, passive or active, you have to decide if you want seams or holes in your system response or whether you want it "tunable" with an active crossover. As mentioned previously, if you can remove the passive built-in crossover easily from your speaker, then, since you plan on spending some serious money on amps, I would imagine that an active crossover isn't outside your price rance, then definitely go for active. If you don't want active, then you would need amps of equal specifications or the same amps. otherwise you definitely will have seams that you will notice. So, after all the posts, the choices are really simple. Active, you can get different amps for low/high and adjust with the crossover. solid state for the low and tube for high depending on your listening desires. Passive, you get the same amps for high/low or amps that are pretty close in specifications and you are good to go. It really isn't rocket science. It is only complicated if you allow it to be. You have two choices.

If you can easily remove the passive crossover, like my Martin Logan Monolith III's it is simple to remove them, since they are external passive crossovers and insert an active crossover to the system (which is what I did), and borrow an active crossover and amps and experiment to make your decision. I am a strong believer that when one is paying a large amount of cash for this type of equipment, borrow equipment first and take it home, insert it into your system and hear how it sounds in your system before purchasing. Asking others for their opinion is okay, however, that is what it is, their opinion. Your's is the only one that matters.

Find good dealers and stores that will allow you to take equipment home for a home demo first. They will have used/consignment/demo equipment or new equipment and take your credit card info. give you the equipment for a week or so and allow you to make an educated decision based on home listening.

Also, get on-line and check. I would bet that there are some active crossovers out there specifically designed for your speakers.

enjoy

Realy tempted to try the active option as more efficient. I have two pairs of speakers PD 80 by Tyler acoustics and von Shweikert VR 4 Jr on two systems. As all of you, guys, know both are 3 way. One pair will be biamped depending on which one is easier to eliminate the built in crossovers. My choice may also depend on and I may take into consideration also other specs and details for each one pair of speakers leading to more rewarding results. I will address the manufacturing companies. My preference now is for the PD's because they are very efficient and easy to drive with less powerful tube amplifiers. A low output tube amplifier can be built on a very simple scheme which could result in a very clear and detailed sound. Last but not least a low output tube amp is usually cheaper than a high output tube amp of the same quality. You see the future set up should be built around the speakers that are already in place. Have heard both Ty and Albert are willing to help by advising. Unfortunately my remote location will not allow these companies to perform the crossover's bypass. But if I won't be 100% sure in advance that the things are doable the active way I will go passive. That's my strategy by now. Thank you again for your competent advise.