I really am impressed by the 306s I picked up a few months back. I have been shifting around my workspace at home, and so have still not done what I need to do to calm down reflections where they are now, but I still have had an easy time working with them. I need to get that in order and would like to investigate options for DSP correction, which I need to learn more about. I actually bought them before discovering this site, and the world of more/better measurements, so it was really great to see that the choice I made based on a much more haphazard afternoon of research actually does measure well. Much more confidence in what I think I'm hearing, haha.
Is what you describe the same as the Bob Katz method for setting levels that he describes in his mastering book?
I too keep my levels in those same ranges, and there the JBLs don't begin to distort, though past a certain point I can hear them get muddied. I'm sure a sub would make a difference there though.
I have worked a fair amount on Focal Twin6 Bes and had great luck. This is in a well designed studio w/ a sub, and the room helps immensely. I have other points of comparison, but with lots of variables that make it hard to directly compare.. I have spent a decent amount of time on other presumably comparable monitors but consistently had nasty surprises in my mixes. Hopefully some of that's just improvement with time, but the measurements support that the Focals should be trustworthy!
And..... NS-10s get used a lot as well. Obviously they are not flat.. Has anyone done a spinorama of one of those?? I would really love to see what is going on there. I was a skeptic for a long time, I basically just thought they sounded awful, but came to see what they are used for, or at least one way to use them. Not that I don't still think they sound kind of awful! I know I've happened across a bit of analysis of why engineers find them useful, something about console bounce was part of it perhaps, but as I recall it was a bit old.. I've assumed it's just a combination of low distortion midrange in the most important bands, maybe lack of resonances created by any attempt to play bass, and the bandwidth limiting being useful so as to focus on the most crucial frequencies for clarity in a mix without being distracted by bass or sparkly extended highs, a filter.