PMC PROPHECY1 STANDMOUNT LOUDSPEAKERS REVIEW
PMC Propecy1 Loudspeakers are the direct replacement of the Twenty5 21i, and are a rather smart-looking standmount aimed squarely at the domestic market.
Jon Lumb takes a look at this standmount loudspeaker, costing £2,875 (RS302 stands – £250).
The origin story for PMC is an interesting one to me. The marketing message for a new HiFi, stating “we looked at the existing market and weren’t happy with what we heard,” is a well-trodden path, and one that often oversells the offerings of the new company. This was an element in the founding of PMC, but when Peter Thomas was charged by the BBC of finding monitoring options to use in their Maida Vale studios, the challenge they found wasn’t so much an issue of sound quality, but simply that most existing products weren’t robust enough for the rigours of playing rock, pop, and dance music at appreciable volumes 24-7.
The creation of the BB5 (Big Box 5, their fifth prototype) has become a landmark, particularly in the world of studio monitoring, and PMC is well known for being used in an extraordinary number of the finest recording studios and mastering labs across the globe, from Maida Vale through to Metropolis. One of the notable ways this founding of the company has shaped the PMC offering is that all Prophecy line speakers come with a 20-year warranty, which is, quite frankly, nuts, in a good way. It’s something that often doesn’t seem to get talked about with audio components, but if you’re spending four, five, or even six figures on an audio component, it should be built to last a very, very long time. PMC is willing to put their money where their mouth is on this front, and I think that’s very commendable.
BUILD AND FEATURES OF THE PMC PROPHECY1
Given the fact that PMC offers the Prophecy line with a 20-year warranty, a chunk of this section writes itself! These are very solidly built speakers. The addition of the cast-aluminium base, required for the new LaminairX end to the transmission line, means these are also comparatively heavy speakers. The previous 21i was 6kg, and only fractionally smaller in volume; the Prophecy1 is a full 10kg by comparison.
Whilst it’s less relevant in the standmount, this cast aluminium base has a notable advantage in the standmount options in the lineup. Up to now, the centre of gravity for PMC floorstanders has been sufficiently high that feet protruding beyond the base of the cabinet were required to provide sufficient stability. This was because the heaviest bit in the speaker was invariably the bass driver, and that’s relatively high up in PMC’s domestic designs. In addition to being more elegant in itself, this also means a more consistent design aesthetic, which may be a consideration if you are running an AV setup that combines floor standers and stand mounts.
I think it’s worth delving a little into the technical aspects of the ATL (Advanced Transmission Line) and LaminairX concepts, as they are unique to PMC speakers (even a transmission line itself is a relatively rare thing to encounter these days). In simple terms, a transmission line is the positioning of a driver at the end of a pipe – the idea being that all the out-of-phase energy the driver emits as it pulls back travels through this pipe, and so long as the pipe is the correct length, emerges in phase with the sound of the driver. This configuration mitigates some of the challenges of more traditional ported designs, which see a more aggressive roll-off of low frequencies below the tuning frequency of the port. The challenge is that you get quite strong reinforcement of the 3rd and 5th order harmonics. PMC deals with the 3rd order harmonic by effectively placing the driver a third of the way along the pipe, which effectively nullifies the 3rd-order harmonic. The 5th-order harmonic is sufficiently high in frequency that the complex absorption inside the ATL removes it.
The LaminairX system then addresses another challenge of the transmission line design. My initial guess was that, because the inside of the transmission line is deliberately quite chaotic in terms of surfaces and angles, the LaminairX system was designed to help align all the sound waves as they exited the line. Thankfully, as I hadn’t been able to get to the launch event for the prophecy series, I got to have a lovely chat with Toby Ridley, one of PMC’s engineers, who set me straight. The issue is that the edges of the transmission line generate friction as air passes over it. This means that the air coming out of the centre of the transmission line is moving appreciably quicker than the air at the edges, which causes all sorts of eddies and currents as it emerges into the room. The fins of the LaminairX systems help reduce this disparity, resulting in a more consistent dispersion of sound.
To wrap up the more technical discussion, the eagle-eyed amongst you may well have noticed that the specified frequency range for the prophecy1 is 50Hz-20kHz, whereas its predecessor was specified at 46Hz-25kHz. This is not a drop-off in the speaker’s performance, but rather a decision by PMC to change the way the frequency response is measured. In this case, PMC has moved from an in-room response measurement to a free-space measurement. This is an interesting trade-off to me. Almost nobody ever uses their loudspeakers in a free-space environment, so you’ll never see those reflected in real-life use. Still, any in-room response figure is highly dependent on the room it’s in, which makes it rather difficult to compare the frequency response from different manufacturers.
PMC has also made significant steps to consider the environmental footprint of the Prophecy line. This encompasses several aspects of the speaker’s design and manufacturing. Firstly, all components are built within Europe, primarily in the UK, thereby minimising transport distances. They’ve also been utilising some new production options for the veneers, which significantly reduce the timber waste that has often been a hallmark of veneers. Based on this review pair in the oak finish, there’s no indication of any compromise in the quality of the finish as a result. They’ve also removed all plastics from the packaging – boxes are now entirely made of cardboard (with plant-based inks for printing), and cloth bags are used to wrap the speakers within them. It’s not something they mention in the marketing material, but I’d also argue that the extraordinarily long lifespan they have designed these speakers for is another significant environmental benefit – not having to manufacture a physical unit as frequently will likely be the most substantial environmental advantage of all.
SET UP
Don’t worry; I’m not going to waste your time (and my precious word count) on the basic process of assembling and connecting a set of standmounts. There are no weird issues to report, and everything is straightforward.
One thing worth noting is that, because this is a forward-firing transmission line design, it is far less sensitive to the distance from any rear wall. If you have a room where logistics dictate that you cannot place your loudspeakers out into the room, but you don’t want to opt for a sealed box design, this is a fantastic option for addressing that challenge.
SOUND QUALITY
PMC has a very clear objective with their approach to what a speaker should sound like, and that’s focused on accuracy above all else. If you’re a recording engineer, this is, of course, absolutely vital for you to do your job well, and PMC makes no changes to how they voice their speakers for the domestic market vs the professional audio users.
I’ll always put on some heavy metal when I’m reviewing or demoing a piece of kit, for the simple reason that I listen to a reasonable amount of it, and I want it to sound good when I do! There does, however, seem to be a real issue with so many heavy metal albums, though (even otherwise well-recorded ones) – by the time you’ve got the volume up to the point that all the low-end grunt has sufficient oomph to it, the top end invariably sounds unpleasantly harsh and strident. The prophecy1 ramps this effect up to 11, such is their transparent and accurate nature. Even Tool’s Fear Innoculum, which is otherwise a fantastic recording, suffers from this issue.
Switching over to other music where plenty of thump is desired, and this issue disappears completely. I went from Tool to Garden Dog Barbeque by GoGo Penguin, without touching the volume control, and the issue disappeared completely. The bass and drums have all the punch you could want, but the top end remains clear and balanced. No stridency, no fatigue. HiFi has evolved a long way from the era where you’d go for particular brands based on what music you enjoyed, because that’s what those brands focused on. And whilst there’s a parallel, it’s somewhat different in its underpinnings – the way the prophecy1 reveals issues in the recording is going to mean that if your music tastes need your system to be rather more forgiving, these may not suit.
For some contrast, I spent time re-listening to “Sunday’s Child” by John Martyn, something of an old favourite here. The overall clarity and even-handedness of the prophecy1 presentation really shines through here. Delicate touches come through clearly; all those little nuances from both John’s vocals and acoustic guitar are a delight.
QUIBBLES
There isn’t a massive amount to quibble about with the prophecy. I feel like the only concern I’d have is that they will ruthlessly expose a poorly recorded or mastered album, particularly if it’s overly bright. That’s not a fault of the speaker, but if it’s an issue, it’s a lot easier to choose a different speaker than to get Metallica to re-record The Black Album. Fundamentally, we have to navigate the world as it is, not as we’d like it to be. Thankfully, improvements in recording equipment, especially at lower price points, have progressed significantly, so it’s increasingly rare for a new release to be poorly made.
They also benefit from being played with some gusto in terms of volume; nothing ear-bleeding, but if you do much late-night listening in an apartment with paper walls, you won’t be getting the best out of the prophecy1. This is essentially just the laws of physics coming into play, and for the size of the drivers/cabinets, PMC has still achieved a pretty phenomenal performance.
CONCLUSION
The prophecy1 is very much in the PMC tradition of loudspeakers. It’s designed to have all the same sonic characteristics as their commercially made studio monitors. Although I haven’t been able to make a side-by-side comparison, they exhibit all the hallmarks of a good studio monitor.
The element I must single out most for praise is the low-end performance for such a small cabinet. Achieving a decent heft and depth in the bass of a standmount invariably comes with compromises to accuracy and detail. The prophecy1 does an excellent job of balancing the constraints here. Bass textures aren’t blurred out, and the bass still has plenty of presence in my room.
All told, the conclusion here really is about you, dear reader. If what you look for in your system is the most accurate rendering of the original recording, then these are definitely speakers to consider.
AT A GLANCE
Build Quality and Features:
Rock-solid build quality and lifespan
Sound Quality:
Clear upper registers
Phenomenal bass for the unit size
Even-handed and coherent sound right across the sound
Value For Money:
These are £300 more than the Twenty5 21i standmounts they are directly replacing. ~10% increase for all the improvements, and factoring in some inevitable inflation is pretty impressive. Additionally, a 20-year warranty is a phenomenal inclusion.
We Loved:
The performance for the form factor is excellent; it demonstrates just how effective a transmission line can be if you’re capable of doing the maths required to design one! The aesthetics are also a significant improvement over the Twenty5 and professional PMC lines
We Didn’t Love So Much:
They’re so very transparent and revealing that it does make you think twice before sticking on recordings that are anything less than stellar, regardless of how musically excellent they might be
Elevator Pitch Review: If you require absolute accuracy, especially when dealing with challenging room placement, the Prophecy1 presents a highly compelling offering.
Price:
£2,875 €3,490 $4,300
Jon Lumb
SUPPLIED SPECIFICATION:
Frequency Response: 50Hz-20kHz (-3dB)
Sensitivity:85dB SPL 1W 1m
Recommended Amp Power: 20 – 200W
Effective ATL™ Length:1.79m (5.8ft)
Impedance:6 Ohm
Drive Units:
LF PMC 5”/125mm LT XL mineral cone with cast alloy chassis
HF PMC 1”/27mm soft dome
Crossover Frequency: 1.5kHz
Input Connectors: One pair 4mm binding posts finished in satin nickel
Dimensions:
H 400mm 15.7”
W 165mm 6.5”
D 260mm 10.2” (+ 23mm terminals and +10mm grille)
Weight:10.3kg 22.7 lbs ea.
