Bi Amping... worth it?

I'm not really sure how much of a difference bi amping would make in my system:

--Aerius i (there are two sets of speaker posts on the back... )
--VTL IT 85

the review in stereophile said that biamping really opened up the sound. But I don't really listen to my music that loud... I mean, it's loud for me! but i have yet to turn the volume dial past midnight....

bi amping with the IT 85 is easy though, and if i found a used ST 85 (which is already matched to be used with the IT 85... i wouldn't need a crossover?), it could be a cheap <1K upgrade.

i could spend that much on cables!
Worth a try!
Yes, it would be worth it (in my not so humble opinion).

If you got an electronic crossover, you would have to alter your speakers. It is expensive to do it right, so I would just start with passive bi-amping. (The improvement if done right is mind-boggling!)

For Martin-Logans it's definitely a worthwhile upgrade.

What is the difference between "passive" biamping and (I'm assuming) "active" biamping?

VTL said that no crossover is needed, because the IT85 and ST85 are "gain matched". Don't know what that means.

When you say "the improvement, when done right, is mindboggling"... how would you do it incorrectly? If I got an ST85, I would run the "high end" on both speakers with the IT85 and the "lowend" on both speakers with the ST85, right? what else should I consider?
I use active bi-amping which is the use of an electronic crossover BEFORE the amps. The signal is split into highs and lows before the amps. Passive bi-amping does not split the signal and therefore no electronic crossover is needed, nor is any alteration of the speakers needed.

With active bi-amping the speakers crossovers must then be altered. My set up was designed for me by Dan D'Agostino of Krell fame.
In addition to removing the low pass filter from my bass section, he determined that I also needed to change the polarity, as the speaker designer reversed the phase in the bass section with relation to the min/highs for passive use. (this is not an uncommon practice)
Also the mid/high section of the crossover also was altered.

The electronic crossover board was also designed by him.

Because of him, not me, my system was done right.

Good luck,
Yes! It really does make a big difference. Gain matched means that the output of both amplifiers is equal. This way you don't have to worry about an imbalance of power to one driver over the other. Should hear improved sounstage in all aspects. Usually much better tonal quality and inproved bass. Since bass sucks so much juice the seperate amplifier on the tweets really open up the transparency. I'm sure you will be pleased with the improvements in almost all aspects. Good luck
Active crossover sounds pretty invasive to my speakers! More of an upgrade than I thought. And obviously more than just the <$1K than I originally thought.

But what about the passive biamping... JC, is this what you were referring to, when you say it "really does make a difference", or were you referring to the active biamping? I guess the question should be, is PASSIVE biamping worth 1k + associated cables?

Thank again guys... I've learned a lot since stumbling across these forums...
Whatta upgrade boom isn't it Dennis?
First place VTL, than considering bi-amping...!
I can only wish the best in your research.

If you will ask speaker manufacturers they will certainly get "upset" since their buit-in crossover is the best match for the speaker and in some way they're right.
By removing the built-in crossover you will loose the value of the speaker and so you should somehow try and listen first if it's true.
Despite this situation I would really recommend you to ask the manufacturer how would you benefit by removing a crossover and using active bi-amplification.

I also plan to bi-amp with McCormack DNA1 on the bottom and VTL MB100 on the top. From what I figured out I can use it either way passive or active: These amps have both high gain(near 26dB), I will have tubie-sweet mids and highs and fast controlled SS bass doubled on 4Ohm load(my speakers never go that low the lowest is arround 6). The triode mode I will only be able to use in active bi-amplification.

So whenever you will look for passive bi-amplification you should match the gain of amps.
Yes I was referring to passive bi-amping. You will need same amplifiers or matched output gain as you suggested you have. With active bi-amping (more expensive) you will need an additional crossover but this will allow use of mismatched amplifiers. Based on the scenario you outlined above I would guess passive would work well
If you reed specs with no gain specified on the amp all you should do is to derive an output voltage from the following equation:

Output Power = V*V/R (squared output voltage divided by load resistance)

We have load resistance specified usually 8 or 4 ohms and from there we can derive an output voltage.

Than we take 20log(output voltage/input voltage) and get the voltage db gain.

Now there is a question:

What can be the tolerance between two amplifiers for a successfull biamp?
Please, share.
If you have matched amps and are passively bi-amping, is it better to run each amp to one speaker or 1 doing LF and 1 doing HF? Is one of these set-ups called "bridged" and the other "mono blocks"? If so, which is which? I'm embarrassed to ask, but I have to start somewhere.
Also, I have a 500w per channel Spectron Musician II amp. One of its many qualities is that it just sounds like it has oodles of headroom. Does the sound benefit as much from doubling up high powered amps? Or is the improvement curve much greater when bi-amping with stuff like 20W tube amps?
Thank you for any assistance in furthering my education.
Patrick, Bridging and Bi-amping are two different issues.
There is horizontal and vertical bi-amping.
In Horizontal bi-amping you use one stereo amp per channel with two pairs of speaker cables/wires connected to the binding posts of a bi-wirable speaker.
NOTE that two channels at the same time from the stereo amp should be fed from one preamp channel so it figures you'll need at least a Y-connector.
In Vertical bi-amping you use each channel of each stereo amp for each pair of speaker binding posts.
NOTE that each of the right channels of your stereo amps should be connected to the right channel output of your preamp and so identical for the left channel so there you'll also need at least a Y-connector.
As it was said above for passive bi-amping it's mandatory to have amps with the same gain or simply to use the same brands of amps.
If you want to biamp 500W/ch amp with 20W/ch you must have an active crossover since the 500W/ch amp will most-likely have a voltage gain of 40dB and 20W/ch will have a voltage gain of 20dB. You will not need to use Y-connectors if you will use an active crossover. The built-in speaker crossovers must be removed prior. The approximate crossover freequency with 500/20 combination is 6kHz i.e your 20W/ch amp will work with freequencies above 6kHz.

Now about benefits biamping either way horizontal or vertical using two like yours existing amps 500W/ch it depends on the speaker if it's voice coils can take 1000W/ch and not to get fried. Also I would recommend getting a dedicated line or make sure that your wires can hold up upto 25 Amperes before you play with this mega-power system. It might benefit for sure if the above conditions are met.
If you're about to use 20W/ch tube monos you should choose an active crossover freequency approximately at 6khz meaning that your 20W/ch monos will only see freequencies 6kHz or above and your 500W/ch Spectron the rest of freequency spectrum. In this case you benefit by limiting the "visible" spectrum of each amp and let them be more resolving and linear on their new "visible" freequencies limited by low-pass and high-pass filter of your active crossover.
The "power" of the amp has nothing to do with the gain.
For instance, ALL Krell amps have virtually the same gain, regardless of the power rating.

Thank you for the reply Marakanetz. Actually, I do not have a 20W amp. I was asking if low-output amps benefit from bi-amping more than high-powered amps. In other words, does something like a duplicate 20W SET amp improve sound moreso than a duplicate 500w class D amp? (ignoring preferences for tube/dig/ss)
Is there Krell amp 20W/ch??...

In all logical sence in order 20W/ch to have the gain arround 30dB the input sencitivity must be 8 milivolts i.e. something between the phono and preamp. So theoretically in such amp you could plug in high-output cartridge directly. Or if you want the challenge please find two amps 500W/ch and 20W/ch with the same gain... I'm already intrigued...
now to finalize...

It's all logically obvious that in active biamping we limit the "visible" freequency spectrum of each amplifier thus easing the task of amplification. It's beneficial for ALL amps in any combination BUT it also changes the speaker curve that might not be beneficial and needs to be checked and researched before the final setup.

There is no way in real life to connect passively 20W/ch amp with 500W/ch amp since YES, the output power does something to do with the amplifier's gain since it's a ratio between input voltage and output voltage.
I can't imagine wanting a Krell with only 20 watts per channel.
I think the gain of all Krell amps is 26 or 27db, regardless of size.

All you guys that are passively bi-amping, what are you using as a Y-adaptor? I too would like to passively bi-amp my speakers but I shudder at the thought of placing a Radio Shack (or derivative thereof) Y-adaptor connecting my Audioquest Opals between the pre and the amp for each channel - seems like it would defeat the purpose of purchasing good interconnects. Anyone know of a good Y-adaptor? - What it is and where to get it? The "best" I have seen so far is Monster Cable (the low-end stuff found at Best Buy and the like) Thanks, guys!
Call the Cable Company ( and talk or e-mail Bob. He, I am sure, can custom make a Y-connector of the same cable as you now use.

Richard (who actively bi-amps)
Treyhoss: I was lucky enough to find from my Audioquest distributor here in Taiwan Y-adaptors made by Audioquest. These are very high quality Y-adaptors that I use to connect my Audioquest Python RCA interconnects to my pre-amp. These Y-Adaptors are in shinny gold finish. You should call Audioquest company in the U.S. to see how you can get hold of them. Hope this helps.
Thanks for the response! I will check both avenues out!
I gave up trying to find some "high-end" y-adaptors for my RCAs. I went ahead and bought the Monster Y-adaptors just to try them out thinking I would upgrade later. I am currently using Wireworld Atlantis III+ interconnects to the y-adaptors from my pre-amp to amp for passive bi-amping. Did not notice any negative effects and have yet to consider replacing them.
I have been biamping for almost 50 years. At one point the second amp came in handy to quickly try out this new fangled "stereo" thing! Although I am still biamped on all five channels some of the reasons for it have diminished.
1. Back when good HI FI amplifiers were rated at ten to twenty watts the extra headroom for the HI signal created by not having it ride on the LO signal was significant.
2. Intermodulation distortion used to run 1 percent or so. Separating the HI and LO signals helped this.
3. Electronic crossovers have virtually no distortion, and can be very exactly set as to frequency and rolloff rate. Also, when you look at the cost of audiophile capacitors and large-wire air core inductors, the electronic crossover hardware is cheap.
Reasons 1 and 2 no longer apply, but reason 3 is still valid.