Many subs in one The SVS 20-39PC-Plus is the Swiss Army Knife of subwoofers. Flip a switch and pop the top and you can turn your PC-Plus into a low bass producing beast. The grill atop the sub can be removed by prying it off with a flat-head screwdriver. This reveals 3 round ports (holes). The ports can be plugged with foam (included) to adjust the tuning characteristics of the subwoofer. By plugging one or more of the ports, you can allow the sub to play as low as 12Hz. There is also a knob on the back of the subwoofer that adjusts the tuning point to 25Hz, 20Hz, 16Hz, or 12Hz. With so many settings and configuration options, I could truly review the sub against itself over and over. I found the out-of-the-box setting at 20Hz with no ports plugged was optimal for me. Therefore, the review is based on that setting.
