Am I wasting money on the theory of Bi-amping?

Bi-amping provides the most improvement when the source signal (most commonly the output of a pre-amp) is divided into bass frequencies for one amp, mids and highs for the other. The dividing is done with an electronic crossover which receives the output of the pre-amp, and has two sets of output jacks, one for each power amp.

The benefit is the result of keeping bass frequencies out of the amplifier that handles the midrange and high frequencies. Bass frequencies use most of the power an amp produces, and cause of a lot of the distortion all circuits create as a byproduct.

If you bi-amp horizontally, you can use one amp particularly good at reproducing bass (solid state), the other an amp good at mids and highs (tube, if you like). Yes, vertical bi-amping does allow you to amply the entire frequency spectrum with the same amplifying circuit, if that’s your priority. But remember, the power supply for both channels of a stereo amplifier is the single transformer most amps contain, so there is a price to be paid by bi-amping vertically.

bi-amping, in my experience, is best with 4 identical channels of amplification and a speaker allowing separate low octave and upper octave inputs. the reason is my priority is always coherency first and foremost. and if the amps for upper and lower octaves are different, unless the speaker is designed with those particular amps in mind, you will always fight for optimal coherency. and in theory that should more control the speaker compared to just two of those same channels, resulting is better performance; the amps are less stressed, the speaker more under control, with a better soundstage, more authority in the lower octaves, and lower noise.

that said, it’s hard to generalize about bi-amping, each case is separate. too many variables. and if you have the budget for 4 channels of amplification, most times investing in better 2 channels of amplification and not bi-amping will equal a higher level of musical result. based on my personal priorites.

OTOH if ultimate dynamics or bass punch is more significant than coherency, then all bets are off and bi amp to your heart’s content. for me though, i’d rather have the very finest first watt and listen happily ever after which would be the better performing 2 channels.

so quality almost always trumps quantity.

one case is tempting, where you have a low wattage SET tube amp, and need something to kick it on the bass, so you find a solid state amp for the bass. maybe your best overall result is with those different amps, but you will always be fighting your bass being solid state and not ’of a piece’ with the SET tubed upper octave amplification. but you might love it anyway. comes down to what you like. no rules.

at the modest level of gear, maybe you have a multi-channel amp you want to use to bi-amp some speakers. in that case, it does make sense to do it. again, hard to generalize.

It’s not a waste. Assuming the passive crossovers in your speakers are good, you still gain the benefit of having separate amps for each channel, which have similar benefits as monoblocks. There’s better physical and electrical separation.

Are you driving the woofers with one side of each amp, and the tweeters with the other? (ie: one stereo 2 channel amp per side)

The benefits should be more about soundstage and separation improvements than any tonal balance changes, but in theory there could be some clarity improvements too. The improvements you may hear are a variable that depends a lot on the rest of the system. What are the amps and the speakers?

There are pros and cons with every choice, and few absolutes. Active crossovers and passive crossovers each have their pros/cons. Most active crossovers can’t address problem areas within the drivers like passive crossovers can. They only act as high, low, or bandpass filters, no notch filters, no shelving networks, no zobels, etc. Hook an active crossover to a driver with issues, and you can have a mess that can't be compensated.  A really good passive crossover with high quality parts can sound amazing. Passive crossovers can be more complicated to design well, and many use cheap parts that effects performance.

I’m taking sort of a hybrid horizontal approach . Tube amp monoblocks on the mid and tweeter with passive crossovers, then an active crossover to an integrated solid state amp that just drives the woofers @ ~ 80hz and down (and the active subwoofer).

@knotscott makes a very important point: electronic crossovers provide only "textbook" filters. TF’s are 1st/2nd/3rd/or 4th order, which create slopes of 6/12/18/or 24dB an octave for each driver. The internal passive crossovers in almost all good loudspeakers do more than provide just those slopes; they also contain parts that create compensation filters for the drivers themselves.

To best bi-amp a loudspeaker, the speaker should really be designed with that as a given. Older Maggies (those with parallel crossovers) are perfect candidates for bi-amping, as their crossovers contain no driver compensation networks, only textbook slope filters. The .7 series Maggies contain not parallel but series crossovers, so need to be modified to allow bi-amping.

Just my opinion, but the difference between bass drivers and midrange/tweeter drivers FAR exceeds the difference between comparable amplifiers. Except of course for planar-magnetic’s, ESL’s, ribbons, etc. Different drivers made of different materials sound radically different from one another.

Amplifier designers have to make compromises in their amps: bigger output transformers in a tube amp produce better bass than does the same amp with smaller transformers. But smaller transformers produce better high frequencies (smaller ones create less saturation of the transformer core, a consequence of magnetic flux).

Of course the above pertains to only tube amps. But ALL amplifiers are designed with compromises made. Using different amps for different frequencies makes a lot of sense. Everyone with a subwoofer is already doing exactly that.