Напольная акустика — PMC QB1 XBD-A

The QB1-XBD-A is a twin-stacked active three-way monitor produced by PMC in Britain for large control rooms, mastering suites and bespoke playback installations. PMC built it by adding a dedicated low-frequency cabinet beneath the full-range QB1-A, so each channel is formed by two enclosures. The design was first shown at the 139th AES convention in New York in 2015, with full production starting in 2016. It can be soffit-mounted or used free-standing.

Key specs that matter

The complement per side is eight carbon fibre and Nomex piston bass drivers of 250 mm, a hand-built 75 mm soft-dome midrange and a 34 mm soft-dome tweeter with an acoustic radiator. Crossover points sit at 380 Hz and 3.8 kHz. Amplification per channel totals 8,825 W rms - two 2,400 W modules for the bass drivers in the master cabinet, two more of 2,400 W for the XBD box, 550 W for the midrange and 275 W for the tweeter. PMC gives a frequency response of 20 Hz to 25 kHz and a peak level above 132 dB at 1 metre. The stack is 1640 mm high, 1092 mm wide and 523 mm deep at its maximum. The master cabinet weighs 150 kg and the XBD cabinet 140 kg.

Engineering and use context

The XBD cabinet holds four identical piston drivers. Stacking it with the master box gives 3 dB more low-frequency headroom than the single-cabinet QB1-A. Advanced Transmission Line loading is extended across both enclosures, with an effective length of 2 x 2.7 m, and vertical strakes inside the line brace the structure and reduce air turbulence. Balanced analogue and AES3 digital inputs are provided, the latter running at 24 bit and 96 kHz, and input sensitivity adjusts from +4 to +20 dBu with a balanced input impedance of 20 kohm. DSP covers driver optimisation, crossover filtering, parametric EQ, shelving filters, delay, phase and level trim. A wired RJ45 desktop controller with a backlit display and jog wheel gives access to these settings and stores up to four user presets. Registering the system within 10 days of purchase raises the PMC warranty to 20 years.

Pairing

All amplification is supplied with the system, so the QB1-XBD-A accepts a balanced line signal from a studio desk or monitoring controller, or an AES3 stream. The weight of 290 kg per channel means the mounting surface or soffit has to be engineered for that mass.

Alternatives

The PMC IB2 XBDS-A is a more compact active three-way twin-cabinet monitor that pairs the IB2S-A main unit with an XBD bass cabinet.