I bought a Roland KC300 but when I got it home and ran a full range signal with reasonable bottom end the cabinet made a fluttery buzzing sound. It wasn't coming from the speaker but from the ported cabinet itself. And this happened at under half volume. Thinking it may have just been that unit I exchanged it for another. Guess what, exactly the same problem. I wasn't about to try a third KC300 and just returned it for store credit.