Just bought my first Kustom rig, K250-1 with 2-15 B cab loaded with JBL D140's. I think the amp and cab sound pretty great as is. But when I removed the back to check the speaker brand, I noticed the ports are blocked. It looks like work that was done a long time ago, and I am wondering if perhaps it was done in the factory. I have pictures to upload, but the icon in the post form doesn't seem to be working for me. Did they block ports depending on what speakers were used?