Напольная акустика — PMC twenty5.23i

The twenty5.23i is the smallest two-way floorstander in the twenty5i series from the British speaker company PMC, a range introduced at the start of 2021 as an update of the earlier twenty5 models. It uses the same pair of drive units as the compact twenty5.21i standmount, placed in a taller cabinet with a longer bass line. Finishes are Walnut, Oak, Diamond Black and White Silk. An ACTIVE twenty5.23i with built-in amplification is listed alongside the passive model, and PMC sells a twenty5i ACTIVE upgrade for converting passive pairs.

Key specs that matter

Below the handover, the work is done by a long-throw 140 mm (5.5 inch) g-weave cone driver whose chassis is cast alloy. Above it sits a 19 mm SONOMEX fabric dome tweeter co-developed with SEAS for the twenty5i series, with ferrofluid cooling, a 34 mm surround and a dispersion grille. PMC specifies 28 Hz to 25 kHz, 8 ohm nominal impedance and 86.5 dB for 1 W at 1 m, with a recommended amplifier power of 25 W to 150 W. The cabinet is 907 mm high, 162 mm wide, or 238 mm across the plinth bars, and 330 mm deep. Each unit weighs 15 kg, and one pair of 4 mm binding posts takes the speaker cable.

Engineering and use context

PMC builds the enclosure from 18 mm HDF, veneered on both inner and outer faces to resist warping with changes in temperature and humidity, and the speaker is designed and assembled in Sandy and Luton in the UK. Low frequencies are loaded by the Advanced Transmission Line, with an effective line length of 2.4 m. The line ends in a Laminair vent, an aerodynamic outlet first developed for the QB1 studio monitors of PMC and carried into the twenty5 family. The tweeter covers everything above 1.7 kHz, which PMC calls one of the lowest crossover points found in any two-way design. For the i version the crossover was substantially revised, with new components in the signal path aimed at a flatter overall response. The network holds nine components, including two second-order electrical filters, an L-pad for the tweeter and an impedance correction circuit for the woofer, and it produces a fourth-order acoustic slope of 24 dB per octave. Metal plinths with damping rings are decoupled from the cabinet by a resonance-absorbing compound to deal with a resonance around 470 Hz.

Pairing

Its moderate efficiency and benign impedance make the twenty5.23i a simple match for most transistor integrated amplifiers. The twenty5.sub is listed as the subwoofer of the series, and the twenty5.ci centre model completes the family for multichannel use.

Alternatives

The PMC twenty5.24i sits one step higher among the twenty5i towers, using a 170 mm g-weave bass unit and a 3 m transmission line.