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PSI Audio A14-M Studio

Nearfield Active Monitors
Published September 2016
By Hugh Robjohns

PSI A14-M Studio

Do monitors now deserve a place alongside chocolate, watches and army knives on Switzerland’s list of exemplary exports? We think so!

There is no shortage of small active monitors in the marketplace, and I’m sure everyone reading this could name a half a dozen different high-quality monitor speaker manufacturers without breaking into too much of a sweat! However, one company who don’t seem to get the recognition they rightly deserve are Swiss manufacturers PSI Audio.

For the uninitiated, PSI Audio were previously known under the Relec brand in the late ‘70s, and the company’s professional monitor speakers are all designed and assembled in Yverdon, on the shores of lake Neuch tel. Good engineering is very high on the priority list, and the PSI factory boasts a 150 cubic-metre anechoic chamber to enable comprehensive testing of every finished monitor, each model being shipped with its own QC measurement chart. Very few other monitor manufacturers can claim to be so thoroughly objective.

I’ve already had the pleasure of reviewing two of the company’s two-way models — the A17-M and A21-M (July 2011) — while my colleague Phil Ward reviewed their larger three-way mid-field sibling, the A25-M (November 2013). Reassuringly, we were both similarly impressed by the level of engineering and overall quality, as well as a revealing, detailed, neutral, and consistent familial character — all vital elements for a true monitor speaker, to my mind!

The smallest monitor in the PSI Audio range has been, for some time, the A14-M Broadcast monitor. To put it in context, this is the Swiss equivalent of the venerable BBC LS3/5A monitor, and the design features a modest 147mm (5.5-inch) bass unit partnered with a 25mm (1-inch) tweeter in a ported cabinet measuring 163 x 243 x 170mm (WHD). Despite its diminutive size, though, the A14-M employs exactly the same technology as the other two-way PSI Audio monitors.

To survive the rigours of broadcast life, the bass unit in the A14-M Broadcast is protected by a raised metal grille; the tweeter is recessed in a profiled waveguide, and thus already reasonably protected. For ease of installation the cabinet also incorporates a U-shaped mounting bracket and a volume control on the front baffle. However, it seems these features, though essential conveniences in a broadcast setting, lend the model an ‘industrial’ appearance, reducing its appeal within the music project studio market. Consequently, PSI Audio decided to give it something of a makeover, with the result being christened the A14-M Studio — and that’s what I’m reviewing here.

All of the core elements are exactly the same as in the highly regarded Broadcast version, which remains in production, but the new version has lost the mounting bracket and the metal grille over the bass driver, and the volume control has been moved around to the rear panel. The result is a very conventional-looking compact nearfield monitor — conventional if you can ignore the distinctive burgundy-red paint finish, anyway!

Technology

Like its larger siblings, the A14-M Studio invokes a bewildering set of technological acronyms, starting with AOI or Adaptive Output Impedance. This feature refers to the power amplifiers monitoring the current flowing to or from the speaker driver, and automatically adjusting the amp’s output impedance appropriately to provide the best possible moving-coil/diaphragm acceleration, helping to create the most accurate signal transient possible. The inevitable problem is then to stop the diaphragm’s movement again, and the AOI system handles that by using the amp as an active brake, minimising diaphragm overshoot. PSI Audio claim that this technology is “almost capable of reproducing a square wave” — the ‘Holy Grail’ of speaker design, and extremely hard to achieve with traditional moving-coil speaker technology!

Controlling the bass-mid driver in the A14-M is a 70W amplifier, while the tweeter receives 30W from its own amplifier, with both being Class-G designs, in common with all other PSI monitors. Class-G is basically a small traditional Class-A/B amplifier supplemented by extra switchable output devices operating on higher power rails. The idea retains the inherent linearity of a Class-A/B amplifier, while improving significantly upon its power efficiency, because the low-power Class-A/B amplifier does most of the work most of the time, operating on relatively low power-rail voltages to minimise power consumption. However, when the required output signal amplitude exceeds the voltage range of this low-power stage, additional output devices operating on much higher rail voltages are switched on briefly to deliver the required high-voltage signal peaks.

Although a Class-G amplifier is far from trivial to design, not least because of the potential of introducing distortion at the switching points, it works extremely well and approaches Class-D technology for power efficiency, while retaining the familiar sound quality of traditional Class-A/B amplifiers.

Another featured acronym is CPR, or Compensated Phase Response, a system which compensates for the inherent phase shifts (or group delay) introduced by both the active crossover circuitry and the drive units themselves. Again, precise phase alignment is critical in achieving an accurate impulse response, and the CPR system uses bespoke all-pass filter stages to provide the required correction. A third acronym is ALG, or Acoustic Load Guide, and this relates to the waveguide profile surrounding the tweeter. This is designed to optimise and control the directivity at high frequencies — dispersion is 100 degrees, both horizontally and vertically — but also extends the bandwidth and maximises the sound pressure level. In fact, the maximum SPL on normal programme material is quoted as 112dB (for a pair of speakers at 1m distance), which is quite impressive for such a compact monitor.

For completeness, I should also mention PSC or Phantom Standby Control. This doesn’t relate to the performance of the speaker as such, but describes an unusual system to switch the speaker on/off remotely. If a common-mode voltage of between 5 and 25 Volts DC is applied to both sides of the balanced audio input (hence ‘phantom’), the speaker is put into a standby condition. Although potentially useful in some applications, this approach obviously requires the signal source to be suitably protected from the switching DC supply.

The Box

Like all the other PSI Audio monitors I’ve reviewed, the A14-M monitors are available either in the company’s distinctive burgundy red paint finish or a black paint as standard, although I’m told any desired Pantone colour can be provided on request. Each cabinet weighs a reassuringly heavy 5.5kg, and the cabinet port is configured in the same way as other models, in the form of a wide but slim horizontal slot immediately below the bass/mid driver. The MDF cabinet is well damped and easily passes the ‘knock test’, sounding completely inert and having no obvious resonances at all.The plain rear panel belies the complexity of the electronics within.The plain rear panel belies the complexity of the electronics within.

The balanced input connection is via an XLR socket on the rear panel, and an associated input sensitivity control is marked as an attenuator ranging from 0 to -20 dB. With an input signal of 0dBu and the control at 0dB, the speaker generates 100dB SPL (measured at one metre). Depending on the signal source level, some may find the control range insufficient, and I think a greater degree of attenuation might be useful given this monitor’s nearfield applications and the associated lower overall monitoring levels. Input overload occurs at +20.7dBu and a green power-on LED on the front baffle turns red if the electronic overload protection limiter is triggered or if excess heat is detected. It also turns red if the unit is put into standby mode via the PSC function.

Also on the rear panel, which serves as a heatsink for the amplifiers, is a mains on/off rocker switch, an IEC mains inlet (with integrated 230/115V AC voltage selector and fuse holder), and a second rotary control which adjusts a high-pass filter. This is intended to provide room-placement equalisation and is marked with a range of 0 to -10 dB. The filter slope starts at about 300Hz and the manual recommends a setting of -4dB for half-space placement (near a wall) or -7dB for quarter-space (near a corner).

The A14-M’s overall frequency response is given as 56Hz to 22kHz (-6dB points), with a tolerance of ±2.5dB, and the crossover is at 3.5kHz. Few speaker manufacturers quote a THD figure, but PSI Audio’s specs give less than 1.8 percent (between 95Hz and 18kHz). This may seem appalling in comparison to, say, a mixing console or a power amp (which might typically specify 0.001 percent, for example), but it’s actually an extremely good figure for a moving-coil loudspeaker!

Listening

I set up the A14-Ms on top of a pair of Neumann KH310s on the production desk I use when mastering and assessing most review gear. They were sited well away from walls and about 1.5 metres from the listening position. The bass control was set flat and the level control turned down nearly to minimum to match the output level of the Neumann monitors. Both were controlled from selectable speaker outputs on my Crookwood mastering console, and I used a wide variety of commercial pre-recorded music to assess the quality, as well as some of my own recordings and mixes.

Immediately on switching to the PSIs, I was impressed with the obviously high standard of sound reproduction. This monitor has an obvious ‘rightness’ and an understated accuracy about its sound presentation. The overall tonal balance is pretty much perfect to my ears; nothing is hyped or overblown, as it so often is in small speakers, using ‘tizz and boom’ to sound bigger and more impressive than they really are. There’s none of that exaggeration with the PSIs, everything just sounds natural, balanced and detailed. It’s the aural equivalent of looking out of the window instead of at an HD TV screen!

Despite the diminutive cabinet, bass extension is quite generous, but still tight and well-controlled, and the timing and pitching of bass instruments and drums is revealed very accurately and informatively. The monitor has the headroom to portray pretty realistic dynamics and transients — at least to the level that you’d want in a nearfield situation — and without any hint of compression or feebleness! Compared directly to the larger three-way Neumann monitor, the A14-M exhibited a remarkably similar, neutral, tonal character, and I could detect no suggestion of forwardness, nor any suck-outs across the mid range.

Stereo imaging was absolutely tack-sharp and stable, too — one of the inherent benefits of a very small cabinet — with a great sense of spaciousness and depth on appropriate material, and a narrow, rock-solid central image when switched to mono. Auditioning well-recorded voices, which is always a very challenging test for any loudspeaker, revealed the A14-M to be remarkably transparent and uncoloured, again with a very neutral tonal balance that was virtually indistinguishable from the Neumann KH310. It’s a sound character I’d describe as typical of the school of classic British monitors. Initially, it might give the impression of sounding dull and uninteresting, but the more you listen and work with it, the more you realise just how much information it is providing and in such a natural manner. There is absolutely no sense of hyped detail to give a false impression of ‘resolution’. What the A14-M delivers is the real deal: this is a genuine professional monitor in every sense, albeit one with a slightly curtailed bass extension and maximum SPL due to its diminutive size!

Not surprisingly, I had no problems with extended listening, and found I could really hear inside any mix to assess and adjust signal processing quickly and accurately — another classic sign of a true monitor speaker. Low-frequency distortion, even at high listening levels, is minimal, and the mid range remains clear and informative at all times, free from the harmonic masking that besets many lesser small monitors when working hard.

Perhaps the most impressive area of performance, though, is the bottom end, which sounds much more like it’s coming from a sealed monitor than a ported one. Clearly, the cabinet is very well designed, with perfectly optimised damping, and the amplifiers’ AOI system must help in exerting near-perfect control of the bass driver. Whatever the technology, bass notes and drum hits start and stop with wonderful precision, remaining separate and clearly identifiable even in busy mixes. Although the bass delivery couldn’t maintain the power or extension of the KH310s (not surprisingly), the character and the ability to hear what was going on in the lower octaves is actually quite similar. So while the A14-Ms might not be the ideal option for serious drum & bass or EDM production duties, they are without doubt extremely competent monitors and would serve well for a very wide range of musical genres, as well as for spoken word (and there aren’t many monitors that I’d be happy to use for that category!).

I must admit to having become something of a fan of PSI Audio’s monitors. They are one of Switzerland’s hidden gems, and the new A14-M Studio retains the impressive qualities of its larger siblings, but in a very practical, compact package, giving away only a modest amount of low-end power and extension. There are precious few compact two-way monitors that match the level of performance PSI Audio have achieved here, and of course such quality naturally comes at a cost. Nevertheless, auditioning is definitely recommended for anyone seeking a serious high-end monitor in a small package.

Alternatives

Comparable two-way active monitors of similar size and quality are rare, but might include the Neumann KH120, Focal Solo 6, Quested SR6 or SR7 at a lower price, and the Geithain RL906 or PMC TwoTwo 5 at a higher price.

About The Author: Phil Ward’s loudspeaker career began in 1982 when he joined UK hi-fi company Mordaunt-Short in a junior design role. After leaving Mordaunt-Short in 1987 for a spell in audio PR, Phil joined Canon as Design Manager for the Japanese multinational’s range of consumer and custom install speakers, and then Naim Audio as speaker design and project manager. Since 2001 Phil has worked as a freelance consultant and writer across both the pro and consumer audio sectors. Phil plays electric and double bass and has recorded, produced and mixed numerous bands and artists. Phil's blog can be found at http://musicandmiscellany.com  

Published September 2016