[sdiy] Low Pass filters and musically useful frequency range

Richard Wentk richard at wentk.com
Wed May 7 09:37:06 CEST 2014

This is normal while mastering. There's all kinds of crap in the subsonic range and filtering it increases the useful headroom. I've used a brickwall FFT at 25Hz to get a good few extra dB of useful loudness for the rest of the audio.

I know some engineers use an HPF to remove *audible* low-end content. Most people don't have giant subwoofers so there's no reason not to have a -3dB point at 40Hz if it makes the rest of the track cleaner and louder - especially if it means you can dial in some extra bass body between 50-100Hz.

But it depends on the music and the output format. You might do it on folk or folk rock, especially if you're mastering an MP3 for earbuds. You wouldn't do it at 40Hz for an electronica mix designed for club play - but you might still HPF at 20Hz.

For a modular HPF 20Hz should be low enough. I can't think of a good reason to go lower for audio - although if you want to start filtering LFOs and ADSRs for special effects, you might want to go down to 1Hz.


> On 6 May 2014, at 21:14, "David Ingebretsen" <dingebre at 3dphysics.net> wrote:
> This actually sounds familiar. I think as I was reading about audio processing hardware. You take out the subsonic stuff to help the base clarity. Interesting thought. I can live with this SWAG.
> Thanks Pete.
> David 
>>> -----Original Message-----
>>> From: Pete Hartman [mailto:pete.hartman at gmail.com]
>>> Sent: Tuesday, May 06, 2014 1:32 PM
>>> To: David Ingebretsen
>>> Cc: synthdiy diy
>>> Subject: Re: [sdiy] Low Pass filters and musically useful frequency range
>>> TOTAL swag follows :)
>>> I was watching a video on production techniques a couple weeks ago, and
>>> the guy doing it recommended for bass setting up a HPF to keep the lowest
>>> of the low end from muddying up the sound.  Not explicitly said, but I was
>>> guessing "on audio playback that couldn't reproduce it well".  He was using
>>> a moderate Q as well so there was a bit of a bump for the low end in that.
>>> Keep in mind, I'm merely repeating what he asserted; though his video did
>>> seem to demonstrate a tighter bass sound by doing so, I have no authority
>>> with which to agree or disagree :).
>>> Could the reason be related to this concept at all?
>>> Thanks
>>> Pete
>>> On Tue, May 6, 2014 at 2:11 PM, David Ingebretsen
>>> <dingebre at 3dphysics.net> wrote:
>>>> The basic question revolves around the output stage of the Moog 914
>>>> fixed filter bank and the fact it incorporates a highpass filter with
>>>> a cutoff around 40-60 Hz depending on how you want to define the -3dB
>>> point.
>>>> Questions:
>>>> 1. As a general proposition and in a purely subjective context, what
>>>> is the lowest frequency that is musically useful?  At some point most
>>>> waveforms start to sound like clicks and pops. Subwoofers can pound
>>>> your proprioceptive system and add a useful effect I suppose but "how
>>>> low can you go" and still be musical?
>>>> 2. Why would Moog add such a high pass filter to the 914? I can see
>>>> blocking DC, but why worry about 10 Hz getting through? Does it have
>>>> to do with being musically useful? I don't think this high pass filter
>>>> was in the 907, so why add it to the 914?
>>>> Thanks
>>>> David
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