Stop Using EQ on Your Bass Like This

When using a high pass EQ to remove rumble from a kick, the signal actually peaks louder than before, contrary to the expectation that removing frequencies would create headroom and make it quieter.

High passing changes the waveform itself. While you remove the fundamental frequency and have fewer frequencies in the signal overall, the peak point in the sample becomes higher than the original signal.

Comparing the original kick waveform with the high-passed version shows the peak points are noticeably higher after applying the filter, demonstrating the counterintuitive effect.

Use a high pass filter together with a limiter to prevent ending up with higher peaks than before.

Audio signals consist of mini sine waves added on top of each other. When phase relationships between different sine waves are aligned, they blend nicely without cancelling each other.

Non-linear EQ filters change the phase relationship between sine waves. After applying a high pass filter, peak points shift because the phase of the signal changes, causing the different frequency components to cancel each other out.

When a kick and bass are combined with aligned phases, they sound blended together. After applying a high pass filter, the peak points shift completely, and the two signals start to cancel each other.

Freeze and flatten the bass sound after applying high pass filtering, then examine the phase correlations to see if the sounds are cancelling each other and get a tighter space.

Linear phase EQ maintains much closer phase alignment when processing, keeping peak points and waveforms closer to the original compared to standard non-linear EQ.

Linear phase EQs can introduce pre-ringing, which is often a problem with percussive sounds where very high pitch and low pitch sounds move around each other.

For simple bass sounds, pre-ringing shouldn't be a problem, making linear phase EQ a better choice for high passing bass sounds.

Using a linear phase EQ like FabFilter with medium settings will align faces much closer together, maintaining the original sound character while cleaning up the desired frequencies.