There are several methods of biamping.
Horizontal biamping - This uses two different types of amplifiers one to drive the upper speakers of both channels the other to drive the woofer section of both speakers. Many folks use a solid state for the bottom and a tube amplifier for the top end so they get a tube sound on top coupled with better defined lower frequencies. This is a form of "passive biamping."
Vertical biamping - Uses two of the same amplifiers to drive both channels. You may either dedicate an amplifier to the top end on both speakers and an amplifier to the bottom end on both speakers or, as you suggest, dedicate an amplifier to each speaker. This is another form of "passive biamping."
Active biamping - This uses an active crossover to split the signal and only send the high frequencies to the channel which will be reproducing them, likewise for the low frequencies. This is the best form of biamping, but also the most costly, since not only are two amplifiers required but also an active crossover.
Horizontal and vertical biamping will have some sonic benefits, but I would test with your system to see how large they are. You can view an extensive thread on the topic at: http://audiogo5.iserver.net/cgi-bin/fr.pl?aamps&990003839
There are some wonderful and concise comments in this thread.
Another link which might interest you is:
although I personally think that the benefits of vertical and horizontal biamping are greater than the author of this does. (I use vertical biamping and it makes a big difference in my system).
The amp does not have to be biampable. For vertical and horizontal biamping, it is easier if there are two preamp outs for each channel, but I don't think very many preamps suport this so, the easy solution is to use a Y cord out of the preamp and run one leg to each channel you will use. I use a Sunfire Cinema Grand, which has two inputs to each channel, and the manufacturer recommends running into one input and then out the other input into the other channel. For active biamping, there will be two outputs from the active crossover for each channel, so you just connect a cord to each.
My experiences with the biwiring and vertical biamping are that the definition and range of the speaker improved with each change, that is, biwiring was better than single wire, verrtical biamping was better than biwirng. I also found that my speakers frequency response improved with vertical biamping. Every system is different though, so you should experiment.
greg: very informative post & right on the mark. BRAVO!
First of all, Greg's thread is very good.
Personal (and limited experience):
I have owned B&W800's (quad wired) for about 9 years and love them. This year, I finally was able to actively bi-amp them (with all Krell). With everything else in the system staying the same except the addition of the 2nd amp and x-over, I experienced the biggest improvement that I have ever experience in my system, bar none.
Although Krell and others recommend that it is better to vertically bi-amp (one stereo amp per side), I have two different amps so I had to horizontally bi-amp them (one stereo amp for the bass and one for the mid/highs). There are some theories about the benifits of horizontal bi-amping such as:
1. Complete separation of the top and bottom frequencies at the amps so each amp must only "worry" about certain frequencies.
2. Complete separation of the frequencies at the speakers so there is no chance of any interaction of the bass to the mid/highs.
3. Ability to use different amps which favor top or bottom frequencies.
Everyone that I know that has gone from bi-wiring to bi-amping, either active or passive, has found large improvement, but as Creg said, much more improvement with active bi-amping, assuming it is done correctly.
I recently biamped my Martin Logan Odysseys using a tube amp on top and solid state on the bottom - I really liked the effect but even more after adding an active crossover - since it allows for better control of gain and frequency separation.
Thanks to everybody for the help. And thanks for the very informative post, Greg. I will be trying out both horizontal and vertical methods and seeing which one works best. One question that I don't think anyone mentioned- how does the power work when you bi-amp? Does a 100w stereo amp then become 200w, since you're using it to drive just 1 speaker?
Its my opinion that Ktsteamer's thread & your responses begin to beg the question: Should mono amplifiers be a consideration?
Who of you have (at one time or another)bi-amped or mono amped? ...have you experienced both? Which do you like best? What are/were the benefits in your system?
If you were building a new system what route would you go (Present systems notwithstanding)?
Thanks for the indulgence,
A 100 watt amp is still only a 100 watt amp. In biamping it becomes somewhat like multichannel amps and though the power of the amp is the same - each amp works less than it would to handle all of the speakers in the load that it is presented.
I tried vertical bi-amping, by borrowing a VT-200 to match with my VT-100. It didn't fare that well. I suspect it was due to the lack of an active crossover to balance the signals. Who makes good crossovers? Has anyone done a real comparison? That is not 2 amps against your old amp but 2 amps against one amp which is the equivalent of the 2. Have you compared 2 100 watt amps against a similar 200 watt model?
"Who makes the best crossover" ... In my opinion it is Krell. Their KBX can cut frequencies like a knife and can be customized by Krell for any speaker. But it is pricy.
A good quality crossover is the Bryston 10 - it retails in the 1400-1600 range. The Krell is better but a lot more - see if you can borrow a Rane crossover 300-550 from a local music store or rent it if a high end dealer will not loan you an active one. It can at least give you an idea of what an active crossover of a higher quality can do for you as far as control and frequency separation are concerned.
I disagree that using two 100 watt amps or two channels of a 100 watt ampis the same as a 100 watt amp. As evidence, often times one will see that an amp can be bridged to provide (at least) double the power of the two channel mode.
Many experts will disagree with that. That's why I said you need to compare 2 100 Watt amps to a 200 watt amp. John Dunlavy believes that the 200 watt amp will win all the time. (SET's not included). A lot of people claim bi-amping is better, but nobody ever wants to do a valid comparison. Two 100 watt amps vs a single 100 is not a valid comparison.
It's sort of an interesting set of tradeoffs comparing the two. The two single amplifiers mean that the high and low frequencies are not intermodulating, which will produce a better sound. This is the opinion I have seen most often from "experts." The single amplifier on the other hand will better divy up the power between the upper and lower frequencies, which will probably let you drive the speakers to a higher SPL. There is also a consideration in that the quality of components used by manufacturers tends to improve with the power of the amplifier, so I don't think that a real world comparison of two 100 watt amplifiers to 1 200 watt amplifier would be an apples to apples comparison.
If that wasn't too clear, when you have two amplifiers connected independently you run out of steam whenever either one reaches it's power limit. On my system the passive crossover crosses over at about 120 Hz. I have seen 240-340 Hz mentioned as the point at which most music contains an equal amount of energy above and below. I can't confirm this, but it seems about right, and for the purposes of this discussion, the exact point really doesn't matter, just that it exists.
Putting these two things together, I think I would run out of power and start clipping on the top end before I ran out of power on the bottom end. Of course, the approach I used is to have more power available on both the top and bottom ends than my speakers can handle, so it really doesn't matter. :-)
Another factor to consider is that with the passive bi-amp system, you are well on the road to having active bi-amping and I have never seen anyone try to claim active bi-amping wasn't better with two 100 watt amps than a single 200 watt amp since this argument would ultimately reduce to the contention that passive crosovers are superior to active crossovers which would be a pretty tough proposition to sell. That is, assuming of course, that the amplifiers used were of the same quality.
I find this thread interesting because Martin Logan has quite a bit of information claiming that the benifits of an active crossover are far more than outweighed by the negative aspects of adding another component into the signal path. It is also interesting that they incorporate a crossover in their Statement speaker system that is also available for the CLS2z's.
pmwoodward - Could you provide a link to the information from Martin Logan? All I could find on their web site was the following paragraph under the ESL Tech technology brief.
"Common low and high pass filter crossovers and the inherent problem of crossing over at higher frequencies produce phase shift and amplitude fluctuation problems when the music signal is recombined. This is because high frequency signals have shorter wavelengths, and changing the distance from the sound source to the ear can present a 180 degree phase shift, and this translates as silence to the human ear".
First, I believe that this statement refers to passive crossovers, not active crossovers. As you noted they do state that they incorporate a crossover in their ESL speakers. One way or the other the thrust of what I saw on their web site seemed to be that no crossover was better than a crossover, not that a passive crossover is better than an active crossover.
That's probably true, but I don't know enough about their technology to comment one way or another. Since we are discussing bi-amping and you can't bi-amp without a crossover of some sort, passive or active, I don't think it applies to this particular discussion thread.
I have an idea. I want to run my SET amp onto a pair of 96 db, full range speakers which I hand built and because it is bass shy, also want to connect my SONIC FRONTIERS POWER 2 to a pair of SW-1, GERSHMAN subs. The input to both amp will have to use the two amp outputs in my SF-Line 2 preamp. To modulate the volume of the bass section amp, I am thinking about getting a pair of the EVS attenuators.
What I am wondering is if this will sound good or will the integration of the lower and high frequency be choppy sounding. The preamp and both amps will be trying to run both of speakers/subwoofers to their lowest to their highest frequency according to the music. The subwoofer has its own built in crossover, but I wonder what is its cutoff point. Will I be more successful adding a crossover to the subwoofer section? Then if I do this, what can I do about the frequency of the full range speakers? Any feedbacks will be greatly appreciated!