If the "sub out" is a speaker level output, you can connect one channel (left or right) to LOC.
If the "sub out" is a line level output ( I think it is ), you can connect the "sub out" directly to the subwoofer amp input without using a LOC.
https://images-na.ssl-images-amazon.com/images/I/31ulzfmYnIL._SX355_.jpg
If the "sub out" is a line level output ( I think it is ), you can connect the "sub out" directly to the subwoofer amp input without using a LOC.
https://images-na.ssl-images-amazon.com/images/I/31ulzfmYnIL._SX355_.jpg