Acoustic Energy AE1 Mk.III Reference Special Edition loudspeaker By John Atkinson   •   October, 2009 One of the great divides in high-end audio concerns the question of how much bass is enough bass? The decision facing a speaker designer about how much low-frequency extension is appropriate is a fundamental one, so to speak: every extra 5Hz of bass will dramatically increase the retail price, as the speaker must be correspondingly bigger. Furthermore, the larger the speaker, the larger its problems, which in turn requires throwing more money at the design to solve those problems.

There is no mystery, therefore, why the highest-performing full-range loudspeakers tend to be large and expensive. But if a designer can sacrifice an octave, or even more, of deep bass, this will permit the optimization of other important areas of performance—midrange clarity, evenness of dispersion, HF purity, stereo imaging—in a relatively affordable design. And, depending on the tastes and preferences of every listener, this could well outweigh the loss of weight to bass instruments and the reduction in apparent hall size due to the truncation in LF of the reverberation.

I first outlined this dilemma in my September 1988 review of just such a high-performance miniature speaker, the Acoustic Energy AE1, from England (footnote 1). Designed by Phil Jones, who went on to design other great-sounding small speakers for Boston Acoustics Lynnfield, Platinum Audio, and his own company, American Acoustic Design, the tiny AE1 sounded larger than it had any right to, with an impressive ability to present low-level details within the sound without their being obscured by high-level information, and with superbly stable, well-defined soundstaging.

I kept a soft spot in my heart for the original AE1, and so didn't hesitate, two decades later, to agree to give a listen to the AE1 Mk.III Special Edition.

The AE1 Mk.III Special Edition
Superficially identical to the 1988 AE1, the Mk.III SE is a new design. Slightly taller and wider than the original, it replaces that model's 1" magnesium-alloy dome tweeter with a 38mm ring-radiator type with a claimed response of greater than 40kHz. The 4.5" woofer is constructed on a cast-magnesium chassis and still features a straight-sided cone spun from aluminum alloy, to which is glued a straight-sided, conical dustcap. The motor now uses two powerful neodymium magnets, and whereas the original AE1 reflex-loaded the woofer with two small, deep ports on the front baffle flanking the drive-units, there is now a single flared port on the rear panel 2" in diameter and 3.5" deep. I had always been a bit suspicious of those long, narrow ports "choking" at high SPLs; the new, single port should be able to handle high volumes of air flow with greater ease.

The AE1 Mk.III's crossover is specified as being a second-order topology at 2kHz using 13 elements. The Special Edition's crossover uses just six components, including both air-cored and ferrite-cored inductors, Welwyn wirewound resistors, and polypropylene film capacitors. The internal wiring is PTFE-coated multistrand silver cable, and while the AE1 Mk.I could be biwired with two pairs of terminals, the Mk.III SE has just a single pair of gold-plated, plastic-sheathed WBT terminals.

The original AE1 cabinet was built of 22mm-thick MDF, asymmetrically lined with a "high-density" material so that the internal surfaces were nonparallel. The finish was utilitarian—a rough, black paint, later upgraded to wood veneer. By contrast, the Mk.III SE's enclosure uses braced 18mm-thick MDF panels mass-loaded with 5mm sheet steel, while the 12mm-thick front baffle is milled from aluminum block and finished in a clear-coat gloss gray. The openings for the two drive-units, which are clamped to the baffle from behind, are gently profiled to optimize dispersion. The rear panel is finished in matte black, the other surfaces in eight-layer, hand-rubbed Piano Black or Cherry Red gloss. (Custom high-gloss finishes are also available.) The review samples, finished in red, were drop-dead gorgeous. No grilles are provided.

Back in 1988, the original AE1 cost $1500/pair. The Mk.III Special Edition, of which only 100 matched and numbered pairs will be made, costs a rather breathtaking $4000/pair.

Listening
With hindsight, it was probably associated with their measured response and dispersion (see the "Measurements" sidebar), but it took me a long time to get the AE1 Mk.III SEs optimally set up in my listening room. With the speakers coupled with Blu-tack pads to 24" Celestion SL stands, the central pillars of which were filled with sand and lead shot, and placed where the Spendor SA1s had worked so well and toed-in exactly to the listening seat, the Acoustic Energys' balance was over-bright. While naturally miked acoustic recordings , such as my own of the Santa Fe Chamber Music Festival on Editor's Choice (CD, Stereophile STPH016-2), benefited from the sense of enhanced detail, any modern rock recording that was itself overcooked in the highs—ie, all of them!—sounded intolerable.

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Footnote 1: The original AE1 is still available, as the AE1 Classic.