# How many amplifiers do I need??



## rf5000 (Mar 13, 2010)

Hey All,

Building a 9.2 theater system. I have (7) Definitive Technology RLS II in walls that i was using for my mains, center, surround side and surround back. I have (2) Definitive Technology RLS III in walls using for my front highs. For processing, I was going to use my Onkyo tx-nr5007 9.2 receiver.

I have a question about amplification. Since I have read that the rear 4 channels and 2 front high channels don't use much wattage and only periodically, would those be fine to run off the receiver? Then just get a 200 or 250 x 3 amplifier for the mains and center? I'm undecided. The Onkyo flagship receiver boasts a Massive Toroidal transformer for High current drive and 4 Independent Power Supplys, but in the same specifications it lists 145 watts per channel with two channels driven?? So is that to say if all four rear surrounds and two high fronts are driven at the same time, it would be way less then 145 watts each?

I know it would be better to by one or two more seperate amplifiers for the rears and front highs, but will I notice that much of a difference? The speakers are each rated at like 10 to 350 watts. Also, I figured 250 watts from a seperate 3 channel amplifier would be okay for the fronts, or maybe I'm wrong there too? Should I be trying to reach that 350 watt mark? Please help with some input. Thanks.


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## fitzwaddle (Aug 25, 2010)

Those are rated as 92 dB sensitivity, I'd think you'd be fine just powering them all with the receiver, no additional power amp(s) needed.


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## KrazyK (Feb 28, 2010)

rf5000 said:


> Hey All,
> 
> Building a 9.2 theater system. I have (7) Definitive Technology RLS II in walls that i was using for my mains, center, surround side and surround back. I have (2) Definitive Technology RLS III in walls using for my front highs. For processing, I was going to use my Onkyo tx-nr5007 9.2 receiver.
> 
> ...


Most receivers are rated at 2-channel driven. It is a marketing gimmick. 
As you increase loads (speakers) the receiver has to work harder to drive all those speakers.
Efficient speakers are easier to drive for a given volume. 
Your speakers are 8ohm loads and are rated at 92db. 

The previous post said you should be fine and I agree to a point.
It's when things get loud that you'll have issues with detail and speaker response.
Having extra power is a definite bonus! 

I can share my own experience moving to more amplification with the same speakers and receiver.
When I added amplification I found my listening volumes actually lowered.
My system gained detail and I didn't have to crank things up to hear dialog etc.
When the action increased I wasn't reaching for the volume to turn things down because my speakers weren't clipping. Overall it was a much improved experience.

I like your idea of driving the front channels separately and using the receiver to drive the rest.
It's a good place to start!
Don't be afraid of using more amplification then you mentioned. Your speakers recommend up to 350watts!
You speakers will love the extra head room!

The only problem will be.............
You'll probable want to get more amps in the future to drive everything else.

Sounds like you'll have a nice set-up!

Good Luck!


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## Tufelhundin (Jan 25, 2010)

As was mentioned above, your speakers are pretty dang easy to drive so an external amp is probably not needed, and the 5007 is a powerful avr. However....in this hobby it's not necessarily what we need, but want.:spend: I am looking at external amps as well and I will get one regardless of need, I believe an external amp will help with the stereo/surround imaging, it will allow me to listen to music and movies with more impact, and it will free up my avr amps to run the "not so much used" front heights and rear surrounds. I'd say get a good 5 channel amp and let the avr handle the heights and rears.

Concerning amps, if you are pretty much set on getting one....start "searching" for the info is limitless and quite interesting. There are some great amps out there that could probably improve the sound of your system and with the demand of external amps, if you decide its not needed & decide to sell you can pretty much get what you paid, I suggest you watch Audiogon and just began to "search" different amps, everyone has a opinion and preference but you will eventually weed through all of the "I have to justify the $$$ I spent" threads and be able to narrow your choices down to a couple, then you can start nit picking.

Then there is the blind test.. and I believe it to be true, however I also believe that certain amps are made better than others......



Now back to reality....as I mentioned earlier, you have a powerful avr and the speakers your running are efficient....so you may not gain much by adding an external.....but there is that need/want issue.:whistling::R


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## erwinbel (Mar 23, 2010)

Here's an article about the power specs of amps
http://www.audioholics.com/education/amplifier-technology/the-all-channels-driven-acd-amplifier-test

In general, the common brands AVR's only have half the power with all channels drivven. So, a 7*145 Watt is tipically 7*70 Watts. But 70 Watts would still be OK if you only used it for "ambient" channels. 9 channels drivven probably even less than half though. 

The Emotiva XPA-3 was introduced just to let you do that: relieve the AVR from the task of powering the LCR. It's 3*200 W, more than enough. If you imagine ever getting 11.2 with wides, the XPA-5 (5*200 W) might be a better investment. If you want more Watts, wait for the XPR-series, they should arrive within the next 3 months. The XPR-7 is anounced with 7*350 W for $1,999. But the XPA-3 would be the best return on investment IMO for $699. The XPA-5 is $899.


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