Fairly sure I've gone up a CAD belt.  Certainly still one of the colours and not reached first Dan yet.  Still, various cans of worms have been conquered.

Today's progress was drawing the speaker mount, front bezel and an impedance matching cone.

What is an impedance matching cone?  It's a cone stuck to the back of the speaker driver's magnet assembly that allows a constant surface area of the duct to flow around the assembly and to the cone.  This avoids a step change in diameter immediately behind the speaker.

The question of the resonance frequency of a tapered, spiral transmission line also raised its head.  The length of the centreline is 0.61 m, and would have 1/4 wave resonance of 139 Hz.  I'm aiming to go for a little lower than 175 Hz, which is the free air tuning of the driver.  However, the inner, tightest path that can be taken is only 0.45 m long and would have a resonance of 189 Hz.  While the outer and longest path is 0.80 m, which would resonate at 106 Hz.  So which is it?

Presently printing the first half snail.  Shall print the other half tomorrow and experiment once it's done.  Whatever the case, it's in the right ball park and can be further lowered with dampening material.  So it should "work" one way or another and might require some dampening material.

Guess I'll find out in a couple of days.  Hurrah for 3D printer noises!