#017 - Mono Your Sub Bass Below 120 Hz with Mid/Side EQ

Stereo content below 120 Hz creates phase problems on club systems where the subs are mono (most are) and creates kick/bass relationships that fall apart when summed to mono. Most producers know to mono their sub bass but use a Utility plugin or stereo collapse which mono's the entire sub channel. Mid/side EQ does this more surgically: mono only the low frequencies, leaving any stereo content above 120 Hz intact.

The technique

1. On your sub bass channel (or sub/bass bus), insert a mid/side capable EQ - FabFilter Pro-Q 3, Brainworx bx_digital
2. Switch the EQ to mid/side mode
3. Select the side channel
4. Apply a high-pass filter at 120 Hz with a steep slope (24 dB/octave or steeper)
5. The side channel now has nothing below 120 Hz, while the mid channel is full-range - meaning everything below 120 Hz is mono, everything above is stereo

The standard alternative - mono-ing the entire sub channel - works but throws away any stereo character above 120 Hz that might be intentional (mid-bass stereo width, atmospheric texture in the bass region). Mid/side high-pass on the side channel gives you the best of both: rock-solid mono low end, intact stereo character above.