Swiss speaker gurus PSI have never failed to impress us with their technical innovations, and their latest model is no exception!
Swiss–based PSI Audio are one of a group of smaller high-end monitor manufacturers that perhaps fly somewhat under the radar of larger, higher–profile brands, but that doesn't mean that they're not highly capable engineering-led organisations. As evidenced by the new A23‑M, little could be further from the truth. I last reviewed a PSI monitor back in the November 2013 issue when I looked at the A25‑M and, as it happens, was extremely impressed. Now, all of five years later, I'm looking at the A25‑M's new sibling, the A23‑M. Although smaller than the A25‑M, the A23‑M still probably falls more towards the midfield monitor category than the nearfield, and in terms of both weight and size it's just about as big as I can comfortable fit in my studio room either side of my DAW. It's not really a monitor for bijou studio spaces, so be warned. It's also a monitor that demands deep pockets.
The three driver components of the A23‑M are arranged in a similar manner to the A25‑M, a manner that seems to be becoming increasingly popular. A bass driver is accompanied by a mid–range/tweeter module, which can be rotated by 90 degrees. Rotation of the mid/tweeter module is useful because it facilitates installing the A23‑M in either portrait or landscape orientation, while retaining vertical alignment of the mid–range driver and tweeter. This is important because the wavelength at the crossover frequency between the two drivers is typically comparable to the physical distance between them, so at positions vertically off axis, their individual path lengths to the listening position will vary by a significant proportion of wavelength, and that will result in phase changes and response anomalies. Now, while such response anomalies can be relatively benign when vertically off axis, they could constitute a bit of a problem in the horizontal plane, so rotating the mid/tweeter provides a simple fix.
Perhaps you're wondering why the orientation of the mid–range and bass drivers is not so important? It's simply because the wavelength at their crossover frequency is much longer, so off-axis changes in path length to the listening position constitute a significantly smaller proportion of wavelength.
I've spent a paragraph on the arrangement of the A23‑M drivers without describing the drivers themselves, so I'm going to put that right now. Somewhat unconventionally, however, rather than start at the top or the bottom, I'm going to start in the middle. The middle is particularly interesting because it's where PSI's major technical development since the A25‑M is to be found: their in-house mid–range dome driver. Most mid–range drivers in moving-coil speakers are conceptually smaller versions of bass drivers, and that's certainly the case for the A25‑M. Being smaller versions of bass drivers, they tend to display the same set of problems — it's just that the problems kick in at a higher frequency. Dome mid–range drivers are more akin to larger versions of dome tweeters, and while they display a different set of problems, they also have a couple of inherent advantages. Firstly, their total diaphragm and voice–coil mass tends to be significantly lower than equivalent cone drivers (significantly less than half is typical),...