Aura NS3-193-8a design:

This is preliminary.  I'm posting here in my archives because I haven't had time to get to it yet, and the future schedule is looking pretty grim.  I may change this design, but if you want to wait for final testing, you may be waiting a while.  Baffle step compensation is not adjustable in this design, and is fixed at around 3 or 4 dB.  That should work well in most situations.  If you're putting these right up against a wall however, you should probably run without a filter.  But I suspect the best and smoothest sound will be mounted on stands, out a ways from the walls.  

The 22uF cap should probably be an electrolytic.  I'd use a Bennic for that.  The 2.5 is available in a Solen poly.  The resistors can be Eagle metal films.  And the coils can be standard small gauge air coils, and the DCR doesn't matter one bit.

In the image above, the transfer function shows exactly what the filter is doing.  The response without the filter shows a little raggedness in the top 3 octaves and a massive low end droop from baffle step.  The final curve with filter is pretty smooth except for a little raggedness in the top half of the top octave.  Those two peaks up there look almost exactly like the old TB W3-871, and are not serious enough to warrant additional components.  I doubt you will even hear those two little bumps, and they completely disappear off axis anyway.

My last bit of advice which will make some of you cringe: glue the speakers onto the baffle with a thin bead of glue.  This driver's high output and pincushion frame design unfortunately make it likely to leak and rattle under the air pressure.  Tightening the screws extra tight only makes the driver frame warp, so use the screws only to position and lightly hold the driver, and some kind of flexible glue to seal.  Rubber cement seems to work ok. just use a tiny bit so it doesn't gush out.
