in my old set up, medyo 89 pa... I used earthquake subs na nasa backboard...

during that time, the MORE important issue was the amp, and the crossover... dami kasi noon nagdadaya using resistors lang for the crossover, tapos isang amp lang sa lahat!... lousy set up.

dapat single amp for the subs alone, another amp for your mids to get proper "bayo" (minimum of 2 amps)... and the proper tuning of the crossover

free air sub should be fine enough... and do change the backboard