@dtximages If you use all 4 subs, you're going to have a lot less issues with bass management, basically set your levels and crossover points, make sure nothing is out of phase, and you should have great bass. That's probably over-simplifying a little, it takes some time spent listening and tweaking a bit to get things exactly where you want them.
I have two SB13 Ultras and two Rythmik F25s. I don't even have an app, just the plate amplifier controls!
I have two SB13 Ultras and two Rythmik F25s. I don't even have an app, just the plate amplifier controls!

