Radio Shack Optimus 5B Speakers. 1993. Audio purists may disagree but the Optimus 5Bs were classic well built 8 ohm Acoustic Suspension speakers with a quality hardwood cabinet and a solid bass and clear midrange. The cabinet measures 25"h, 14"w,"11.5"d. The bass driver is 12" with a rubber surround. Three 4.5" midrange/tweeters are original. There are high and low gain switches.They weigh 37lbs. each. A piece of 3/8" trim is missing but easily replaced.