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

Greg is right on the money. Increasing power potential is always a great thing, but if you can shorten the signal path between the amp and the speakers by removing passive components in the crossover, that will get you even better results. While this would also require some type of crossover between the preamp and amp, the benefits of this type of installation have to be heard to be believed. Sean
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If a speaker requires that all four binding posts be hooked up in order for all of the drivers to operate properly, one can passively bi-amp with out a problem. There is one hitch to this though...

If the speakers are improperly wired internally AND someone is using two different amps to run their speakers, you could run into big problems.

The reason that i mention this is that this is the exact situation that we ran into with my Father's speakers when we pulled them apart. The lower midrange driver was "cross-wired". In other words, the positive of the midrange was connected to the "high end" binding posts and the negative of the midrange was connected to the "low end" binding posts. Luckily, my Father never tried bi-amping his speakers.

What this would have done is tied the output stages of each amp together electrically. Depending on the design of the amps and the voltages involved, this could result in "smoke". While this was obviously a mistake from the factory, it would have been a costly one for the consumer. In such a situation, i can picture someone standing there with one wire in each hand and blackened soot all over their face saying "what the hell happened???".

In this type of situation, i sincerely doubt that the manufacturer of the speakers wouldn't have stood behind their mistake and paid for the repair of one or both amps. The really bad part is that someone might have the amps repaired and not realize that it was a problem with the speakers, possibly repeating such a disaster.

As such, i would suggest connecting just the high frequency section of the speakers in normal fashion and make sure that all the drivers work as they should. When your sure that this works fine, connect the low frequency section and make sure that all of the drivers used in that frequency range are working okay. Once you've done that, hook the positive to the high end section and the negative to the low end section. You should have silence. If it is silent, connect the negative to the high end section and the positive to the low end section. That too should be silent. If you get sound out of either of these "non-standard" wiring configurations, the speaker has internal wiring problems or is not a "true" bi-wire / bi-amp capable design. Sean
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I hate to say that anything is an absolute as there are almost always exceptions to every rule. With that in mind, it would be pretty safe to assume that you should be "okay" even with goofy internal wiring in the speaker so long as you were running multiple channels from the same amp. There are some amp designs that i can think of this causing problems with, but none of the multi-channels that i know of use this approach.

As a side note, i did this for a while when the two channel amp that i use for the mains in my HT system was sent back to the manufacturer for inspection and upgrades. I had another 5 channel amp that i wasn't using, so i ran four of its' channels to passively bi-amp the mains with. Since it was from the same manufacturer, there wasn't a drastic change in sonics either way. Sean
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Increasing power typically results in a more consistent presentation regardless of volume. This translates to maintaining a more cohesive and liquid presentation as spl's are increased rather than the grain, glare and distorton that we experienced when pushing the system with the smaller amp. By removing all of the negative attributes brought about by the limited headroom of the smaller amp, one can listen at higher levels with less fatigue for longer periods of time. That's because you aren't hurting your ears as much due to a reduction in multiple types of distortons. All of this with increased coherency. Then again, going to a bigger amp that lacks proper design and uses lower grade parts may actually sound worse than a lower powered amp that was well built and designed. Quality first, then quantity. Sean
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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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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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Planckscale: It is typically cheaper in the long run to plan ahead / think about future moves than to just buy what you can get by with now. If you take that approach, i can pretty much guarantee that you'll end up upgrading later and spending more money doing so. Then again, many of the folks selling the "standard" Sunfire's and Cinema Grand's at reasonable prices are moving up to the Signature versions. Following that path isn't a bad thing ( i did it myself ), but if you've got the money now or can swing the difference in a short period of time, i would hold off and just make one big jump rather than two more costly jumps. Other than that, you can't have "too much" power. That is, unless you're "wreckless" with the volume control : ) Sean
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