We have a beautiful new Rotel RSX-1056 receiver with specs of 75 watts/ch, 8 ohms, Five Channel Driven. We use 50/50 for movies/music. It "can" run 4-ohm loads just fine according to Rotel, so long as the unit has lots of ventilation space for heat dissipation - however on the receiver and in its manual, it clearly states "8-ohm minimum" for the speaker requirements.

We are currently using the receiver with a 5.1 speaker setup having these specs:


- 2 X Kef Coda 8, 6-ohm nominal, 10 to 100W, Sensitivity 2.83v @ 1m 91dB, Frequency Range +/- 3dB 45Hz - 20kHz.

- 2 X SRS Labs Klayman Signature Series Flat Panels, 4-ohm, up to 100W long term, 150W short term, Sensitivity 91 dB @ 1 watt/ 1 meter, Frequency Response 80Hz - 20kHz +/- 3dB.

- 1 X SRS Labs Center Speaker, 4-ohm, up to 80W long term, Sensitivity 90dB / W / m, Frequency Response 100Hz – 20,000Hz / ± 3 dB.

- 1 X Denon powered subwoofer model DSW-40, 8" woofer, downfiring, 37lb.


We do realize that this speaker setup looks kinda strange with the brand mixing and such, but the Kefs and Klaymans really do complement each other with their respective sound signatures.

We are worried that our speaker setup with its 4-ohm and 6-ohm elements is potentially straining the RSX-1056 receiver, and so we are now considering adding a 5-channel amp.

The new amp would be either the Rotel RMB-1075 with 5x120 watts /ch / 8 ohms, and 5x200 watts /ch / 4 ohms,

or,

the more expensive Outlaw Audio 755 with 200 watts RMS x 5, and 300 watts RMS x 5 @ 4 ohms.

The Outlaw Audio 755 amp would be about $400 more than the Rotel RMB-1075 amp... BUT... the Rotel might be enough power for us anyway?

If it were you, would you even add one of these amps to the system at all? If so, which one would you choose, and why please?

Thanks in advance to all that reply...

I have 4 ohm speaker (Polk LSIs) and I sold a lower wattage amp (Outlaw 7100) for the Outlaw 770 which has 200 W @8 Ohms 7 channels driven/ 300 w @4 Ohms 7 channels driven. I found that the extra power really opened up my speakers and made them realize their full potential.

It's better to have too much power than too little. Most speakers are 'ruined' by underpowering them rather than overpowering. If you watch movies a lot, the explosions, car chases, and etc. will tax your amp more than dialog so it is nice to have the head room if you need it and better for your speakers.

Separate power amps typically perform better than amp sections included in receivers, even when dealing with good quality receivers. This becomes even more true when venturing into the realm of the more difficult loads presented by 4 ohm speakers. Adding some sort of external amp should definitely benefit your system.

The speakers in your system all have fairly typical efficiencies (90dB to 91dB). My speakers have similar efficiencies, and the 200W available to my mains (using M200's) and 165W available to my center and surrounds (using a 750) works very nicely. The RMB-1075 shouldn't have any trouble driving your speakers comfortably. The one system I've heard with an RMB-1075 in it had a somewhat harsher sound than I like, but from some other comments I've read I think that harshness was due to the RSP-1068 that was upstream of the 1075. (And of course there's also the matter of personal preference...) The Model 755 would give you some extra headroom, which might come in handy later if you changed speakers and of course wouldn't hurt anything in the interim. Both are good amps.

Either of those amps would be fine for you. Why didnt you buy a pre/pro to start with and an amp? I ask that, but I have a receiver with an amp setup myself... If I were you, Id probably side with the Rotel amp. If you like Rotel, then stick with them. For resale also having matching components is better... Or when you move up to a pre/pro made by Rotel, then you could have matching components still. Granted you could get say an Outlaw pre/pro and then you would be better served with having gotten the 755.

NewBuyer,
I can't speak about the Outlaw amp as I have not heard one of any model. I do currently own a Rotel RMB-1075 amp running B&W DM604-S3's, a B&W LCR600, and B&W DM302's for front, center, and surrounds respectively. The amp is amazing. I have pushed this setup pretty hard and the amp drives all channels very effectively.

I did have a Rotel RSP-1068 pre/pro in front of this amp with the same speaker set up listed above and the sound came across as very bright. Uncomfortably so, IMHO. I now have an Outlaw Model 950 pre/pro and I think it sounds amazing.

If you can get your Rotel dealer to let you demo the 1075 in your home, do it. At the same time, you could use Outlaw's 30 day return policy. That would give you the chance to try them side-by-side.

later,
simp

Thanks for the replies!

So is it true then, that at "normal" listening levels (i.e. slightly higher than background music level, not party loud), there would be no audible difference at all between the lower wattage Rotel amp and the higher wattage Outlaw amp?

I haven't heard the Rotel amp in my system, so I can't compare it directly to my Outlaw amps, but at "normal" listening levels the two should be pretty indistinguishable.

Thanks gonk! So does this mean that most people should really not buy the 755 (or similarly high-current expensive amp) unless they really want to listen at skull-splitting levels? Or have really, really hard to drive speakers?

The 755 and 770 are valuable for anyone with lower efficiency speakers, anyone who thinks they may upgrade to lower efficiency speakers later and don't want to have to replace an amp at the same time, or anyone who wants to be sure they have a good power reserve when watching movies at or near reference level. Wingnut is a good example - her Polks are about 88dB efficient (not significantly far removed from the 90dB and 91dB efficiency of the speakers in your system) and rated at 4 ohms, and she is running a 770 because the 7100 (165W at 4 ohms) didn't produce as open a sound as she felt the speakers were capable of.

i believe this notion of "headroom" is pretty stupid, yes. while you may not want to drive your amp to the max at every second of its operation, you dont need copious amounts of unused available wattage.

it could never hurt for future upgradeability...

who doesnt want the ability to listen to their system at skull splitting levels though? you dont do it because you like it, you do it because you can...

rotel is a very established and good audio company. outlaw is a good audio company as well, just not as established.