Is the ssp2500 replacing a unit that you were using.? Or is this a first time hook up.What is your dit front end? Are you patching digital coax, or glass? Here`s a test,turn the volume control all the way down on your sub.Unplug the the sub patch cable from the SSP2500. Turn the volume control up just a little quarter turn,and holding the patch cable in your hand quickly thump the center pin of the patch cable with your index finger.If you don`t hear the woofer respond turn the volume up just a little more. Try again,do you here it now.If you do then we can assume the sub is ok.Please respond back after you try this.