20khz Shelf EQ

[d3d0]

Hi there,

My first post here can't wait for Live 9 like everyone else haha, been watching the forums for a while now though, you guys are the best!

Maybe you can help me out, I've been analyzing a lot of mastered tracks and I always notice that there's a significant drop between 20khz and 24khz on 95% of them. How can I achieve such EQing? I tried and tried and to no avail I can't get anything close to as sharp and as accurate of a drop. (I'm working @ 88.2khz, that's how I'm able to see this drop)

Cheers!

[Winterpark]

but the real question is... can you hear how sharp the roll-off is after 20kHz?

[Tarekith]

Are these MP3's you're looking at?

[d3d0]

I don't think anyone can hear it haha but it is clearly visible on Spectrum.

And yes I'm looking at mp3s!

[Tarekith]

By default most MP3 encoding algorithms are filtering out the extreme highs. Don't try to copy that in your own productions though, IMVHO.

[fishmonkey]

not only that, CD-quality PCM discards all frequencies above 22.05 kHz...

[miekwave]

not only that, CD-quality PCM discards all frequencies above 22.05 kHz...

Correction. frequencies above 22.05kHz turns into Nyquist aliases frequencies

[fishmonkey]

not only that, CD-quality PCM discards all frequencies above 22.05 kHz...

Correction. frequencies above 22.05kHz turns into Nyquist aliases frequencies

not if the downsampling is done properly, in which case the audio is low-passed before sample rate conversion...

[GUY SMILEY]

Hi there,

My first post here can't wait for Live 9 like everyone else haha, been watching the forums for a while now though, you guys are the best!

Maybe you can help me out, I've been analyzing a lot of mastered tracks and I always notice that there's a significant drop between 20khz and 24khz on 95% of them. How can I achieve such EQing? I tried and tried and to no avail I can't get anything close to as sharp and as accurate of a drop. (I'm working @ 88.2khz, that's how I'm able to see this drop)

Cheers!

work at 44.1. you will see the drop off you require.
alternatively work at 88.2 and then downsample to 44.1.
is this a joke post ?

[d3d0]

Thanks for your responses. It wasn't a joke post. The downsampling is done by the Ableton engine when exporting the wav @ 16bit/44khz. I use LAME afterwards to convert the wav to a 320kbps mp3. However, when I import one of my mp3s there's no drop between 20khz and 24khz so I don't get it.

[GUY SMILEY]

when I import one of my mp3s there's no drop between 20khz and 24khz so I don't get it.

MP3 conversion doesn't code audio above a specific frequency. It simply ignores it and then splits the remainder of the spectrum into a number of filter 'sub-bands', each of which is then psycho acoustically interpreted for maximum 'bang per bit'.
For the specified bit-rates, these are the cut-off frequencies ;

320kbps 19.5kHz
192kbps 18kHz
160kbps 17kHz
128kbps 16kHz
96kbps 15kHz
64kbps 11kHz
32kbps 5kHz

Any MP3 you look at will therefore not have any information above these frequencies.

Any analogue to digital conversion that you carry out in any process applies brickwall (anti-aliasing) filtering to ensure that no information above the nyquist frequency is let through. Any which fails to be filtered successfully causes aliasing (which is not desired). Early digital recording systems simply used analogue input lowpass filters (which didn't work so well) although modern A/D convertors use complex digital filtering and over-sampling methods.

[Tarekith]

Getting back to the important point, DON'T go willy nilly low passing your tracks, god that drives me crazy. That information is not inherently bad around 20kHz, and you'd be surprised at how much lower in the frequency spread you'll affect if you even try to. Takes all the sense of space an air out of a track, doesn't solve ANY problem for 99% of the people out there.

Wish I could find who started this silly "tip" and give them a stern talking to

[Tone Deft]

this topic is as pointless as asking how one would maintain the correct nitrogen to oxygen ratios in their studio so they don't pass out and die.

[d3d0]

Guy Smiley, that makes total sense, thanks a lot for the info.

Tarekith so you're saying don't lowpass @ 30hz for example, when I have a subbass at 48hz?

Tone Deaf, as is your comment

[Tone Deft]

you'll see what I mean, I hope.

the first rule of 99% of audio gear design is that you can ignore content outside the audible range. you've invented a problem that doesn't exist.

strive to use fewer effects than looking for ways to use them. this is more important when you're still learning.