I have a question:I have a pair of Altec Design 20 speakers found in an abandoned theatre which were used for surrounds & apparently Altec made them with a cutout for a second woofer but without the 2nd woofer. I have four spares of the same woofer that is used in these encloures & my question is what do you need to do to add a second woofer & do I need to holesaw out 1 or 2 bass ports since I'm using them with my stereo?