proper way to strap 2 mtx 1501d (04 models)

[doogie 0]

so i have 2 1501d (04 models) an i want to strap them, i have the basic idea from reasearch that i did but i have never done it before. so i understand that the + from the speaker goes to the + of the master amp, an the -from the speaker goes to the + of the slave amp. my question is does the - from the master amp go to the - of the slave amp. also if im missing anything. thanks for your help