Drawmer’s CMC2 is one of the more affordable monitor controllers to offer both mono‑sum and right‑channel‑invert buttons. The former on its own delivers the Mid signal to your speakers, while pressing both at once gives you the Sides.
Some monitor controllers have facilities that others don’t, and I can see why you’d want separate mutes for the left and right, and even a ‘left‑right swap’. But why do some have a ‘polarity’ button? If one channel is ‘upside down’ surely it needs sorting before the signal hits the monitors. What am I missing?
Anonymous, via email
SOS Reviews Editor Matt Houghton replies:Yes, if a signal had an inverted channel you’d want to correct that earlier, but this facility is primarily there to solo the Sides signal. Most models have a Mono or Sum button, and that ‘sum’ of Left+Right leaves you with the Mid component of Mid‑Sides encoded stereo. Apply polarity inversion to the right channel first, before summing to mono, and you get Left-Right instead: in other words, the Sides. Hearing the Mid lets you check how a mix sounds on mono playback devices. But why might you want to hear only the Sides? Actually, there are various possible reasons...
For instance, you can hear what’s lost on mono playback: musically important information in the Sides can help you figure out exactly why a mono mix sounds ‘wrong’. It can also shine a light on the damage caused by lossy data‑compression formats such as MP3. If you need to match the channel gains in a stereo signal chain, you can run identical signals through both channels, and adjust until they null in the Sides. And when recording with a stereo mic array, too much direct sound from a central source in the Sides is a sign that your aim is slightly off to one side.
A polarity invert facility on your monitor controller allows you to check very quickly whether the stereo image becomes more or less focused when flipped.
Finally, some really wide recordings, mixes, or effects can naturally sound a bit out‑of‑phase. A polarity invert facility on your monitor controller allows you to check very quickly whether the stereo image becomes more or less focused when flipped, so you can confirm that there isn’t (or perhaps is!) a polarity fault somewhere else.
Plenty of monitor controllers, even expensive ones boasting great technical specs, don’t have this feature. But while the dedicated buttons are convenient, if you’re working in your DAW, you can achieve the same thing by using plug‑ins in the monitor path.