I have two Delta 15s. They're the older ones... Just Delta 15. Anyway, WinISD has them in their database and the specs are correct. Just wondering what the differences are between building two 15" cabs or one 2x15" cab. If I do go with the 215 do I separate them somehow? I've heard something about phase inversion when stacking speakers & that's why some companies offset them. Yeah, just don't know. This is my first build but my guit player just got a dovetail jig so that's pretty damn cool & my drummer builds cabinets (albeit uber expensive kitchen cabinets) for a living so I'm hopeful. I just don't want to screw up the measurements.