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Discussion Starter · #1 ·
Have an RX-A800 (rated 95wpc); Boston Acoustics speakers with 89dB sensitivity, fronts rated to max of 200w.


Room is about 3,000 cubic ft. Starting with 5.1, but plan to soon upgrade to 7.1 when I find dipole/bipole surrounds at a good price.


Curious whether I will likely need external amplification, especially when I go to 7.1?


Before purchasing the BA's, was planning to buy Polk Monitor 70s and found lots of suggestions that these would need external amplification, likely 200wpc.


Would my BA's need that much - or could I do with 125 or 150?



Thanks
 

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You do realize the difference between 100wpc and 200wpc is only 3 dB, and the difference between 125wpc and 150wpc isn't big enough to justify doing the math for, right?


I haven't seen a bench-test/review of the A800 to tell you if it's delivering on the 100wpc claim, but based on other products, it's probably not doing it ACD. It is, however, probably very close (close enough for us to not care, especially since ACD is not real-world).


I would probably leave well enough alone - especially if everything is working properly right now. If you're really curious, grab an SPL meter, and see what it tells you.


The "suggestions" telling you that Monitor 70's "require" external amplification are bad advice and should be written off - you could hook up the biggest, meanest, most ridiculously power sipping speakers ever designed to 25wpc and be perfectly satisfied, assuming their placement, sensitivity, your room, tastes, etc worked out with that.


Read some of this over, to get an understanding of what's going on:
http://www.physics.mcgill.ca/~guymoo.../lecture11.pdf
http://myhometheater.homestead.com/splcalculator.html

And grab the link in my signature for more.


Now, the only case where I would suggest external amplification, with all of the above said, is if your A800 falls off a cliff with seven channels connected, and you have it going into auto-protect during intense passages on some movies, or it can't approach your SPL targets. Then yes, I would consider an external amplifier - 100wpc or better should be perfectly suitable (the issue, if this ends up being the case, isn't the power per channel, but the inability of the receiver's PSU to drive all of the amplifiers at once).
 

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Note that there's many threads similar to this you can read to get all the opinions.
 

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Discussion Starter · #4 ·
Thanks both. I am still finishing the room, so don't have everything hooked up yet - question was more theoretical, especially given that I had read so many things about the Polk Monitors requiring external amplification.


I definitely plan to hook it all up and see how it sounds first off, and grab an SPL meter as walbert suggests.


Thanks again.
 
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