Nothing particularly exotic. The cabs are what we call today a ML-Voight pipe horn [aka ML-TQWT], i.e. it's an inverse tapered TL that over time I've changed the terminus to a vented one [hence the ML = 'mass loaded'] to progressively lower the tuning as lower frequency sources became available. Built like the proverbial 'brick outhouse' also with 3/4" marine ply over a 2x4 framework. Basic baffle framing is 2x6. Heavy duty, well damped casters on rear with grab handles to move them around since the calculated empty weight is around 245 lbs. The drivers are [4] spec matched mid '50s 515B re-cones done in '69 [~ 20 Hz Fs, 0.2 Qts, 20 ft^3 Vas].

Current horns are [temporarily] stock 511s with 802D with new GPA high power diaphragms yet to be installed. XOs are lightning blasted N501-8As modded for larger larger with and with a HF by-pass cap wired around the pot. My plan is to get a pair of 511/? drivers to make another dual horn pair to functionally get an 805's mids 'fullness' except with response out to 20+k Hz and a better vertical power response.

GM