"The impulse response is exceptional, with very little overshoot and a very rapid decay envelope. This in part explains the resolution and speed which this 'phone conveys. This data wasn't averaged or smoothed in any way. I just took it from the first production set I was building for RMAF 2014."

Yet it's still the same tired old driver. That was poster Halcyon on InnerFidelity.com. No amount of excellence in housings will change that. Also, it's still a $999 resin-plastic printed cup. For $999, I expect hand-painted Japanese cherry wood or something more than 3D-printed plastic. Sorry Mr. Clark. I'm sure your heart is in the right place but the economics of pricing and the contents of the product don't quite match. YMMV of course. Despite the miles, it does beg a question. What will happen to the MrSpeakers™ business if Fostex discontinues that driver?

3D-printed cup close-up shows fine lattice work maze and bass alignment set screw.

As to no excellence in housings changing the Alpha Prime's driver choice? Here I beg to differ. Even ear pads are far more than comfort bits. They stand in for size, geometry and absorptive vs. reflective behaviour of your room as seen by your speakers. Leaving windows or doors open is equivalent to air leaks in a headphone's ear cushion. The pad's relative thickness and inner diameter creates specific air volume aka room size. Any pad angles relative to the head are equivalent to speaker toe-in. The driver housing itself is the speaker cabinet. Here we all know how MDF, wood, aluminium and various composites alter the sound, never mind what happens to the rear wave by way of wall liners and stuffing. The $995/pr transmission-line 1st-order Meadowlark Audio Kestrel which 15 years ago had me leave my gig at Mesa Engineering to join Pat McGinty used very ordinary cheap drivers. Even so, it managed to make them sound anything but cheap. And driver modifications in speakerdom are nearly de rigueur. Few admit to off-the-shelf units. One invariably sees "built to our specifications" whilst the names that follow are all the usual suspects. Halcyon has a point but I think he overstressed it. As to plastic, expensive audiophile cables use it in their heat shrink and dielectric, many speaker drivers in their diaphragms and capacitors in their sleeves. More to the point, Japanese Cherry wood simply couldn't be worked into Dan's ultra-fine lattice. It had to be plastic. For wooden cups with rebuilt T50RP drivers, Halcyon would have to give his business to ZMF's Zach Mehrbach.