Brief Summary

As more and more monitors go digital, with on board DSP and calibration, it would be easy to see all-analogue monitors as the dinosaurs of the monitor world. PSI are a company who are definitely proving that analogue can do clever too…

Going Deeper

It was at NAMM 2023 that I found myself speaking with Paul Mortimer of Emerging, the UK distributor of PSI Audio. During the conversation I confessed that I had never heard a pair of PSI monitors properly, and Paul told me that I really should. He undertook to send me a pair of PSI’s at some point. He wasn’t talking to me as the editor of Production Expert. He just wanted me to hear a pair. Time went by, and it was only this year that I raised the matter again with Paul, and he sent me a pair to try at home. I mentioned these on a podcast a few weeks ago and spoke of the impression they made on me at that point. I had no specific intention of writing up my experiences, but I've enjoyed my time with these monitors so much that I felt it was too good an opportunity to pass up. So here goes.

PSI aren’t the biggest or most prominent monitor brand out there. There are other brands which have greater market penetration and one is more likely to find oneself in front of when visiting studios. However, several people whose opinions I respect have have spoken very positively about PSI and having had some time with them, I think I now understand why.

This Swiss company have been producing speakers since the 70s and superficially it might be difficult to understand what if anything makes them different. They are unapologetically professional in nature and while for the price of a pair of 2-way PSI A17-M, (£3600 inc vat for red, £3700 for black or white) you can get some very respectable compact 3 way monitors, there’s more to a pair of monitors than just how many drivers it has. It is what comes out of those drivers which makes the difference and on this point the A17-M are something special.

Description

The pair of A17-Ms I received weren’t in PSI’s trademark red, or more accurately a very tasteful burgundy. I was a little disappointed to find them finished in a lightly textured, and slightly iridescent, metallic black. It looks great, I just like the red. I’m an unapologetic woodwork snob and the knock test revealed reassuringly rigid cabinets with chamfered edges which I assume to be MDF. Mounting options are more important than ever in these days of Atmos installs and while there are no mount points as standard, you can specify a cabinet with mount points in the side panels for a yoke which is available for all models including the A17-M. 

The branding is located on the one side, something I really like and which adds to the general air of not trying too hard. Being a two way, front ported design the front baffle is uncluttered, with a single LED and a deep waveguide carved into the baffle which leaves the one inch soft dome tweeter reassuringly protected. The, approximately 6 inch, bass/mid driver sits above a narrow slot bass port at the bottom of the baffle. The 320 x 200 x 230mm (HWD) and 8.4kg dimensions put this firmly in the extremely popular 2 way desktop category and considering how many bargain models there are in this category, why would someone spend 3 way money on a 2 way? The answer lies within…

A Peek Inside

The pair of monitors I received had been loaned out on multiple occasions, and considering this the fact that there was a loose transformer in one of the units is no reflection on the build quality of these monitors. I have to say the build quality is impeccable throughout. It's more of a reflection on exactly how hazardous sending pro audio equipment via a courier is: These people can burst a flight case! However, this did necessitate me dropping the back panel off one of the monitors and while in there I couldn't help but notice the meticulous assembly and the complexity of this monitor. I've been inside many active monitors and in so many is there really isn't that much to see. Not so in this case.

This, very crowded, circuit board hints at some features which set this manufacturer apart. We are used to the idea of active monitors which are clever in some way. Even very accessible models benefit from all sorts of DSP driven features. The advantages of Class D amplifiers, crossover filters realised in DSP, rather than in analogue form, and digital speaker management and correction, have all fed a narrative that DSP outperforms ‘old-fashioned’ analogue approaches. Particularly if you're not lucky enough to have five figures to spend on your monitoring system. PSI definitely challenge this with some extremely clever technology that is entirely analogue.

Here are three examples of clever analogue design, which when coupled with bespoke drivers in a well constructed cabinet combine to show that there is still plenty of life in analogue.

Class G/H Amps

The class D amplifier has many advantages including efficiency and light weight. Early iterations were something of a compromise, but modern versions are very good indeed. Some companies stay with older class AB amplifiers, but today these are relatively unusual, though some manufacturers combine class, AB amplifiers for their HF, drivers with class D amplifiers for the more power hungry, bass drivers. Without going too far into different amplifier classes, PSI use an unusual class G/H amplifier design. This amplifier topology features the clever use of multiple power supply rails which seamlessly switch so that the higher power rails are only in use when needed, bringing power consumption and heat down, allowing the sonic advantages of class AB to coexist with the lower power consumption more usually found in class D designs.

Compensated Phase Response

Crossovers are a fact of life in loudspeaker design. It is not possible to combine wide flat frequency response with adequate output level from a single driver, and inevitably, the process of managing the region at which one driver takes over from another always creates issues to some degree. Principal among these are inconsistencies in the phase response between drivers. The filters necessary to create a crossover network affect phase and when frequencies are heard from both drivers, as they will be to some degree around the crossover point, these phase differences are audible. Use of linear phase filters in the crossover may seem a natural choice and in DSP monitors this approach is sometimes used. But a linear phase filter always introduces significant latency and if your monitors have a low latency mode, this is a sign that such filters are in use. Any monitor which uses DSP will inevitably have some degree of latency, and the lack of latency in an analogue monitor is a distinct advantage of not introducing any digital components into the monitor. The fact that an all analogue monitor also eliminates additional AD/DA conversion being another.

But if you take an all analogue route does that mean that you can’t do anything about crossover phase issues? Well no, and PSI have a system in place known as CPR. CPR stands for Compensated Phase Response. PSI use a series of carefully adjusted all-pass filters to compensate the phase and ensure the signal is unaffected down to very low frequencies (150Hz). All done in the analogue domain which keeps latency negligible. What does this mean in practice? In use it means improved consistency through the frequency spectrum and better stereo imaging.

Active Output Impedance

I have long been a fan of the tight timing and dry bass response of sealed box or infinite baffle speakers. However, this performance in the time domain does come at the expense of level and bass output. There are of course some great sounding ported monitors, but I've also heard many which have left me less impressed. Without going too far into the behaviour of ported cabinets the timing issue, which can particularly affect designs which try to get too much bass out of too small a box, is a largely a question of how quickly sounds stop. If you think about what it is that a bass driver does when reproducing music, all that is doing is changing direction by starting and stopping, and the more accurately it can do this the better the results will be. A strong magnetic field is required to get the relatively heavy assembly of voice, coil and speaker, diaphragm in motion and when the polarity of the waveform is reversed, an ideal speaker would change direction immediately. This doesn't always happen as quickly as is should and various forms of active brake have been tried in the past to assist with this, for example JBL’s LSR32 used a technology called DCD to magnetically limit driver excursion. Adaptive Output Impedance or AOI is PSI’s solution to the issue of driver control and goes much further than just limiting excursion. A driver’s magnet gives the current in the voice coil something to push against and if the impedance of a monitor, which naturally varies with frequency, is inconsistent this affects the performance of the system.

In order to correct all of these variables in the performance of a driver, such as resonance and the speaker’s suspension, which contribute to inconsistencies and ultimately distortion, PSI’s AOI incorporates a feedback loop in which the speed of the transducer affects the output impedance of the amplifier. Giving a more consistent response based on the actual performance of the driver. Functioning as a kind of error correction system, the transducer moves to its intended position in response to the amplifier’s output. If the driver continues moving the Active Output Impedance then behaves as an active brake, controlling driver overshoot. And because this system is all analogue, it does so without the latency penalty of a DSP system.

Why AOI Matters

I suspect that this active output impedance system may well be responsible for some of my overwhelmingly favourable response to this impressive little pair of speakers. The transient response of this ported set of speakers sounds comparably tight and dry compared to my sealed box Neumann KH310s. Considerably, smaller and lighter than the KH310s I was very impressed by the bottom end response, which felt more generous than my 310s. The recommended listening distance for the A17 is up to 2m, making them perfectly appropriate for my purposes. The amplifiers are 170W and 45W (LF/HF) giving a max SPL@1m of 115 dBSPL. Combine that with the bass extension to 44Hz at ‑6dB and you have a very capable monitor indeed. 

Sound

I've had these monitors a little longer than most of the monitors I have in for testing purposes, and as such I've become extremely accustomed to them to the point where I kind of take them for granted. When I first started using them I was struck by the accuracy, transient detail, consistency of soundfield, and the usually mutually exclusive combination of extreme detail, combined with a notable lack of harshness. As initial listening tests and auditioning well known reference material gives way to actually using monitors for mixing you quickly start to understand whether monitors are good or just striking. I can without hesitation say that assuming that all PSI audio products perform as well as the A17-M do, I would recommend them. They are every bit as good as monitors I've used which cost significantly more. For me, as someone who would usually overlook a desktop two-way monitor as not something I would be interested in, I can now reflect that that would have been a mistake. There are several options for similar money in the compact three-way category of which I have always been a fan, which I would now definitely pass over in favour of these fantastic little two ways.

A sign of a good monitor is that you take a good monitor for granted, you don't think about it, you almost forget it's there. This is a clear sign that your monitoring isn't in the way of the music. And these monitors from PSI Audio were never in the way of the music.