Hey, what did my EQ do? (spectra plots for nerds...)

[des0free]

I was trying to gain a better understanding of what frequencies (tones) are present in my recorded tracks (guitars, bass, vocals, etc.) and what affect the EQ curves I was applying was having.

So I decided to use my computer audio analysis code to calculate and plot before/after spectra, averaged over the whole song, for each track (see plots at bottom of this post).  One can clearly see the effect of my low and high pass filters in these plots, my small intermediate frequency boosts and cuts are only barely evident (the plots could be zoomed for closer inspection).

I think this could be useful, because one may be able to develop a feel for what frequencies are good/bad to have in certain cases and use the plots to help decide where to cut/boost.  For example there are lots of articles online that talk about certain frequencies; e.g. quoting from an article on acoustic guitar EQ (https://www.behindthemixer.com/eq-acoustic-guitar/):

150 – 300 Hz range: Use to beef-up the tone of the guitar but as mentioned, it's easy to get muddy again so only boost frequencies in this area if it CLEARLY improves the sound.

300 – 600 Hz range: Can be boosted if you have a thin sounding guitar.

600 – 800 Hz range: Your meaty mid-range sound.  Cut this to give better tone and better distinguish the guitar from other instruments (more on cross mixing in a moment.)

1,000 – 3,500 Hz range: These frequencies can push the guitar to the front of the mix and affect note definition.  Boost these frequencies when looking at fingerpicking-style guitar and lead (not rhythm) guitar.

3,500 – 12,000 Hz range: It's all about the sparkle.  This range adds brilliance and can make the guitar jump out.  This range can be further broken down into 3.5-5 kHz, 5-8 kHz, and 8-12 kHz.  Start at the 3.5 to 5 kHz range for adding that sparkle to the acoustic guitar.  If you want more, jump to the next range and boost a little there. 

These are all plots of signal power vs. frequency (ranging from 20-20,000 Hz) (i.e., they show the relative strengths of different frequencies in each overall track). Before my EQ is plotted blue, and after EQ is plotted red:

 

[Ferryman]

The other thing to bear in mind is also how the different instruments and EQ interact in the mix, because you can get "mud" building up across the spectrum if there is too much going on in the same space. I use a plugin called Tonal Balance Control from Izotope which I find very helpful to look at the overall mix. The fancy version lets you compare the EQ balance of your mix against different musical genres. All done with AI and clever stuff like that. 

[des0free]

The other thing to bear in mind is also how the different instruments and EQ interact in the mix, because you can get "mud" building up across the spectrum if there is too much going on in the same space. I use a plugin called Tonal Balance Control from Izotope which I find very helpful to look at the overall mix. The fancy version lets you compare the EQ balance of your mix against different musical genres. All done with AI and clever stuff like that.

Thanks for making me aware of that.  I should be able to do something similar with my home brew software, as I have thought of that too, but maybe I should look into trying that software too.

[AndyR]

Interesting. I don't yet have the experience to relate the graphs to what it sounds like... starting to get some sort of feel, though.

For years I've been going by a set of recommendations gathered from various places to tweak things until it "sounds better" (and the day after I make my changes, discovering that, actually, it's not better after all!)

But I've just been learning over the weekend about using a Multiband Compressor plugin, not to compress, but to LISTEN to the balance of frequencies and to the changes that EQ tweaks make.

If you have a Multiband Compressor plugin, and your plugin allows Mute/Solo of bands, it's perfect for this:

1. Apply the plugin to the source you want to check (a track, a submix, the main out)
2. Set up bands for the frequency ranges you want to listen to
3. DO NOT apply any compression to any of the bands (Off or Ratio 1:1 on each)
4. Solo the bands to listen to the material - it's a revelation!
5. Tweak other stuff (mix levels, eq or compression on individual parts, reverb, whatever)
6. Solo the bands again to hear the effect the changes have had on material

It's helping me understand why certain changes "work" - which, for my sort of personality, is VERY useful to speed things up and make them less "trial and error".

[guitarron]

Interesting. I don't yet have the experience to relate the graphs to what it sounds like... starting to get some sort of feel, though.

For years I've been going by a set of recommendations gathered from various places to tweak things until it "sounds better" (and the day after I make my changes, discovering that, actually, it's not better after all!)

But I've just been learning over the weekend about using a Multiband Compressor plugin, not to compress, but to LISTEN to the balance of frequencies and to the changes that EQ tweaks make.

If you have a Multiband Compressor plugin, and your plugin allows Mute/Solo of bands, it's perfect for this:

1. Apply the plugin to the source you want to check (a track, a submix, the main out)
2. Set up bands for the frequency ranges you want to listen to
3. DO NOT apply any compression to any of the bands (Off or Ratio 1:1 on each)
4. Solo the bands to listen to the material - it's a revelation!
5. Tweak other stuff (mix levels, eq or compression on individual parts, reverb, whatever)
6. Solo the bands again to hear the effect the changes have had on material

It's helping me understand why certain changes "work" - which, for my sort of personality, is VERY useful to speed things up and make them less "trial and error".

I need to try this multi band compressor trick. This is good thread

[TPB]

I have the spectrum plugin but usually don,t know what I looking at I use the mutiband compressor on the mix buss then tweak and listen this is a good way to bring vocals to the front if they have been buried. I turn the knob past where I think it sounds good then back it down. But then I am half deaf so what sounds good to me could be crap LOL
Tim