The Minimus 7 family of speakers has been offered at Radio Shack stores for 27 years, being introduced in 1978. It has undergone a few minor design changes since its introduction but the basic design remains the same because it was very good to begin with. The enclosure is cast aluminum with a punched metal or wire mesh grille. A few were made with wooden enclosures and a few had cloth grilles. The long excursion LF speaker is 4 inches with a rubber surround and the HF is a 1 inch fabric dome. The original design was an acoustic suspension but the later is a reflex alignment. The enclosure is not subject to vibration but it can rattle against a hard surface if it is placed on one, therefore hard rubber feet are a good investment. The enclosure can benefit from some additional internal fiberglass damping material and the network capacitor is an electrolytic which can be replaced with a film type.