We like shoot-for-the-stars products. It’s always fascinating to see what a company can do when the sole concern is maximising sound quality. This is what the range-topping Fact Fenestrias represent for PMC – an opportunity to take a fresh look at every part of loudspeaker design and come up with engineering solutions that are as free from budget constraints as they can be.

Build

PMC has long had firm beliefs on all aspects of speaker design and so was always unlikely to follow a totally different engineering path just because there’s more money to spend. The Fact Fenestrias still use a wooden cabinet for example, though PMC has been highly imaginative in the way it has gone about reducing cabinet resonances, but more on that later.

It’s also no surprise to find the use of a transmission line to tune the speakers’ low frequency output either, as the company has long promoted the use of this type of arrangement. Why? The claim is that it gives lower distortion and more powerful bass for a given cabinet size compared to the usual reflex port configuration.

What’s a transmission line? The bass unit’s rear-firing sound is channelled through a carefully damped folding path within the speaker cabinet until only the lowest frequencies remain. These exit through an opening in the cabinet to augment the forward-firing bass sounds from the driver. The type and amount of damping are critical to getting the transmission line to work properly, as is getting the length just right. PMC has been designing these for decades and so has plenty of experience in optimising the results. 

The Fenestria has two transmission lines, both 2.4m in length; one for each pair of the four flat 16.5cm damped carbon fibre bass drivers. Great care has been taken to manage the airflow out of the transmission line in order to minimise turbulence and drag. The result is less noise and increased efficiency. 

The rest of the drive unit complement is highly developed but relatively conventional. There’s a development of PMC’s capable 75mm dome midrange (with its rear chamber to absorb any unwanted sound coming off the back of the diaphragm) and a 19.5mm Sonomex dome tweeter (with an unusually large 36mm wide surround) that uses a powerful Neodymium magnet assembly. Even the tweeter’s grille is shaped to aid the unit’s dispersion characteristics.

While these drivers are impressive enough, it’s the way they’ve been implemented into the Fenestria’s structure that’s even more interesting. They are both attached to a small, heavily shaped aluminium baffle that’s decoupled from the main speaker body to isolate both higher-frequency drivers from the vibrations generated by that quartet of bass units. Not only that, the tweeter itself is additionally decoupled from that aluminium baffle by a dedicated suspension system designed to minimise any unwanted mechanical energy from the dome midrange affecting the high frequency driver’s output.

The Fenestria’s array of drive units are linked with a three-way crossover that’s housed in the plinth of the speakers, and mounted compliantly to, you’ve guessed it, reduce the amount of mechanical vibrations fed into the circuit. The crossover points are set at 380Hz and 3.8kHz, which are fairly conventional values. Take a look at the fourth order, 24dB/octave network and you’ll spot that it’s populated by some of the best components available from brands such as Mundorf and Clarity Cap. Even the speaker binding posts are unusual, being bespoke and made of copper and plated with Rhodium for good long term conductivity. 

Look around the back and you’ll find three sets of speaker terminals to allow tri-wiring (if you want) and also two dials to adjust bass and treble outputs. These two controls offer subtle tweaks rather than large changes of character and are useful to optimise the speaker’s balance in a listening room.

One of the Fenestria’s technology highlights has to be the main cabinet design. PMC has adopted a technique used for controlling the swaying motion in skyscrapers (caused by earthquakes or high winds) and applied that to the cabinet sides.

This takes the form of compliantly-mounted panels on each side of the cabinet, which stand proud of the actual speaker box, and are tuned to resonate so as to oppose the vibration generated by the cabinet’s side panels. It’s a clever solution that avoids the excessive mass of most high-end cabinet designs and the huge cost and resonance issues of using metal. It must be obvious by now that the control of resonances is a theme that runs throughout every aspect of the Fenestria’s design.

At 1.7 metres tall these PMCs are huge speakers, but won’t look overbearing in most rooms thanks to the slim proportion of the front panel. They’re a modular design that has to be assembled, with each pair of bass drivers in separate boxes that lock together, with the midrange/tweeter array fitting on later.

The overall standards of build are as good as we would expect at this level, and there is a choice of three finishes: Tiger Ebony, Rich Walnut, White Silk. Such is PMC’s confidence in these speakers that it offers an impressive 20 year warranty on the product.

We would leave initial assembly to the dealer, as well as the optimisation of the positioning. At 80kg for each cabinet these aren’t so easy to move around and it takes a certain amount of experience to properly optimise the sound, even if the Fenestrias are well-behaved and fairly unfussy by high-end standards.

We end up with them placed around a metre out from the rear wall and well away from the sides to make the most of the speaker’s expansive stereo imaging. Our test room is reasonably-sized at 5 x 7m, with a 3m high ceiling, but even then we feel the need to knock back the Fenestria’s bass output just a notch – using that rear panel control to avoid the lows being overstated. A bit of angle towards the listening position helps to firm up the stereo focus.

Compatibility

No one should consider a pair of speakers at this level without having a top class system in place. Our sources are Naim’s ND555/555 PS DR and Linn’s Klimax DSM music streamers with the Technics SL-1000R turntable providing an able analogue back-up. Our main amplification is the usual Burmester 088/911 MkIII pre/power combination, but PMC were also kind enough to leave a pair of 600-watt Bryston 7B Cubed monoblocs to enable us to push the speakers harder, if needed. All cables are upmarket offerings from Chord Cables and Vertere Acoustics.

Those who know PMC’s products will be relieved to know that the company hasn’t forsaken its traditionally even-handed approach to sound quality. The Fenestrias presentation isn’t hyped in any obvious way in a bid to justify that high price tag. No, what these speakers do is far more interesting than that. They sound natural and subtle, displaying a degree of finesse that’s extremely rare, even in leading-edge speakers. PMC’s aim for these floorstanders is to deliver the music signal as faithfully as possible, reducing any speaker generated distortions to a minimum. That’s why so much work was done to reduce the influence of cabinet resonances and the unwanted effects of vibrational interactions between the drive units.