Equipment Sales: Smart Research C2 Stereo Compressor

At a Glance
Commercial studio, broadcast
Key Features:
Switchable external sidechain, “crush” mode, stereo link, auto or manual release time, detented controls
Sunset Sound™ at 323-469-1186

by Loren Alldrin
reprinted from Pro Audio Review – March 1999

Sometimes, hitting a stereo mix with a touch of compression is just what the doctor ordered. Some compressors don’t do so well in this role – they seem to either suck the life right out of the music, or they remain a little too transparent. The ideal mix bus compressor adds punch and character, tightens up dynamics and, if you’re lucky, actually adds a bit of sheen to the overall sound. Enter the English-made Smart Research C2 stereo compressor, a solid state processor that really delivers the goods in this applications.


That the C2 ($2,995) has a lot in common with SSL’s legendary analog compression circuit is no accident: Alan Smart was an engineer with SSL for many years, having installed and serviced countless SSL consoles in studios worldwide. Now, what started as a garage project has turned into one of the best-kept secrets among recording engineers. Based on the way this compressor sounds, however, I think the secret will be out soon enough.



The C2 is a two-channel compressor with switchable link mode. “STEREO” mode links both audio channels equally to the control settings and gain reduction of Channel 1. Both channels offer external sidechain and process I/O buttons; underneath the Stereo button on the leftmost side of the C2 is the crush button (more on this later).
Channel knobs include threshold, ratio, attack time, release time and makeup gain. Each channel has a VU-style meter that tracks gain reduction. Unfortunately, the C2 doesn’t let one switch the meter to monitor either the input or output levels.

The threshold and makeup gain knobs are the only continuously variable knobs on the compressor. The ratio and release time knobs are detented with six possible positions, while the attack time control offers seven positions. Compression ratios include 1.5:1, 2:1, 3:1, 4:1, 10:1 and limit. Attack times settings are 0, 0.1, 0.3, 1.3, 10 and 30 milliseconds (ms); release times include 100 ms, 300 ms, 600 ms, 1.2 seconds, 2.4 seconds and auto. The C2 offers XLR-balanced, +4 dBu I/Os only; sidechain inputs are also on balanced XLR connectors. A three-position switch selects various output options, including balanced, pin 2 hot unbalanced and pin 3 hot unbalanced.

One can pretty much forget using the C2 with -10 db signals, as the threshold control only goes down to -20 dB. This control bottoms out at -4 dB with a -10 dB signal, which isn’t nearly low enough. On the other side, the makeup gain control offers a generous range from 0 dB to +20 dB.

Crush mode drives the C2 into not-so-subtle FET distortion. When engaged, the C2’s output level jumps up nearly 3 dB and upper harmonics are accentuated. It appears the compressor also adds a dose of equalization in this mode, which serves to carve out the mid- and low-mid frequencies a few dB. The amount of distortion added appears to be fixed and is unrelated to input level, output level or the amount of gain reduction applied. Hence you could use the C2 to add some distortion (but no compression) by taking the threshold all the way up and engaging both compression and crush modes.

In Use

The C2’s obvious similarities to the SSL compressor had me eager to try it on a stero mix, and it didn’t disappoint. The pop/rock mix I first ran through the compressor was fuller, tighter and slightly clear-sounding with the C2 dialed in. The mix actually picked up a touch of nice high-frequency sizzle, which is in stark contrast to the many compressors that dull the signal. The C2 just punched up the energy a few notches, and made the mix sound more cohesive. Taking the Smart Research compressor out of the mix gave me instant withdrawals.

Changing attack time, release time and compression ratio let me find several useful settings, each with a slightly different sound. Normally, I feel blessed to find a single setting that works for the song. After a few minutes tweaking, I settled on a semi-fast attack time and autorelease. The C2 continued to impress me song after song and I ended up mixing a full album through it. With every mix, I found the auto release time impossible to beat with a manual setting. The C2’s very low 1.5:1 ratio was perfect for stealthily adding more punch to an already good mix.

The C2 is every bit as impressive on individual instruments and voices. With the right settings, vocals leave the compressor with dynamics tamed and character intact. I had to dial up a healthy 12 dB of gain reduction before the compression really called attention to itself; milder settings were barely noticable. Again, the C2’s 1.5:1 ratio at a low threshold did a great job smoothing out vocals.

Drums picked up lots of attitude when passed through the C2, and careful adjustment of the attack and release time controls allowed me to dial in a wide range of sounds. The compressor was equally adept at fattening individual tracks or a stereo drum submix. For adding extra edge to loops or gritty drums, the crush button is very cool.

The fact that the C2 doesn’t dull the sound makes it great fit for acoustic and electric guitars. On strummed acoustic, I was able to control exactly how much pick sound I wanted with the attack control (or eliminate it completely with the 0 ms setting). I really liked the sound of the C2 on the bass as well, and was surprised to find the crush button useful yet again. Crush mode added extra growl and definition to the sound, which was perfect for some songs.

Crush mode sounds a bit like a distortion-based exciter. The effect is pronounced but usable, especially with edgier music styles. Crush tends to push an instrument forward in the mix and accomplishes much of the opening up usually done with EQ. Even lead and background vocals cut through better with the crush engaged. Breathy vocals picked up some extra wisp with crush engaged.

The C2 has a nice soft knee for ratios below 10:1, instead of a hard transition into gain reduction. This makes the compressor more transparent in one sense, while still adding character to the signal.
Overall, the C2 is very well-behaved – it doesn’t add ugly compression artifacts at anything less than extreme gain reduction. Though it gives you enough control to get into trouble (especially with ultrafast attack times), it’s generally easy to make this compressor sound good.

Where signal hygiene is concerned, the C2 is a class act. Its noise and distortion specs are top-notch, and I never found this compressor to have an adverse impact on the signal. At 130 dB, the C2’s dynamic range exceeds that of 20-bit digital. This is analog proccessing at it’s finest.

Product Points
Smart Research C2 Stereo CompressorPlus

  • Unbeatable sound
  • Easy, responsive controls
  • Cool crush mode


  • Could use more control settings (on detented pots)
  • Stereo link mode keys off left signal only

The Score

Though expensive, the Smart Research C2 offers a dose of solid-state compression at its finest.

Considering the C2’s cost, there are a few things I wish it delivered. The C2 could use more (and finer) steps in the ratio, attack time and release time controls. Having attack time jump from 3 ms to 10 ms to 30 ms leaves some pretty big holes and I was longing for intermediate values when dialing in some sounds.

Crush mode is a great tool; I just found myself wishing for more control. A variable crush knob, or a handful of different settings, would put this effect over the top. A link mode that summed left and right signals to the detector would also be a good addition. With the detector watching the left side only, loud sounds panned to the right will sneak through unscathed.


The Smart Research C2 is a world-class compressor with a punchy, crisp sound. It offers easy controls, use-it-on-everything versatility and impeccable sonics. Those who can afford the C2’s luxuries will enjoy better tracks and tighter mixes right out of the box.