An inventor has created a speaker system out of concrete blocks, separating the working parts from the heavy parts to reduce shipping costs. According to Mother Nature Network:

Daniel Ballou of Studio Dashdot ... designs the speaker face (with all the electronics and speakers) and the rear around the form of a common concrete block ... Put them together and you get a solid speaker that isn't going to vibrate, even if you pump the bass up to 11.
The Cinder Speaker ships as a pre-assembled and pre-wired front panel, including a 5” driver, tweeter, crossover, and input jack. The back panel includes mounting hardware that spans the cinderblock and seals the enclosure.

Watch this video and read more commentary from Mother Nature Network here.