All comments welcome.
What slope are you proposing James, normal HPFs come in 12 or 24 db/octave.
For live use displaying the frequency that the HPF is set to is relatively unimportant, but if you have the ability to display it then why not.
The 2 main uses for it are -
1. Taming a bad room or stage with low frequency resonances muddy up your sound.
2. Cutting low end that you cannot hear that eats up power amp output and speaker excursion.
In case 1 you increase the frequency until the problem goes away or is acceptable.
2. You increase the frequency until you notice your sound changes then back it off until it just returns.
12db/octWe could do either 6dB/octave or 12dB/octave. Preference?