The reason I said the M80 looked flatter is the high-end portion of the curve, where the M80 stays at ~87 db and the LFR660 drops to ~82 db. Also, what I don't think I mentioned in this thread is that I got the HP woofers on the M80 (not available for the LFR660) which Axiom says flattens out the lower end. Axiom doesn't have curves for the HP versions, so I made some assumptions there. The LW/SP curves are what I meant by "room resonance", and there the LFRs clearly have the edge.
Don't get me wrong, I like the LFR600; but to my graph-eyes, with some hand waving to fill in the blanks, the M80HP is flatter.
The more I think about it the more I think it was unreasonable to compare across the base lines. I'm thinking the performance of the larger speaker is washing out the improvement of the LFRs. (And the lower-end LFRs don't have quite the same advantage as the upper-end LFRs on the LW/SP curves anyway.) I should have sucked it up and got the LFR880s. (Which is now on my radar as soon as my wife gets over the actual size of the M80s in the living room.)
