Recalling hybrid mixes is much quicker if you never have to adjust parameters on your hardware outboard.
Mixing gets so much easier when your processing chains are configured to deliver the same results in response to the same levels!
Gain staging and reference levels have been hot topics in audio for years. But there’s another, closely related and very important subject that I think gets overlooked: calibration.
At some point, and long before I used hardware gear myself, I understood that it makes sense to use a test tone when you want to recall an analogue mix or just to ensure that the output of an analogue device is the same as it was yesterday (believe me, that’s not a given). But the idea that calibration using tones can actually be a creative tool itself didn’t occur to me until I dove into Michael Brauer’s ‘Brauerize’ technique about six years ago. Vance Powell has likewise shared valuable workflow lessons concerning calibration.
What’s more, calibration is equally beneficial when working 100 percent in the box. There’s a reason why Brauer and his assistant went the extra mile to reproduce the analogue Brauerize calibration settings as closely as possible when he went all‑digital.
Calibration can do many things for you that are all very helpful. These are the most important ones:
- It will establish a familiar level structure that’s the same for every mix.
- As a consequence, your mixes will be very consistent level‑wise.
- It removes a lot of technical fiddling from the mix process so you can focus on creativity.
Let me give you a practical example from the studio I work in regularly. There’s lots of outboard in the racks, all hooked up to the converters and set up as hardware inserts in the DAW. Because different people use the studio to mix, I proposed establishing a fixed calibration so recalls are super easy. First, compressor parameters such as attack, release and ratio were set so as to give a great sound as a starting point — and no‑one has since felt the need to change anything. Our reference level is ‑18dBFS for +4dBU, meaning a test tone at ‑18dBFS within the DAW measures 0VU on an analogue meter. So I sent a ‑18dBFS test tone from the DAW and calibrated every compressor so that this tone generated 3dB of gain reduction, with 3dB make‑up gain applied on the output, so that they all return a ‑18dBFS signal back to the DAW. This means that when fed with a signal conforming to the gain staging and level structure we tend to work with, they give a predictable amount of compression while maintaining a consistent level. This plays nicely with the way hardware inserts work in most DAWs: if you want more or less compression, you can simply send more or less signal from the DAW, meaning that as long as no‑one changes the parameters on the hardware compressor, saving and loading a DAW session is enough to fully recall the mix.
All these calibrated devices can also give you valuable information when your gain staging is off. If a lightly picked acoustic guitar yields 6dB of compression right off the bat, it’s an indicator that it may be unusually loud. Of course that may be exactly what you want, but it’s useful to have that warning.
Going Soft
Calibration is equally useful if you mix entirely in the box. I suggest taking your favourite compressor plug‑ins and making presets that do exactly what I described above. Create a tone at your reference level, be it ‑18, ‑20, ‑16 dBFS or whatever you use, adjust the compressor parameters to a setting you typically use or start with, set the threshold to deliver 3dB of compression (or 1dB if you prefer) and the output level to maintain unity gain. You can even save this as the default preset if you wish.
Why would I adjust the compressor’s threshold every time to suit the mix, when I can make the mix suit the threshold?
Where I find calibration even more important is on buses, because then you essentially mix ‘into them’. For instance, in my personal hybrid home studio setup, I have all my multi‑bus compressors calibrated to give the desired amount of compression and maintaining unity gain with a ‑18dBFS stereo tone. My final master bus compressor then is calibrated to give 1dB of gain reduction with a ‑14dBFS tone and unity gain. This works super well when using a ‑18dBFS reference, since all those signals add up at the master bus. I have the compressor on from the beginning, and when I hit it too hard, I know the mix is too loud. Why would I adjust the compressor’s threshold every time to suit the mix, when I can make the mix suit the threshold?
You can even calibrate your EQs. Let’s say you use some kind of Pultec on the master bus, which is very popular. If you want a familiar starting point, set the tone at your preferred master bus level (as stated, that’s ‑14dBFS in my case, meaning 4dB over my reference), switch the tone frequency to 100Hz and note the level your DAW meter is showing. Now turn up the low frequency of your choice on the Pultec to add 1dB of level. Switch the frequency on the tone to 10 or 12 kHz and turn up the EQ’s high frequency of your choice to add 1dB of level, too. (You’ll realise those increments on a Pultec are not accurately labelled in dB!)
But it doesn’t stop there. A beautiful way of calibrating your parallel processing chains is to follow Vance Powell’s method. Instantiate a test tone of your reference level on an audio track and route it to the master. Now also send it at unity gain to your parallel chains one at a time and set the latter’s return faders so the level on your master bus goes up by 1dB. Depending on the nature of the parallel chain, test tone frequencies other than 1kHz may work best; Vance Powell likes to use 400Hz because he feels that’s more “in the music” than the standard 1kHz tone. For parallel bass or kick drum processing, 100Hz may be the way to go.
I find this method to be a great starting point for all kinds of parallel processing, but feel free to adjust it to your needs. Oh, and of course it would be good practice to calibrate the parallel chain itself beforehand. If you want your parallel drum compressor to give about 6dB of compression, use your reference tone to set it up. In case you use a tried and true setting on a parallel that just works, leave it be. Since we are adjusting the fader anyway, unity gain is less important within a parallel chain.
Speed Boost
After years of using and fine‑tuning my calibrated mixing setup I have got it to a point where just by routing and sending the tracks to the buses and parallel chains in my template, everything falls into place immediately. I start by finding my initial balance, just using the faders and pan controls, with all tracks routed to the final stereo bus and the final master bus compressor engaged so I get a feeling of how loud the mix can and should be. By now I know exactly where the drums should be level‑wise, so I typically start with those and adjust everything else accordingly. When I’m happy with the balance and the response of the master bus compressor, I export this state as a reference and then route and send everything to the calibrated multi‑buses and parallels. Depending on the track count, this takes two minutes at max, and when I hit Play and compare against the reference state, everything immediately sounds 80 percent more like a record: more glue, more punch, more excitement, just like that. If later in the mix I should feel I’d better back down, I have a master VCA in place to turn down all tracks whilst maintaining their relative balance. This way, I can easily adjust how hard I want the whole mix to ‘push’ into the setup. Sometimes I end up where I was, sometimes I end up as much as 3dB lower; this is just about listening and knowing when I’ve hit the setup’s sweet spot.
Some final words: this should only serve as an appetiser in case you haven’t yet made use of this powerful tool, or a reminder of how beneficial it can be for your workflow in so many different places. In any case, make sure you find a calibration that works for you and you alone, and stick to it. If, after doing a couple of mixes, you feel the same things don’t really fit, adjust accordingly. Once you’ve found your own calibration, you’ll be able mix with confidence and speed. Who wouldn’t want that?
How To Calibrate A Plug‑in Compressor
First, mute your speakers! You need a plug‑in generating a sine‑wave test tone at your chosen frequency and level. Every DAW should have one, and if yours doesn’t, there are free plug‑ins out there. For general calibration, I recommend the standard 1kHz sine wave. You could use your DAW’s meters, but I recommend using a VU meter, which many DAWs also have on board. This has the advantage that your DAW’s pan law will not affect the metering. There’s free VU meters, or Klanghelm’s affordable and excellent VUMT. Now create a mono and a stereo track in your DAW, insert the test tone generator in the first slot of each and set it to sine wave, 1kHz and your chosen reference level. As said, I’m using the popular standard of ‑18dBFS. Now insert the VU meter on the third slot and verify it reads 0VU. If not, check the VU’s internal calibration.
Calibrating a UAD 1176LN compressor plug‑in in Cubase. The compressor is instantiated in the second insert slot in the channel, between a tone generator and a VU meter.
Now insert the compressor to be calibrated in the second slot (use a mono instance on the mono track, stereo on the stereo track) and set parameters such as ratio, attack and release to your most‑used settings. Then, depending on the topology, adjust the threshold, input or peak reduction control until the compressor shows you the desired amount of gain reduction (I recommend no more than 3dB). Now adjust the output or make‑up gain until your VU meter reads 0VU again. Save either as default or as a preset. You can also save presets for 1, 2 and 3 dB of gain reduction, or presets using different ratios. Usually, the lower the ratio, the more gain reduction you can start with.
Calibration In The Real World
The author’s calibrated hybrid mixing setup.
To illustrate the points made in the main text, it might be helpful to provide a quick rundown of my own hybrid setup and how it’s calibrated. Here’s how the most important parts are set up to work together, based on a calibration level of ‑18dBFS=0VU. My two stereo main multi‑buses are calibrated as follows:
- Rhythm (drums, bass, percussion): 3dB of compression, unity gain, plus EQ boosting lows, mids and highs each 1dB with appropriate test tones, combined output +1dB.
- Instruments and effects: 1dB of compression, unity gain, no EQ.
My mono vocal buses are each calibrated to give 5dB of compression at unity gain (though I typically start the mix with the send lowered to give between 1 and 3 dB and leave room to push). My main parallel buses are calibrated as follows:
- Rhythm parallel: 5dB of compression, unity gain, fader set to add 1dB of level to the mix.
- Instruments and vocal parallel: 3dB of compression, unity gain, fader set to add 1dB of level to the mix (since so many signals are sent to this parallel, it usually compresses between 4 and 6 dB in practice).
My whole master bus chain is calibrated to ‑14dBFS=0VU (4dB over reference) and set up as follows:
- SSL Fusion: drive set to my liking, output compensated for unity gain.
- Insert (pre‑EQ): SSL XR626 compressor set to give 1dB of gain reduction, unity gain.
- 1.5dB boost at 50Hz and 1dB boost at 12kHz, measured with corresponding frequencies on the tone generator.
- HF compressor set to bring the 1dB of high boost back to unity with the 12kHz test tone.
- Stereo image to my liking, transformer on.
- Output further adjusted for unity gain with the whole chain.
Parallel Sends: Unity Or Bottom‑up?
Generally, there’s two approaches for using sends: you can either start way down and raise the sends until you hear the desired effect, or you can leave the sends at unity gain and only adjust the return levels.
Both approaches work with pre‑ and post‑fader sends, and if you use the second approach with post‑fader sends, what you get is an exact copy of your fader balance. This approach works really well for parallel processing that is shared across many tracks, Andrew Scheps’ infamous ‘rear bus’ being a prime example. This also makes calibrating those parallels rather easy when using Vance Powell’s method mentioned in the article.
Keep your speakers muted! Set up your first parallel chain and send to it from a tone generator track at unity gain. Pull the parallel chain’s return fader down. This time, insert the VU on the master bus. With your active tone generator track routed to the master bus, it should read 0VU for a stereo tone or a lower value for a mono tone, depending on your pan law (most likely ‑3dB). Now raise your parallel’s return fader until the VU on the master bus has gone up by 1dB. Repeat this process one at a time for every parallel. Note the fader values in the template for later reference. This way, you make sure your most important parallel processing all starts adding the same level to the mix. I do ride my two main parallel buses on almost every mix, but I always start at the default values just because it works so well and the overall mix balance isn’t changed. Feel free to experiment with adding different gain values and find out what works best for you.
Speaker Calibration
As well as gain staging, the word ‘calibration’ is often used in association with studio monitoring. Many people consider it good practice to have a monitoring setup that is configured to give a fixed sound pressure level in response to a known input level. Like calibrating your processing chains, this can make it easy to hear straight away whether things are too loud, too quiet, too bright or too dark. But calibration can also mean using a tool like Sonarworks Reference, Trinnov or Genelec GLM to correct the frequency response of your speakers — and in an immersive setup, it also involves time‑aligning the many speakers to optimise time of arrival at the listening point.
For more detail on calibrating monitor levels for mixing, read Hugh Robjohns’ article from SOS May 2014: www.soundonsound.com/techniques/establishing-project-studio-reference-monitoring-levels