One key difference is a revised crossover network featuring custom-made chokes and tuning by PMC founder and designer Peter Thomas. The driver complement remains twin PMC-designed 170mm bass drivers with cast magnesium chassis, and a SEAS/PMC co-developed 27mm soft dome tweeter. In between these is PMC’s legendary 75mm dome midrange unit, isolated in its own enclosure. The speaker also gets a brushed aluminium serial number plate, a certificate signed by Peter, and an array of nickel finished driver bolts.
With no fancy parabolic panels, the flat-sided cabinet reaches back some 400mm, terminating in a rear panel with tri-wire terminals. Chunky inner panels brace the sail-like sides and guide the backpressure from the tandem LF drivers into a convoluted path through the cabinet, resulting in a folded transmission-line loading. This exits via a port the size of a cat-flap at the foot of the fascia, fitted with a fixed foam bung.
The PB1i Signatures were amazingly tolerant of room positioning. Give them a bit of space at the side and a couple of feet at the rear and you are good to go with only the toe-in angle to tweak. PMC’s excellent setup manual suggests aiming the crossover point about half a metre behind the listening position, and this proved to be spot-on.
AND DO THEY GO LOUD
The transmission-line loading here does spectacular things for bass reproduction that standard box cabinets of this size can only aspire to. Speed and timing across the LF range was a surprise. It doesn’t necessarily feel like it is plumbing sub-bass depths like a dedicated sub but the low-to-mid bass range was wonderfully articulate, with precious little bloating or overhang.
What’s more, the 75mm midrange dome is fluid and its crossover to the super-smooth tweeter is audibly seamless. What we have here is a rich and fullbodied speaker with incredible dynamic dexterity and a top end that refuses to get out of shape, even when pushed hard. Time to rock and roll!
The PB1i Signatures let rip with a taut, energetic rendition of ‘Black Sabbath’ from Ronnie James Dio’s Heaven And Hell live CD. As the beat built to the fast-paced final verse the PMCs carved a huge sound with physical bass and infectious pace. That superb bass breathes greater life and presence into the entire audio spectrum. Female vocal in particular, like that of Laura Marling on Alas I Cannot Swim, ws blessed with tangible body and depth, a trick I have often noticed when partnering speakers with a top-flight subwoofer.
Those looking for choral magic may prefer a speaker with a lighter midband. Otherwise, the PB1i Signature delivers power and passion that cuts straight to the heart of the music, its punch and silky top end combining to create a rich, fast sound ideal for rock.
Originally published in the Yearbook 2011
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