If bi-amping is so great, why do some high end speakers not support it?

dkzzzz, tone controls are one of those things that purists as you say, don't like.  I agree with you and I know many designers who also do.  That said, I've never heard digital EQ that didn't somehow change the sound of the spectrum elsewhere in the speaker.  Many of you will disagree and that's fine, but I've heard a lot of digital EQ done with very high end system and or speakers that have it built in and I haven't felt the results were worth it as you help alleviate one problem, while cause another one.

I've heard a system using a parametric EQ that, to my ears, did a really good job, but you really have to know what you are doing when using one.  Many of us love 70/80 rock and could really use a pre that offered it in somehow.  Most of the recordings are really hot on top and they mess with the rest of the spectrum also.  I have been in a few studios back in the day and saw engineers making tiny adjustments, but it was always riding a gain pot and it almost seemed that they wanted to justify their jobs and validate what they do, lol.  Not taking shot's at the engineers, but we hear what we hear on the recordings and most will agree that they aren't usually the best sounding.  Great music though and that's what it's about.

Sorry I caused some confusion by writing bi-wire where I meant (vertical) bi-amping. I asked a more specific question in a Vandersteen thread I had already started.

my comments are limited to biwiring of which there is science ar work the case can be made that a bass cable in close proximity to midrange cable WILL modulate the HF signal by changing magnetic field.
hence Vandersteen staking out a strong scientific and listening based preference for external biwiring...
download one of his manuals for a nuanced approah to getting more out of your system ( speaker placement in the room using,,,,eek math !!!) as well and bi-amp, vertical bi-amp, biwire, etc

Another bit of a news from bi-amping experiments. Have you ever tried to run tweeter only and listen to the quality of your treble/tweeter alone? Holly cats, I tried that on a several recordings considered to be really well mastered and I came to unfortunate conclusion that my tweeters are compressed hot mess. I know to some this might sound like revelations of an audio-novice, but I never considered testing any speakers by listening to transducers separately just to see the quality of the sound they are capable. Try it with your speakers, but don't say I did not warn you. 

My first foray into bi-amping around 1987 was a total disaster: I tried bi-amping my Magnepan MG 3A using an ARC D115 mkII on the Treble/Midrange and a very powerful (400W) solid state amp on the bass that I had on loan from a dealer. The Magnepan passive XO-1 was used to split the signal. I was unable to adjust the volume level of the solid state amp so the sound was unbalanced and distorted (too much bass). Fast forward to 2005: I was now using an ARC VT100 mkII to drive my Magnepan MG 3.5. The sound was good but was limited in ultimate dynamics, bass impact and occasionally experienced clipping on crescendos. I had a pair of Kenwood L07 monobocks for several years in my closet. So I decided to biamp my Maggies using the L07s on the bass and the VT100 on the treble/midrange. However, this time, I purchased an active electronic x-over from Marchand (XM126). After much experimentation with slopes and levels the resulting sound was completely transformed. Dynamics, bass impact and control and overall sound were significantly improved.

With the experience gleaned from biamping my MG3.5, I was able to bi-amp my Magnepan 20.1 with excellent results. Bi-amping allowed me to keep my VT100 mkII to drive the treble/midrange, with the L07s driving the bass. Otherwise I would have to purchase a more powerful and expensive amp to drive the 20.1 full range.

In theory, the insertion of an active x-over devise in the signal path between the preamp and amp has deleterious effect on the transparency of the system. However, this was ameliorated to some extent by my selection of a tube x-over. Additionally, I built my own x-over modules using top grade caps and TX-2575 low noise film resistors. Thus the loss of transparency was virtually unnoticeable. In summary, biamping can be beneficial to the sound of your system, but careful matching of amplifiers is imperative and requires a quality active electronic x-over.