Despite an end to the Loudness War, getting louder masters for bass-heavy genres is still a consideration for engineers working in these styles. Here Erman Aydöner shares with us his moves for healthy masters without skimping on the low end.

Listening In On Low End

Keeping on top of a trend towards mixes with greater low end extension, engineers have in recent years been expanding existing monitoring or investing in new gear.

When I started mastering, the lowest frequencies I was seeing on a spectrum analyzer were at around the 50-30 Hz range. Using just Yamaha NS10s, which can only reproduce down to 50 Hz or so, was working for most of the mixing engineers at that time. But in the last decade, on many projects, the frequency content has extend downwards. Mixing engineers started adding subwoofers to their NS10 sets. And now, many use monitors which are much more powerful in the low end. This is a result of increasing popularity of using 808 kicks, sub-kicks and/or sub-bass on Hip-Hop, Rap and even many Pop projects.

The Problem With Bass And Compression

As many reading this will be aware, there is a big difference between the way we hear low end, and the way most dynamic processors respond to it.

Two of the most important expectations from a mastering engineer on those kind of projects are to make the track loud enough to compete with other songs, and to make the low frequencies powerful (or, at least, not to lose the low end power that mixes have). And the challenge starts here!

Making a track louder can be done by controlling its dynamics with the use of compressors and/or limiters. Compressors are triggered when signals exceed the threshold. Fletcher-Munson curves illustrate how we percieve mid frequencies as the most powerful. But in reality, a kick, bass, or other low frequency signals in a mix will contain more energy. Our equipment does not respond like our ears do and compressors respond to bass content more readily than midrange information. As a result, when a limiter is pushed hard to make the material louder, bass frequencies get compressed and lost. And all those 808 kicks and bass lose power.

Achieving Even Compression

There are some known tricks to prevent this and have loud tracks with big bass. One is using a compressor and/or limiter with side-chain and using a high-pass filter on them. That might work in some situations for some engineers. But I never get satisfying results with this method while mastering.

To increase level with dynamic processors, without them killing the bass can be fixed with using EQ into the limiter. Then any energy slightly higher up the spectrum can be restored with a second EQ.

The way I generally work uses a two step process. First step is done by using a high quality EQ. I prefer using something like iZotope's Ozone Equalizer, Crave DSP's Crave EQ or FabFilter Pro Q. They all have M/S function, so I can dive more in depth with them. Sub bass synth sounds generally have their real dominance in the 50-120 Hz frequency range while 808 kicks share much of their boombastic character in this range. There will definitely be a fight in there!

The way I find to stop that fight is to lower the 80-120 Hz range, where bass and kick mostly fight for, just about 1-1.5 dB. This way my limiter after the EQ reacts less to crowded bass frequencies. Now we have lost some energy from the kick. Do not worry! Then I push the 130-160 Hz range 1-1.5 dB to give some power back to the kick. Boosting this frequency range also helps the kick to be heard easier on smaller speakers.

Optimising The Low End For Club Playback

Erman also likes to deploy one EQ technique sometimes overlooked; MS equalisation. He also uses this for the pre-limiter EQ described above. Taking into consideration the advantages of exploiting systems with extended mono sub bass, and minimising excessive width in the low end, he talks us through his workflow:

We can use a low shelf on the sides to lower the frequencies below 100-120 Hz a few dBs. This is a technique used for "club masters" for mono compatibility of the program, because having too much stereo bass information can cause phase problems. Keeping bass frequencies in the mid channel is much easier for club playback systems.

It is also risky to cut loud stereo bass signals on vinyl discs. So, disc cutting engineers sometimes use elliptical equalizers to move some bass information from sides to center.

Per-Band Processing Using Dynamic EQ

‘Priming’ limiters and compressors using EQ is one way to avoid over-reducing the low end, another more focussed approach can be to use dynamic EQ.

Again, we have to select very high quality plugins or devices to minimize phase related problems. I get the best results with iZotope's Ozone Dynamic Equalizer and FabFilter's Pro Q 3. I always try to be kind while using dynamic EQs on mixes. 1.5 - 2 dB of gain reduction is the most I try to have on any active band.

My first move is to use a low shelf to compress sub bass frequencies. Ozone Dynamic EQ has "baxandall shelf" and that works very well for this purpose. Using a filter point below 70-80 Hz range with medium attack and release times is my starting point, but be cautious! If you go too fast with the release time you might get a sustained sub-bass sound which might have a negative effect on the mix. Also fast attack and release times can lower the punch of the kick.

If I hear a fight between kick and bass, then I compress the 80-120 Hz range. This range is where bass and kick are both strong on most of the mixes. If we gently control this area then the fight between them might settle down a bit.

Adding and expander band at 130-160 Hz range and pushing up the kick just a few dBs would be very helpful. The expander will only add gain while kick hits if you set the attack and release times according to your program. As a result, you will have controlled bass and pronounced kick in the mix.

The last suggestion would be to use a high quality equalizer after your first and "hardest hitting" limiter. That limiter would probably lower the power of your bass frequencies. You can push up that area with the EQ moves after that. Lastly use a second light "safety limiter" to control the peaks.

The Loud Lowdown

With each genre having its own considerations, some throw up more technical curveballs than others. Heavier styles that feature loud guitars, or lots of bass need careful consideration where others might be luck to see a compressor anywhere in sight!

All the tricks above have to be considered as starting points only. Every mix has its own vibe and unique frequency balance. You have to treat every mix differently. After you find the right moves on the right frequencies then you will get louder tracks without loosing your bass frequencies.

Photos by Troy T on Unsplash, Techivation onUnsplash