Doesn't work for me and quickly determined that a direct 15"-12" scaling was marginal at best, ditto simple scaling ratios, so......remembering a few design rules-of-thumb, came up with something that looks good in HR using published specs. Horn + vented rear chamber is ~70.1 L net/75 Hz Fb, though a high CR throat [St] is required, so may need a simple 'bullet' phase plug if an 800-up XO is used; otherwise 5-600 Hz.


With an 80 Hz XO to the 'sub' + vented rear chamber, HR predicts 125 dB/m/2pi/250 W, so thermal power compression [TPC] should be fairly low unless used outdoors on a hot day.


Double St, shrink the rear chamber and use a 120 Hz XO nets another 6 dB/500 W, though TPC will likely wick some of it away.


Go sealed rear chamber with either and the horn is basically a one note tooter with a too high XO point [>120 Hz]. This driver really wants to be a big a$$ ~40 Hz bass horn XO'd around 500 Hz, i.e. W.E./Lansing/Altec to the core...........


WRT converting HR's round horn to an 800 series cab profile, I leave to others.


GM