Even though the Onkyo's amplifiers aren't being used to power speakers they are still powered up and functioning. If there is a protection circuit in the amplifiers sensing distortion it might still turn the unit off. Also the unused amplifiers may be creating heat. It's hard to say.

Polks and Onkyo are a bad match if the goal is to play LOUD. Polks require a little more power to get to the same volume as comparable speakers and Onkyo receivers have never been known for driving difficult loads.

I'm not knocking either product. They are both nice units just the wrong tools for this job. Klipsch speakers would have been the a much better choice to play loud with very little power. My guess would be that Klipsch speakers with the Onkyo would play louder than the Onkyo/Outlaw/Polk by a very, very wide margin.

How hot is the Onkyo when it shuts down? Move the unit from its present location to provide better air flow and check for problems. If this doesn't solve the problem, unplug everything except a source and try to get the receiver itself to shut down.

Yep, if you want really loud, the Polks are a poor choice. You need some thing about 10dB higher in electrical sensitivity. Klipsch and JBL are two mass market brands that have higher sensitivity. You have found out just how buying power works. You have to buy twice as much real power to make an audible difference, this will give you approximately 3dB of volume increase. Three dB is about where you can notice a difference and not much more. You need to buy approixmately ten times the real power to get ten dB - or twice as loud - which is where most people find a real difference. All of this gets distorted in real life by the dynamic nature of music. Better to get your volume from high sensitivity speakers than by buying more watts.

http://myhometheater.homestead.com/splcalculator.html

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http://myhometheater.homestead.com/splcalculator.html

Wow, Jan that link is killer. Good point about ventilation.

93cbra

Are the top vents blocked? They should have at least 2 to 4" of clearance

Is the unit in a closed cabinet?

hturning off sounds like a heat problem. I own a modest Onkyo receiver for my TV system and it has never shut down, though I do not listen a painful levels.

perhaps moving the receiver from the other gear and improving air flow might make a difference.

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I have nothing connected to the L/R speaker outputs on the Onkyo, the outlaws are connected to the "front left and right" pre outs.

Is the receiver trying to run these two channels without a load? Or do the pre-outs disable the l/r fronts? I don't know, so I'm asking the experts here.