Multiband parametric processor sounds like a generic description, yet Waves' C4 is anything but a lackluster signal processing plug-in. Although the software essentially comprises four of Waves' Renaissance Compressor plug-ins that operate individually on four separate frequency ranges, C4 offers much more than ordinary compression. In fact, it's a very flexible sound-shaping tool that provides a combination of limiting, equalization, expansion, and compression functions both independently and simultaneously.
Waves' C4 is available in TDM and native versions for Mac and Windows (TDM, $800; native, $400). The TDM version reviewed here features a 48-bit processor that dithers the output to 24 bits before transferring it to the TDM bus. The plug-in requires an entire chip on a Pro Tools 24/Mix system or a Mix Farm card. Both of the plug-in versions function identically.
Out of ControlC4 has three variable low-, mid-, and high-frequency crossover points. Those points divide the input signal into four frequency ranges, as well as a Q control that adjusts the slope of the crossover filters. All four of the frequency bands include variable controls for threshold, gain, range, attack, and release, as well as Solo and Bypass switches. C4's Master controls include Threshold, Gain, Range, Attack, and Release; you can adjust the corresponding controls for all four bands simultaneously. Master controls also include a Manual/Auto-Release control switch; a Behavior switch with Opto (classic opto-coupling) and Electro settings (the inverse of Opto mode); and a variable Knee control that you can adjust in 76 increments from soft to hard.
Most compressors offer individual gain-reduction meters. C4, however, features a DynamicLine display that shows detailed information such as the crossover points and slope, the moving EQ curve, the maximum change in dynamic range, the fixed gain, the frequency center points, and the effective gain change. Dragging movable band center markers horizontally changes the band's frequency center and vertically adjusts gain, which makes it easy to mold and shape the sound as you desire.
All Together NowThe plug-in offers more than the average compressor, equalizer, or expander. For example, you can tighten up the low frequencies of a kick drum or bass guitar with compression; cut or boost the low-mid and high-mid EQ; deess vocals; and expand the treble frequencies to add glassy, shimmering high-end sheen to vocal harmonies. By setting the Range controls to boost the gain, you restore dynamics to an overcompressed signal. Also, you can use the processor to remove high-end hiss and excessive low-end hum. By automating the crossover controls, you can even create dramatic filter sweeps.
Whereas you can apply the plug-in to any audio signal, it is best suited for use on sounds or tracks that cover a wide frequency range, such as sampled drum loops or a stereo master output track. C4 works best for mastering applications such as getting the maximum perceived loudness out of a mix or giving a somewhat lifeless mix a professional polish. C4 may not be a cure for sloppy mixing, but it can definitely enhance a good mix and bring out the best in your recorded performances. Once you've heard what C4 can do for mixes, you'll probably end up using it to master all your material.