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Resonant Highpass Filter - Why So Little Love?

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Resonant Highpass Filter - Why So Little Love?

Postby ITHertz » Mon Nov 09, 2020 1:54 am

Hi Folks,

Lately I've been spending most of my time mixing (in the past I've mostly done editing). I'm not a drummer so I've spent a bit of time looking into drum mixing.

Something I've noticed across a lot of instructional material is that drums tend to be treated in a similar way - reduce extreme low end, boost around fundamental, cut lower mids and possibly boost some high end. Other than the mid/high end component, this creates an EQ curve much like that of a resonant highpass filter. So I'm curious as to why resonant highpass filters aren't found more often in mixing hardware/software? They would appear to be an ideal tool for working with modern pop low end, especially 808-heavy material.

I'm aware of bx_subfilter but other than that there doesn't seem to be much on offer, except of course for synth filters.

Thoughts?

Cheers,

Chris
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Re: Resonant Highpass Filter - Why So Little Love?

Postby resistorman » Mon Nov 09, 2020 4:03 am

The Eiosis air eq has a resonant lowpass filter. I use it for cleaning up bass all the time. Also great for tweaking HF.

https://www.soundonsound.com/reviews/ei ... eq-premium
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Re: Resonant Highpass Filter - Why So Little Love?

Postby ITHertz » Mon Nov 09, 2020 4:14 am

resistorman wrote:The Eiosis air eq has a resonant lowpass filter. I use it for cleaning up bass all the time. Also great for tweaking HF.

https://www.soundonsound.com/reviews/ei ... eq-premium

Thanks resistorman, didn't know that one had resonance.
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Re: Resonant Highpass Filter - Why So Little Love?

Postby The Elf » Mon Nov 09, 2020 9:14 am

A number of HPF models have a deliberate boost just above the cut-off point. The stock Cubase EQ has this feature, for example. It was also very much a feature of the old SSL EQs, which remain a favourite of mine.

So maybe not as rare as you think.
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Re: Resonant Highpass Filter - Why So Little Love?

Postby Matt Houghton » Mon Nov 09, 2020 11:21 am

I'm not so sure there is 'so little love'. I used to use them a lot. That I don't now is probably mostly due to the fact that I tend to reach for an EQ (Pro-Q3) that has so many nodes available and can achieve the same thing with more control using HPFs, low shelves and peaking filters.

But eg Little Labs VOG has proven popular — ditto Boz's free Bark of Dog

But also note when mixing multitrack drums that most such filters introduce phase shifts (and those that don't can introduce pre-ringing) — so if putting one of these on eg your kick drum, make sure you listen out for what happens to the kick's relationship with the overheads/room mics, low tom etc. (It might be OK, it might not, but you have to listen). Drum sample triggering for replacement/reinforcement has also become easier in recent years... and you can often achieve the same thing that way without messing with the existing phase relationships in a multitrack recording.
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Re: Resonant Highpass Filter - Why So Little Love?

Postby Martin Walker » Mon Nov 09, 2020 3:58 pm

The Elf wrote:A number of HPF models have a deliberate boost just above the cut-off point.

Indeed they do, and another common feature is that the boost tends to occur an octave above the cutoff frequency, so for example a 30Hz highpass filter would have its boost at 60Hz.

The amount of resonant boost above the cutoff is also a bit of a style thing - some designers prefer it very damped (maybe only 0.5dB), while others will add a bit more welly. The size of the bump can also vary with the slope of the highpass filter - the most popular for low-end rolloff tends to be 12dB/octave with a bump an octave above, whereas if you're offered an 18dB/octave rolloff this is more likely to abandon the bump.


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