I have now lived with a production pair of AT-1s for more than a month, and you’ll find my opinion fundamentally unchanged. Atlantic tweaked that initial design I saw in invisible ways, including slight driver adjustments and a reconfigured crossover circuit, but the AT-1s I’ve been enjoying are visually identical to what I first saw.
The Atlantic tower’s plus-size port is the only external sign of what Tribeman and designer Phil Clements (of Solus/Clements Loudspeakers) have dubbed H-PAS (Hybrid Pressure Acceleration System), a new vented-enclosure wrinkle that the team describes as combining elements of acoustic-suspension, inversehorn, and transmission-line designs. Atlantic asserts that H-PAS extracts more low-frequency acoustic output from a medium-size woofer’s motion — which physics doom to fall off more or less rapidly in every loudspeaker type short of garage-size — than any previous passive, unequalized design.
It’s a hell of a claim, but after several conversations with Boaz Shalev, Atlantic’s resident H-PAS egghead and finite-element-analysis wizard, I understand it well enough — barely — to accept it. H-PAS is said to deliver dramatically greater system efficiency and dramatically lower distortion over the bottom two or three octaves of sound than any previous cabinet contrivance, including traditional vented, horn, and transmission-line layouts. If this calls up visions of perpetual-motion machines and 200-mpg miracle carburetors, you’re not alone.
And yet, at least as manifested by the AT-1, H-PAS performs as advertised. A bit paradoxically, however, the AT-1’s ability to make real bass may not amaze less critical listeners on first hearing, because plenty of similar-size speakers produce subjectively impressive bass — usually by a rising response through the octave of 120 to 60 Hz, before falling off sharply below that. But in my room the modest towers gobsmacked me with what I judged to be unfettered output to at least 30 Hz — and by “unfettered” I mean flat or damned near flat, not –6 dB or –10 dB (or more) at 30 Hz, which is how every other speaker remotely close to this size would measure.
