There is something I am not understanding about your post, and I suspect other 4520 owners will be equally concerned.
You say that you measured the 4520 as having 190W RMS power in stereo mode. You say your speakers are very efficient, and that the McIntosh amps are only drawing 3W of power.
But then you say that the 4520 starts to distort at -18 on the MV, and becomes unbearable at -10 on the MV, and this is only at about 82dB, measured at your MLP? How can that be so, if your speakers are so efficient?
I must say, if the 4520 amps were distorting unbearably at the modest MV levels you mention, how come we don't have hundreds of postings reporting the same findings? As I say, I must be misunderstanding your test, because it is really very hard to believe.
Hi Jerry, just some corrections from your post, the power ratings from the Denon AVR-4520ci I'm quoting are from the manual (page 202). I was never sure exactly how much power they were pulling, until I had the MC601 hooked up, I can use the McIntosh "true watt meter" to estimate how much power I'm using at that moment. I was actually surprised how little power was required, but I guess the math works out if you play around. My speakers can put out 89db with 1 watt, at 1 meter. More power is needed the further you get away from that 1 meter, and obviously different frequency ranges are going to use more power and open rooms are going to use more power to achieve the same pressure since those measurements are conducted in closed chambers.
The 82dB I mentioned in my previous post is actually recorded at -18db on the Master Volume. At -10 it's in the low 90's range at my listening distances (if I'm remembering correctly)
Just because the Denon AVR-4520ci is rated at 190W RMS does not mean it can put that out without picking up noticeable distortion along the way. Like I mentioned earlier, it's going to depend on a lot of variables. For movies I will run my volume to nearly -15db and never worried or listened for distortion. Since 90% of the movie is background low volume music scores or the actors talking. The movies only get considerably loud for short portions.
If I listen to -15db through my Oppo for music I will be going deaf one of these days. It's just two situations. I guess it's either how the track is mastered on movies versus music?
But, I can say without a doubt, at -10 my ears were hurting with playing music through the AVR-4520ci, and it sounded horrible in comparison versus either of my McIntosh gear, it wasn't subtle. It was literally as I stated, night and day difference.
If you have a local Best Buy Magnolia room nearby, I know they have the lower model McIntosh integrated MA5200, and the AVR-4520ci on their panel. Go level match them with your SPL Meter, and have the rep A/B them for you. Like I said, at lower volumes the differences are so subtle I wouldn't recommend someone to spend big money on these amplifiers, at louder volumes, it a pretty massive difference.
I've been looking for data for the real distortion numbers from the AVR-4520ci and can't find anything. But, I know the McIntosh gear is around 0.001% THD across the full power spectrum and all audible frequencies.
Since I will be going to a bigger listening room/ Theater at the next house I know I will need the extra power, so this was an early purchase to prepare.
I hope this helps. If your ever in town, your welcome to swing on by.