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Need advice on bi-amping

Hello,
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.

Andy

andyprice44
elevick
2,638 posts
 
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.
kr4's avatar
kr4
3,693 posts
 
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.
andyprice44 OP
133 posts
 
I might step back a re-think this. Probably just save my pennies up for a better amp.

Thanks for the advice

Andy
gregm
3,409 posts
 
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!
etolarry
5 posts
 
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.
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