I just built myself a 175L sonotube with 2 4" ports tuned to 22hz. As i first played it i noticed that the sub was making a ticking noise. I hooked it up to TrueRTA, and it sounds like a jackhammer just not as loud. It is not bottoming out, as it makes that noise at very low volumes, at all frequencies. The noise seems to get louder as the frequency increases. Whats the problem here??