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Dual-channel Dynamics Processor By Paul White
Published April 2015


This all-analogue compressor-gate promises versatile utility for the budget conscious.

Despite the ever-improving quality of software compressors, some of us still have a need for quick hands-on access to simple-to-use outboard dynamics processing, whether it be for studio or live use. The ART SCL2 aims to satisfy this demand for those on a budget. It provides two channels of versatile yet easy-to-operate compression, and offers an expander/gate stage too, to tame low-level noise or spill. Unusually, the manual gives no clue as to what form of gain-control element is used. ART tell me, should you be interested in these things, that it’s a VCA design — but when it comes down to it it’s only really the ease of use and the sonic result that matter.

Generous LED metering displays both the gain-reduction and output level simultaneously. The user also has the option of using each of the two channels independently, as mono processors, or as a stereo pair in linked mode, with the left-hand set of controls governing the behaviour of both channels.

This is a 1U rackmount processor, and it is mains powered via a rear-panel IEC inlet which, thankfully, means that there are no fiddly wall-warts to accommodate. The analogue audio inputs and outputs are presented as both balanced XLRs and balanced quarter-inch jack sockets. There’s also side-chain access for external keying, via a TRS jack wired as a send/return insert loop. Both the inputs and outputs can handle signals up to +20dBu in level, while the frequency response is a very wide 10Hz to 100kHz ±0.5dB.

The compressor section features the expected threshold, ratio, attack, release and output-level controls, but there’s also switching for hard- or soft-knee operation. Individual ‘hard’ bypass buttons are included for each channel, while the one-knob expander/gate section can be switched to expander or gate mode, an LED at the end of the main display indicating that the threshold for whichever you’ve selected has been crossed. A fully variable compression threshold allows the compressor to go from 1:1 (no compression) to hard limiting, with a 3:1 ratio sitting in the middle of the control’s travel. In soft-knee mode the ratio control sets the maximum ratio that will be applied; the ratio increases progressively towards this value as the signal approaches the threshold.

While the attack and release controls allow the user to set the nominal operating range (attack 25-100ms; release 100ms to 3 seconds) there’s a degree of automatic adjustment that fine-tunes the settings to suit the dynamics of the input material. There’s also a button located between the attack and release controls to engage the fully automatic Auto mode, which determines the time constants based on the incoming programme material (for details on how such controls react to the signal, go to This is particularly useful on material that has constantly changing dynamics.

Despite its wide-ranging controls, I found it pretty difficult to get into trouble with the ART SCL2. Even at its more extreme settings, it still managed to sound controlled and purposeful. When used more gently, in mastering-style applications, it added girth without detracting too much from the overall transparency, although, as with any single-band compressor, the high end could often be punished for the sins of the bass. Longer attacks and moderately fast release times worked well to add a little attitude to percussion, while medium ratio settings covered all the necessary ground for evening up vocals and acoustic guitars. You can get this compressor to pump if you wish, by setting fast attack and release times, but the result isn’t as drastic as with many other compressors that I’ve tried. Whether that’s a good thing or not, I’ll leave it to you to decide! In soft-knee mode, it was difficult to provoke any unkind side effects, which would perhaps make operation feel a little safer for novices.

In truth, there’s not much to get really excited about with the SCL2, but while that might sound like a criticism, in a budget processor like this, it’s really a compliment. This is one of those compressors that just gets on with the job in hand without creating any fuss — something that’s possibly down to the automatic fine-tuning that occurs even in manual mode. The fully Auto mode also takes the pressure off if you’re working with changing programme material, or for the newbie who’s not too confident in setting the attack and release values themselves.

That expander/gate section can be helpful in cleaning up spill or background noise during pauses, where the compressor naturally adjusts its gain to maximum. Unless you particularly need hard gating, expanders are usually more forgiving, as they’re a little more subtle in operation, and that’s certainly true here. However, as with gates, you still need to be very careful when setting the threshold, so as not to cut out anything that matters.

It’s hard to justify purchasing a compressor like this if you work mostly with software — it’s not the kind of ‘special’ device that you’d plumb into your DAW in place of a plug-in — but if you have a hardware-based studio or also work in the live-sound arena, the ART SCL2 could be a useful ally. It’s very versatile and won’t eat far into any budget. A concise description might be ‘a safe pair of hands’, which is just what some people need!


Similar budget processors are offered by Behringer, Samson, dbx and Alesis, to name a few. Pushing the budget just a little, and sacrificing some functionality, you might also consider the higher quality RNC compressor by FMR or the Golden Age Project Comp 54.


  • Easy to set up.
  • Soft- and hard-knee modes.
  • Built-in expander/gate.


  • No obvious cons, given the price.


A practical workhorse compressor that’s well-suited to general studio or live-sound applications where the budget is tight.


£130 including VAT.

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ART Pro Audio (716) 297-2920