PMC was formed in 1990 and they produced their first loudspeaker, the BB5-A, which was a large studio monitor. The first production versions were sold to the BBC and Metropolis Studios.

PMC uses "Advanced Transmission Line" technology in all of their loudspeakers. This is a means of loading a drive unit in a cabinet in such a way as to absorb the unwanted frequencies that radiate from the rear of the speaker driver. The speaker is mounted at the end of a folded line within the cabinet, which is lined with foam of varying absorbency. The lowest frequencies are allowed to pass through the line and emerge in phase from a vent on the front or rear face of the cabinet, in effect acting as a second bass driver. By absorbing the unwanted bass frequencies, the upper bass and midrange are not masked by harmonic distortion.

The ATL design enables the speakers to produce higher sound pressure levels and deeper bass extension than is possible with similar sized speakers using either ported or sealed cabinets. The speakers can also be played at lower volumes without any loss of frequency response.