According to the Tannerds on the Yahoo group the ideal infinite baffle size for a 15" Gold is 75L, which I suspect is about what mine are. This leads to a pretty tight, fast sound, but lacking some of the scale and bass extension. Above that one apparently needs ports, and size can be anything between 75L and 300L depending on port tuning, with 200L being the theoretical ideal (York I believe). I've no idea how this plays with the 12" driver. Tony. PS Link [URL="http://tech.groups.yahoo.com/group/tannoy/message/14908"]here[/URL], but you'll need to be a member to read it.