The Professional Monitor Company Limited, better known as PMC, is a British loudspeaker manufacturer, established in 1991.

[4] Metropolis now has around fifteen[citation needed] of them installed at its recording and mastering facility in West London.

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 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.

[citation needed] The speakers can also be played at lower volumes without any loss of frequency response.