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Reference 4 Studio Edition Review at ProTools

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I have to admit, when I was first asked to review the Sonarworks Reference 4 calibration system, I was sceptical. The intended function of this software/hardware package is to calibrate your imperfect monitors to your imperfect acoustic environment. It generates an EQ curve to compensate that you use to mix into on your stereo bus within your DAW. The idea is to ensure you are monitoring in as neutral a context as possible. So what’s not like? It sounds like a great idea!

Although I was initially sceptical, I realize now because I was fighting my own preconceived notions about mixing and monitoring. No monitors are perfectly flat, and no room is acoustically perfect. You “learn” to work in your environment and that’s that. You learn to compensate through trial and error and experience until your mixes sound good. Period. Well, not so much. You’ll have to read through to the end of the review to see how my prejudices have been modified through the experience of using this system. 

So, What Exactly is Sonarworks All About?

First of all, Sonarworks Reference 4 comes in two flavours. The Studio Edition, which is what I used for this review, is designed to work on headphones and speakers. The less expensive Headphone Edition is a modified version, set up to work with headphones only. They also offer a premium bundle that includes pre-calibrated headphones with the Studio Edition.

There are four components to this calibration system. The first is the Reference 4 Measure app that resides in the Application folder. This is what you will use to run the calibration routine to “measure” your speakers and their relationship to your room. Once it is done you will save this profile and load it into the second component of this system, the Reference 4 Plug-in. This is a standard plug-in, designed to be used at the last insert slot in your mixing signal flow; presumably the stereo bus within your DAW.

The third component is the actual mic itself, the omnidirectional XREF 20 measurement microphone that ships with the Studio Edition package. Each mic has a unique serial number that you will input into the downloads section of the Sonarworks web site. You are then provided with a custom profile for your specific mic that is used by the measurement Measure app when performing its acoustic measurements. The final component is a stand-alone application called Reference 4 Systemwide. Here you can load either your speaker or headphone profile so that all the sound running through your system audio is run through the calibration curve.

The Sonarworks reference system uses several advanced technologies to measure and calibrate your speakers; including the Automatic MicrophonePositioning System (AMPS) and Perceived Acoustic Power Frequency Response (PAPFR). There are a few more complex names and acronyms involved. But let’s skip that and look at how this system actually works!

Reference 4 Measurement in Action

Happily, Sonarworks holds your hand throughout the calibration routine with very clear on-screen instructions. First is to make sure the corrections are correct and there is no direct monitoring in place. Which is a very useful warning for someone using a UA Apollo setup like I am! If you haven’t already, you are then prompted to download and choose your XREF 20 microphone’s unique calibration profile. After a few more audio interface setup prompts, the measurements begin. The on-screen graphics help you position the microphone to the necessary positions in relation to your speakers and physical setup. Finally, a profile is generated for you to save and use with the DAW plug-in and/or Systemwide app. Watch the video a the top of the story to see how I set up my system.

Mixing With the Reference Plug-in

Cards on the table here, it is a bit surprising to hear how different your speakers sound once you have the Reference plug-in set up on your stereo bus with your new custom profile in place. The EQ curve generated by the calibration process looked drastic to me. Could my room actually be this “bad”? I was assured by Sonarworks that this was not an untypical curve. Clearly, the positioning and acoustics in my room are affecting one speaker more dramatically than the other; at least down in the 150 cycle range. I’ll admit, I was reluctant and hesitant. I am used to trusting my ears with my setup in my particular room with my specific speakers.

I did an interesting experiment. I took a mix I did a month ago and remixed it with the Sonarworks plug-in in place on the stereo bus. It was a very revealing experience. At first, I was startled that the level was so much quieter. I quickly learned this was a result of the default clipping protection that was enabled to compensate for the relatively dramatic curves needed to calibrate my set up. This was easily defeated by disabling the function and moving the output fader back up to unity output level. I used the same EQ plug-ins as in the original mix. But I found myself reaching for and adjusting bands that I don’t normally go to. I have to admit that when I played back the final bounced version through my system on my IK Multimedia iLoud Micro Monitors, the new mix sounded really good! The moral of the story, for me at least, was to fight through your initial comfort zone being invaded and take the leap of faith. This system actually does work!


Despite my initial apprehension, I can honestly say that I do believe almost everyone can benefit from using the Sonarworks speaker and headphone calibration system. For inexperienced users, you will start off on the right foot; mixing to as neutral sounding speakers, or headphones, as possible. For experienced engineers who work on the road or in different studios, this is an invaluable tool. Simply run the Reference Measure app in your new environment and use the plug-in on your master bus. You will be able to rest easy, knowing that you are mixing in a consistently calibrated environment, despite the room or the monitors being different. For experienced home studio engineers, and I include myself in this category, the benefits are also absolutely worth it. Although we will have the hardest time taking the leap. It does require a bit of getting used to. But after a short time mixing with the reference plug-in in place, I forgot about it and didn’t notice it; and just went on mixing as I normally do. The proof is in the pudding, as they say when you playback your mixes on other systems and hear how much more accurately they translate. There is a free trial available at the Sonarworks web site. If you have an hour or two to spare setting it up and mixing with it for a while, you will see and hear the benefits for yourself quickly enough!

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