global eq, I know its been stated, or an eq built in , that is a dial for a fm curve.
Exactly this ^^^^^^I wouldn't use BMT as much as a Filter block at the end of the chain that makes the changes you need.
IMHO, this would ideally be a block in the AxeFX itself. We'd just have an Equal-Loudness block with a couple of knobs to dial in the amount of forward or reverse correction. You could try to be exact with it, or use it as an effect.
The actual math is "impossible" since it requires two point measurements of loudness (to, from).Exactly this ^^^^^^
The curves are well-known, and were shown in F & M's original work for many different volume levels, so the rate of change in each frequency band relative to the others and to the perceived volume change should be a doable bit of math.
One knob for +/- 100% EQ curve ought to do, though a second knob with a 0-200% volume adjustment would be helpful in some cases, no doubt. If nothing else, it would provide one more place to control volume with controllers....
The curves are mostly similar, so going "up" in volume relative to the volume which the sound level at which the sound was dialed in, one would need would subtract a fair amount of bass and a little bit of the very high end. The 1k - 6k range part of the curves stay relatively the same shape all the way from 0dB to 120dB, so the main adjustments would be outside that range. The ear is poor at picking up bass until sound is fairly loud, so the rate of change in the correction would be fairly steep on the bass side, as the required bass output level for perceived equal loudness only changes about 20dB between 0db and 80dB. The very high treble has a smaller change in slope above 6k, possibly almost negligible, but if we're in there and adjusting EQ, might as well adjust that too in order to keep things sounding as "flat" as possible with the volume level changes.The actual math is "impossible" since it requires two point measurements of loudness (to, from).
That said, the curves remain very similar for different volume deltas and , in my experimenting, an approximate curve produces great results.
The +/- % knob is exactly right. You'd basically dial in the dB diff between reference (loudness making the patch) and current (loudness playing patch).
+1 on this...one knob that controls the FM curves...then add to the new performance feature in the axe 3...easy.... or an eq built in , that is a dial for a fm curve.