Isolate upper and lower frequencies with EQ


Here is what I did to discover this…

I wanted to isolate the upper and lower frequencies of a synth sample.

I duplicated the track with the original sample on and put and EQ5 on each track.

The first track, I set the EQ to low pass at 500hz

The second track, I set the EQ to high pass at 500hz.

This should make the two tracks combine together to sound exactly the same at the original sample.

With the Renoise EQ5, it doesn’t. It sounds, well… odd. Not sure if it is a phasing issue, or if the roll off on the EQ5 is not consistent, or whatever, but it sounded wrong.

I tried exactly the same thing again, but this time replacing the EQ5 on each track with a Sonalksis EQ and it worked perfectly. Sounded exactly the same as the original.

Not sure how this works, to be honest, but something odd is going on with the EQ

Well, sorry to report something so late in the day, but I only just noticed it.


You can more easily do this with Filter3 and Butterworth 8n. For the actual problem I have no idea. Maybe 500Hz is a cutoff point like in regular filter where the sound is already attenuated -3db (, which would result in possible drop at that frequency. These are two different EQs that of course perform differently. Did you try to play around with Q or freq?

I didnt play around with anything other than the frequency, because I thought that technically, if they are both set at the same frequency and the same Q, things should mesh perfectly…

Also… I don’t think it is anything to do with 500hz per se. I tried it at a load of other frequencies and it caused similar anomalies

It will sound different because of the soft rolloff. Try to imagine how both EQ graphs look combined. Use the Filter3s Butterworth LP/HP for such tasks.

OK, cool. Sorry for the confusion (on my behalf!)

I wonder why though, even if they have soft roll off, if the high pass and low pass have the same roll off respectively, and they are set at the same frequency, surely they should not effect the outputted sound?