Need advice on bi-amping

I am thinking about bi-amping my front towers. First I will list the components I currently have or will soon have in my system that will be relevant to the question.

Onkyo PR-SC 5507 Pre/Pro( on the way)
Rotel RMB-1575 (5 channel - 250w per channel)
B&W 804D towers
(second amp not yet purchased)

At the moment I am using this system as my 5.1 home theater/2-channel music setup. The rotel amp only has 5 outputs so, they are all used in this 5.1 configuration. I have the B&W 804d connected to the rotel amp with a single cable. What I am thinking about doing is purchasing another amp so I can bi-amp my towers. The onkyo processor has the option to re-assign two of the surround outputs for bi-amp ability. I would then use the rotel amp to power my front towers and buy another amp to run my center and surrounds. This will be a passive bi-amp setup because I am leaving the stock crossover network installed. What I am trying to achieve is tighter, more powerful mid bass response and more detailed highs.

If I do passive bi-amp my towers, would I gain more power and amp headroom this way? It seems like it would work as the woofer section is seperated from the mid/high. This way each section is getting a full 250w feed and not splitting it. I could be totally wrong about this. If so, somebody please explain how this works.

In your opinion, do you think this would provide an increase in sound quality? I know there are some of you out there that are running your speakers in this configuration. What are the pro's and con's of doing this? Thanks in advance.


There is little or nothing to gain from bi amping in this way. You can try it and decide for yourself.
A cheap way to go would be to bi-wire your speakers. Kimber seems to make that sort of speaker wire their own speciality. However, if you bi-amp, get two of the same amps. In each amp, one side would be highs and one side lows. In case of very demanding bass, each speaker would have and entire amp to draw from. Or, get a lesser amp for highs and a more powerful one for lows. That wouldn't be my choice, although I have used it. I would expect any improvement to be subtile. I got a surprising amount of improvement in my system when I put every component on Vibropods--they absorb vibration and come in an assortment of weight bearing loads. The clarity was clear to me with each component. If you want a real change in what you are hearing, you may need to consider new speakers. Our tastes do evolve, and our listening priorities can change. Good luck.
I wasn't sure if that would work the way I thought it would. I suppose I just need to step it up and purchase a nice stereo amp for my towers.
Bi-wiring is of even less value than passive bi-amping.
You really need to match the center to the right and left. Keep in mind that for theater the center does most of the work. Also, doubling the wattage will only gain you 3db. My suggestion-biamp the mains and see if it makes a difference. Use the 5th channel to power the center(which u can set as small on the pre) and buy a little rotel for the rears? However, dont waste a dime until you see if biamping helps.
That 3dB wattage gain is theoretical since the power driven through the LF is the limiting factor such that the additional power though the HF is rarely realized.
I might step back a re-think this. Probably just save my pennies up for a better amp.

Thanks for the advice

Going a bit against the grani:
The onkyo processor has the option to re-assign two of the surround outputs for bi-amp ability.
IF the amp allows you to choose frequency as well, so much the better. Anyway, why not borrow a cheap 2 channel amp and try it out. Since you use a 5 channel Rotel, try to find a used 2-channel from the same company.
You will get some sonic improvement which usually translates into slightly "clearer" sound -- i.e. you get the impression there is better separation between instruments and voices. You have more power on tap because you have added two extra channels -- you are just relieving some of the strain put on your present amp...

I used to passively tri-amp simply because I happened to have amps lying around that happened to have identical input sensitivity. The result was not stellar -- but improvement there was.
Of course, as these things go, active bi/ multi amping is in another league altogether!
I toyed around with this idea in my system, which is very much like yours. I have the 803D's in front, 805D's in back, HTM2 Center, my sub has its own amp so we'll leave that out. I started with the RMB 1095, 5x200w. I wasn't happy with this amp alone. I ended up with an RB 1092 driving the front, and an RB 1091 monoblock running the center speaker and using two channels of the 5 channel amp for the rears,(all bi-wired.)This gave me the sound I wanted for the budget I have.