PMC Twenty5 21i

The Twenty5 21i is a 2-way bookshelf speaker from PMC, designed to deliver an expansive sound despite its small dimensions. It sits on a stand or a shelf and suits both stereo listening and use as a surround speaker within a home cinema set-up.

Its architecture is built around Advanced Transmission Line (ATL) technology, a 1.72 m quarter-wave line folded within the cabinet. This bass-loading principle harnesses the energy of the mid/bass driver more progressively than a bass-reflex or a conventional sealed enclosure, allowing a compact speaker to reproduce more extended and better-defined bass. The Laminair port, paired with this ATL line, is designed to limit air turbulence and preserve the quality of the bass signal.

The speaker pairs a 14 cm mid/bass driver with an aluminium chassis and a 19 mm SONOFLEX dome tweeter cooled by ferro-fluid, with a crossover frequency set at 1.7 kHz. The stated frequency response runs from 46 Hz to 25 kHz, with a sensitivity of 86.5 dB / 1 W / 1 m and a nominal impedance of 8 ohms. It handles a power rating of 75 W and pairs with amplifiers delivering between 30 W and 150 W.

This compact format is aimed at listeners with limited listening space or wishing to keep bulk to a minimum, without giving up a well-judged reproduction of bass, midrange and treble. It fits equally well into a desktop or small living-room stereo system as into a home cinema set-up alongside a centre speaker or larger floorstanding speakers.