Neat Acoustic’s Ultimatum range is a three-strong expression of Bob Surgeoner’s distinctive take on loudspeaker design. It comprises a stand-mount Ultimatum XLS, the flagship XL10 tower, and this, the XL6 floorstander. The logic behind having three flagships instead of just the one behemoth design is simple; people don’t just live in man-caves, and some of those with high-end audio aspirations do not live in similarly high-end palaces with rooms large enough to accommodate said behemoth. As the name suggests, the Ultimatum makes a bold statement; it just makes it for people in varying domestic circumstances. It’s that kind of pragmatism that defines almost everything about Bob Surgeoner and, by extension, everything about Neat Acoustics too.
Unlike many modern loudspeaker firms, the accent in design is placed on ears over meters. Neat Acoustics is not a measurement-free environment, and the products rely on tried and trusted loudspeaker designs, but when it comes to the final sign-off for loudspeaker design, the way it sounds in a domestic setting takes precedence. Despite suggestions to the contrary, observation-led product design is all too rare in today’s loudspeaker world, and Neat receives praise and opprobrium in equal measure from the Twittering classes as a result. Once again, though, this reflects the pragmatism of the company; given a loudspeaker spends most of its time being listened to instead of being measured, perhaps assessing how it sounds might actually prove useful! Who would have thought it?
Ultimatum started life as a single design, the 150cm tall MF9 from 2001 (which spent six years on the drawing board). This was quickly joined by three more models, which eventually morphed into the XL range seen today. In the process, one of the four designs – the 120cm tall MF7 – was sidelined. The three remaining models all share many common approaches and even common parts. They all feature a pair of upward-firing 25mm EMIT planar/ribbon super-tweeters on the top-plate, they all use the same 26mm SONOMEX domed tweeter, all use the same 168mm NEAT-designed mid-bass unit with an aluminium phase plug, and they all use isobaric bass loading in the design of the birch ply enclosure. The 1m tall XL6 and the 1.5m tall XL10 use NEAT’s other 168mm driver (the one without the phase plug) for pure bass duties. The difference is the size of the enclosure dictates both the number of drive units used and, as a result, its the complexity. In the XL6, this means small sealed chambers for the supertweeter and the tweeter, a rear ported chamber for the forward firing mid-bass unit, a second (larger) ported chamber for the internal down-firing primary bass unit, and a similarly-sized sealed box for the other driver in that isobaric design, which fires out of the base of the loudspeaker. This makes the outriggers and feet mandatory and unpacking the XL6 a little more complicated than most.
Isobaric loading is relatively uncommon (in part because of the complexity of the enclosure, the need for the tightest of matching in the drivers in the isobaric chamber itself, and – as it is usually sealed – requiring a very tightly sealed inner chamber, making construction a bit ‘spendy’). Isobaric enclosures, like many designs, dates back to Olsen in the 1950s. It requires two identical drivers to operate at the same time within a fixed and common body of air on one side of each diaphragm. The pressure between the cones is constant (assuming driver identicality) and the drivers are often laid out in a cone-to-magnet design (otherwise the phase of one driver needs to be inverted). The two drivers operate in tandem, effectively making a performance akin to one drive unit in twice the cabinet volume. In other words, isobaric loading effectively yields a driver with twice the moving mass, half the compliance, and half the impedance of a single bass unit, but achieving the low frequency extension afforded by a cabinet nearly twice its actual size. This can come at the expense of some non-linearity, if different air circulation properties cause the isobaric chamber to act non-symmetrically. However, outside of some pretty wild listening sessions in the rainforest in the height of summer, such non-linearities are more ‘notional’ than ‘actual’ and playing at party levels for protracted periods leaves the XL6 with distortion-free bass far more than what you might expect from a 1m tall box.