monitoring problem

[mudflaps]

im running a mix plus system and im sending pro tools out of outputs 1 and 2 into a soundcraft spirit, coming out of the control outs into a set of ns 10's. when ever the master fader gets close to 0, i get some low end pops (sounds just like a kick drum that has been edited and needs to be crossfaded) ive bounced to disc with the master fader at 0 and the mix sounded fine. so I know there is something wrong with my monitor setup. could this be a +4 -10 issue?

[Russ M.]

You're probably overloading your analog in since a level of 0 in ProTools is 18-20 db above your nominal input level of your analog gear.. depending on the calibration of your converters -18 or -20 is equal to +4 on your analog equipment. That puts your level at +22 to +24 which is 4 to 6 DB higher than your analog can handle given your analog equipment max level of +18. It's even too close for +24 output equipment.
Run a 0 db 1khz tone out of protools and watch your meters on your analog gear...