use bridged mono and bi-wire or use stereo mode and biamp? pros & cons?

[dpolmann]

I have N804's and HTM-2 up front. I acquired three amps second hand, to use one for each speaker. On advice of my B&W dealer, I set up the amps each with their own custom-made Y-cable. The left pre-out goes to one amp in both L & R channel. That amp is wired to the left N804 in a passive bi-amp mode. The right pre-out and the center pre-out each go through Y's to their own amp L&R channel, and are similarly wired to their respective speakers. The amps I am using are all Rotel RB980-BX at 120 wpc. NEWBIE QUESTION: I see lots of threads suggesting more power is better, but I am perplexed about the classic question of passive bi-amp vs. bi-wire (I've read about it, and you'll probably agree it's just not obvious). Given that I COULD switch each amp to bridged-mono, getting 380 watts each that I can dedicate to each speaker, SHOULD I? Bi-wire it? Will the performance characteristics of the amps degrade (lower damping factor, higher distortion, other)? I know the 380 exceeds the speaker ratings, so how much is too much power for these speakers? Does anyone have experience with this type of comparison? I'm sure to hear "try it and see how your ears like it". OK, I could do that. ops: But, I am hoping for feedback from someone other than my local salesman (who by the way doesn't work there anymore) and I'm sure you guys have good thoughts on this! Thanks in advance for your patience and kind words.

[Aussie Geoff]

Dan,

This quote from B&W should help (I got it for another perupuse re the 803D speakers - but it is right on the money re your quesiton:

I have to admit that I am always in two minds over the question of bi-amping. Is it the right route or, given a certain budget, are you better off getting a single, more powerful amp? If you listen fairly loudly such that you often approach the voltage limits of the amplifier, then I would go for a more powerful amp to lessen the likelihood of clipping. Bi-amping gives you no more total power transfer. A RB-1080 (or RMB-1095) in bi-amp mode still delivers just 200W worth of sound level. What matters is the voltage swing. What bi-amping can do is give each amp an easier load. For example, the difficult part of the load of these speakers (most of ours come to that) is the low point in the impedance just above the box/reflex resonance peaks in the bass - around 100 - 200Hz. If you split the amp load, the one feeding the MF/HF of the 3-ways does not have to cope with this current-sucking region and may perform to a better quality level by being less stressed. Once you get to the better amps, though, this is actually less of a problem as they tend to have better current reserves.

Personally I'd be trying the bridge mode ASAP and then the bi-wire - you'd learn a lot for very little cost (just the Y RCA connectors wasted if (as I believe) you will prefer bridle mode.

Re the power - not a problem - we are only talking peaks of 380W and with a more powerful amplifier - unless you play at insane levels - you are less likely to damage your speaker becuase it isn't clipping..

Geoff

[dpolmann]

Geoff - I appreciate your input. I'm pondering your reply.

[johan]

Hi Dan!

I've just changed from biamp to bridged mode a couple of days ago. My speakers are N802 and my amps are 2xNad 218 (2 x 200w). I used to biamp each amp for each speaker (2 x 200w into each speaker) but now each amp is bridged (1 x 700w into each speaker). And I have to say I thought all this talk about Natilus being power hungry was a bit exaggerated. A least I thought 2 x 200w / speaker was enough. But it wasn't, there were a lot going on in the bass that I hadn't heard before, I didn't thought those speakers were that powerful, a big difference! And you can't blame Nad for being one of the big ones, what would they do with a big Krell, Levinson etc? But there is a downside to bridging though, distortion increases bla bla..(dont know anything about electronics). Anyway, the sound is a bit harsh and not as smooth as before. There isn't as much air surrounding each instrument either. I can't really tell you more because changing configuration made me use another type of cable and I can't say how much of the difference is due to that.
So there are downs and ups to both things so you have to try them both to decide what you think is best.

If money weren't an issue it would all be very simple; look for an amp with loads of clean power. But thats when it gets really expensive.

One thing you can say about our dear BW speakers is that they really let you know when you change anything. And happily they will reward you when you change anything to the better!

Good luck Dan and let us know how it all turns up!

Johan