Reflector Audio Square Two

These unusual coaxial speakers bring the concept of horn‑loaded monitoring into the 21st Century.

When I decided to design and build my own set of studio monitors, one thing I picked up pretty quickly is that speaker design is a set of compromises, the most obvious being a triangular plotting of size, low‑frequency extension and output level. If it’s small, it won’t go very low, and if you use EQ to correct for that, it won’t go very loud. If it’s small and loud, it won’t go low, and so on.

Another is that in order to achieve full frequency extension at a reasonable volume and with reasonable bass extension, you’ll need more than one driver to cover the whole frequency range. This is a deviation from the theoretically perfect but physically unachievable speaker, known as a ‘point source’, which radiates all frequencies perfectly from a single point. The necessity for multiple drivers leads to one particularly frustrating issue: imperfect phase correlation between the drivers. A full discussion of all the issues involved with driver integration would not fit into this review, but suffice it to say that manufacturers spend a lot of time trying to align the phase of drivers, using both physical and digital means.

In a design like the Kii Three or the HEDD Type 30, for example, linear phase can be selected as a listening mode. This is achieved using digital signal processing, which keeps phase within roughly a ±50‑degree window (generally above 200Hz, though this varies), but it incurs a latency penalty. As a result, such a setting is only useful when you don’t mind a delay on your sound output.

Another way to tackle driver phase discrepancy is by using a concentric design, where a tweeter is put either directly in the centre of a woofer, or suspended in front of the woofer cone. Many manufacturers use variations on such a design, including KEF, Tannoy, Genelec, Kali, PreSonus, Equator Audio and Geithain. Like all speaker design choices, this also introduces its own potential issues, which need to be compensated for with other physical and digital design considerations. Now Reflector Audio have approached the concept of a concentric speaker from a different angle. In the Square Two reviewed here, the job of reproducing the low end is split between four separate drivers that exit through individual holes in the baffle, while a mid‑ and high‑frequency driver fires through a horn in the centre. For a quick run‑down of the why and how of horn loading, see Phil Ward’s review of the Ocean Way HR5 monitors in SOS January 2021.

I first encountered Reflector Audio products at NAMM a long time back, where they had some very eye‑popping gigantic speakers called the Q1818s. Come Covid, a listening party with these giant monitors was cancelled, and the designers decided it was time to make a smaller and more generally practical speaker using similar acoustic design principles. Like the Q1818, the Square Two is designed to create a virtual point source using a horn‑loaded tweeter surrounded by four woofers. While the Q1818s were very high‑end main monitors, the Square Two is more of a midfield to long‑nearfield design, and so usable in far more studios.

Drivers

The distinctive design of the Square Two is mostly a result of its interesting driver setup. Horn design is a bundle of essays on its own, but suffice to say it’s relatively uncommon to see horn‑loaded compression drivers in studio monitors these days. Very large main monitors are the notable exception (Augspurger are one example), where high levels of projection and volume are essential. Compression drivers are rare outside of ‘I need lots of volume’ applications, and this is where they tend to be used due to their high efficiency.

Both the tweeter and woofers in the Square Two are Italian: a Faital Pro HF1440 in the horn and four 18 Sound 5W430 woofers surrounding it. The four 5‑inch woofers are roughly equivalent to a single 10‑inch driver in surface area, but with the workload divided across the four drivers. With the drivers aligned perfectly to work as a single source, the only down sides to such a design are weight and expense. The former is not = much of a problem for this application once you’ve set them up, but the latter means such a design must inevitably land in a higher price range.

On researching both drivers, I noticed that the high‑frequency compression driver had a fair bit of low‑frequency extension, while smaller woofers have the benefit of increased high‑frequency...