The Professional Monitor Company, aka PMC, is a major hi-fi loudspeaker manufacturer, with its roots in studio monitoring. PMC was established in the UK in 1991 by Peter Thomas, an ex-BBC engineer, and his business partner, Adrian Loader. The company’s first product was a large studio monitor: the BB5-A. The British public service broadcaster was one of PMC’s first customers, and still uses those monitors at the BBC Maida Vale studios in London, England.
Last summer, SoundStage! Network founder Doug Schneider and I spent a couple of days listening to the magnificent PMC MB2S XBD monitors, first at PMC’s UK headquarters in Biggleswade, Bedfordshire, and later at PMC Studio London. During those visits, we hatched a plan to obtain a suitable example of the breed for me to review. For a few moments, I dreamed of reviewing a pair of MB2S XBDs at “Gorse Towers,” until I realized that the resulting couple of months of musical ecstasy would be followed by 30 years living in a dilapidated bedsit after the divorce lawyers had taken my house, car, pension, and record collection.
Robbie Williams, an MB2, and a mug of tea
It’s all very well for singer Robbie Williams to stand proudly next to his giant MB2S monitors, grinning cheerfully with a mug of tea in hand, but he isn’t married to my wife. If she came home to find those towering, 6′ cabinets in our living room, her reaction would make an interrogation by the KGB seem like a pleasant afternoon diversion.
Construction and technology
No such fate awaits the purchaser of PMC’s Twenty5.26i loudspeaker ($15,950 per pair, all prices in USD), because it is a particularly elegant design. The tall, slender cabinet is constructed from 18mm Medite-branded HDF, which is veneered both inside and out. My review pair came in genuine walnut veneer, but PMC also offers them in oak, and in Diamond Black or White Silk painted finishes.
Each cabinet measures 40.9″H × 7.6″W × 17.3″D, with an unusual sloping profile that makes the speaker look like it’s leaning backward by about five degrees. The sloping front baffle aligns the acoustic centers of the three drivers vertically to ensure accurate time alignment. I must confess I found this effect somewhat disconcerting after working my way through most of a bottle of Malbec.
The Twenty5.26i is a three-way design, and features PMC’s Advanced Transmission Line (ATL) bass-loading and Laminair vent technologies.
Designed in conjunction with SEAS, the 0.75″ ferrofluid-cooled, soft-dome tweeter has a 1.3″ roll surround and is protected by a metal grille. PMC claims this design combines the wide dispersion of a small tweeter with the improved excursion of a larger driver. In the 26i, this tweeter crosses over to PMC’s own 2″ soft-dome midrange at 4kHz (PMC used ATC’s famed midrange driver in some of the company’s early models, but now employs its own design), which then crosses over at 400Hz to the company’s G-weave bass driver. Designed for high power handling and low distortion, the 6.5″ long-throw woofer has a cast-alloy frame and a woven glass-fiber cone with an oversize 3.5″ dust cap. Glass fiber was chosen over paper for its ability to cope with the back pressure on the driver generated by the transmission line—a defining element of all PMC designs.
It’s worth recapping what a transmission line is and why PMC uses this form of bass loading.
In a conventional sealed loudspeaker, whenever a drive unit moves inward—particularly one with large displacement, like a woofer—the air in the cabinet is compressed. Similarly, as the driver moves outward, the air in the cabinet is depressurized. To a degree, the drive units in a sealed-box loudspeaker are always fighting against air pressure, which is one reason why sealed-box loudspeakers tend to have lower sensitivity but good bass extension, rolling off at just 12dB per octave. Subjectively, sealed loudspeaker designs seem to have a lot of snap. They react quickly to transient signals and are the easiest to site near room boundaries. But the rearward energy from their drivers is lost—essentially converted to heat.
Ported loudspeakers offer higher efficiency because they don’t have to overcome differential air pressure. Subjectively, they give the impression of more bass from a smaller box. On the downside, the rearward radiation exiting the port can interact negatively with the primary radiation from the front of the driver. In addition, bass rolls off at 24dB per octave, so ported speakers often don’t go as genuinely low as sealed models. And depending on the port design, they can suffer from boom and overhang on bass notes.
The transmission line is an attempt to harness the benefits of both approaches. Transmission-line speakers have a damped tunnel inside the cabinet that absorbs rearward mid- and high-frequency output from the drivers, but allows low-frequency output to emerge in phase with the frontward radiation. This approach enables superb bass extension and linearity, higher output than an equivalent sealed-box speaker, and rolloff that approximates that of a sealed design. Subjectively, a transmission line offers the speed and agility of a sealed design (or a well-tuned reflex port design) and isn’t as sensitive to placement as a ported speaker. The mathematics and physics of designing effective transmission-line loudspeakers are complex and expensive, which is probably why so few companies make them.
On PMC’s speakers, the port (or ports) at the end of the transmission line, where rearward energy vents into the room, has five vanes that streamline airflow, making it less turbulent. This Laminair technology increases the speaker’s efficiency and improves bass definition, PMC claims.
I was surprised how easy it was to move the Twenty5.26i floorstanders around. This results from the modest weight of 55.1 pounds per cabinet, and the fact that the tweeter and midrange drivers are protected by fixed metal grilles. By contrast, my ATC SCM40s ($5999 per pair) weigh 68.3 pounds each and do not have fixed grilles, so require a high degree of care when moving to avoid damaging pressure being applied to a drive unit. In addition to the fixed grilles, PMC supplies a magnetically attached fabric grille for each speaker that runs almost the entire height of the cabinet. Don’t for a moment think that the weight of the cabinet belies any weakness in construction; this loudspeaker is as inert to a knuckle rap as any I have encountered.
To the rear of the cabinet is a pair of rhodium-plated copper binding posts, which are directly coupled to the crossover board. The ultra-thick copper tracks on the crossover’s black, military-grade glass-fiber circuit board minimize signal loss and enable high power handling. The crossover incorporates steep 24dB/octave filters to ensure each driver is operating within its optimal range.
One aspect of the 26i’s design had me in raptures right from the start. For each speaker, PMC supplies two steel bars to be attached to the front and rear of the speaker’s base via rubber damping grommets and bolts. These bars, which extend beyond the width of the cabinet, have tapped holes for floor spikes. PMC provides the most gorgeously machined spikes I have ever seen. They have large, knurled adjusting rings that sit above the metal bars, which makes it insanely easy to level the loudspeaker—just turn the knurled adjusters by hand until the speaker is perfectly level. PMC also supplies precision-machined spike cups to protect wooden floors. Derived from PMC’s flagship Fenestria model, the rubber mounting grommets are designed to isolate the loudspeaker from the floor to prevent vibration being reflected back into the drive units.
Most audio companies provide their loudspeakers, stands, or racks with conventional spikes that feature a locking nut that requires you to lift a heavy component off the ground with one hand while getting underneath it with a spanner in the other, so that you can loosen the locking nut, turn the threaded spike to adjust its height, and then tighten the locking nut—which often causes the spike to move. This task must be accomplished at floor level, with a gap of just an inch or so below the component. After a half-hour of cursing and swearing, you put the thing down, realize it’s still rocking, and decide you can’t be bothered anymore. I hope there’s a special place in hell for whoever came up with such a hateful piece of engineering, which seems to have been adopted almost industry-wide. PMC looked at this problem and came up with a brilliant solution.
Per PMC’s guidance, I positioned the loudspeakers approximately 10′ apart and slightly toed-in toward the listening position, with the backs of the cabinets around 12″ from the wall behind them. With its benign impedance curve, the 26i is very easy to drive, so my Naim Audio NAC 82 / HiCap / NAP 250 amplifier combination proved ideal. Sensitivity is rated at 86dB (1W/m), which enabled good in-room output from my 75Wpc Naim amplifier. Sources included my Naim NDX streaming DAC and two turntables: my Michell GyroDec / SME IV combination and Rega’s Planar 10 ’table and flagship Apheta 2 cartridge, which came in for review around the same time I was auditioning these PMC speakers.
From the beginning, the sound signature of the Twenty5.26i surprised me. I had expected to spend my time exploring organ works recorded at Liverpool Cathedral, where the 64′ pipes can generate 8Hz tones, or Yello tracks specially selected for their deep bass. But I quickly realized that these PMC floorstanders are far more subtle and nuanced. Sure, they can go low, but it was the detail retrieval in the higher frequencies and mids that took me aback. If anything, the impression of bass slam and extension was less noticeable than on my ATC SCM40s.
I opened proceedings with “Fight for What’s Right” by The Rua, from the band’s 2014 album, Essence (16-bit/44.1kHz FLAC, F.O.D. Records). I stumbled across this Celtic-influenced trio last year and loved its blend of melodic rock and soaring vocals—or maybe I’ve just got a thing for beautiful Irish redheads. Fronted by a lead singer whose voice blends mellifluousness, youthful exuberance, and soaring passion, this is a band that really knows how to craft an anthem. How The Rua didn’t roar into the stratosphere I don’t know, because its songs are laced with fine hooks, great melodies, and solid lyrics.
From the opening line, Roseanna Brown’s powerful mezzo-soprano cut through the mix like a blowtorch through a glacier. There was excellent transparency to the vocals. As the drums rolled into the chorus, I could feel Brown lift her projection as her voice soared skyward on the wings of John Barry–esque strings. It was an arresting delivery and amply demonstrated the excellent dynamic range and nuance that PMC has engineered into the Twenty5.26i. Several times during this track, when the drums roll from stage right to left, I was struck by the tautness and speed of the PMCs. With their precisely engineered transmission-line bass loading, they were every bit as fast as my sealed-box ATC SCM40s, which is high praise indeed. But they didn’t deliver quite as much upper-bass punch as the ATCs, and I sometimes missed this extra warmth, especially on bright recordings like Essence.
In 2022, to celebrate the Swiss pro-audio company’s 70th anniversary, Nagra released its 70th Year Anniversary Collection Album (Fidelio Technologies 2XHDFT-V1223). This double album contains selected recordings from Nagra’s extensive archive—all of them sublime. I settled on the L.A. Network’s “Take 5,” from Dave Brubeck Redux (1966). The soundstage had superb depth and width, and a great feeling of three-dimensionality. That’s one of the characteristics of these PMCs: they create a lot of acoustic space. I suspect that’s partly because they are reproducing the extremely low-frequency ambient cues that are present on the recording. It may also be a function of the time alignment arising from the sloped arrangement of the drivers. The drums, which are a prominent feature of this track, sounded wonderfully taut and precise. It was easy to hear subtleties like accented playing and the varied sounds of the drum skins, depending on whether they were struck in the center or on the edge. The freeform jazz piano was rendered with superb dynamics and an excellent sense of rhythm and attack.
Although they can certainly play loud, the PMCs really impressed me at low volumes. They provided a remarkably consistent sound, from whisper quiet to mosh-pit loud! Because they can provide a detailed insight into recordings even at background listening levels, these are brilliant loudspeakers for people who—for reasons of domestic harmony or consideration for neighbors—need to listen at modest levels. The treble response and midrange were delightfully revealing of absolutely every single detail of cymbals, strings, and vocals. This makes them less forgiving of poorly recorded material with a bright tonal balance, which can on occasion sound a little “hot” due to the subtle treble lift.
There are few instruments more difficult to reproduce convincingly than the piano, so I turned to a gem of an album from Ricky Ross, the lead singer of Deacon Blue: Short Stories, Vol. 1 (16/44.1 FLAC, earMusic). Recorded in Germany at Chameleon Recording Studios Hamburg, this album has superb sound. “Wages Day” features Ross singing and playing a Steinway Model B grand piano. The PMCs faithfully portrayed the sonority of the Model B, with the gradations of Ross’s playing captured in all their glory. There was a real sense of hammers on strings and fingers on ivories. The percussive nature of the instrument was realistically presented, with all the notes clearly delineated; and the whipcrack-fast PMCs reproduced the very highest piano notes with admirable sparkle. Equally commendable was the way the British floorstanders revealed every nuance of Ross’s soulful Scottish brogue.
A somewhat surprising loudspeaker, then—having experienced earlier transmission-line designs from IMF Electronics and TDL Electronics, I was expecting to hear incredibly extended but potentially boomy bass. But PMC has refined its transmission-line designs to the point where they sound extremely controlled and tight. The Twenty5.26i goes low but with zero overhang; bass is very clean, all the way down.
Despite its size, this loudspeaker was extremely flexible in terms of placement. It wasn’t sensitive to room boundaries, and never boomed. On the contrary, it had an extremely articulate and controlled bass response. My only gripe was that the low end was somewhat dry. Just occasionally, I found myself wishing for a little more upper- or mid-bass fullness so that tom drums hit a little harder and pianos sounded a little more sonorous.
The top end was just slightly accentuated, which tended to reveal more detail. The superb midrange driver delivered bags of detail, with wide dispersion and excellent tonality. Vocals were a highlight for me; for their price, these PMCs were outstanding at revealing the unique timbres and techniques of the various singers I heard throughout my listening.
A pair of Twenty5.26i floorstanders offer excellent imaging and soundstage depth, with great insight into the acoustic spaces of natural recordings. Their ultra-revealing nature reflects PMC’s professional mixing and monitoring heritage. I believe that speaker companies whose origins are in monitoring seem to have a greater ability to convey musical insights, a trait which was amply demonstrated here. And the spike-leveling arrangement is pure genius. PMC is so confident about the 26i’s overall build quality that the company provides a 20-year warranty.
To sum up, PMC’s Twenty5.26i is the kind of loudspeaker that you can simply buy and sit back to enjoy for decades—without ever experiencing a burning urge to upgrade.
. . . Jonathan Gorse
- Turntables: Michell GyroDec turntable, SME Series IV Tonearm, Audio-Technica AT-OC9ML/II cartridge; Rega Planar 10 turntable, Rega RB3000 tonearm, Rega Apheta 2 phono cartridge, Rega P10 PSU.
- Phono stage: Trichord Research Dino Mk 3 phono stage with Never Connected Dino+ power supply.
- Streaming DAC: Naim Audio NDX.
- Preamplifier: Naim Audio NAC 82.
- Power amplifier: Naim Audio NAP 250.
- Power supply: Naim Audio HiCap.
- Loudspeakers: ATC SCM40.
- Cabling: Chord Company Sarum T loudspeaker cables, Naim NAC A5 loudspeaker cables, Naim interconnects on all Naim amplification, Chord Company interconnects for phono stage and other primary sources, QED interconnects for secondary sources.
PMC Twenty5.26i loudspeaker
Price: $15,950 per pair.
Warranty: Two years, parts and labor; extended to 20 years on product registration.
Biggleswade SG18 9ST
Phone: +44 (0)1767 686300
PMC Speakers USA
17922 Sky Park Circle
Irvine, CA 92614