Finalizing Tools for review:
- DC Offset
- EQ, Compression, Limiting on your master bus
Now that you have done most of the balancing, there are just a few tweaks you may wish to make to your final mix. There are a few things you want to do every time you are finishing a mix, as well as a few others that are more subjective, depending on the content. However, all of these processes are going to take place on your final stereo mix. Engineers refer to the stereo mix produced by the combination of all the tracks as several different names, including the summing bus, 2 bus, 2 mix, and the master bus. These all simply mean all of the instruments are summed up into two tracks; stereo left and stereo right. This is the same configuration you hear today on the radio, CDs, MP3s, etc.
Now that you understand how the audio is summed together, lets discuss some options for processing this final stage in mixing. One thing you can try is removing all sub-audible frequencies from the recording using a very steep high pass filter at a very low frequency, around 25hz. This is referred to as DC Offset Removal. Even though the sound waves at this low a frequency are not easily audible, they contain a lot of energy that eats away at your headroom. Removing these lower frequencies will free up more room for the rest of the frequencies to be louder, while removing any untamed sub-bass that you may have overlooked. Just because your listening environment doesn’t reproduce those frequencies, does not mean that other listeners have the same limitation, so make sure to be safe and ensure they do not have to tolerate a noisy low end.
Now that you are left with the audible frequencies of your mix, you have a few more options. You may want to add some EQ, compression or limiting to the final mix. Of course this would all be to taste, and it is only recommend if you are not sending the mix to a mastering engineer. It is their specialty to make these final adjustments. But, if the whole project is to be done at home, then these can be done yourself. You should only have to use a light amount of these effects to give a final polish to your sound and bring it up to listening level. If you find yourself using these effects to an extreme on the mix bus, go back to the mix itself, something is wrong there. This should be your final polish, not the defining characteristic of your sound.
Before you finally print your stereo mix, there is one final step: Dithering. Dithering is an incredibly complicated process used in audio to convert bit depth down to the standard 16 bit for CDs, etc. This inevitable bit rate conversion can create a series of patterned errors, which translates to a distortion or addition of unpleasant noise to your final mix. For this reason, dithering should be a standard process for your final mix, as it counteracts the distortion. Be sure to add only one dither on your master fader after all other processors. You do not want to dither more than once, as a dither adds random noise to the signal each time, and multiple dithers start degrading the sound rather than improving it.