The enclosures are not sealed. Mine sound awesome, no polyfill. The poly fill mainly aids in enhancing bass by tricking the sound wave into acting like their in a larger enclosure than they are, plus some dampening it might add. The sound you describe , seems more like a problem than a characteristic of how these speakers should sound. Are you sure you didn't trim too close to the speaker surround and possibly have an unsecured speaker surround? That would cause the sound you are talking about.