Originally Posted by alexandru27
I keep reading though that bi-amping brings very slightly noticeable (if any) improvement on SQ - someone here told me that too.
Then why would they bother to implement this capability on some receivers, if this doesnt really work on sound quality (note that I dont need/hope to get a simply louder sound by biamping)?
The honest reason is purely marketing. Back when 7ch receivers started becoming standard, the vast majority of people were only running 5.1 setups (probably still the case). So people were buying receivers with 7 amps built in, but only had 5 speakers... and if you read old discussion forums from 8-10 years ago you see lots of people wondering if they can use those "wasted" amps to help their system.
So, essentially, it's based on the (unfounded) psychology of feeling like you are "wasting" some of the stuff you paid for with your 7 channel receiver. Around 2005 or so, it started becoming more standard for 7ch receivers to allow the extra two (surround back) amps to be reassigned to bi-amp the front speakers.
The important thing to understand is that the major limiting factor in receivers is the shared power supply, not the amps itself. Hooking up the extra two amps doesn't really add much available power, because all 7 amps are drawing from the same power supply. You MIGHT get a tiny bit of additional headroom, but that is likely to add up to 1-2dB of additional headroom at the most. A lot of people don't understand that power demands are logarithmic, i.e., raising the volume 10dB requires TEN TIMES the power. So even if you doubled the power, you'd only get around 3dB of extra headroom... and that's at the MAX limits. At normal volumes (where you aren't close to maxing out the amps) it's meaningless.
With receiver bi-amping, you won't come close to doubling the power, because of not only the shared power supply issue but also because the tweeter requires much less power than the woofers. So again, at best you are gaining a tiny little bit of headroom. So, as Selden said, it won't HURT, but it's unlikely to help, and you end up running more wires. Probably better to use those extra two amps for Zone 2 or front heights or something useful.
Also: is this biamping feature available only if I choose to connect only the 2 front speakers (for 2 channels/stereo sources), or is it available also in 5.0/5.1 channel listening?
It doesn't matter how many channels you are listening to, it just uses 4 of the receiver's amps to power the two front speakers. Doesn't change anything else.
But what if I will listen in surround sound (DTS, Dolby etc.) with biamping and all speakers connected - will the fronts sound obviously louder than the other speakers? Will this affect the result obtained by Audyssey in calibrating speakers?
No, they won't sound louder -- that's the point of calibrating. It equalizes the volume of all the speakers. Adding extra power increases the HEADROOM available, it doesn't make the speakers louder at a given volume. Regardless of how much power you have you want the speakers to be calibrated to each other.