PMC EB1i Transmission Line Loudspeaker

PMC EB1i Transmission Line Loudspeaker
PMC EB1i Transmission Line Loudspeaker

The EB1i is still a substantial loudspeaker of course. Standing well over a metre high and weighing in at a consternating 48 kilos you wouldn’t want to bump into it in a dark alley – or anywhere else for that matter (might scuff the lacquer!). It features a ten-inch bass driver with a flat carbon fibre and Nomex diaphragm, backed up by PMC’s trademark transmission line (TL) loading, although the EB1i deviates slightly in this department. It has an extra chamber at the end of the line, above the place where it vents. The purpose of the TL is to augment the speaker’s output at very low frequencies, by channelling output from the rear of the bass driver down a long, heavily damped “pipe” that’s designed to remove all but the lowest frequencies. In effect it’s a mechanical low pass filter that has the benefit of loading the bass driver resistively and which is said to produce the lowest octaves in phase with the direct output.

The purpose of the additional chamber in the i series is to give greater control over the response produced by the TL, effectively rolling it off more steeply and smoothing out ripples that affected the original. This change is also claimed to make the midrange sound clearer which is immediately apparent when you play something familiar through the EB1i. PMC’s have always had a more obviously open balance than average but this is even more noticeable here. The source of all that mid-band detail is a three-inch fabric dome, with its own plastic enclosure. PMC goes to great lengths to make sure that this enclosure is well damped, using bitumastic sheets and carefully selected foam, which is said to absorb the rearward energy from the driver. The size of the housing also damps the dome acoustically and allows it to operate cleanly down to the 380Hz crossover point.

Other revisions for the i series also include veneer on all faces of the slightly higher density MDF cabinet, plinths that you no longer have to bolt on yourself and a rather nice chrome and enamel automotive style badge.

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