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Audacity pt 2 EQ & Compression

Pete Thomas

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In part 2 we get a little more adventurous. The download is currently the same tutorial file as part 1.

Caveat: We have already discussed the difference between computer or home stereo speakers and studio monitors. Before you get into these slightly more advanced aspects of mixing, you must be confident that your speakers are giving you a reasonably accurate picture of the sound of your mix. If not, then you may well be enhancing what you hear while you mix, but actually making it worse on other systems.

It may not just be the speakers that are an issue, it could be that the actual room you are mixing in is accentuating certain frequencies. Recording studios spend thousands on acoustic treatment. This is not just soundproofing but also to make the room a better mixing environment.

See Home Studio Acoustic Treatment

To get round this problem, the best you can do is experiment by trial and error. Learn the idiosyncrasies of your system and room. Add some EQ and/or compression, then listen to the results on as many different systems as you can to see if it still improves your music in the way you originally heard.

If in doubt, don't use EQ or compression.

The method

In part 1 we mentioned two methods by which we can apply effects. With the reverb tutorial we made a duplicate track that was 100% wet, and created a new track mixing the original dry track with the wet track to get the desired level of effect.

This time we still duplicate the track but apply the effect to the duplicate and use that in the mix (we mute the original and keep it as a safety).

We are doing it this way partly to show you another way of working, partly due to the limitations of Audacity, and partly because it makes more sense if you do choose to use EQ or compression along with reverb, to add the reverb after the EQ/compression, see below: Combining Effects). Again, it is actually easier in other more advanced software.

Note that if your backing track is a commercial track, or else from BIAB or iReal Pro, there is a good chance that there is little to gain from adding EQ or compression, so we will mainly concentrate on your saxophone track at this stage,


Using EQ in Your Mix

"We can fix it in the mix" is frequently a myth. Any sound engineer will tell you it is far better to get things as good as they can be right at the start of the process. So when it comes to the actual tone of your saxophone, you should experiment when recording so that you have the best sound to work with. Get the best microphone and other recording equipment you can, and experiment with the position of the mic to get the best sound, or else when you come to the mix you may be attempting to polish a turd. Not impossible, but Audacity is not the ideal tool for such a job.

So assuming you are happy with the recording, let's do some EQ. I am not going to advise on a specific EQ, as this is subjective. (Again, if in doubt, don't)

  • Duplicate the track
  • Mute the original for safety
  • Name the new track (e.g. Sax EQ)
  • Select the track Sax EQ
  • Go to MENU: Effects >Equalisation. (Note there is no All Wet button as EQ is always applied 100%)

NB: Instead of presets you can choose from the "curves"

  • Choose a curve, (e.g. treble boost or treble cut) or play with the parameters yourself.
  • Click preview to listen to it. (You can select a specific part of the track before doing this)
  • Redo this until you're happy with the sound of the EQ.
  • When you are happy that you have improved your track click OK
Tip: If you edit a curve you can save it under Save/manage Curves with a unique name

At this stage it is a good idea to export your audio to a wav or mp3 file, and if possible listen on different devices.

Once you are convinced that this is an improvement, you can now go ahead and finish your mix by adding room and reverb to this new EQ'd track using the method we used in part 1. Alternatively if you are feeling adventurous you can now apply some compression first.

Compression

Why?


Good question. Compression can be your friend or foe. Very basically it reduces the dynamic range. You have probably heard people say compression is bad, however it is used on nearly all commercial recordings and is particularly important for listening in less than perfect situations. Imagine an extremely dynamic piece of classical music playing in a car. Without compression you would find a comfortable listening level for a loud section, but a very quiet section would then be inaudible under the noise of the car.

Very simply, when a track is compressed, the louder "peaks" of the audio are reduced, while the quieter sections remain the same. This means we can then raise the overall level. Although the peaks (which were reduced) won't necessarily be any louder than they were before, the quiet bits will be. The result is that the average level is louder.


However when overdone, compression can make music sound lifeless and in some cases very tiring on the ears. Lately there has been a lot of controversy regarding some record labels wanting their music louder then everyone else's.

Loudness war - Wikipedia, the free encyclopedia

In the accompanying tutorial file, the saxophone track is quite dynamic and could benefit from some compression. This means that it will actually be easier to find a comfortable level so that you can hear the quiet bits above the backing, but without the loud bits taking over.

How?

There are several parameters, but the main ones at this stage are threshold and ratio.

Threshold: Audio signal lower than the threshold will not be affected. Any audio above the threshold is reduced.
Ratio: This is the amount by which it will be reduced, and is expressed as a ratio, e.g. 2:1, 10:1, etc

In the example below we can see some obvious peaks in the level of the audio. Here the threshold is set to lower those peaks. The audio lower than the threshold is not affected. Using a 3:1 ratio, the peaks are reduced.


Example:




Measuring loudness

Loudness is measure in decibels (dB). With digital audio one confusing thing is that the loudest a signal can be is 0dB, so lower levels are expressed as a negative figure (down to -∞)

NB: Compression will only be applied if there is audio above the threshold, so if your audio signal peaks at -5dB and you apply a threshold at - 5dB, then nothing will happen.

How much compression?

How much compression is applied can be thought of as the amount (in dB) by which the loudness has been reduced.

It is always best to use your ears to judge the optimum amount of compression, and for this trial and error is a good way to start. However you may want to understand a few of the more mathematical aspects which can help you understand what you are hearing. (If not ignore this section)

Because we use these two parameters of threshold and ratio, we can get the same amount of compression in two different ways.

Here are a couple of examples:

NB: for the sake of clarity we shall assume the audio peaks at 0dB, however this won't necessarily be the case.

1. If you apply a threshold of -9dB and a ratio of 3:1, then there is 9 dB of audio to be compressed. It will be reduced to one third, ie there is now 3dB of audio above the -9dB threshold so the audio will now peak at -6dB. (9 - 3 = 6)

2. If you apply a threshold of -12dB and a ratio of 2:1, then there is 12 dB of audio to be compressed. It will be reduced to one half, ie there is now 6dB of audio above the -12dB threshold so the audio will now peak at -6dB. (12 - 6 = 6)


Although the amount of compression is the same, the end result will sound different. This may be easier to understand if you compare the waveforms:


Threshold -9dB
Ratio 3:1



Threshold -12dB
Ratio 2:1



The lower the threshold, and the higher the ratio, then the more actual compression is applied.

Threshold -12dB
Ratio 4:1



Adding Compression to your saxophone

(You can try this with the demo track to hear how the effect works)

  • Duplicate the saxophone track
  • Mute the original
  • Rename the duplicate (e.g Alto comp)
  • Select the track Alto Comp
  • Go to MENU: Effects > Compression
  • Apply Threshold = 20dB, Ratio = 5 dB
You should see that the wave form has changed considerably. You can now increase the gain of the track in the CP. (Alternatively when compressing if you tick Make up Gain for 0dB then the compressor will automatically increase the actual level of the clip to maximum. In this case you will want to reduce the track gain when mixing


Combining Effects

Of course you can combine the two, and either EQ first then compress, or compress first then EQ. The results may sound different, but both ways are valid, and it is worth experimenting.

When combining don't forget to duplicate and rename as you go along.

Example Workflow for combination of effects.:

  • Duplicate the track
  • Mute the original
  • Name the track (e.g. Sax EQ)
  • Add the EQ to duplicate track
  • Duplicate the new EQ'd track ready for compression
  • Mute Sax EQ
  • Rename the duplicate (e.g. Sax EQ comp)
  • Compress Sax EQ Comp

You now have:

  1. The original track (muted)
  2. EQ'd track (muted)
  3. EQ'd and compressed track

Now we get even more adventurous and add reverb using the method we learned in part 1

  • Duplicate Sax EQ Comp (don't mute it)
  • Rename to sax EQ Comp Rev
  • Add reverb to this track (Remember to tick Wet Only for 100% reverb)
  • Now balance the level between the two tracks as before.

Adding Compression to the Final Mix

This is one of the things that mastering engineers do to enhance a final mix.

As Audacity does not allow you to add an effect to the mixed outputs, we are going to export our mix to an audio file, then import it into a new Audacity project.

In this situation we are going to use compression to make the track sound louder, even though the peaks of the audio will not be any higher. (They cannot exceed 0dB). As you know , compression lowers the volume, so after compressing we raise the level of track to its maximum. This is done automatically in the compressor when you tick Make Up Gain.


  • Export the audio as usual, but choose the format WAV 32 bit float. (this is the best format to retain maximum quality when re-importing to Audacity). Normally an audio export would be 16 bit (for CD) or mp3 (for streaming)
  • Import into a new Audacity project
  • Guess what? Yes, duplicate and rename the track
  • Mute the original
  • Add Compression to taste
  • Use the Make Up Gain option in the compressor.
  • Compare to the original, it should sound louder but not over-compressed.
  • Export as normal wav or mp3. (For mp3 I like to drop the level on the track by 1 or 2 dB for better sounding mp3 conversion
You can also experiment by unmuting the original and balancing the compressed and uncompressed versions. (This is called parallel compression). Make sure the output meters are not going into the red.

One final thing to make your track sound better

Please remove Jamie Aebersold saying "One, two, a-one, two, three, four"

To do this:

  • Select the count in on the track/s
  • MENU: Edit > delete
 
Last edited:

jbtsax

Well-Known Member
Subscriber
Messages
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I have finally gotten enough experience with BiaB and Audacity to feel somewhat comfortable making recordings of my playing along with backing tracks. Now I am at the stage where I want to learn more and get the most out of the equipment and software I have. The old saying, "when the student is ready, the teacher will appear" applies in this case. I discovered (re-discovered?) the treasure trove of information about recording, mixing, and equipment and it is exactly what I need at the present time.

I just want to thank Pete for all of the time and effort he has put into these tutorials on recording and mixing and every other aspect of saxophone playing. The longer I hang around the Cafe the deeper my understanding of the depth of Pete's talent, knowledge, professional skills, and musical ability becomes. On top of that he is a great guy (chap?) to so freely share all of this with us. As my best friend who is also a professional musician would say, "He's the real deal". Thanks Pete for all you do.
 
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