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Do You Hear What I Hear?

What to listen for when choosing a Mastering Engineer



Picking the right mastering engineer for your music can be a daunting task for even the most seasoned of independent artists and bands. Although methodology and taste can vary greatly from one engineer to another, there are certain technical realities that are universal. Knowing how to listen out for them, will help inform your decision.



How Low Do You Go?


Much of a mastering engineer’s work is done in the sub and low frequencies. These frequencies are the most problematic to monitor properly, most lack the necessary technology and/or listening environment. Because of this, Artists/Mix Engineers will often ‘chase’ the lows; pushing the low-frequency elements such as bass lines and kick drums louder in the mix, in order to ‘feel them’. This has the effect of making the mix ‘bottom heavy’; the mid and high-frequency elements feel squeezed, sat upon a big tablet of low.

In order to check the low-frequency elements in a mix properly, you must crank the volume to around 85 dB SPL*. It is only at this level that humans hear all frequencies as equal. Sound Pressure meters are relatively inexpensive, but you can often purchase an app for your phone that will be perfectly adequate for the job. If possible a high-quality Home Cinema or HiFi setup should provide the best listening environment; but for most music makers, the infamous ‘car test’ still represents the best way to hear subs and low frequencies. Armed with your Sound Pressure Meter, you will now have a much better chance of hearing the low frequencies properly. *85 dB SPL is quite loud, particularly in a small space. It is best to gradually increase the volume to 85 dB SPL and to limit the amount of time you spend listening at that volume to a short number of minutes. If you experience any pain or discomfort, stop listening immediately.

Should the Bass Actually Hump My Face?


The bass and kick should feel tight with a good sense of definition and separation between the two. Sub and low-frequency elements need not be too dynamic. Typically they provide more of a ‘weight’ or sense of ‘pressure’. If too dynamic, the kick and/or bass will ‘bounce’ the mix against the master limiter, causing the mix to ‘wash in and out’. You can usually start to hear this on cymbals and similar. In more extreme cases, the overly dynamic kick and/or bass can cause the mix to distort in time with their bounce (as they drive the mix against the limiter too hard).


It is usually best to have the sub and low frequency in a mix panned straight down the center*. This, in fact, dates back to the days of printing to vinyl; but is also good general practice, as it shares the ‘load’ of the low frequencies evenly across both left and right wires (be them speaker or headphone). It’s important to remind ourselves, all recorded music ends up as electrical current. How well we manage that load will have a direct bearing on playback quality. *In some cases, the artistic vision of a piece of music might call for a ‘hard-panned’ bassline or kick drum. And though creative freedom and self-expression should always be the ultimate decider, be advised that such an arrangement could cause problems if ever trying to print to vinyl.

Because humans begin to hear frequencies below 250 Hz as mono (i.e. we become unable to detect left from right), many mastering engineers will drop their mixes into mono below 250 Hz. Whether this is to be considered good practice or not, largely depends on the type of music you’re making and, more specifically, the nature of your production. It is important to check that a ‘slurring*’ of stereo information is not taking place in the low-mid region (around 250 Hz). *This could be noticeable with, for example, low driving electric guitars or synths that have been panned hard left or right.

Boom! Shake the Room?

A quick shuffle through Spotify’s Global Top 50 will reveal two prevailing schools of thought when it comes to subs. The first is to hi-pass tracks around 20 Hz allowing for a good weight of sub frequency. This sub frequency is tightly controlled for dynamics and provides the mix with a greater sense of depth and height*. *Adding subs to your final chorus (or progressively as your track develops) will make the mix feel ‘taller’. The second approach is to hi-pass around 40 Hz*, leaving a ‘slice’ of sub tucked underneath the kick or bassline (depending on the make-up of the production). The advantage of this second approach is it makes the life of the mastering engineer easier, as that 20 - 40 Hz range takes up a lot of ‘real estate’ in the mix. This allows for more space for the rest of the instrumentation and makes it easier to master to higher volumes. Typically the lows are allowed more dynamic freedom and, in doing so, give the impression of greater weight of low energy in the mix. *There are mastering engineers who will hi-pass at 50 or 60 Hz, making for a quick and easy path to a loud master. This technique is seldom correct for the track and should, more often than not, be considered the act of a lazy technician.

Both of these approaches have their merits and their suitability will depend largely on the type of music you make and, of course, your chosen output media. CDs and streaming media/download have no issues with subs are low as 20 Hz. It is, however, common practice to hi-pass at 40 Hz when mastering to Vinyl (due to the technical limitations of the media).


Ain't No Valley Wide Enough


Width has become a preoccupation for music-makers in the 21st Century. It has become synonymous with that ‘professional sound’ and is often used to judge the skill set of a mastering engineer. In truth, however, with the middle and side processing now included as standard in all DAWs as ‘stock plugins’, offered as stand-alone applications by all plugin manufactures, and, more often than not, included as an extra in most other plugins, creating width in mixes no longer requires any skill whatsoever. Music-makers can now push their productions to rangers of up to 400% and beyond the width of the original material. Unfortunately, in employing m/s processing they also risk ruining the phase consistency of their mixes. This is most noticeable when the mix played back through a mono speaker (for example a phone speaker), where entire musical elements might be seriously diminished or vanish entirely from the mix. M/S processing can also result in a lack of ‘drive’ or ‘body’ in the mix and can, for some listeners, create a sensation akin to motion sickness.

It’s Not What You Do, It’s The Way That You Do It

The measure of a mastering engineer is whether they can create width while, at the same time, maintaining mono compatibility and the drive/body of the mix. This can be achieved by, among other things, understanding how frequency relates to our perception of width (we are most sensitive to left/right at around 12 kHz); how careful use of saturation can increase width (we hear square waves as wider than sine waves); and how frequency relates to phase (m/s processing is less destructive in the higher frequency ranges). A simple rule of thumb applied to m/s processing is that it is best used on ‘ear candy’, ‘ambient’ or ‘fizzy’ effects and elements, such as reverbs, delays, and high-frequency elements. Production elements that are intended to drive or give body to the mix are usually best left without m/s processing. M/S processing is sometimes used by engineers to ‘clean-up’ the mono image of a track. Reducing the amount of ambient (for example), once a track is played back in mono, may actually be desirable. If you are unsure of which techniques a mastering engineer is employing in order to achieve width, it is best to check their work via a mono speaker - i.e. your phone’s speaker. It should also be noted that excessive use of M/S processing will make it impossible to print your record to vinyl.

All The Way to 11?



Long before Spinal Tap (Britain’s Loudest Band), loud was always synonymous with rock ‘n’ roll, but had to contend with the technical limitations of Vinyl. With the advent of CDs loud quickly become to ‘be all and end all’ of mastering. Like width, loudness became the measure of a mastering engineer’s skill set; and, interestingly enough, just as is the case with width, it is, in fact, the manner in which the mastering engineer achieves loudness, that is the measure of their abilities.

Any monkey with a limiter can make something loud. It requires no skill whatsoever.

Simply slamming a mix against a limiter will result in a loud track. Unfortunately, the harder audio hits a limiter, the more it begins to distort; the more the tone of the music begins to sound brittle and harsh; the more high-frequency artifacts* are created; the more we begin to lose low-frequency information; and, of course, the more you lose dynamics. The result is akin to shoving your music up Robocop’s a*se (you wouldn’t even buy it for a dollar). * High-frequency artifacts contribute to downstream clipping which takes place when lossless formats such as WAV are converted to lossy formats such as OGG (all streaming platforms currently employ lossy formats).

Achieving a loud master, while maintaining fidelity, dynamics, and the full spectral range of the production requires no small amount of skill, experience, and patience. And is typically achieved by employing a series of limiters to apply increases in gain in stages, while at the same time engaging other processing to help steadily increase the loudness of the track, throughout the signal chain.

Proof the Pudding

One of the best ways of checking the ‘quality of loudness’ of a mastering engineer’s work is to listen via a low-quality stream. The lower the quality, the more subject to downstream clipping the master will be. This, in turn, will exaggerate any potential technical flaws in the mastering process, making them easier to hear. I strongly suggest checking mastering engineer's work via low bitrate YouTube*. *In the interests of fairness, nothing sounds good at the very lowest rates. It is, therefore, best to compare with your favorite mainstream releases.

Another valuable test of the ‘quality of loudness’ is to simply turn the music down. Gradually turn the music down so you can barely hear it. Now compare it with your favorite mainstream releases. Does it sound as ‘big’, ‘exciting’, and ‘dynamic’ as your favorite releases at low volume?



What Condition Your Condition Is In

As has already been mentioned, comparing the work of potential mastering engineers with that of your favorite releases will give you a good idea of the standard of their work. I’d also suggest including one or two reference tracks by independent artists (working at a similar budget to yourself), so you can realistically compare what is possible at your current level of production. These ‘reference tracks’ should be applied to all of the various elements we covered above. It is only by comparing the work of mastering engineers to music you know well and love, that you’ll be able to make a judgment with any real sense of perspective.



In addition to reference tracks, and has already been touched upon, you should make use of different listening environments to help inform your ears. Listening via earbuds, phone speakers, car stereo, HiFi (or parents’ HiFi ...possibly Grandparent’s HiFi), computer/laptop speakers and TV speakers will all give you a different perspective on the quality of mastering and bring out different elements (both good and bad). All the time making sure to compare with your chosen reference tracks, in order to maintain a clear perspective. Finally listening via the different streaming platforms and, if possible, media will give yet more useful information. Each of the major streaming platforms makes use of a range of lossy formats and has their own standards/methods of application for loudness normalization; a skilled mastering engineer must be able to ensure quality playback on all of them.


This is no easy task and remains a moving target, as the industry and technology continue to evolve at a rapid rate.


It’s Good To Be King


The truth is that one mastering engineer is never going to be right for every project. As I strive to achieve higher and higher standards, I have come to realize that the question of ‘the best mastering engineer’ becomes less relevant the higher you climb; and, in fact, the question of ‘the right mastering engineer’ becomes more pertinent. Once you begin to compare technicians of a particular standard, it is their judgement and taste that is paramount (their technical ability is a given). The tests I’ve outlined in this article are intended to help you separate the ‘time-wasters’ and ‘lazy practitioners’ from serious professionals. Once you have done so, the question becomes which mastering engineer is right for your music.

And that, at the end of the day, is a quesion only you know how to answer.

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