As well as owning some 15" reds, 15" golds 15" HPD's and 12" silvers and 12" golds I recently acquired some CPA 12's. Think theyre from the nineties. These are smallish trapezoidal cabinets housing a 12" 3134 dual concentric, ported with 2 ports. Their leaflet, which can be found on hilberink says they used DMT technology in the cabinet (unusually constructed with metal extrusions for corners), and having had mine open I can say the remarkably dead - and heavy - cabinet is also cross braced inside a la B&W matrix. The driver has a VERY open cast basket and paper cone/tulip waveguide, originally (think I read somewhere) for open baffle mounting. And air cored chokes in the crossover and Van den Hul internal wiring. These were designed for installed high quality pa duties, theatres, clubs etc. And, while having the usual tannoy efficiency in the high nineties, will accept 350 watts peak. Yet when they come up on ebay they don't fetch much money at all compared to golds...yet these sound extremely nice with most of the tannoy magic of the classics intact, a little more modern, maybe, and edge of your seat, but fine and dynamic with a good soundstage.