I'm using an Mbox Mini to monitor and record audio with a Mac-based Media Composer system, and even with the volume maxed, the general level monitoring Avid is very low compared to all my other Mac audio like iTunes, which blasts at ear-piercing volume with the control here.
In the Audio Project Settings, there is a pulldown under HW Calibration to change from -20 dbFS, but trying to change to -14 I get a warning, "Changing the software Hardware Calibration MUST be synchronized with physical changes to your Audio I/O Peripheral", whatever that means. I haven't tried it. I don't want to do anything that will affect me down the line with regard to outputs and exports.
In the audio mixer, I can raise the Master volume for each sequence by +3 or more dB to get something like a normal monitor level, but again, this seems odd and I'm a little wary how it will affect exports.
Mid 2010 Mac Pro running Yosemite 10.10.5
2 x 2.4 GHz Quad-Core Intel Xeon
22 GB 1066 RAM
ATI Radeon HD 5770 1024 MB
Three USB, two FW 800, SATA port card
Does the Mbox Mini have user accessible calibration settings on it, or can it be set via software?
I think this is something that refers to Mojo and Adrenaline. In any case, I don't think it will change the output volume of your device (unless, of course, there's a way to do that to the device itself, as queried above.)
I just tried changing from -20 to -14 on my MacBook Pro and got the same message. Clicked ok and nothing happened. To be expected, since I'm not running any kind of I/O peripheral.
I would check to see if there's some way to change the output level of your Mbox, either via a small, recessed pot on the back (or underneath), or via software supplied by the manufacturer. And maybe check for a firmware update for that device, too. Sometimes fixes like this can be fixed via firmware updates. Just make sure you can revert to the older firmware if needed before upgrading.
Canon XF-300, Canon 5DMkIII, Canon 7D MkII, Avid Media Composer 7.05, Adobe CC 2015, iMovie Pro.