Someone may be skeptical about headphones equalization, but this is not the case with this powerful software I am going to review now. So, let me introduce you Sonarworks Reference Headphone Calibration – headphones equalization at its finest.
It all started circa 2 years ago when Rudolfs from Sonarworks (very helpful and nice guy btw) posted a thread on Gearslutz telling the world about their startup and software they’ve been working on for quite some time. I’ve always been a GS lurker and as a headphone enthusiast this really caught my attention. That time I remember owning an Superlux HD-681 which was my go-to bargain phone to use at my workplace.
When Sonarworks first released their software, they’ve also supplied some generic / average headphone equalization profiles and Superlux HD-681 was amongst them. Luckily, Sonarworks was looking for people to try their new software.
I’ve contacted them and they've kindly offered me to try their new software with my HD-681 and to my surprise, I remember it made them sound really good. Being impressed with what the software can offer, I’ve definitely started to see the potential of headphones equalization as never before.
Sonarworks for the win!
Purpose Of Headphones Equalization
The question is - why would you want to equalize your headphones? The answer is ridiculously simple - you want to get the best of your headphones. Whether you're an audiophile listener or serious studio guy doing mixing / mastering work (times have changed for the better), it can definitely help, period.
Headphones in their stock form often sound coloured and don't provide ideal, balanced frequency response. Either too bassy, or too bright. Or dull. Equalization can seriously help correct these types of problems.
If I can suggest you headphones for equalization - try to avoid headphones with too much physical transducers distortion. The best candidates are those with lowest possible THD, since equalizing won't raise their distortion numbers too much. Please bear this in mind if you're going to buy some new headphones.
DAC / Headphone Amp Quality
I cannot stress enough that headphones equalization would be less effective if you'd be using poor quality DAC and / or headphone amp. Luckily, there are plenty of awesome DAC / headphone amps out there nowadays, so my recommendation would be to carefully choose your gear in this regard. You have been warned.
DSP Technology Behind
Equalizing headphones using digital signal processing techniques is a science on its own and I won't dig into deeper details how it works. Basically, you need a very high quality measurement head that simulates people's hearing (that's pretty expensive stuff btw) together with a high quality and neutral headphone amp.
Then go measure the headphones and apply a correction EQ curve according to a very carefully chosen compensation curve (this is pure science).
Luckily, Sonarworks seem to have done their homework and developed their own compensation curve that thanksfully works very well for us, studio guys.
Playing With The Software
I will be reviewing the current version, which at the moment is 18.104.22.168, and in the VST plugin form in the Reaper 5.31 DAW, all running under Windows 10 Pro x64. DAC / headphone amp used for my subjective sound evaluation is RME's Babyface Pro. The VST plugin also runs perfectly under JRiver Media Center v21.
I remember Sonarworks guys have been improving their GUI all over the time, and I must say that in its current version, it is very well laid out, looks fresh and is very simple to use. There are informational hints / explanations all over the GUI so you definitely won't get lost.
The main GUI can be divided into following sections - EQ Profile Chooser on the top, Frequency Response Curves with Input / Output level meters with Output trim slider in the middle and finally section for setting target reference curve (Calibrate), simulating other headphones / loudspeakers (Simulate) and for fiddling with the filter phase type (Advanced).
Ultimately, it has a status bar on the bottom with Mono Monitoring function. Oh, and it also has On / Off switch and even Dry / Wet control. Cool. Let's now take a look at every section in more detail:
EQ Profile Chooser
This section lets you choose your headphones calibration profile. It can either be an average profile or individually calibrated one (more on that later). As simple as clicking on the profile name and choosing your preferred profile from Windows Open file dialog.
At the moment of writing this article, Sonarworks kindly provides us with 45+ profiles with every installation of the software. They seem to be improving over the time and perhaps will provide more and more profiles.
Average profiles are precise down to +/- 3.0dB, as stated by Sonarworks. This is because of the headphones production variations - not all headphones of the same brand and model measure equally.
Frequency Response Curves
This section is really cool because it visually shows you what is going on with the equalization. The most important curves shown here are Before, Target, Correction and After.
Before curve shows the frequency response of the measured headphone:
Target curve is the ideal frequency response we want to achieve - for us, studio guys, this should be ruler flat:
Correction curve is the frequency response of the EQ filter that must be applied to the Before curve to reach Target curve:
After curve shows the actual frequency response of Correction curve being applied to the Before curve. Ideally, it should match the Target curve, but due to EQ limit settings (to prevent equalizing headphones too much) and filter phase type, the curve could differ a little bit:
Sonarworks folks also cleverly thought about possible clipping scenarios, because equalization in general usually changes overall output gain of the processed signal.
This is where the Avoid Clipping button / switch comes in very handy. What it basically does is that it reduces the output level of the processed signal with the gain that the equalization curve can possibly introduce. I suggest having this turned on all the time, otherwise you risk clipping.
In this section, you can set your preferred reference curve (the Target Curve in the above section).
Flat doesn't need an explanation. With Custom, you can adjust low and high frequencies (somebody may need this) and interestingly there's also something called B&K 1974 optimal curve.
I've found that the Flat always sounds best to me, no matter the headphone profile. But this all comes to personal preferences, of course.
This is an attempt to try to simulate the sound of some popular headphone models and loudspeakers.
You can choose to simulate the sound of an Sennheiser, AKG, Beats or Grado headphones or even choose to simulate NS10 or Focal loudspeakers.
May come handy for an extra checking how the mix will sound through different transducers. Personally, I would prefer to see more options here.
The quality of the equalization process can be partially affected by used EQ filter type.
Sonarworks offers us 3 types of filters here - Minimal Phase, Mixed Phase and Linear Phase filters.
Linear Phase filter always sounds best to me, but as usual, your mileage may vary.
Dry / Wet, On / Off
You can always turn equalization on / off by clicking the Calibration button. You can instantly hear differences pre / post equalization.
And if the equalization is too much for you, you can always turn the Dry / Wet knob to adjust equalization strength to your tastes.
Status Bar shows you the actual sample rate, plugin's latency and there's also another clever feature for us, studio guys. If you want to hear the processed signal in Mono, just click the Mono Monitoring button / switch.
Activation process is very straightforward and Sonarworks offers two methods - online and offline activation. I can't say anything about offline activation, because I didn't need to activate that way.
Online activation is as easy as it gets - you input your email address and activation key and if everything goes fine, you'll have your software activated.
I only miss some kind of deactivation / reactivation scheme there, because when I've upgraded to Windows 10 this year, it didn't reactivate properly. Fortunately, support guys at Sonarworks always helped me in this regard and rumors are that they plan better activation process in the future versions of the software.
Before revealing the final testament - how the software sounds, let me elaborate a little bit about custom calibration.
I’ve been fortunate enough to also own Sennheiser HD800 for quite some time. I’ve never liked how stock HD800 sounded. Lacking bass, too bright and piercing at times. Otherwise, it has spectacular distortion figures and imaging capabilities. Yes, there are physical mods possible, but I was always afraid of damaging them. Luckily enough, Sonarworks also offers custom headphones calibration services in addition to their software. Interesting, I thought.
Sometime in the middle of 2015, couple of private messages answered with Rudolfs from Sonarworks via Gearslutz, ultimately convincing me to send my HD800 to Sonarworks headquarters in Latvia for custom calibration. I pulled the trigger.
A week later, I received my calibrated HD800. Boy, I have never heard headphones sound this good. I know how neutral and balanced frequency response should sound like, and Sonarworks calibrated HD800 is as good as it gets, period. Pure awesomeness.
For individual calibration, they promise at least +/- 0.9dB precision.
I don't hesitate to say that giving my HD800 for custom calibration at Sonarworks has been one of the best invements I've ever made. Before calibration, I couldn't properly mix / master on HD800 (you've probably heard about the term "guessing game").
After HD800 calibration, I stopped using my primary monitor speakers (it's been 1.5+ years now), because I can 100% rely on the Sonarworks calibrated headphones to get the work done. And it works - it just translates, no more guessing games since the calibration.
So, how does it sound?
To me, Sonarworks linear phase EQ sounds very natural, extremely tight in the bass region and it doesn't seem to smear transients. I attribute this to the correctly implemented filter phase response and extremely low filter THD (measured and verified using VST Plugin Analyser):
Although I can hear slight differences when using Minimal or Mixed phase filter types, the Linear phase just sounds a little bit tighter to me. Your mileage may vary of course.
And calibrated HD800? Buttery smooth and neutral, while still having their precision abilities. Literally, the sound is so effortless that it probably can't be described, must be heard. Absolutely no complaints here.
If you're into equalizing your headphones and aiming for better sound, whether you're audiophile guy or studio professional, I can't recommend Sonarworks enough.
Their software for equalizing headphones simply works and the people "behind the scene" are very nice too - my customer support experience has always been top notch and the guys were always willing to help. I have even sent my HD800 to recalibrate again with fresh earpads - no problems at all.
Thank you Sonarworks for creating such an awesome piece of software!