I am looking at possibly building a sub-woofer for my stereo/home TV. there is a 12" (listed above) for sale on CL for 35 dollars. the person states in the ad "It sounds good at low to medium - high volumes with heavy bass. I have noticed at high volumes with heavy bass loads it makes a quiet slight sound flapping noise. I reduced the gain and it doesn't do it anymore." is it worth getting for a first time sub or does it sound like it was abused? Thanks for reading. Bruce