lol really this post should be called amp bridging I thought u ment amp’s crossover. Anyway u can only bridge a amp 1’s u can’t do it twice, so if u wanted to bridge it, that would be it, it could then only run ur sub and nothing else.
You can bridge the amp, It will make the Sub louder and clearer as it will be recieving the correct power.
If the amp has a “MONO” setting, Then you can switch it to this, and Take the + Wire from channel one, and the - Wire from channel 2.
BUT if it dosent, then you will need to wire your 2 speaker wirings to a splitter box (Or just wire them together yourself) and then to the sub as 2 wires rather than 4.
Ive got 4 Channels running my 2 6X9s. Sounds much clearer than when it was 2 channels.