Stereo Integrity HT 15" D2....tapped horn.

[m R g S r]

The outter most part of the surround shouldn't really move...it's okay if there isn't much clearance on the baffle board, just as long as it's not sitting ON the surround.

 

[MemX]

The SI website has some measurements on their plans at the bottom of their page:
Stereo Integrity | HT Subwoofers
but they don't particularly specify an inward-facing cutout.

Looking at the roll surround relative to the rear mounting face (which it would rest on if mounted 'normally') I think the recommended cutout size is fine, and Nick at SI told me the same by email when I was asking about the 18s.

I can confirm for sure in a few weeks, hopefully, when my boxes are built!

Just realised I didn't come back on this!

I have the recommended cut-out sizes for each of the 18" SI HT drivers in my PPSL build (16.7" diameter, IIRC) and both seem fine.

 

[Patrick Bateman]

These drivers are currently for sale on their Facebook page.