PREVIEW: Point-source Main Monitors

Monitors / Monitoring

Published July 2024

We take a deep dive into the innovative tech behind Genelec’s new flagship loudspeakers.

Every so often, a product comes along that seems deserving of SOS coverage, but can’t easily form the subject of a conventional review. The new Genelec 8381A is one such example. Standing a metre and a half tall and weighing in at a colossal 235kg, it’s not something that could easily be shipped to a reviewer or set up in a test space. And at around £60k per pair, it’s not something anyone sane is going to buy on the strength of a review alone. Nevertheless, the 8381A is a product that breaks new ground in several ways, so even if it’s not practical to put it under the usual review lens, it does seem worth investigating — hence this ‘Tech Preview’, which I’ve compiled by grilling Genelec’s Andy Bensley, Jussi Väisänen, Juha Holm and Aki Mäkivirta.

Out Of The Walls

The Genelec 8381A is a main monitor, and thus belongs to an entire product category that doesn’t see much coverage in SOS. That’s partly because few of us with project studios have the budget or the need for such things, but also partly because main monitors are typically designed to be built into the fabric of the studio. Genelec’s own 1236A three‑way speaker, for example, will usually be found soffit‑mounted within the front wall of a control room, rather than free‑standing.

In‑wall mounting is often the absolute best option from an acoustic point of view, but it only makes sense as part of a full‑on, permanent studio build. This requires a huge investment of money, materials and time that will have to be written off if you ever move to a different studio. Genelec, along with other manufacturers such as Amphion and Ocean Way, have identified a growing demand for systems of the same power and quality that can be set up in less conventional or controlled spaces, and follow peripatetic high‑end producers on their travels. The result is the 8381A, billed as the world’s first point‑source main monitor.

Point To Point

What does “point source” mean in this context, and why is it significant? Well, room acoustics aren’t the only reason why main monitors are traditionally mounted in the front wall of the studio. Another reason is because they need to be several metres from the listening position in order to sound right. The sheer size of the individual drivers in a conventional main monitor means that their respective contributions to the sound don’t integrate properly until you get quite far away from them. And this is one reason why studios also have nearfield monitors, because you can’t approximate nearfield listening by simply moving closer to your main monitors and turning them down.

Coaxial drivers have been a major focus of development at Genelec in recent years, leading to the highly successful The Ones series of monitors. The idea behind a coaxial system is to have the tweeter mounted in the centre of the woofer, so that they appear to the listener as a single full‑range device, regardless of listening distance. All the Ones are three‑way models, with the bass drivers also arranged in such a way as to make the entire speaker behave, as much as possible, as a point source.

The result is the 8381A, billed as the world’s first point‑source main monitor.

The largest of the Ones, the 8361A, has apparently been a big success for Genelec. In conjunction with the W371 adaptive woofer system, it’s often able to perform the role that was mentioned above, offering something approaching main monitor performance in a format that can be used free‑standing, at nearfield distances if necessary. For the company’s 45th anniversary, they decided to create a new flagship that would take this concept to several new levels.

Each 8381A is driven by a pair of RAM 81 amplifier units.The 8381A is thus not a three‑ or four‑way but a five‑way system, with each speaker comprising two main components: the four‑way top/mid driver and the “adaptive double low woofer system”. Unlike the W371, the 8381A sub is not optional, but an integral part of the system. And whereas standard subwoofers are often positioned elsewhere in the room, the 8361A’s woofer system is closely integrated with the mid/top part and forms a stand for it. As with other Genelec models, it’s an active system, but in this case the amps are separate units rather than being built into the speakers.

Like most of Genelec’s current selection of active monitors, the 8381A has built‑in DSP, and it forms part of their Smart Active Monitor range. This is significant for two reasons. Firstly, Genelec’s GLM software can be used to measure and correct the frequency response at the listening position. And secondly, it can freely be integrated with other SAM models. You could, for example, have 8381As as your main studio monitors, and augment them with different The Ones models as surrounds and overheads to build up an Atmos rig. GLM will handle all the necessary alignment and correction functionality, and even offers speaker switching and monitor control courtesy of the new 9320A SAM Reference Controller. This stands in sharp contrast with the ‘traditional’ way of doing things, where the performance of a main monitor is largely defined by the architecture of the room and the wall within which it’s mounted, and where any DSP correction would typically be performed by an external unit, requiring laborious and complex setup from an expert.

Big Beasts

In the all‑black finish (white is an option), the 8381As bear a passing resemblance to the obelisk from 2001: A Space Odyssey, and give off the slight air of having their own gravitational field that can bend light around them. You’d definitely want to check the load‑bearing capability of your floor before ordering a pair, and have clear plans in place for getting them up any stairs. As well as the mid/top section, the woofers and the amps, the system also includes a choice of angled wedges to ensure that the first of these elements targets the correct height at the listening position.

Treble and upper midrange are catered for through a relatively conventional coaxial driver, with the tweeter sitting in the centre of the larger midrange driver and the crossover at 1.8kHz. Below 500Hz, the upper midrange driver hands over to what is definitely the 8381A’s most distinctive feature: an array of four five‑inch drivers arranged in a square formation around the edges of a sophisticated waveguide that houses the tweeter/mid driver. Genelec’s research showed that it would not be possible to achieve the necessary sound pressure levels in this frequency range by simply making the main coaxial driver larger or driving it harder, and that attempting to do so would introduce unworkable levels of displacement and hence distortion. At the same time, they felt it was important to retain the impression of a point source within this range, rather than handing over to a subwoofer.

The result was this novel driver array, with the four drivers equally spaced around the waveguide and housed in domed enclosures. Both the ridged waveguide and these domes are the result of laborious computer modelling aimed at minimising interference between the coaxial driver and this midrange ‘filler’ array. There was no off‑the‑shelf driver or enclosure that would work in this role, so everything had to be developed and manufactured in‑house.

There is quite a bit of physical separation between the bass drivers in the two units, and this is entirely deliberate.

Making Adaptations

The physical separation between the front‑firing 15‑inch bass driver and the side‑firing woofers is entirely deliberate and allows the 8381A’s response to be tailored to room acoustics simply by varying the crossover frequencies.In the bass region, by contrast, the 8381A turns the ‘point source’ philosophy on its head. The upper unit that contains the coaxial mid/tweeter and the four‑way ‘filler’ array also houses a forward‑facing 15‑inch driver, while the woofer system that sits beneath it is home to two side‑firing 15‑inch drivers, and a bass reflex structure that vents to the rear. There is therefore quite a bit of physical separation between the bass drivers in the two units, and this is entirely deliberate. In the frequency range where wavelengths are measured in metres, the human ear cannot readily detect which direction sound is coming from; there would be relatively little benefit in creating a monitor that behaved like a true point source down to 30Hz even if it was possible. But it’s precisely in this frequency range where room modes inflict damage.

Hence, what’s adaptive about the “adaptive woofer system” is the crossover frequencies. Because the low‑mid array, the front‑firing bass driver and the side‑firing woofers all occupy significantly different positions within the room, they all excite the space in different ways. So, rather than attempt to generate all the low‑frequency sound at a single point and use EQ to compensate for the vagaries of the room, the GLM system intelligently varies the crossover frequencies to try to minimise cancellations at the listening position. The crossover between the low‑mid array and the front‑facing driver can operate between 250 and 150 Hz, while the sub unit can take over anywhere between 100 and 50 Hz, depending on what GLM deems most appropriate for the space.

The end result is a main monitor that, in principle, behaves like a sort of supersized coaxial nearfield above 200Hz or so, but which works with the room acoustics to deliver the most balanced low‑frequency response possible in the space. As I said at the start of this article, I’m not writing a review here: I haven’t set up these speakers in a known space, been through the calibration procedure myself or compared them with other competing models. I have heard them, though, and been suitably impressed. The sort of environment in which these speakers are typically demo’ed is rarely acoustically perfect, especially at the low end, and a speaker that can put out high SPLs at frequencies down to 20Hz would often cause more problems than it solves — especially at the kind of listening distance that is usually required with main monitors. To my ears, the 8381As sounded focused through the midrange even close up, and even in demo spaces that were far from perfect, the bass response sounded even and true down to very low frequencies. Ideally, of course, we’d all be mixing and mastering in purpose‑built rooms where all the modal resonances have been eliminated by careful design, but in the real world, that’s often impossible even at the top level. The 8381As don’t eliminate the faults of the room, and I’m sure Genelec would never claim otherwise, but they have the potential to deliver a true main monitor listening experience in environments where that might not otherwise have been possible.