Floorstanding loudspeakers — PMC MB2S XBD

The MB2S XBD is a twin-cabinet passive monitor from PMC, the British Professional Monitor Company founded in 1991 by Peter Thomas of the BBC and Adrian Loader. It takes the MB2S studio monitor and adds an XBD bass cabinet with a second 12-inch driver. It is used for music recording, mastering and post-production in stereo or surround, including at Studio Hilversum in the Netherlands, and the main and XBD boxes may be stacked vertically or set up alongside one another.

Key specs that matter

This three-way system uses two 310mm (12-inch) PMC Radial bass drivers, a 75mm PMC fabric soft-dome midrange and a 27mm twin-chamber fabric soft-dome tweeter with ferrofluid cooling. Crossover points are 380Hz and 3.8kHz. Frequency response is 20Hz to 25kHz, sensitivity is 91dB at 1W/1m and nominal impedance is 4 ohms, with 250 to 900W of amplification recommended. Peak SPL reaches 124dB at 1m. Three pairs of 4mm sockets allow tri-wiring or tri-amping, with PMC's amplifier guidance of 120W for the HF, 120W for the MF and 600W for each bass section. Stacked, the system measures 1,740 x 380 x 535mm and weighs 88kg per channel, finished in Neo Black.

Engineering and use context

PMC's Advanced Transmission Line (ATL) loads each bass driver with a long, folded and damped channel. Each of the two cabinets has its own 3m effective line, so the XBD box repeats the arrangement of the main cabinet and adds 3dB of low-frequency headroom below 380Hz, allowing larger rooms to be driven to higher levels. In surround systems this extra headroom can handle the .1 effects channel without separate subwoofers. The Radial bass driver is built for large, controlled excursion and resists power compression thanks to cooling through its cast alloy exoskeleton and rear-vented magnet. The 75mm midrange dome covers the wide band from 380Hz to 3.8kHz, so most of the vocal range is carried by a single driver with no crossover point inside it. The passive crossovers are 32-element, fourth-order networks housed in external enclosures that can be mounted on the rear of the XBD cabinet, isolating them from cabinet vibration.

Pairing

A low-impedance passive system of this size needs powerful amplification, ideally tri-amped with the largest amplifiers driving the bass sections. It suits medium to large control rooms, either soffit-mounted or on stands.

Alternatives

PMC's MB2 XBD SE is the domestic version, with 93dB sensitivity, a SONOLEX tweeter and wood finishes.