RB-1080 & RMB-1075 - good 7 channel combo?

[Bitece]

Would it be problematic to power a 7.1 theater with a RB1080 powering the mains at 200watts/channel and 10 the 1075 powering the center and 4 surrounds at 120watts/channel? I know the surrounds don't need the extra power but will the center channel suffer? I don't own any superaudio or dvd-audio discs. The system will be dedicated to 2 channel music and dvd home theater.
Even in a 5.1 config does the wattage to the mains need to match the center channel?

[Aussie Geoff]

Bitece,

I have done what you are planning for 2 years and it worked really well. Make sure your Centre speaker is set to SMALL and you should not have a problem unless you have relatively hard to drive speakers (let us know what you have).

I know from two years on this forum that the combo you are planning is very popular with lots of members having it.

PS - I have renamed your thread to get more responses for you

Geoff

[Bitece]

Any ideas for a 5 channel setup incorporating the 1080?

[phuz]

It won't be a problem. Just use an SPL meter to make sure all of your levels are set so that each speaker is playing at the same level in surround modes.

I'm using a 1056 for 3 channels (rear/center) and an RB-990BX 2 channel amp for my mains (5.x, no sub right now). Big difference in power there, but awesome performance all around.

[Dmantis]

I disagree,

having all that extra power on your mains and not matching it to your center and surrounds will cause a difference in dynamic range during action scenes.

The proper amp to match closer to the rb1080's awesome power output would be the RMB1095.
I do however understand why most people would want to use this setup in a 2 channel first then home theater 2nd system.

I have experience with using different power output amps for home theater and had extremely difficult times trying to calibrate the system to work flawlessly. It's very distracting when the main speakers overpower the center channel. even the rears have a difficult time keep up.

As suggested , if this the way you want your system configured, running the center and rears in small will help. When you spl your system, set the mains 2db lower then the center and rears. Match the center and rears perfectly.

What kind of speakers do you own? If there hard to drive speakers , I suggest you go with the RMB1095 and don't look back.

Dan

[DrJRapp]

I disagree,

having all that extra power on your mains and not matching it to your center and surrounds will cause a difference in dynamic range during action scenes.

Dan

I disagree with your disagreement. I run this exact setup and have never experienced any audible lack of dynamic range during ANY scenes. I do run efficient speakers, the Klipsch 7 series, and my mains, the RF 7s are considered difficult to drive due to impedance dips down to the 2-3 ohm range.

As suggested , if this the way you want your system configured, running the center and rears in small will help. When you spl your system, set the mains 2db lower then the center and rears. Match the center and rears perfectly.

Dan

Your recommendation on how to set up the mains doesn't hold true at all, it will vary from system to system. With all due respects I think you may not understand the difference between gain and max power output. A more powerful amp will not necessarily sound any louder, at the same listening level, it will just be able to be driven harder and to a higher level. ie: I have a 1050 that I use for zone 2. Recently when my 1080 blew a channel and for six weeks the 1050 had to wear a different hat and power my mains. System balance remained exactly the same, I didn't have to change a single setting in my system since the gain of both amps was similar. Of course my whole system couldn't be driven as hard before running into clipping the 1050.

[Bitece]

I'm working on the speaker selection. I'm pretty confident that the 1080/1075 with the 1068 will be my electronics. The speakers are next and are proving to be a rather difficult decision!

[Stevebez]

I started out with the 1075 only and then grew the system by adding a 1080.

Have to say its a great combo.

This works especially well if you have "large" fronts and "small" surrounds. If you had a large centre and you really cranked up the system you may need to drop the db gain slightly on the fronts for the sound field to remain matched and not for the center to be drowned out - actually this is much too strong to put it this way. The center will not be drowned out at all but lets say marginally muted but in all likelihood unnoticable.

Even so I find it very difficult to see a center channel driven by a 1075 to be "drowned out" or even muted. The 1075 has got plenty power reserve especially if the surrounds are not being pushed hard the center will not lag at all...

I would not change my system to a 1095 / 1080 combo as I dont need such high power for my surrounds - the speakers are only rated at 100w anyway and unless you listen to 5ch/7ch stereo you will not need the extra umph.

Does not stop me dreaming of a 1095 / 1090 combo though...!!!

Regards Steve

[Azeke]

If the speakers are properly calibrated, I believe your 1080/1075 combo would be fine, unless as previously mentioned you are driving difficult speakers, i.e. 4 ohm, inefficient, etc.

I own the 1095/1080 combo and did that only because I wanted to maintain the 200W balance throughout my system, that was a personal choice however.

BTW, 7.1 channels is a beautiful thing if you have the room. Your mileage may vary of course.

Just my quick thoughts,

Azeke

[csuzor]

I believe matching the input sensitivity relative to the amplification power is the key to matching different power amps.

The RSP series have 1V output
The RMB1075 (120W) has 1V input, the RMB1095 (200W) 1.5V input
The RB1070 (130W) has 1V, the RB1080 (200W) has 1.5V, the RB1090 (380W) has 1.8V

Assuming you calibrate the channels at the usual listening volume, and music is low in dynamic range, and you don't change volume, you shouldn't care about this difference (unless you start clipping on the lower power amps).

However, when you change volume, or have large dynamic ranges, the difference in input sensity helps to maintain a similar increase in volume for each of these amps.
The slope Power Vs InputVoltage is similar (or somewhat similar).

I didn't do the math, and I don't know if the RSP outputs a linear voltage with Power required or a non-linear voltage on a scale like dB, but I suspect that Rotel did not accidentally decide on these different input sensitivities.

My conclusion:
any of these amps can be mix-n-matched in terms of power capability, as long as the listening volumes are neither very low nor very high.

Interesting to note that the RSP can never push the input of the bigger amps to the max... seems like it's all about "reserves of power" rather than "usable power".

Christophe

[Radec]

I have the combo mentioned and feel it is a great combo. I have the center set to small, fronts to large, and with a bit of calibrating they sound great. I will say you will need a SPL meter to match them, but you should do that anyway. I'd say from my experience with these units unless your center speaker is a monster to drive I see no problem.

[spiffnme]

I ran a 1075 and a 1070 for awhile and it was great. I then sold the 1070 and used an Odyssey Stratos to power the mains, using the 1075 for the center, and surrounds. In neither case did I feel the 1075 didn't "match" the amp being used for the center and surrounds during a movie. By haveing a beefier/better amp running your mains, you also get the benefit of better sounding 2 channel music.

I say go for it. The 1080/1075 combo should be sweet.

(Though I must admit, I've now gone back to 5.1, as the added two channels in the rear really didn't make enough difference to me for to rationalize the added expense)