In part I of “Prepping a Session to Mix,” we discussed my template mixing session layout in Pro Tools, how I organize and prepare individual tracks for mixing, and how important it is to have a starting point for mixing so the process is as streamlined and straightforward as possible. Now that we have the mixing session set up properly, we can move on to part II of the pre-mix process: calibrating the mixing system and outboard gear, as well as preparing a second Pro Tools session on our designated mix computer where the final mixes will be recorded.

Calibration and documentation are two essential elements when utilizing outboard gear in the mixing process. I’m able to calibrate my analog mixing signal chain to an accuracy of 1/100th of a dB, which is critical for creating a perfectly balanced mix and for recalling a mix later down the road. Documentation is equally important in recalling mixes, so I make sure that any changes to standard calibration, as well as all use of outboard processing, are noted. To get a handle on how I calibrate my mixing system, I’ll begin by briefly recapping my signal chain from my original Pro Tools session to a second Pro Tools session on my designated mix computer.

I use 32 D/A outs from PT, 1-16 through an Apogee DA-16X and 17-32 through an AVID HD I/O, that go to 2 Roll Music RMS216 Folcrom Passive Summing Devices where the 32 channels get summed down to two channels and go through a pair of JCF Audio LEVR’s (they are summing amplifiers Josh Florian designed and incorrectly spelled as did the Folcroms were misspelled) as a gain stage for the level reduction created by the passive summing device, then the stereo signal goes to my JCF Audio (Josh Florian) Latte 2-channel A/D D/A converter which is AES out to yet another Avid HD/IO, where the audio gets converted back to digital and recorded to a separate PT session at 192kHz and 32-bit float on my mix computer.

Throughout this signal chain, there are two stages that need to be calibrated: the pair of JCF Audio LEVR’s and the JCF Latte. I check the calibration by sending a 1kHz sine wave at -18dB out channels 1 and 2 of Pro Tools on my original computer, which goes through the Folcroms and then the LEVR’s. I read the output of the LEVR’s with my Fluke multi-meter (Fluke 189 • True RMS Multimeter) set to the DB scale and make sure the level is set to +4dB. I also make sure my analog VU meters read this signal as exactly 0dB. For calibrating the Latte, I send the same 1kHz sine wave at -18dB out of PT on my mix computer and check the output of the D/A on the Latte to make sure it is also +4dB.

Calibration also allows me to customize my various compressors for individual instruments. For instance, one of my API 525 compressors is set up for lead vocal, another 525 is set for acoustic guitar, my Universal Audio 1176 is set for electric guitar, and so on. This way, when I patch the lead vocal into my vocal-designated 525, there’s a 95% chance that it’s hitting the compressor just the way I like. If I need to make any adjustments, I make sure to document them after the final mixes have been recorded so that I can recall the mix perfectly if need be. All of my documentation is done in “Teaboy.”

Compressor calibration process is a useful skill for any engineer utilizing outboard compression. Buttons, switches, and detented knobs on outboard gear are easily documented, but when it comes to recalling the settings on a compressor with continuously variable knobs, it’s a bit trickier. Here’s a brief description of how I calibrate the input and output levels on an API 525.

I begin by putting the ceiling at 10 (I’ve found 10 gives a good healthy signal and it’s important to use the same setting every time) and all other settings where I normally use them, compression mode (2:1) and release time set at its fastest (0.1 sec). Then, I send a 1kHz sine wave at -18dB to the compressor, set the output knob to max, and read the output level of the compressor with a Fluke multi-meter set to the DB scale. This gives me a value that represents the level of the input knob, since the output is maxed out and serves as a constant. I adjust the input knob until it matches my designated input calibration level and now the input knob is set. Next, I begin to lower the output knob until the combined level of the input and output knobs match my designated combined calibration level.

If you need to document the input and output knob levels, perhaps because the settings were changed at some point, then the process is reversed. First, you’d notate the combined level and then max out the output knob to get a reading on the input level.

At this point, all calibration is complete. My analog mixing system is dialed in, my customized compressor settings are in place, all of my EQs are zeroed out, and my main VU meters are calibrated to zero. Now it’s time to set up the session on my mix computer.

I create a blank session at 192kHz and 32-bit float and create a stereo auxiliary input track with a set of Dorrough meters on it and a stereo audio track where the final mixes will be recorded. Then, I make sure to set the tempo, meter, and grid resolution to the same settings as the session from which I’m recording. I also make sure in the “Session Setup Window” that the Start Time is: 01:00:00:00 and the Pan Depth is: -2.5 and the sample rate is 192 and the Bit Depth is 32 Bit Float. To link my main Pro Tools computer to the mix computer, I connect the two as satellites via Ethernet cable. WiFi capability needs to be disabled and Ethernet enabled on the mix computer in order for this to work. Once the two are connected as satellites, I check to make sure that they are synced together properly. To do this, I click on different memory locations on the original computer to make sure that the bar/beat locations match up perfectly. When all of this has been checked, I set up the version playlists that I will be making of the variations of the mixes. Over the years, I have come to realize that 7 versions are necessary, and they are as follows:

T1 – Final Mix: full track with all vocals and instruments T2 – Lead Vocal + 0.5dB: final mix with lead vocal up 0.5dB T2b - Lead Vocal - 0.5dB: final mix with lead vocal down 0.5dB T3 – Lead Vocal A Cappella T4 – Background Vocals & Harmonies A Cappella T5 – TV Track: full track with BGVs but no lead vocal T6 – Instrumental: no vocals or BGVs

On Mixs T1 T2 & T2B I use the Volume Trim mode to adjust the level + or – ½ db and that way it still follows the automation rides.

Once these are in place, I switch back to playlist T1, set the stereo audio track to input monitoring, and monitor from mix computer.