Rotel Component Inquiry (2 x 1075's) ???

[Joe Rock]

First off, what a great forum...being my first post, I would like to express my appreciation of such a well organized and informative forum. Keep it up!

To All Rotelian's: I have seen the light, after a few years of interest in Home Theater I have decided to quit playing around and enter this Hobby a bit more serious. Rotel has become my equipment of choice. I am planning on purchasing the Rotel Pre/Pro RSP-1068 along with the RMB-1075 Amp. So far so good right? Well this is where I am in need of some assistance. I have recently aquired an Infocus DLP projector and I am currently building a dedicated home theater in our basement. I am planning for a 7.1 system. My question arises due to my new speaker configuration. Let me tell you a bit about my speaker specs:

Center (2) (6 ohm, 400w)
Front Mains R&L (4 ohm, 400w)
Surround R&L (6 ohm, 400w)
Back R&L (6 ohm, 400w)
Planning on two subs (leaning toward SVS)

Here's my issue, i would like to do two center speakers...one above and one below my perm wall screen. I originally started thinking about the RB-1080 to power my mains and then the 1075 for center and surrounds. But with the addition of another center channel @ 6 ohms and the risk of showing a 3 ohm load (2 centers)...I started thinking about (2) 1075 amps.

10 Channels (my thought process)

4 channels - Bi amp my two mains
2 channels - 2 center speakers
2 channels - surrounds
2 channels - backs

Is this possible...is it physically possible to spilt interconnects to send signal to more than one channel of an amp. How is Bi-amping done exactly?

I hope I was able to explain my situation well enought for comments. I look foward to your responses and/or suggestions.

Joe

[hired goon]

G'day,

Is this possible...is it physically possible to spilt interconnects to send signal to more than one channel of an amp. How is Bi-amping done exactly?

You can buy Y-connectors that split an RCA cable. These connect to the pre-outs of the RSP-1068, and then to two amps.

Try a search in this forum for "bi-amping splitter" and you'll see quite a few threads pop up, such as this thread.

--Geoff

[Joe Rock]

Geoff,

Thanks, I have been reading different posts on Bi-amping and or Bi-wiring. Appreciate the link!

I guess I may have sounded too naive on the possibility question of Bi-amping. I know its possible to purchase RCA's at Rad Shack for splitting the signal, but I should have asked...is it recommended to do this? Do higher quality interconnect companies recommend this type of usage? Do these high end companies make cables for this type of operation? Or is it frowned on by the industry?

Joe

[hired goon]

G'day,

is it recommended to do this? Do higher quality interconnect companies recommend this type of usage? Do these high end companies make cables for this type of operation? Or is it frowned on by the industry?

I haven't listened to bi-amped speakers before, so I really cannot say. I'd assume that the splitter would have to be high-quality to ensure that the outputs are equal to the input. If so, then you can power your two front centre speakers via a splitter.

As for bi-amping your front L/R speakers, I'm not sure that that splitting the signal and using one amp per speaker is the best method -- you are still sending the same signal (albeit twice) to the speaker. The point of bi-amping (I assume) is to have one amp handling the bottom-end, and one amp handling the top-end, for more efficient output. That would necessiate some sort of crossover between the splitter and the amplifiers: one amp for the bottom-end, one for the top-end. But then you're getting into tricky territory, as the crossovers have to be matched to the speaker you are using.

Perhaps someone more knowledgeable can outline the benefits of bi-amping, and the proper way of achieving it. In any case, you should try to listen to such an arrangement first.

--Geoff

[ajpoe]

Geoff,

Thanks, I have been reading different posts on Bi-amping and or Bi-wiring. Appreciate the link!

I guess I may have sounded too naive on the possibility question of Bi-amping. I know its possible to purchase RCA's at Rad Shack for splitting the signal, but I should have asked...is it recommended to do this? Do higher quality interconnect companies recommend this type of usage? Do these high end companies make cables for this type of operation? Or is it frowned on by the industry?

Joe

I would take a look at this thread by Andrew, too. Those splitters of of higher quality than your standard Y cable. I purchased some very similar from Parts Express and I like them very much and do not notice and loss of quality. (Splitter at Parts Express)

AJ

[Andrew Pratt]

Beofer jumping into the dual center channels you might want to read up on that a little more (if you haven't already). Many people don't think that it works that well while others find it work fine. Either way what you purpose with the dual 5 channels amps would work very well. I used to run something similar up until last week when I sold my other 5 channel amp to buy the Rotel 1080 for my mains.

[NonSense]

Joe

I wouldn't consider myself an expert in the field, but here is my two cents.

I have never had a chance to listen system with the configuration you propose, but I would urge you to do some experimenting with the dual front center channel setup before you commit. In my opinion, good home theater is all about the imaging (not just the power). I might have some concerns with this sort of placement and amplifier arrangement. You might not be able to achieve a proper center image. An important requirement for home theater setup is that the delay for each channel be calibrated to the optimal listening possition. With two center channels located at slightly different distances from the listening possition, I would expect a possibility of phase errors and even nulls at certain high frequencies. (Darn superposition!) These could probably be calculated. At minimum, you should consider keeping both at the same radius from (and facing) the listening position, as you will not be able to independently adjust because you would be splitting the center channel out on a Y-cable (only 1 adjustment setting per channel).

In some cases, IMO, more does not always mean better. This would, again IMO, apply to certain applications of bi-amping. Unless you go to the extent of adding active filtering prior to your bi-amping, you are not likely to see all the benefits. The advantage of bi-amping with active filtering, is that you are sending only the desired limited bandwidth signal to the amplifier which is controlling either the high freq. or low freq. set of drivers. (Also, the amps are often bypass the internal passive crossover networks for exceptional driver control)

A long winded argument could be proposed, that a single 180W amplifier in bi-wire configuration, would outperform 2x120W amplifers in bi-amp configuration (full freq to each amp, w/ speaker crossovers intact). (As 2x120W's is not equivalent to 240W's) If both were of similar calibre, 1095 vs. 2x1075's or 1080 vs. 2x1070.

If it were me, I would axe the 2nd front center. Stick with your original proposal, 1075 and 1080, or if you can make the stretch, 1095 with either 1080(for mains) or 1070(2x rear center channels, as there is fewer source material in 6.1 and 130W sould be plenty once calibrated) . If your center is really rated for 400W's, the extral juice of a single channel of the 1095 into the single center channel should be plenty. I don't know how large your auditorium is but a single 400W center channel, powered by 180W's should be up to the challenge. (Unless you have balcony seating?)

If money is tight, The RSX-1056 which is usually comparable in price the the RSX-1068, is capable (if I am not mistaken) of having it's 2 main channels redirected to the rear center channels for 7.1 operation. Then you could start with a RSX-1056 and RMB-1095 and get all 7 channels (for about the price of a 1095 and 1068). Then later you could get an RB-1080 (or RB-1090) for your big mains. Even the lower wattage of the 1056's amps should be enough to do a good job on the rear centers once balanced out with an SPL meter.


Enjoy

[Joe Rock]

Thanks for all your input. I am glad I posted my questions...from my research on this forum and your responses I have decided to drop the dual center idea. In my 15' x 35' dedicated theater room, I think 1 center will do the job. I plan to go with the RSP-1068, RB-1080, RMB-1095 combo. I think this will be enough power for clear HT reference levels. Thanks again!

[Andrew Pratt]

Good choice :T