Bi-amping with RSX-1055 and RMB-1075

[4_everyman]

I want to use an RMB-1075 in a bi-amp configuration to drive my center front and center back speakers. The speakers are Polk CSi40s and they have two sets of terminals, so they are bi-amp/bi-wire capable. My receiver is an RSX-1055.

The RSX-1055 has two center channel pre-amp outputs (CTR1 and CTR2) and two center back channel pre-amp outputs (CB1 and CB2). The owner's manual for the RSX-1055 says that if you're using one speaker, you should use the CTR1 and CB1 outputs

Which the better/smarter way to connect the RSX-1055 to the RMB-1075?

A. Use ONE pre-amp output (CTR1, for example) and a Y-cable to go between the RSX-1055 and two of the RMB-1075 inputs
OR
B. Use separate patch cords for CTR1 and CTR2 outputs to go to two of the RMB-1075 inputs

Obviously, i'd do the same thing for the center back speaker. I'm just not sure if one method is preferrable. Thanks, folks.
Rgds,
--Pete

[Kevin D]

As far as the front center, I would use both outputs and just go to the 1075.. They are the same output and you won't lose signal from a splitter.

Now on the center back, if you only have one speaker back there, you have to use the CB1 output and a splitter.. Make sure to use the setup menu to specify that you only have one rear center.. When you turn it to two, the Rotel creates stereo center rears and you will be sending different information out CB1 and CB2..

On a side note, since the 1075 is designed in three sections(left side, right side, center), I would use the front left/right inputs for the front center and the rear left/right inputs as the rear center.. This would balance the signal load over both sides of the amp. If you were to use the left side for front and the right side for rear you would wind up stressing the left side a whole lot more than the right..

Kevin D.

[Andrew Pratt]

I'm curious why you wouldn't want to use the more powerful amps in the 1075 to bi amp the fronts and a single channel for the centre then simply use the redirect features on the 1055 to power the rears?

[4_everyman]

I'm curious why you wouldn't want to use the more powerful amps in the 1075 to bi amp the fronts and a single channel for the centre then simply use the redirect features on the 1055 to power the rears?

An excellent observation, Andrew. The answer is - i already am. I didn't want to bore you all with a list of my gear, but perhaps it would've made my posting sound more sensible.

The deal is, i have two RMB-1075 amps. Here is the configuration i'm trying to set up -

Amp1 is powering:
* Left Front LF
* Left Front Mid/HF
* Right Front LF
* Right Front Mid/HF
* Auxiliary Left front speaker (not bi-amp capable)

Amp2 will be powering:
* Center Front LF
* Center Front HF
* Center Back LF
* Center Back HF
* Auxiliary Right front speaker (not bi-amp capable)

The "auxiliary" front speakers mentioned above are a set of Polk RTi38s that i'm using in conjunction with the RTi150s (literally on top of!) to provide more mid-range and high end. It's unconventional, to be sure, but i tried it as an experiment and was amazed by the results.

Finally, i'm driving my L/R rear surround speakers directly from the surround outputs of the RSX-1055.

Yeah, it's undoubtedly overkill, but i'm very impressed with the clairty of the RMB-1075. My center front and center back speakers are bi-amp capable so i went a little overboard in the power department. So you can see that i'm trying to get 10 channels of amplification out of the two RMB-1075s while relying on the RSX-1055 to drive the surrounds.

So...am i making a little more sense now?
Rgds,
--Pete

[aud19]

I seem to remember someone posting a while ago that the most succesful bi-amp configuration would be 2 identical amps powering the LF and Mid/HF respectively. Perhaps you should try that configuration... plus all the speaker posts would technically be labeled correctly...for less confusion...lol Then you could use the 1055's amps for the rear channels as suggested.

Jason




Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide

[4_everyman]

As far as the front center, I would use both outputs and just go to the 1075.. They are the same output and you won't lose signal from a splitter.

Got it! Thanks.

Now on the center back, if you only have one speaker back there, you have to use the CB1 output and a splitter.. Make sure to use the setup menu to specify that you only have one rear center.. When you turn it to two, the Rotel creates stereo center rears and you will be sending different information out CB1 and CB2..

Wow! I just learned something. I did not know that about the center back speakers. That's very helpful to know.

On a side note, since the 1075 is designed in three sections(left side, right side, center), I would use the front left/right inputs for the front center and the rear left/right inputs as the rear center.. This would balance the signal load over both sides of the amp. If you were to use the left side for front and the right side for rear you would wind up stressing the left side a whole lot more than the right..

OK, this is not as clear to me. I know that looking at the back of the amp, the outputs are arranged in three groups:
[Right surround & Right front]
[Center]
[Left front & Left surround]
...but i had no idea it was designed in three sections. I was under the (possibly mistaken) impression that it was basically just 5 amps of equal power output and that there wasn't any pairing of channels, as such. Kevin, where can i learn more about the design to make sure that i use it properly? These front/rear center speakers have one tweeter and two 6.5-inch midrange/bass drivers. They shouldn't be too demanding on an amplifier.
Rgds,
--pete

[Kevin D]

...but i had no idea it was designed in three sections. I was under the (possibly mistaken) impression that it was basically just 5 amps of equal power output and that there wasn't any pairing of channels, as such. Kevin, where can i learn more about the design to make sure that i use it properly? These front/rear center speakers have one tweeter and two 6.5-inch midrange/bass drivers. They shouldn't be too demanding on an amplifier.
Rgds,
--pete

I have no idea.. Part of my knowledge that I just pick up.. Did a quick check of the manual and it's not there.. Either from the Rotel product book, or dealer lit.. I KNOW the 1095 is designed this way and am pretty sure the 1075 is the same..

The way the amp is laid out, things are shared, whether foils or capacitors, or whatnot.. The left side with front and rear, the right side with front and rear, and the center. The center amp is placed along the front utilizing the entire front heatsink. Since 60-70% of a movie comes out of the center channel, it does more of the work and needs the bigger heatsink. The other two fall on each side having no exposed heatsinks..

I know that on the 1095 if you short the leads out or do anything to kick the protection circuit on, both lights for that particular side come on.. IE if I short the right front lead, both the right front and rear protection lights come on, meaning I've lost that section until I do a power cycle not just that channel.

Since we've all ready established that the center contains 60-70% of the soundtrack, putting both bi-amp channels for the front center on one side of the amp would use those shared components on that side more than the other possibly causing some form of sonic imbalance down the road..

All hypothetical, I just figured it would be a good idea to split them across two sides of the amp..

Kevin D.

[aud19]

All the more reason to connect them the way I stated if you ask me.... (Though no-one did...lol)

Jason




Need a new display? Questions about new display technologies? Visit RPTVs, plasmas, and other monitors @ HTguide

[Andrew Pratt]

I know that on the 1095 if you short the leads out or do anything to kick the protection circuit on, both lights for that particular side come on.. IE if I short the right front lead, both the right front and rear protection lights come on, meaning I've lost that section until I do a power cycle not just that channel.

Same thing happens on the 1075 too ops:

What I'd do is connect the front left and right speaker to seperate 1075's so that when in stereo mode each front speaker has the full draw of all the current available in the power supply without haveing to fight the other channel...its sort of a quasi mono block that way