I recently split a 210 cabinet, similar to Mike Frye's article in SP, drivers are a pair of 420A's reconed as 416's by GPA.

I would normally not sacrificed a vintage cabinet, but the original was in poor shape and seriously delaminating. I reused the horn flare and much of the bracing lumber. The rest is some cabinet grade birch plywood.

A210 24

Some additional pic's are in the link below.

I ended up keeping a small port at the bottom as well as a 4" opening in the rear behind the woofer.

I'm still working on integrating it into the rest of my system but it has very impressive low frequency output and mates well with the A-5's

Split Altec 210 Cabinet

- Gary