Hercules DJCONTROL INPULSE T7 Manual page 73

We do not recommend that you connect two pairs of
headphones at the same time (i.e. one to the 1/8" / 3.5
mm mini-jack output connector, and one to the ¼" /
6.35 mm jack output connector). If both pairs of
headphones do not have the same impedance, they
will have different output volumes.
73