Believe

[HbGuitar]

My standard monitor output is calibrated to 60 dB SPL when generating -14dBFS pink noise...which yields 70 dB SPL when mixing to K20 (slow response, C weighting)

Do you see this as being the most effective point on the Fletcher-Munson equal loudness curve where the ear's frequency response is most linear?

Good question......I suppose its a compromise point. I guess the holy grail for Fletcher-Munson is ~85 dB SPL. But 70 dB SPL is a sound level that I like to monitor on, especially for long periods. And of course, I can push to ~80-85 dB SPL on occasion for short bursts.

As you know, the Fletcher-Munson equal loudness contours developed in 1933 have been largely superseded by ISO226 which was initially based upon the work of Robinson and Dadson (1956) but later updated in 2003.

Interestingly, ISO 226 and FM show close correlation across the entire frequency range (20-20,000hz) below 60 dB SPL but responses above 60 dB SPL deviate considerably, with ISO226 showing much less linearity than FM in the 100 -1,000hz range......so I guess this muddies the water a little on how linear the ear's frequency response becomes with increasing SPL