Subtractive EQ - An alternative to gating?

[Mark WarnerParticipant]

I was thinking I hadn't posted anything in the Reaper area for a while and wondering what I could perhaps contribute to help other Reaper users (and other DAW users) when I realised that there was something I used a lot and took for granted that everyone would already know about it, but maybe if your new to Reaper, mixing or digital tools then perhaps this is new to you.

What is Subtractive EQ? - It is the ability to analyse a sound source and remove elements from it.

What is it best used on? - I use it mostly for sources recorded via microphone that have unwanted background noise. especially vocals. Its very good at naturally removing background noise on quiet tracks as well as loud ones. Unlike a gate, which opens and closes and tends to produce sharp starts and stops and still has unwanted noise behind the vocal, subtractive EQ has no sharp starts stops and removes noise from the whole recording and doesn't just cut the quite parts.

How it's done (in Reaper) - I use the Reaper VST called ReaFIR (FFT EQ+Dynamics Processor) but I am sure other EQ VSTs will also have this functionality. Insert this VST as an FX on the track with your raw vocal. You need to ensure that the vocal contains a few seconds of recorded ambiance, just the room, so don't use a gate when recording otherwise what follows is not possible. However you can record with a low cut filter to take out hum etc as normal.

Now click on the "Mode" drop down menu, top left of the VST and choose "Subtract". Next select/highlight a region of the vocal that has nothing but the ambiance / room sound. Set Reaper to loop this area when played. To the left of the "Mode" menu in the VST is a check box "Automatically build noise profile", check this and press play in the transport controls ensuring that the start postiion is with the looped area. Let it play for a couple of seconds. As it does this you will see a red line building in the VST window. This is the finger print of the noise to be removed. Press stop and now, very important before you do anything else..... uncheck the "Automatically build noise profile" check box. If you hit play again before this you will have to reset and start again.

• This topic was modified 6 years ago by Mark Warner.
• This topic was modified 6 years ago by Mark Warner.
• This topic was modified 6 years ago by Mark Warner.
• This topic was modified 6 years ago by Mark Warner.
• This topic was modified 6 years ago by Mark Warner.

[Mark WarnerParticipant]

I still can't get the missing text into the above post so I am posting it here bekow.
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What you should instantly notice is that the background noise has gone from the looped section and if you unloop and continue to play into the vocal you will find that it has also gone from the vocal as well and it sounds very clean and clear with no gate artifacts.

Things to be aware of - If you try to remove a noise which has a frequency close to one you need, it will effect the quality of the vocal.Try to remove as much as possible before using subtractive EQ by using low cut filters. The less the subtractive EQ has to remove the more natural it will sound.

Below is a screen shot of the VST noise profile applied and before and after clips of my daughter doing a voice-over for film and TV. This was recorded using an sE2200t mic, 1073 pre - 1084 EQ with 160db low cut going through a DBX 560a and an 1176. My studio does not have an isolated sound booth but you would not necessarily know this from the processed recording.

Cheers - Mark

• This reply was modified 6 years ago by Mark Warner. Reason: missing text

[Arthur LabusModerator]

Great tutorial Mark !
ReaFir is, as part of ReaPlugs VST Suite, available for free (VST32/64):
http://www.reaper.fm/reaplugs/

[Pedro Pitta GrozParticipant]

Great Mark! Except for that feature, I never use ReaFir. It seems too powerfull. I've been somehow afraid to dig in it.

[Mark WarnerParticipant]

No worries guys, I will try again to get the rest of the text up as soon as possible. I forgot that it is also available on its own so good call.

I know what you mean about being almost too powerful. I use it for very specific tasks like subtraction. The rest of the time I use ReaEQ for general cuts and boosts. The subtractive thing though is a killer function. I use it so much. As well as vocals, I do a lot of Analogue to Digital master tape transfers for clients. Again it is just brilliant and removing tape hiss and mechanical noise from a tape. 🙂

• This reply was modified 6 years ago by Mark Warner.

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