Mike, I have to agree with you. I bi-amped my Apogee Duetta Signatures using a pair of totally rebuit and upgraded Threshold Stasis 2 amps and a highly upgraded/highly-modified Marchand XM-9 electronic crossover a few year ago and have never looked back. The upgrade to bi-amping was the most major improvement that I ever made to this system and I've made more than a few.
Is bi-amping a simple solution for the person who just wants to power-up the system a take a listen and not think about the details? No, not at all.
As many know, when you bi-amp a system, in most cases, you totally by-pass the existing passive crossover in your speakers. Now that your amps are connected directly to each driver - with no capacitor in series to block DC - you now need to be concerned about your power-amps' DC offset. Too much DC offset and you will cook your more delicate drivers over time - even with no music playing. Woofers and bass panels can absorb a good amount of DC without damage. Even some ribbon MRTs can survive 200mVDC without damage over time; however, most anything over 50mVDC will move the driver's diaphragm or ribbon away from its "home" position which negatively impacts the driver's design performance. Employing amps with a low DC-offset and the regular use of a multi-meter is a must with a bi-amped system.
Now, once you decide to bi-amp, not only will you need to be concerned about finding the correct crossover point, you will need to be attentive to the slope of the existing passive crossover which you will be bypassing verses the slope of the electronic crossover. If the slope is different, you may need to invert the phasing of your mid and/or tweeter drivers in order to have correct overall phasing. A lot of information about crossover slope phasing is available with a search on the Internet. At least this is a one time thing.
Anyway, what Im saying is in addition to the added cost, is that bi-amping is not for everyone for the reasons stated above. Bi-amping does improve amp-to-driver efficiency through the elimination of the speaker's power-consuming internal passive-crossover system.
Somehow, I get the impression that some folks think bi-amping is like bi-wiring but with two amps and some sort of "Y" cable, but nothing could be further from the truth.
Bi-amping takes some effort to make sure everything is properly set up and requires some maintenance attention in order to make sure that your mid/tweeters doesn't become toast!
BTW, my guess is that Magnepan made a business decision as to not allowing bi-amping of the 20.7. Maybe to reduce ribbon warranty claims?
Is bi-amping a simple solution for the person who just wants to power-up the system a take a listen and not think about the details? No, not at all.
As many know, when you bi-amp a system, in most cases, you totally by-pass the existing passive crossover in your speakers. Now that your amps are connected directly to each driver - with no capacitor in series to block DC - you now need to be concerned about your power-amps' DC offset. Too much DC offset and you will cook your more delicate drivers over time - even with no music playing. Woofers and bass panels can absorb a good amount of DC without damage. Even some ribbon MRTs can survive 200mVDC without damage over time; however, most anything over 50mVDC will move the driver's diaphragm or ribbon away from its "home" position which negatively impacts the driver's design performance. Employing amps with a low DC-offset and the regular use of a multi-meter is a must with a bi-amped system.
Now, once you decide to bi-amp, not only will you need to be concerned about finding the correct crossover point, you will need to be attentive to the slope of the existing passive crossover which you will be bypassing verses the slope of the electronic crossover. If the slope is different, you may need to invert the phasing of your mid and/or tweeter drivers in order to have correct overall phasing. A lot of information about crossover slope phasing is available with a search on the Internet. At least this is a one time thing.
Anyway, what Im saying is in addition to the added cost, is that bi-amping is not for everyone for the reasons stated above. Bi-amping does improve amp-to-driver efficiency through the elimination of the speaker's power-consuming internal passive-crossover system.
Somehow, I get the impression that some folks think bi-amping is like bi-wiring but with two amps and some sort of "Y" cable, but nothing could be further from the truth.
Bi-amping takes some effort to make sure everything is properly set up and requires some maintenance attention in order to make sure that your mid/tweeters doesn't become toast!
BTW, my guess is that Magnepan made a business decision as to not allowing bi-amping of the 20.7. Maybe to reduce ribbon warranty claims?