Tannoy Monitor HPD 15-inch

Model designation: Monitor HPD-385

The HPD-series was the last model in the classic series first launchedin 1947. All models from the Monitor Black through the Silvers, Reds, Goldsand lastly the HPD’s uised the same basic design with minor refinementsto LF cone surrounds, dustcovers, rear-loading of the HF diaphragm.

Perhaps the most significant performance changes were achieved throughthe use of more sophisticated crossovers on the later models like the MonitorGold’s and Monitor HPD’s.

Desirable features of the HPD series are:

Ticonal-G magnet (a trade-name for Alnico)
Very low-resonance LF cone (around 20Hz, versus closer to 30Hz for all previous designs). A down-side is that the high-compliance close-cell roll-surround on the LF unit disintegrates after about 15 years, requiring replacement).
High power rating of 85 Watts integrated programme material
A more transparent dust-cover than the Monitor Red and Monitor Gold, giving better treble clarity
Well controlled LF cone with the so-called “girdacoustic” ribbed strengthening on the rear face