Loudspeakers

When, in the early 1950s, Harry Olson published his seminal work describing the impact of cabinet shape on speaker frequency response – the product of wave reflection at sharp boundary edges – he concluded that the ideal form factor was spherical, with the driver(s) flush-mounted. Engineering a ball-shaped speaker is not trivial but Devialet has picked up the concept and run with it, realising not only an ideal low diffraction cabinet but, with a 110mm annular midrange surrounding a 25mm dome tweeter and DSP to align the two drivers’ acoustic centres, the Phantom Ultimate transcends the mere coaxial to become coincident. The result is a speaker with excellent off-axis uniformity, freed of the time misalignments and lobing effects that arise with non-coincident drive units. Moreover, the two 200mm ‘push-push’ convex dome bass drivers not only constitute part of the sphere but are also sufficiently close to these acoustic centres that, wavelengths being what they are at sub-200Hz frequencies, they become the final piece in Devialet’s full-range ‘point source’ loudspeaker.

Inside the Phantom’s ABS shell and polycarbonate/glass-fibre moulded chassis (with alloy core) lies not only the latest Astra-based iteration of Devialet’s ADH amplification [HFN Aug ’25], condensed here onto an ASIC, but also a host of DSP running on an NXP i.MX8 ‘system on a chip’. Then there are those two new dome woofers, whose hard, rigid, one-piece ABS polymer shells are both lighter and more resistant to the knocks and bumps of everyday life than alloy. As with earlier Phantoms, these are conceived to work into a very limited six-litre, gasket-sealed air volume. But the Ultimate’s woofers use under-hung motors (so the voice-coil is shorter than the magnetic gap), offering improved linearity while maintaining a generous ±13mm excursion. However, while the mid/treble driver’s responses, 4th-order phase-corrected crossovers (200Hz and 2kHz), etc, are governed via ‘static’ DSP, the bass units are managed by SAM. Devialet’s ‘Speaker Active Matching’ is a far more sophisticated, predictive control based on a real-time model of the bass unit’s behaviour under all conditions. SAM will not pass a high amplitude/low bass signal that would force the woofers to stray from their linear region.

As with Devialet’s earlier Phantoms, the drivers are powered by four ADH amplifiers, including 2x300W modules for the bass. Power has not been increased in the Ultimate 108dB, but the system is globally more efficient – the custom switchmode PSU, the amplification and transducers are all improved, with heat and distortion reduced, and output boosted. Thanks to SAM, ADH, and other technologies, coupled with the physical robustness of its high-efficiency dome woofers, the Phantom claims to exceed the bass extension of a typical floorstander 10x its size. The result? A response specified at 14Hz-35kHz (–6dB) and a maximum output of 108dB SPL for this flagship ‘Ultimate’ of Phantoms [see PM's Lab Report]. PM