Well I have just fired up the 875 with the M80's and I am reasonably happy. I need more time to test with good source material to make a more rounded view. I had the impedance set to 6 ohms and no probs with the reciever cutting out. I ran it pretty hard and it did get a bit hot but I understand that this is normal for this receiver. I did expect that I would have unbearably loud sound coming out at high volumes but this is not the case. I measured sound level at peaks of 108 db coming out of the M80's from 1 metre. From my calculations this means I am only putting less than 50 watts into the speakers at this spl.
Axiom M80 SPL in room = 95 db /1 w/1 m
= 98 db /2 w/1 m
= 101db /4 w/1 m
= 104db /8 w/1 m
= 107db /16w/1 m
= 110db /32w/1 m
= 113db /64w/1 m
= 116db /128w/1 m
= 119db /256w/1 m
= 122db /512w/1 m
I can hear the M80's start to distort at around 110db which only equates to an input power of 32watts. The 875 has plenty of headroom and I am sure that there could be no clipping at 32 watts. Interestingly when I set the impedance to 4 ohms on the 875 I still got about 110db out of the M80's before distortion occurred. In 4 ohm mode the 875 is limited to 55 watts per channel.
Does anyone know why the M80's don't seem to be handling much power? I am sure it is not my ears distorting as it sounds like the woofer cones are breaking up at around 110db. The excursion of the woofers at 110db seems large. With the 875 I should be getting peaks around 119db = 256 watts.
