Is it best to use a 5-channel amp for biamping??

I should add that by using your 5-channel amp this way you are, in effect, vertically biamping, which works better for Logans than horizontally biamping. Cheers.

Jetmph: With a Sunfire Cinema Grand, you would be neither vertically or horizontally bi-amping. That's because all of the channels are fed off of one common power supply. If running an amp with a dedicated power supply for each channel, it still wouldn't be vertically or horizontally bi-amping.

Vertical bi-amping implies that one power supply ( or amplifier ) feeds the left speaker while a separate power supply ( or amplifier ) feeds the right speaker. Horizontal bi-amping implies that one power supply ( or amplifier ) feeds the high frequencies of both speakers and a separate power supply ( or amplifier ) feeds the low frequencies of both speakers. Since every section of the speaker is being fed from one common power supply, there is no difference in this case as far as "vertical" or "horizontal" is concerned. So long as the power supply is big enough to feed all channels simultaneously, the biggest difference in performance will be increased dynamic headroom and the reduction of dynamic compression. The sonic results of this should be increased spl capacity and a more cohesive presentation, regardless of volume.

Since the power supply in this amp was designed to feed 5 channels of amplification and only four would be pulling on the power supply, i think that this type of installation with this specific amp should work great. The fact that Planckscale can experiment with the voltage / current outputs for the top end on his ML's is simply icing on the cake. Sean
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Jetmph, Sean... keep them coming! I have been contemplating on buying the signature series, but with you inputs so far, it seems the standard Cinema Grand will do just fine in this configuration.

It is interesting to see that everyone here so far thinks that this configuration will work well with the Logans.
It was because of inputs such as these that I was able to buy my first (most probably will be my last) subwoofer - the Bag-End Infrasub-18!

Thanks

If i was spending the money, i would buy the Signature. Then again, that's me : )

Seriously though, i own both the Signature and non Signature versions of the two and five channel amps. In my HT system, the standard versions worked well but ran out of steam when really throttling the system hard. Bare in mind that they did much better in this regard than some other amps rated for even more power. From there, i went to the Signature versions which gave me more of the headroom that i needed. I will say that there are differences in the sonics between the two channel and the multi-channel and from what my ears tell me, between the Signature and the standard models. In my system, the Signature versions ( both two and five channel ) sounded best.

As to a different point of view, my Dad was running my Sunfire two channel amp for a while with another amp for his center and surrounds. I temporarily brought over my 5 channel Sig and let him run that for a bit while we were getting some other things straightened out with his system. After getting things where i wanted them, i ended up bringing over the standard Cinema Grand and setting him up with that. In his opinion, the standard Cinema Grand was sonically superior to the Signature version. That made me happy, as i thought that the Signature sounded better in my system. As such, we were both happy campers sonically and i didn't have to spend any more money : )

As a side note, the Architectural Series are supposedly slightly beefier than the "full size" versions. This has to do with power supply revisions, etc... Due to the smaller chassis and limited heat dissipation though, they may run slightly hotter.

One thing that i would suggest with ANY Sunfire amp is that you should get some type of solid "cone" type footer underneath them. This elevates the amp off of the support shelf, allowing it to breath better. The "weird" thing about these amps is that they dispurse their heat from the bottom plate, not out of the top or sides. As such, soft footers placed underneath the amp can be damaged from the heat if you stand on the throttle long enough.

I would also suggest a good heavy gauge power cord. Even though these are "high efficiency" amps, they can still pull TONS of current if called upon to do so. If you really want any of these amps to work their best, especially if you have low impedance / low sensitivity speakers, a dedicated 20 amp line is a must.

If buying used, the first or second production run of their amps have permanently mounted cords, all of those produced after that make use of IEC's. While i hate IEC's for their poor connection qualities, they are convenient when it comes to trying various power cords. Sean
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Go the the MartinLogan Owners forum and ask for feedback about Sunfire amps. Some are happy; others have issues.
(www.martinloganowners.com)