Bi-Amping from an AV Receiver?

[Ayreonaut]

I just bought some full range speakers for my mains. I want to use them in a straight two channel configuration for music (and use them as mains for surround.) Buying new amps will have to wait since I just blew my AV savings, so I'm trying to milk the most from my current 80W/channel 7.1 AV receiver. My speakers can be bi-amped. I know that some AV receivers allow you to configure the two the surround back amps to serve your main L/R speakers in a bi-amp mode.

My reciever (Denon AVR-1905) does not have this option. It does have a 7CH STEREO surround mode, and in this mode the front left channel signal is also output to the surround left and surround back left channels. Likewise with the right. It seems that I could select this mode and bi-amp my mains using the main amps and two surround amps. Is there any reason that wouldn't work out well?

Now the interesting part. When I want to watch movies in 7.1 the surround amps must be wired to the surrounds and the main amps must be single-wired or bi-wired to the mains (not bi-amped.) Rather than rewiring every time I want to go between stereo and surround, I could design and build a switch box to reconfigure my connections.

Would that be brilliant, worthless, or stupid and dangerous?

[JCD]

Mind you, I've never attempted what you're trying, and I'm only going with my 'prejudices', but I'd vote for "worthless". I've heard some people say they've heard improvements from bi-amping speakers, I've also heard some people say they've heard no improvement unless the speakers had an active crossover. My feeling is that the improvement, if there is one, would be pretty marginal and not worth the time/effort to build a 'switchbox' like you describe.

Like all things in audio, I fully expect a different opinions to surface.

Oh, a quick question, what amp are you going to save up for?


JCD

[Ayreonaut]

JCD wrote:

...what amp are you going to save up for?

I've hardly begun to search. Maybe a couple of Outlaw Model 2200 M-Blocks?
With mono blocks, when I get a center I could add one more.

[Otto]

I'd have to agree with JCD. Are your new speakers really power hungry?

[Ayreonaut]

No, not at all. They're pretty efficient. (claimed 91.5 dB, John Atkinson meausred 90.5 dB.) They have a nominal impedance of 6 ohms and minimum impedance of 4.25 ohms, so they aren't that hard to drive.

I simply have no experience with bi-amplification and was curious. I don't know whether bi-amping would improve anything or not. They sound pretty **** good now, but they aren't "broken in" if you believe in such a thing.

How would upgrading to a good amp help where bi-amping wouldn't? I guess headroom isn't the only issue.

[russ.will]

I am running my 3806 & Kef Q5s biamped and found the improvement to be so big that I flogged my rear surrounds within a week. I listen at quite high levels and the extra headroom provided by the extra amp purely devoted to the treble unit, resulted in a far more refined, less fatiguing listening experience. Particularly with music. This might not be true for everone though.

The 3805 was a popular amp that didn't actually support biamping, but people did it anyway. Audioholics had an article on it if I remember and the same method would apply to you. Some people had hum problems and your auto EQ will no longer work, if you have it.

Russell

[Ayreonaut]

Russ,

Thanks for the information! I dug up the article on Audioholics, and it looks like it might work. I had considered the Zone 2 setting on my reciever, but learned from the article that I need to loop the main preouts back to an unused source input. I can't wait to try it out to see if it works for me.

[nova]

I have done this on and off with my 3805,... I did not really see an improvement in headroom or anything else, on the other hand I did not see any loss of performance either .

One thing it will do is allow a little more flexibility in your set-up. eg: I bumped the 12" woofers in my mains by +4, so that was kind of fun to listen to music and movies (for a while). So if you have a tricky room, or speakers that lack a little midrange punch, lack a little bass etc. you can give it a little boost (or cut back a little) relative to the other half of your speakers

[Danny]

In my experience with Bi-amping (I've worked on 2ch systems with 4 amps per channel) there is only really a difference when you use an active crossover, otherwise you still suffer the problems associated with passive crossovers.

[Ayreonaut]

Well guys, now I've been there and back again. The Audioholics review warned that some people will get a hiss, and I got a slight hiss and an audible hum. The sonic benefits were slight, if any, and the hum was unacceptable so I put it all back the way it was. I did leave the main speakers bi-wired since the wires were already in place.

My manual for the Denon AVR-1905 is not very good. Are the A and B terminals for the mains are in parallel or series?

[Otto]

Speaking from experience with a AVR-170something, I believe they are in parallel.

[Ayreonaut]

Thanks, that's what I figured. It was much easier to bi-wire with bare wire connections by using both the A and B terminals. They need to be in parallel for that and I figured that they were. The output level seems correct, I just wanted to check my deduction.