Tannoy HPD 385A, HPD 315A, HPD 295A (1970s)
A series of integrated drive system loudspeaker drivers from Tannoy, used in classic British speakers of the 1970s and 1980s.
Overview
The Tannoy HPD series - the HPD 385A, HPD 315A, and HPD 295A - were integrated drive system loudspeaker drivers introduced in the 1970s. They formed the core of many of Tannoy's classic speakers from that era, including the Arden, Devon, and Berkeley models. The HPD was designed as a successor to the Monitor Gold series. It offered greater power handling and better cost efficiency, and it kept the brand's signature Dual Concentric configuration.
Design
HPD stands for "High Power Design." The drivers used a ferrite magnet, where the earlier Monitor Gold drivers used Alnico. The crossover design was similar to the Monitor Gold line's, which points to a consistent engineering approach in Tannoy's high-end passive networks. The drivers were noted for their sturdy construction and dynamic sound.
Context
The HPD series succeeded the Monitor Gold and was used widely across Tannoy's speaker range in the 1970s and 1980s. Some audiophiles prefer the sweeter midrange of the Alnico-based Monitor Gold. Others favor the HPD for its greater punch and dynamics.
Market
Common issues with vintage HPD units are foam surround rot, drying ferrofluid in the high-frequency horn, and aging capacitors in the crossover. Refoaming kits and replacement ferrofluid are available from specialists. Re-capping the crossover is recommended for best performance. When refoaming, repairs should replicate the original factory method and install the foam "under" the driver cone. The HPD series remains highly sought after by collectors and restorers.
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