No, You Cannot Bi-Amp

JohnK, thanks for your comment.

To be sure it's clear to everyone, I'll repeat that the issue I cited, involving a large disparity in power capability between the high frequency amp and the low frequency amp, just applies to PASSIVE biamping, in which the only crossover that is present is the one in the speakers.

I'll add that my comment was intended to apply to the situation where a single pair of speakers is being passively biamped, with the single pair of speakers having been designed to provide reasonable results (in particular, some semblance of flat frequency response) when driven by a SINGLE amplifier.

John's comments about combining Class D and SET, etc., apply to a different situation altogether.

Regards,
-- Al

Almarg's arguement makes sense to me. I believe that using two amps via the passive crossover ought to be called "dual amping" to distinguish it from true biamping using a line level crossover.

I performed testing to determine how powerful an amp is needed to drive my MG1.6 after lows are removed to an auxillary large cone driver system which I use as a subwoofer. I tested for a wide range of crossover frequencies. What I found was that the high frequency signal needed a lot more "power" than I expected. "Power" is in quotes, because what I was measuring was voltage peaks when playing music at high volume. Voltage swing is what is necessary to avoid distortion. Because the peaks are very brief there is no doubt that the power is actually low. But, because of the way audio amps are designed you have to buy power to get voltage.

Bottom line... don't skimp on the high end amp.

A long time ago I had new Mirage M3si speakers which could be biamped.

So I did what anyother audiophile would do, I tried biamping.
I bought two Brytson 4B amps.

I tried them every which way, and then even as mono blocks.

No magic solution.
Perhaps it was the fault of the speakers, but back then the amps and speakers were well respected.

What I eventually settled for was a one amp solution and I even turned my back on the bi-wiring option.

The best sound I got was with one Bryston amp in stereo, and an easy rewire of the Mirage speakers(just re-arranging the internal speaker wires at the posts, no soldering required)so that one pair of speaker wires was all I needed.

Perhaps bi amping and biwiring do make a difference in other situations, but in my case they weren't worth the expense or bother.

Now I have Ref 3A Grand Veena which are also bi wireable(not biamp as I understand )and so far I prefer to run single wire (Nordost Heimdal) with the Nordost jumpers in the diagonal position.

I tried various speaker wires and none of the biwiring configurations I tried were any better than the way I have them wired now.

I ran my Maggie IIIas with an Audio Research D400 for years, then bought another D400 and used the XO1 passive crossover but quickly got myself a Marchand electronic crossover which cross to a pair of subs below 50hz then uses same slopes as Magnepan suggests bass to mid/high

To my ears the difference was pretty significant and and I haven't been a teenager for decades (sorry just being flip)

I thought one advantage was the quality of the crossover itself and limiting the bandwith each amp must produce

Supposed to audition the 3.7s in a couple weeks so will find out 1st hand what they sound like "out of the box".

Audio Research says that the D400s will drive the low impedence load presented by bridging the amps and driving Maggies so can use both amps still but again my ears will be the judge

I doubt I will pull the trigger until I can hear the 20.7 and check out some other models at the Capital Audi Fest this summer but "once you go Maggie you seldom/never go back" :-)

MikeH

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 I’m 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?