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Sonifex RM-2S10 Squeezes Much Into a Little

User Report: London-based broadcaster likes its number of inputs, size and cost

LONDON: — Over the last few years, as we at Global Radio have added services and outputs to our broadcast site and also transitioned many circuits to digital, we’ve outgrown our existing CTA monitor panels. Our key points in looking for a new monitor unit were the number of inputs, physical size and cost.

After much searching we decided upon the Sonifex RM-2S10 units. We now have three of these spread among our 54 broadcast racks providing monitoring of a mix of local sources and sources from our outside source router.

Inputs and outputs

The Sonifex units have 10 stereo analog inputs and 10 stereo AES digital inputs. The meters on the front are switchable between a number of scales and algorithms. Ours are set to EBU PPM. There are a few settings that are definable by the supplied software, like adjustment of the equalization that is applied to the speakers and the control of the audio selections.

The AES inputs have selectable 110 ohm termination, which can be useful for monitoring across AES sources without double terminating them. Although the handbook warns of the consequences of incorrect termination for digital connections, in practice we’ve found no problems. Some DIP switches on the lid of the unit offer a selectable input range of either –18, –12, –6 or 0 dBFS for the digital inputs.

The input selection knob selects the inputs 1 to 10 and pushing the button selects between the analog and AES input banks. There is also a handy LED indicator that illuminates to show signal presence on a particular input. The LED glows yellow to indicate which of the sources you’re listening to.

In two of our areas the unit’s built-in speakers offer a sound that is more than acceptable. However for our main monitoring unit we use the two XLR outputs on the rear to drive an external pair of monitor speakers. These outputs are selectable via another DIP switch of being either pre- or post-front panel volume control. They are also selectable between analog and AES. The headphone socket on the front cuts out the monitor speakers when a jack is inserted. Both the headphone and speaker outputs pass through a protection limiter which has proved handy quite a few times when selecting between sources of varying and unknown volume.

There are a host of available controls to allow the monitor speakers to have a combination of phase reverse, mono, sum + difference, dim and mute left and right channels applied.

The audio inputs are connected to the unit via two standard 25-pin D-subs on the rear panel. There is also a choice of either USB or RS-232 for accessing the software functions of the unit. There is also a connector for controlling some of the GPI functions of the unit. We have ours connected to our talkback unit so that it dims the monitoring speakers upon incoming talkback.

The only thing I’d like to see on a future model is the option to label the inputs, maybe through some kind of OLED or LCD screen, but I realize there is also a shortage of real estate space on the front. With 20 inputs it’s a struggle to remember what everything is.

These units offer a good amount of inputs in a small amount of rack space with reasonable-sounding speakers and have just worked well from the day they were installed.

Simon Price is broadcast engineering service manager with Global Radio.

For information, contact Fraser Jones at Sonifex/Independent Audio in Maine at (207) 773-2424 or visit or