Karlson Bass Cab Project (1)

Here's the challenge:

The size of the outer box is fixed:

I want to turn it into a good high-power (SPL) Bass Cabinet.

I would use either a 12" like the MCM (price and specs are good!),
or a 15" woofer.

The shape seems to cry out "folded horn", "tapped horn", "Karlson-mod" or something!

It should be loud enough for medium/small gigs,
but not require scads of amp watts to drive it, hence my 'horn-tech' appeal.

Here's the idea:

I turn the top half of the cab into a bass-guitar-cab,
with the speakers facing down.
To protect the speakers during transport,
you could have a shorting-jack to freeze the cones.

Now the bottom is like a speaker-cover with wheels.

You wheel it around face-down,
but for playing you unclip it from the wheels/bottom,
and tip it on its side.

The inside dimensions are about 20" x 26" x 14" = 4.2 cu. ft.

Minus some reinforcement/folding hornwork, say about 4 cu.ft. or less.

Is that enough for a couple of 12" or a 15"?

It needs a good cleaning out.
It had some drum parts, and alot of deteriorating foam in it.

Please, those of you who love THs, or Karlsons, or FHs,
give me a clue in the way of a usable blueprint.

I'm an ok carpenter, but I'm not a pro speaker-builder!

It could be in the form of a slip-in inner cabinet,
or just a framework using the outer-cab itself, with reinforcements.

All ideas welcome! 

...

Okay, I just measured the inside of lid, and it will allow
an additional (outer dimensions)

20" w x 26" t x 6" deep extension, of lets say 3/4" plywood front
18.5" x 24.5" x 6" (internal) = 2379.5 cu in = 1.38 cu ft.

That brings the cab to well over 5 cu ft of space available internally.

Thats the same or larger than a Marshall cab.
i.e., it should support 4 x 10" and give good bass,
or 2 x 12" as a simple closed cab (or small ported).

but I'm still thinking there's now room in here for a Karlson... 

Here's what I was picturing:

This frame would snug-fit inside the box, extending it 6 inches.
2 inches would overlap, for something to screw to (total of 8 inches).

This makes the box effectively about 20"x20" x 26" (external).