My first Pis, Theatre 4s, had the horn set back 3/4" from the woofer baffle; next I built 2Pis with a sloped baffle, then various pseudo 4Pis with 3677s and own boxes with the horn on top.I just ordered Eminence H-290s and soon there will be a pair of textbook 4Pi Pros with everything inside the box. These days, you have to do whatever you can to lower the Cx of your speakers; lower drag means better mileage.