[snellemin]

naah, it could be your amp. These woofers need some power to sound good. I would stick some pillow stuffing in your box. It could be that your box is leaking air if the woofers are in their own chambers. I also use to add dynamat inside the box itself.

Here's a link of the box that holds 4 of those woofers. http://www.cardomain.com/ride/426334/2