As I've done with other designs, I like to place my electronics in an external box mounted to the rear of the speaker. This simplifies securing the components & also takes their mass out of the enclosure's internal volume equation.

A simple MDF box that I could screw to the rear of the speaker was all that's needed.

A little weather stripping to keep things from vibrating, a few screws & a speaker wire jack & that's taken care of.