It appears that this driver is meant to be mounted internally.

The gasket sits proud of the frame and is attached to the cone which is attached to the frame. It looks like it should not be removed, for fear of damaging the cone. (The screw issue is relatively minor.)

First of all, are there any comments on the above? And second, are the wave-lengths involved ( up to 350Hz at the most - more likely 200 since I am building a mid-horn, too) so great that how the thing is mounted is largely irrelevant with regard to edge diffraction? Finally, if it is mounted flush, does a gasket need to sit between the frame and the box? If so, do I need to remove the gasket from the front and use it, and is that feasible?

This question should be pretty clear if you have a 2226 to look at.

You can route the speaker cutout hole and mount the driver flush if you want to, but there is no diffraction and no difference acoustically. Since the driver isn't seen, I don't think it makes any sense aesthetically either.

The cast frame driver is true enough that it make a good seal right against the wood, so you probably won't need a gasket underneath. If you find that you do, then use the O-Ring supplied with the driver or use some tar or silicon and run a bead. I prefer not to do this because it is messy and makes later removal awkward.

After you have assembled he speaker, run some music with good bass content and feel around the enclosure for leaks, including the edge of the driver where it meets the baffle. If there are any leaks, then you can go inside and seal it with silicon. If you've done a good job of making cuts and the driver cutout hole is round and properly sized, you won't have any leaks.

Olson Did study that provided many cons to mounting a driver internal to the baffle. Much better to cut a hole and drop the driver into the hole and mount from the outside. The driver sitting on top of the baffle is a far better mount for accoustical performance. Hary Olson's accoustical engineering

Bill

I always double the baffle so the second layer "embraces" the speaker surround. This pic is for a 2226. I rout the holes in each baffle piece and then put the speaker in to align the 2 pieces while I screw and glue.