Subwoofers — Monitor Audio Radius 390

The Radius 390 is an active subwoofer from Monitor Audio's Radius Series and the larger of the two Radius subwoofers, above the Radius 380. It uses Auxiliary Bass Radiator (ABR) loading in an 18 mm MDF cabinet (CARB2 approved). Monitor Audio designs the Radius subwoofers in the UK and has them made in China.

Key specs that matter

The driver complement is one 250 mm (10 in.) C-CAM long-throw driver and one 250 mm (10 in.) auxiliary bass radiator. Amplifier power output is 200 W at 1% THD+N from a class D amplifier with a switch-mode power supply (SMPSU). Low frequency limit is 30 Hz (-6 dB), and the upper frequency limit is variable from 40 to 120 Hz at 24 dB/octave. Connections are a stereo RCA input, an LFE input and a 12 V trigger input on a 3.5 mm mono mini-jack (5 - 12 V). Input impedance is above 20 kOhm. Power consumption is below 0.5 W in standby (ErP approved), below 10 W typical idle and 200 W maximum rated. Dimensions are 348 x 330 x 345 mm (H x W x D) including amplifier and feet, and unpacked weight is 13.76 kg.

Engineering and use context

A three-position Bass EQ switch selects Music, Movie or Impact. Movie mode gives a relatively flat response down to 35 Hz, Music mode is 2 dB lower but extends to 30 Hz, and Impact mode is 3 dB higher and reaches 40 Hz. Phase is switchable between 0 and 180 degrees.

The crossover frequency control works only with the stereo RCA input. On the LFE input the low-pass is left to the connected AV amplifier or processor. With the power mode switch on Auto, the subwoofer turns on when it senses a line-level signal above 3.5 mV and goes into standby after about 15 minutes without signal. A 12 V trigger lead is supplied, and an LED on top of the cabinet shows red in standby and green in operation. The mains voltage selector is factory set for the region and sits under a clear plastic cover.

Pairing

A source with a line-level pre-out or subwoofer output is required. There is no speaker-level input. An AV receiver connects to the LFE input. With Radius Series speakers Monitor Audio specifies a crossover setting of about 80 Hz.

Alternatives

The Radius 380 is the smaller subwoofer of the same range, with a 200 mm driver, a 200 mm auxiliary bass radiator and 140 W.