Полочная акустика — PMC ACTIVE twenty5.21i

The Active twenty5.21i is the smallest of four two-way models in the Active twenty5i series made by the British firm PMC (Professional Monitor Company). The line takes the powered layout of the firm's studio monitors, where each driver gets its own amplifier fed by an active crossover, and applies it to the domestic twenty5i cabinets for the first time. PMC announced the series in February 2024 with UK availability from April 2024, and pitches this compact version at small and medium rooms, on a stand or a shelf, or as an effects channel in a multichannel setup.

Key specs that matter

Two 100 W rms amplifiers sit in each cabinet, one per driver. The bass unit is a 140 mm g-weave cone with long excursion, mounted in a cast alloy frame, and the 19 mm SONOMEX fabric soft dome tweeter is a PMC and SEAS design which is ferrofluid-cooled and uses a 34 mm surround behind a dispersion grid. Signals divide between them at 1.65 kHz. PMC quotes 46 Hz to 25 kHz and an effective transmission line length of 1.72 m. Input impedance is above 14 kOhm, and a 1 V rms signal produces 96.5 dB SPL at 1 m on the low gain setting or 106.5 dB on the high one. The cabinet measures 340 mm high, 162 mm wide and 269 mm deep with connectors, plus 9 mm for the grille, and weighs 6.15 kg.

Engineering and use context

The incoming line-level signal passes through a computer-modelled analogue crossover specific to this model before reaching the power stages, so each amplifier handles only the band meant for its driver. Pre-amplification, filtering and a dual-band power limiter for driver protection are built into the same electronics. Bass loading comes from PMC's Advanced Transmission Line, which the company offers as an alternative to ported or sealed enclosures. Owners of passive two-way twenty5 and twenty5i speakers can reach the same result with an upgrade pack that replaces the rear panel with an input, crossover and amplifier module joined to the drivers by one multipin plug, with a jumper selecting the model and fitting taking about five minutes. Registering the speaker within 10 days of purchase extends the warranty to 20 years.

Pairing

No power amplifier or integrated amplifier is needed. A preamplifier or streamer with a volume control connects directly through balanced XLR or unbalanced RCA inputs, and the two gain positions let the speaker match sources with different output levels. Each cabinet also needs its own mains lead.

Alternatives

The PMC Active twenty5.22i is the next standmount up in the series, with a 170 mm bass unit and a 2 m line reaching 39 Hz.