Is too simple to be true?

I want to try this just for the fun of it. I recently acquired a Tannoy SFX 5.1 sub (horrible thing). I sold the plate-amp, the driver, and remarkably the feet on Ebay. I was about to throw away the empty box out when a question arose . . .

The sub had an 8" down-firing driver which would now be on the floor because I sold the feet. Ignore the measurements because I haven't yet done the math but if I attached a partial 'picture frame' around the base using 25x25mm timber around the side and rear elevations would I have effectively created a 6th-order bandpass sub? In this instance gap between the sub and the carpet creating and additional chamber?