Mixing Low Frequencies: Why Bass Should Be in Mono
One of the most overlooked aspects of mixing is controlling low-end frequencies. If your bass and sub-bass are spread too wide in the stereo field, your mix can sound unfocused, and you might run into phase issues that weaken the low end. In this post, we’ll cover why keeping frequencies below 300Hz in mono is crucial and how you can do it effectively.
Why Keep Low Frequencies in Mono?
Lower frequencies—especially below 300Hz—are where the fundamental power of your mix comes from. Human ears struggle to pinpoint the direction of these frequencies, so keeping them centered ensures a more solid and punchy mix. More importantly, stereo low-end can introduce phase cancellation when summed to mono, which can make your bass sound weak or inconsistent on different playback systems.
Why Apply This Technique at the Output Bus or Mastering Stage?
You might already be keeping your bass and kick drum in mono, but there’s a catch—stereo effects like reverb, chorus, and delays can still spread low-end frequencies back into the stereo field. That’s why it’s best to apply this technique on the output bus or during mastering, ensuring the final mix keeps the low end centered while preserving stereo width in the higher frequencies.
How to Mono Your Low End
Using Nugen Audio’s Monofilter
One of the best tools for this job is Nugen Audio’s Monofilter. This plugin allows you to define a frequency threshold—say, 120Hz or 200Hz—where everything below it is collapsed to mono while leaving higher frequencies untouched. This gives you a focused low end without affecting the stereo width of your mids and highs.
Using iZotope Ozone’s Imager
Another great option is iZotope’s Ozone Imager. It not only lets you visualize the stereo spread of your mix but also control how wide or narrow different frequency bands are. You can simply pull the width down on the sub-bass range to keep it centered. iZotope also offers Ozone Imager as a standalone plugin, making it an accessible tool for tightening up your low end.
Final Thoughts
Keeping your low-end frequencies in mono is a small but powerful step toward a professional-sounding mix. By applying this technique on your output bus or during mastering, you ensure your bass remains tight, punchy, and phase-coherent across all playback systems.
Try using plugins like Nugen Audio’s Monofilter or iZotope’s Imager to dial in a balanced and controlled low end.
