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Ex Machina Soundworks Pulsar

Three-way Active Monitor By Phil Ward
Published March 2021

Ex Machina Soundworks Pulsar

The physics of loudspeakers have hardly changed in a century — but DSP and material science have come a long way, and the Pulsar takes full advantage.

The last pair of monitors I reviewed were priced around what I consider to be the entry level for serious active monitoring. The next pair, and the subject of this review, retail at about six times that price — entry level they are not. They are the Pulsars, from New York‑based startup Ex Machina Soundworks. Although pretty large for a nearfield monitor, and heavy too, at 25kg each, at first glance they look relatively plain: near black, rounded‑edge boxes with a couple of drivers on the front and a metal panel on the back. But delve a little deeper and there’s some serious DSP and materials technology within. A graphene tweeter, for instance...

Before I get on to the specifics, a correction: I said that the Pulsar front panel carries two drivers, however one of those drivers is a 176mm‑diameter, compound dual‑concentric unit, in which the tweeter is mounted at the apex of the midrange diaphragm. So the Pulsar is in fact a three‑way system. Beneath the compound driver (or alongside it, if you install the Pulsar in landscape orientation) is a conventional, closed‑box‑loaded, 210mm aluminium diaphragm bass driver. There is no reflex port or ABR.

The rear panel houses switches to select between high‑latency and low‑latency operation, and LF correction options for full‑, quarter‑ or half‑space operation.The rear panel houses switches to select between high‑latency and low‑latency operation, and LF correction options for full‑, quarter‑ or half‑space operation.The aluminium plate around the back serves the dual purposes of amplifier heatsink and connection panel. Despite its 192kHz internal digital signal flow, the Pulsar offers only a balanced analogue XLR input. Also unusual is that there is no input sensitivity adjustment, and I found the sensitivity subjectively a little lower than normal (see ‘Sense & Sensitivity’ box). However there are a couple of option switches, one offering sub‑300Hz EQ profiles for corner, wall‑mount and free‑space installation environments, and one offering low or high latency options. If you’re wondering why on earth you might want to use monitors on high latency mode, it’s because the Pulsar’s DSP power can be used to equalise both amplitude and phase response. This time‑ and frequency‑domain correction results in 40ms input‑to‑output delay, which is potentially an issue if the Pulsar is to be used for tracking or in an audio/visual context. In the low‑latency mode, only the amplitude response is equalised, leaving the time domain response au naturel and yielding an input‑to‑output latency of just 2ms. I’ll investigate the latency options with a little FuzzMeasure analysis a few paragraphs down the page.

Graphene Tweeter

So, to the Pulsar’s graphene tweeter. If you’ve not had your finger on the pulse of high‑end materials science in the last 15 years you might not know that graphene was first isolated by Andre Geim and Konstantin Novoselov of the UK’s University of Manchester. In pure form, graphene is a sheet material formed by a hexagonal lattice of carbon atoms just one atom thick, so despite the extraordinary mechanical properties that make it, in terms of tensile strength and stiffness, the strongest known material, it’s not a lot of use. However, it can be incorporated in a number of different ways into composite sheet materials that, while not as mind‑bendingly strong as the pure form, still offer mechanical properties that few other materials can approach. The tweeter diaphragm of the Pulsar is made from one of those materials: GrapheneQ, manufactured by Ora Sound in Canada.

Ora Sound describes GrapheneQ thus: “GrapheneQ is over 95 percent graphene oxide by weight and is formed by depositing flakes of graphene into thousands of layers that are bonded together with proprietary cross‑linking agents.” The result, say Ora, is a sheet material that’s relatively easy to form but has bending strength of up to twice that of aluminium, combined with around 60 percent of the density. Let’s call it twice as strong and half as heavy. GrapheneQ also displays an order of magnitude higher self‑damping and offers very high thermal conductivity.

The implications of GrapheneQ for driver diaphragms, in particular tweeters, are significant. The high bending strength means that a typical 25mm tweeter dome will remain pistonic (ie. moving as a whole rather than with some parts of its surface area lagging behind others) to well above the limits of audibility, and the high self‑damping means that when the...

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Published March 2021