Author Topic: Cut Very Low Frequencies?  (Read 19729 times)

Axis

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Re: Cut Very Low Frequencies?
« Reply #15 on: February 18, 2016, 07:54:34 pm »
Just keep in mind that a sharp cut creates a phase shift around the cutting frequency, so even though you can't hear much below 20Hz, the phase shift created by the EQ will definitely affect the overall balance in the low frequency range, so you need to be careful.  Using a linear phase EQ might help, but you need to watch out for transient smearing.  To summarize, I try to avoid sharp cuts or boosts on the master, and always get rid of unwanted frequencies on individual channels or busses.

Article by Ethan Winer regarding EQ and phase shifts and what your sound really experiences. Interesting read nonetheless

http://ethanwiner.com/EQPhase.html

Articles are great, but it's always useful to check for yourself.  Open up any synth, make a simple saw wave patch, and play a low note (say, C2).  Then add an EQ with a sharp cut around 30Hz.  The fundamental of the C2 note is around 65Hz, so you should hear no difference, right?  Try for yourself, the difference will be quite audible.  It will become obvious if you look at the waveforms (1st one is no EQ, 2nd is with EQ - I used FF Pro-Q2 with a 36db cut at around 30Hz):



Moreover, without the EQ, I have -6.8db of headroom (top picture).  With the EQ, all that headroom disappears due to the phase shift introduced by the EQ.  This can be fixed by switching to linear EQ mode (in which case the waveform will not be affected), but linear phase EQ adds smearing to fast transients.
« Last Edit: February 18, 2016, 07:58:02 pm by Axis »

Bertie South

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Re: Cut Very Low Frequencies?
« Reply #16 on: February 18, 2016, 08:33:42 pm »
I remember reading on here that you shouldn't use linear phase EQ for low-passing (or was it high-passing?). If it's also bad for transients, what things is it good for?
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Xan

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Re: Cut Very Low Frequencies?
« Reply #17 on: February 18, 2016, 08:54:15 pm »
Linear phase EQ is what?

Keep in mind, I use ableton's stock EQ8. I just try not to do a 24db slope, if I can.

Kenny Troy

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Re: Cut Very Low Frequencies?
« Reply #18 on: February 19, 2016, 03:38:30 pm »
Linear phase EQ is what?

Keep in mind, I use ableton's stock EQ8. I just try not to do a 24db slope, if I can.

Analog EQ

With any analog equalizer, the bands being boosted or cut are subject to phase-shifts due to the latency created by the change in amplitude within that band in relation to unaffected bands.


Linear EQ

The way that the equalizer algorithms are configured are completely different for linear-phase equalizers.

Linear-phase is exactly how it’s described: linear. For the varying wavelengths of varying frequencies, linear-phase equalizers adjust phase accurately to the degree of zero phase-shift. This can only be achieved digitally with such accuracy. This non-existent phase shift, leaves the actual amplitude of the waveform almost unchanged in many instances where a minimum-phase equalizer may cause drastic amplitude changes

This information can be found here -

http://theproaudiofiles.com/linear-phase-vs-minimum-phase-eq/

ShawOfficial

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Re: Cut Very Low Frequencies?
« Reply #19 on: February 20, 2016, 06:30:27 am »
You don't "have" to do anything.However cutting those super low frequencies would be a good idea.The more you cut,the more room you have for the other frequencies.That's one of the reasons you should practice subtractive equalizing.I always have an eq on the master which cuts below 20Hz and everything above 18K Hz and around.Also,if you,for any reason,want to boost some frequencies on eq on the master output,for boosting you should always linear phase eqs.

Do you feel you lose the sizzle at the top cutting at 18k?
I've tried it before and I don't know how I feel.
To be honest with you,I sort of believe that all sounds over 18K should be cut cause the sound after 18K Hz won't be audible or even if it is,it'll probably be spoiling your mix.Anyway,if a cut to 18K is filtering out your main sounds,you could try eqing them individually(and no matter what sort of an excuse you might have,be sure to eq everything),or you could just keep the cut till about 19.4K or just 20K and place a high shelf at 18K of around -1.5db to -7db
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