The EVM series and the SP series aren't the same. The SP-15B is a smaller magnet version of the SP-15, both of which were originally designed for hi-fi use (complete with whizzer cone). They are lower Fs, higher Qts, and lower sensitivity than the EVM's. The Electrovoice website does give a suggested box/vent size, but I'd sure like to find the detailed T/S numbers and see what a Pi-aligned enclosure would look like.

Thanks very much for the info, and your effort. The search continues ...

James