They connected to the ProjectMix yeah?
Somewhere on the desk there may be a Control Room volume pot which controls the main out volume, as long as the speakers are connected correctly at the back. (i.e main outs and not another output)
Also, have you messed around with the volume at the back of each speaker? I only have mine set at half on each, as otherwise the possibility of them being damaged is higher should there be a sudden outburst of loud sound come unexpectedly.