The BSS DPR 901II is the second generation of Brooks Siren's dynamic equalizer that allows you to compress or expand selected bands of frequencies rather than the conventional cut or boost approach. You can precisely focus on problem frequencies and then process the sound with more precision than either a regular equalizer or a limiter and equalizer combined. The sidechain listen function lets you pre-monitor the EQ processed sound before it goes to tape.

The DPR 901II is a dual-channel unit that can be used on two mono sources or linked for a stereo pair. Each channel has two independent sections each with frequency selection and frequency width (Q) controls.

A single knob varies the balance between compression and expansion at the selected band of frequencies while another knob sets the threshold level at which these processes begin. There are also separate switches that toggle the equalizer, compressor and filter on and off.