I built these out of an MDF frame similar to a model airplane fuselage and covered in three layers of 1/4” Masonite. There are two ported chambers inside, one for the woofer and one for the midrange. The tweeter is sealed. I built the crossovers after reading three books on the subject and using computer software to design them. The rear baffle has flared ports, adjustable level controls mounted in 3/8” thick aluminum plates and the bi-amp terminals. They weigh 120lbs each and are finished in polished urethane paint. They sound very nice.