Date: 2024-12-09

Active loudspeakers are something of a rarity in high-end domestic audio, yet in professional recording and mastering studios, they are the de facto industry standard. It may be that for some hi-fi hobbyists, taking away the task of mating any number of external amplifiers with a pair of passive loudspeakers removes the joy of the inveterate tweaker. For others, however, it's an elegant and synergistic way to enjoy great sound at home.

PMC – which stands for Professional Monitoring Company – has been active (pardon the pun) in the pro audio speaker market for decades but is now bringing its thirty-plus years of expertise to mainstream music lovers with a range of high-quality active designs. The Active twenty5.21i is the smaller of two standmounters in the series that also includes two floorstanding models. They are also available as conventional passive speakers, and owners of these can have theirs upgraded to active status with the internal amplifier module retrofitted.

UP CLOSE
At first glance, the speaker appears to be a typical square box design until you notice the reverse-rake rhomboid cabinetry that makes it look italicised. My review sample is finished in walnut, though oak and black versions are available. Measuring 340x162x269mm [HxWxD], the speaker features a 140mm mid/bass driver with a long throw g-weave cone mated to a cast alloy chassis. The 19mm tweeter is a collaborative design by PMC and Norwegian transducer specialists SEAS. It's a soft fabric dome made from Sonomex that is ferrofluid-cooled.

Each driver is directly coupled to a dedicated 100W Class AB power amplifier, so the speaker must be powered by the supplied IEC mains cable. Both balanced XLR and unbalanced RCA cables are accepted from the source device, which must have a volume control as no level adjustment is available. In circuit, ahead of the power amplifiers, is a bespoke analogue crossover, which splits the frequency bands of the incoming line-level signal to mid/bass and treble, respectively.

PMC's Elliot Whyte explains why his company is such a fan of active operation: “It provides superior control of the drive units within a loudspeaker for absolute precision of musical reproduction. Audibly, it also improves dynamics, transparency and resolution, and perhaps what's most appealing is that it lets users have a fuss-free system that only requires a source and a preamp.”

As a result of the onboard amplifiers, the Active twenty5.21i's metal plate on the rear panel gets hot when powered up for any length of time; in effect, it acts as a heatsink. The manufacturer says that it's not necessary to keep the speaker(s) permanently powered up, as the power amp modules reach optimal operating temperature very quickly.

As you would expect from PMC, this speaker uses a transmission line to enhance bass response – which, in this case, is the company's proprietary ATL (Advanced Transmission Line) system. This operates over a bandwidth of around two octaves, centred on the main resonant frequency of the line. It works by placing the LF drive unit at the end of a long tunnel that snakes through the small cabinet. As it is highly damped, it absorbs all but the high and mid-frequency energy radiating from the rear of the transducer, allowing lower bass frequencies “to exit the line in-phase with the frontal radiation from the drive unit, greatly enhancing its bass performance”, as PMC explains it.

The manufacturer says the Active twenty5.21i is equally happy when mounted on a speaker stand or a bookshelf, but I strongly favour the former. For the purposes of this review, heavy-duty Target stands were used, and IsoAcoustics ISO-Pucks provided further isolation from floor-bound vibrations.

THE LISTENING
The Active twenty5.21i has a very studio monitor-like character, by which I mean it doesn't set out to impress and just gives you the facts about the recording, plain and true. This, ironically, is one of its most impressive facets. Compared to some similarly sized speakers voiced for the domestic market, it isn't brightly balanced. It's common for small standmounters to feature a well-lit top end to grab the listener's attention, especially in a dealer dem room. But this is a more even-sounding design with a strong bass. It doesn't quite plumb the depths of my huge 15-inch Tannoy monitors but it is way stronger and deeper than my diminutive BBC LS3/5a monitors.

The Beatles' Come Together is a blast through a pair of these PMCs. Its iconic bass line remains agile and tuneful while losing almost nothing of the low-end heft you get through a much larger drive unit. Small bass-reflex designs often present Paul McCartney's bass as spongy with a 'one note' approximation of bottom end. This speaker's articulate bass response clearly shows how well a transmission line can work within a small cabinet.

It's not just the fine lower bass articulation that impresses, though, as the Active twenty5.21i is remarkably coherent throughout the frequency range. There's no mid/bass hump to hype the bottom end, as the PMC transitions smoothly through the midrange into the treble region. Vocal intelligibility is excellent, and what often sounds like John Lennon making a “shoop” noise at the beginning of the song is clearly heard as him saying the tragically prophetic phrase “shoot me”.

The ability to accurately express the human voice is the true benchmark of well-designed small speakers, and this speaker is outstanding. Experiencing great recordings of excellent vocalists is a joy. Listening to Rumer's 2012 cover of Jimmy Webb's song about fellow songwriter P.F. Sloan is a mesmerising experience. The natural warmth of her close-mic'd vocals is beautiful, with none of the artificial thickening you get with the unwelcome midrange colour of inferior designs. The clarity and separation of the instrumental backing is spot on, too.

Given that her voice is reminiscent of Karen Carpenter, a spin of The Carpenters' version of Calling Occupants of Interplanetary Craft seemed appropriate. This reveals the Active twenty5.21i's strengths, not least of which is its ability to convincingly portray larger scale works. With the speakers set up in front of my huge Tannoys, it is hard not to imagine the symphonic elements of the track being bolstered by the larger speaker.

There's a lot going on within the mix of this track, and the PMC's superb resolution misses none of the fine details. Unlike some professional monitors, particularly those of the “if it sounds good on these, it'll sound good anywhere” type of studio monitor – Yamaha NS-10, take a bow – this speaker doesn't spew out a torrent of harsh, fatiguing detail. Rather, it paints a bigger and more complete picture, which allows subtle nuances to reveal themselves in a natural fashion.

Indeed, when positioned correctly with a modest amount of toe-in, a pair of Active twenty5.21i project an immersive soundstage with a panoramic stereo spread and rock-solid central image. Laura Marling's Alexandra is a lovely modern recording that is full-bodied yet intricate and proves to be a highly involving listening experience via the PMC. The upfront lead vocal projects with pin-point precision, surrounded by lush stereo backing vocals and widely panned percussion and guitar. Everything is in its rightful place.

THE VERDICT
PMC's Active twenty5.21i is a great choice for those demanding superb sound without the hassle of large loudspeakers and multiple amplifier boxes. It serves up a lucid and detailed rendition of the music, built upon the firm foundation of tuneful bass. Fed by a high-quality source from a device with a volume control or via a dedicated preamplifier, this could be all the hi-fi you ever need.