FabFilter

When trying to cut the low frequencies, I still get them coming through to the final output.

For example, if I only have 1 track and put a brick-wall frequency high-pass filter at 20hz on the track, I still get frequencies below this coming through to the main master.

When I try it with high-frequencies by using a low-pass cut (brick wall) the output matches exactly what I am cutting on the source channel. But not so with the low frequencies.

To replicate this bug, just have 1 channel with Fabfilter EQ 3 on it, put a shelf to cut all frequencies below 20hz (or any frequency of your choice using BRICKWALL), then go and open a FabFilter Eq on the main outputs and notice that the there are still frequencies below 20hz getting through to the main outputs.

If I try this with the high frequencies by 'brickwalling', they correlate / match exactly on the main outputs.

Not so with the bottom end.

Hi Bruce,

There are a couple of things that could be going on here. Could you send us a small video and/or test session that illustrates this? Please send it to info@fabfilter.com

I suspect one of the two following things could be going on here...

1. While the brick-wall filter is the nearest thing we can actually achieve to a "perfect" brick-wall filter, it is not a brick-wall in the true sense of the word. Unfortunately making a perfect brick-wall filter isn't possible as there is no filter type in the digital (or analog) domain that can actually do INF/dB per octave. The filter we use does attenuate more than 100dB per octave and is the closet thing to a brick-wall that is possible, but it is not "perfect".

2. Depending on your analyzer resolution its still possible you see some frequencies below your cut-off point. What resolution are you using?