Mixing for Optimal Loudness
Loudness can be quite a contentious subject amongst audio engineers. The "Loudness Wars" have been raging since the 1980's and record labels have been pushing engineers to produce louder and louder masters. To accomplish this, mastering engineers tend to apply copious amounts of peak limiting. This can make things sound brittle and has lead to the sonic degradation of some otherwise well-produced tracks.
Whatever your opinion on the "Loudness Wars" may be, some degree of loudness is necessary for most pop productions. This can help the music to sound aggressive, punchy, and more emotive. Here is the trick: loudness must be achieved in the mixing stage. Mixing for loudness is more about perceived loudness than peak level. The human ear has a non-linear frequency response. A 3kHz sine wave will sound much louder than a 80Hz sine wave when played at the same volume. Taking this into consideration and achieving an appropriate harmonic balance when mixing is critical. Here are some tips for achieving optimal loudness in your mixes.
Tip #1: Equalization
Using EQ can help balance the frequency spectrum. Low frequencies produce much more energy than high frequencies. Too much low end can reduce the perceived loudness of your mix. Be sure to clear away any unwanted sub frequencies when mixing. Insert an EQ with a highpass filter on your bass instruments. Place the cutoff between 30Hz - 60Hz to clear away any sub frequencies.
Peak limiting can sometimes produce unwanted harshness in a mix. EQ can be used to deal with this issue before it becomes a problem. Place an EQ on your stereo bus. Cut some frequencies between 2kHz - 5kHz using a bell with a wide Q. It is important to focus on the audio core when applying sensitive EQ moves. Place Reveal on your DAW's master bus and engage Critical Listening mode when making EQ adjustments. Working in this manner ensures that engineers make the most precise adjustments possible.
Tip #2: Balancing Bass Harmonics
Balancing bass harmonics is important when mixing for loudness. Often the fundamental frequency of a bass instrument is much louder than the upper harmonics. This will reduce headroom and cause a mix to sound quiet. Be sure to deal with any loud resonances or fundamental frequencies in your bass guitar and kick drum.
Use LowLeveler to balance bass instruments in the most transparent manner. Place LowLeveler on your bass instruments. With Reveal on your DAW's master bus, engage Critical Listening mode. Now listen to your bass in context of the full mix. You may find that your bass guitar or kick drum almost disappears. If this is the case, adjust LowLeveler's Upper Harmonic section. Now turn off Critical Listening mode and listen to your bass. In this context, make any necessary adjustments to the Low Bass (Fundamental). This workflow ensures that all your bass instruments are harmonically balanced and will translate accurately to any listening system.
Tip #3: Saturation
Saturation is often used to accentuate the harmonic content of a source. This can increase the perceived loudness while doing little to the peak level. Tracking through warm preamplifiers which create subtle harmonic distortion helps greatly when mixing for loudness. Saturation can also be applied with plug-ins or hardware processors during the mixing stage.
To apply saturation in the most accurate manner, it is important to focus on the audio core. To do this, place Reveal on your DAW's master bus and engage Critical Listening mode. Insert your saturation module of choice on a given source and listen in context of the full mix. Now make any neccesary adjustments to the saturation settings. Working in this manner allows engineers to apply saturation with a great deal of precision, ensuring that the signal does not suffer unpleasant degradation.
Tip #4: Bus Compression
Bus compression has been a popular method for increasing loudness for many years. A good bus compressor can help glue a mix together, causing elements to breathe and move as one. There are many popular models and designs of bus compressors which produce different sonic characteristics. A VCA compressor can help a mix to sound punchy and aggressive. An optical compressor may help to smooth out the transients, creating a warm sound.
When applying bus compression, be sure to make subtle adjustments. It is best to use a relatively long attack time and short release time. This will help to maintain the transient content, while raising the overall level. For bus compression, gain reduction of more than 2-3dB is rarely needed.
Tip #5: Peak Limiting
Peak limiting is necessary to acheive competitive commercial levels. However, limiting should be applied with a great deal of care. Place the limiter on your master bus. The output gain should be set to -0.3dB. This will provide a little bit of headroom and ensure that your mix does not clip when played on consumer listening systems. Various limiters may have slightly different parameters. Adjust the threshold or input gain until gain reduction is applied. Gain reduction of 3-4dB is usually fine. However, you should always use your ears and listen for any distortion artifacts created. To do this in the most accurate manner, use Reveal's Distortion Listening mode.
Place Reveal on your master bus, after your limiter. When adjusting the threshold or input gain, enable Distortion Listening mode. Listen to the loudest section of your song and adjust the settings until you start to hear distortion being created. Now reduce the amount of gain reduction until you no longer hear any artifacts. Turn off Distortion Listening and listen to your mix.
This workflow ensures that a necessary amount of limiting is applied in the most transparent way possible. Using these tips you will be well on your way to crafting louder mixes which translate to every listening system.