hey guys, I was hoping that somebody could help me out. here's the deal, I have a 1970 Traynor super twin 15. It is a very solid built cabinet. recently upgraded the speakers the original Yorkville/Traynor Marslands to JBL E140's. The problem is the cabinet is not ported but sealed. I put in the heavier JBL's, and have some very ugly sounding air leaks from the back panel. I'm afraid if I seal the back panel, that I could damage the much heavier speakers. should I seal it? Or do I have to port it? thank you for your help!