LS3/5A

The BBC's 1975 miniature monitor, still built under licence by one of the original licensees. It is a sealed 12 mm birch-ply box with beech fillets, 30 cm tall, holding a 110 mm doped Bextrene cone and a 19 mm Mylar dome crossed at 3 kHz — a specification nobody would arrive at today, and the reason it sounds the way it does. Two numbers explain what it asks of a system: 15 ohms nominal, which is high enough that many modern amplifiers never see the load they were designed for, and 82.5 dB, which is low enough that Rogers asks for 30 to 80 watts to drive a speaker that stops at 80 Hz. Every pair is measured and matched by hand and the results filed against the serial number, so a driver can be replaced years later without breaking the match.