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Mixing & Mastering

So You Think You've Finished Mixing? A Guide to Preparing Your Mix for Mastering

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You know what it feels like to finish a mix. Having spent hours, possibly days, perfecting your track to the nth degree, it feels great to finally have a song to be proud of after all the hard work and effort.

But what if you took your mix just that little bit further. Before the crucial mastering stage, there are some very simple, and often overlooked, practices and techniques which can be applied to your mix in order to make sure your track stands out from the crowd and better yet, your final master is as good as it possibly can be.


Step 1: Check Your Levels

Once you've finished your mix the first place to start is to take a look at the levels on your master bus. (Technically, you should be monitoring this all throughout the mix but we'll assume that hasn't happened). All major DAWs contain a basic meter on the master bus channel. Reset your meter and do a whole pass of the track to check exactly where your song peaks (i.e., where the level reaches it's highest point during the pass). Typical mastering engineers want roughly 3 dBs of headroom on the mix to give themselves the most flexibility - this is especially true if you are working in 16bit rather than 24bit.

If you find yourself with excessive levels on the master bus (or even clipping) there are a couple of options to try. If you have maintained respectable levels on each individual channel, lower the overall level by simply reducing the master fader a few dBs as appropriate, ensuring the integrity of your mix stays intact. However you may only be temporarily fixing problems that lie deeper in your mix session.

If you find that individual channel levels are to blame, it's probably a better idea to reduce channel levels equally and individually so by the time the audio reaches the master bus there are no level issues - i.e., you've reached an acceptable master bus level completely naturally. Remember to maintain respect with any particular routing you have used - e.g., don't reduce a bus as well as your respective channels as this will throw the balance out.

If the levels still look unusually active, delve a little deeper and check if any individual plugins are clipping. If a plugin has been set to force hot levels out to your DAW, there's a good chance clipping will occur. (Some analogue clipping can sound great, but digital plugin clipping is the total opposite - you really don't want this on your mix!) Most plugins have an input/output level trim so if a channel looks to be overworking itself, check the inserts for any clipping and adjust accordingly.

A channel may clip and affect your master bus level if an Insert is forced to process to an extreme. Above, the "In" meter shows the input channel level is acceptable, however when the EQ plugin kicks in you can clearly see the level clipping upon outputting.

To demonstrate just how easy it is to accidentally clip a channel, here is an example of a quiet synth part meant to "pad" out a song. This kind of part can easily get lost in a mix, as that's the parts purpose:

As you can hear, it sounds totally fine. However, it's very easy to accidentally clip something which is quiet in the mix, particularly if it's been recorded hot. Here's the same synth part, but with an inserted EQ plugin with a clipped output:


Step 2: Check the Inserts on the Mix Bus

There is a lot of healthy debate over the dos and don'ts of inserting effects onto the mix bus. It's quite easy to overload the bus to help the track shine (especially if you're doing quick mixes to send to a band for approval, for example) but be very careful of wandering into the mastering engineer's domain.

Some mixers feel they need to limit the creative control of the mastering engineer by overly processing the master bus (perhaps with mastering-style EQ or limiting) and this is sometimes for a perfectly rational reason, especially if a top-line reputation is involved.

Regardless, I would never recommend adding a limiter to your mix bus. Quite often, digital limiters don't offer the same sonic finesse of analogue limiters used by most mastering engineers (particularly in the higher frequency spectrum) and you'll be depriving a mastering engineer of an essential part of their job. Let them do what you've hired them to do.

That said, it's very common to subtly process your master bus - generally this is to help "glue" your mix and add a little sparkle and consistency. One common approach is to gently process a mix through the classic SSL bus compressor to give your mix extra unity and to utilise its iconic individual "sound".

By all means, experiment and have a play around with your master bus but make sure you use inserts with caution. Always question why you're adding an insert to the bus - if you have any doubt, you probably shouldn't do it!


Step 3: Don't Dither!

I've already mentioned how careful you need to be when adding inserts onto the master bus - however if you do decide to add a little "fairy dust" to your mix then be aware that some plugins could apply a dither algorithm. The plugin should have an option to turn this off, so make sure that dither is always switched off unless you are reducing your bit rate on mix-down.

If you've recorded at 24bit I would recommend bouncing your mix at this bit depth ready for the mastering engineer and not to worry about the dithering process. Dithering is a vital part of mastering but let your mastering engineer apply this at the final hurdle and certainly don't do it for him during the mix bounce.


Step 4: Check Your Mix in Mono

If there's one process for you to try it's this one. Checking your mix in mono is vital and truly under-valued - there are countless reasons why your mix may end up being heard in mono.

If your song is broadcast on the radio, often it will be in mono if the signal is particularly weak. Even advanced technology still utilises mono signals - most radio iPhone applications broadcast in mono, unbelievably! When listening in mono, your track could run into major phases issues when processing reverb or delay and sometimes the effect can be totally lost.

To demonstrate, here is a guitar part with a delay effect in stereo:

And here is the exact same part, heard now in mono:

As you can hear, the delay effect has been completely destroyed on the second example. Would you be happy with the mono sonic representation? Obviously there will have to be a degree of compromise but this will naturally vary mix to mix, especially if the effect is essential to your "mix vision".

The TT Dynamic Range Meter is a great free plugin which monitors the dynamic range of your master bus. In addition, it can process a mix in mono. Simply place the meter on your master bus and click the mono button. (You can download the TT Dynamic Range Meter for free at http://www.brainworx-music.de/en/downloadrequest).

Above all, it's essential to make sure your mix translates throughout multiple scenarios so spend time making sure your mix works as best as possible in mono - you never know who could be listening!

The free TT Dynamic Range Meter is a great way to visually check the dynamic range of the mix and includes a handy mono button at the bottom.


Step 5: Check Your Imported Samples

Have you imported any samples into your project? Most DAWs can cope with audio files of multiple bit depths, as they will usually be converted during the import process. (If not, make sure they are!) However it's useful to check the bit depths of your imported samples in advance. It is common practice to record and mix at 24bit but sometimes you may find you want to use samples at 16bit - however this doesn't mean you shouldn't use them.

It's important to note that converting a 16bit sample to 24bit will not make the initial sample any better in quality, however it ensures that any processing or plugins you use on the 16bit sample are operating at 24bit, which will give a higher fidelity value to the sound, post-processing.

Above is an example of the Pro Tools "Import Audio" function. Here, a snare sample is at 16bit 44,100Hz whereas the project is operating at 24bit 48,000Hz. As a result, Pro Tools will convert the audio to match the project sample rate and apply all further processing to the snare sample at 24bit 48,000Hz.


Step 6: Don't Get Caught Short!

Imagine this. You've secured your first major mix job with a major label. You've worked until the early hours for days on end polishing the mix. Eventually, it's submitted, you're paid, deadline achieved! Two weeks later you get a late night call from the label, "We need a new radio edit with a more upfront vocal. It needs to go to the radio plugger tomorrow."

A good mix engineer is always aware a mix recall may need to happen - so make sure you're not caught short and you're well equipped to deal with the scenario. Print the audio of any plugins you're thinking of uninstalling. Did you use any outboard gear? If so, get a print of it just in case. Perhaps take a picture of the settings. Upgrading your OS? Will your plugins still work?

Make sure you've got the means to cope with any recalls that need to happen. Generally though, once something is released you'll not need to worry!


Step 7: Some Final Advice

Here are some quick tips that really can make all the difference:

  • Rest your ears! You will find that sleeping on a mix after a hard days work will often open your ears up and give you a fresh perspective. If possible, it's always worth revisiting a mix the next day before you really do call it 'finished'!
  • Check your export marker points! It seems obvious but it's a common mistake. Don't start the export the precise moment the song kicks in. Give the mastering engineer a few seconds to manoeuvre. The same applies to the ending. Unless it's for creative reasons, make sure you export to the very end of your track - double check any overhanging effects!
  • Get to know your mastering engineer! It's always great to get a working relationship going. Send them the song in advance and if possible, get their opinion on the mix. Any mastering engineer worth their salt will always hear your mix with the master in mind and may be able to point out where you could improve your mix in order to get the best out of the mastering session.

Conclusion

Reading this tutorial you'll have noticed the emphasis placed on respecting the mastering process. It's often overlooked in our ambition to make mixes sound as professional as possible from the offset.

If there is anything to take away from reading this tutorial it's that you should always mix with the mastering engineer in mind. Remember, if you're beginning to question any of the finishing touches you're adding then you're almost certainly in the mastering engineers territory. However, if you have a vision or direction for your mix then this must be incorporated at the mix stage; no matter how good a mastering engineer might be, he can't fix your mix.

And as luck would have it, that's our job!

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