Originally Posted by Joostheizen /img/forum/go_quote.gif
I have a question regarding bi-amping. I have 2 x Rotel rb970bx power amps (2 x 60 watts each). I would like to use them both to achieve BI-Amp... (1 for high and 1 for low frequency). However, according to the Rotel manual, I will need to use 2 x pre out (2 x left and 2 x right) to connect to back of my SR5007. Marantz SR5007 has set of pre out for a 7.1 ch amplifier connection (2 x front, 2 x Surround, 2 x Surround Back and 1 x centre, 2 x sub (which I won't use).
So I am assume I just need to use a splitter then.
Use a splitter - make sure you use one RB970BX for each side (ie front left>splitter and RCA>RB970BX>one wire each tweeter and woofer). In this set-up you're putting only one woofer/set of woofers on each amp, so
theoretically there will be less current requirement on each amp. Whether differences are audible will depend on other factors, basically, whether each RB970BX was lacking in current to begin with and if so, will such a configuration get you enough headroom on each side, at the listening level you (and your neighbors) are comfortable with. Given you're coming from an HT receiver, chances are you might notice better driving of the speakers, although one RB970BX might be enough to do that (since stereo amps aren't as prone to BS measurements as surround receivers measured at 2khz with one channel driving a stable 8ohm load then the box says 160w x 5 (although that is a Marantz, not an old Yamaha or Onkyo).
Alternately, also try using both amps to power one Front and one Surround channel on each side, then try if the Receiver's amp (or through gain settings if you can reduce and level-match the others) can have the Center catch up and with no tonal difference between the Center and Front speakers. Or see how it does with a Phantom Center (not sure if your receiver has this either).
In this scenario, would I be getting 120 watts x 2 as I'm using both Rotel power amps? Is it even worthwhile to do this, as I really want to bi-amp. I really need advice on this. Thanks in advance!
It's worthwhile because you already have the amps and will only buy the splitters. However, take note that it's still going through the same crossover. Not that the passive crossover is such a bottleneck that it should be avoided all the time without due consideration to its benefits,
but often if the speakers sound like they're driven better it's because you have an active crossover that sends an already limited range of frequencies to each amp channel without using the amp output to run the crossover (or parts of it getting in the way, like the caps), plus probably gain controls to suit your listening room or tastes. In my car, my Pioneer 860MP receiver splits the signal for the tweets and midwoofers (and also the sub), the 75watt channels get 2.5khz and up while the 150watt channels only get 70hz to 2khz (sub amp gets 50hz down). Then the receiver also applies -4db gain on the tweeter output and -2db gain on the sub (plus time alignment on each transducer, but that's only a requirement if you're in a car other than a McLaren F1). Result? A mostly (not literally) flat response where I only EQ-out some reflections reinforcing 5khz to 6.3khz.
