4: Control of LF in a mix – Overview of Low frequency control in a mix

After an extended absence from this Blog, in part due to my attention being on other works, I return with a better understanding of how to keep a mix “Balanced” (Evidenced by my recent feedback from recorded and live assessments).

Therefore I feel that one of my points in this topic: “Balance of LF in the mix overall” (see 1st post) is of slightly less importance now than it may have been upon it’s conception. Nevertheless, I find that this point ties quite nicely to the use of dynamics to control bass within a mix, and therefore shall discuss this as one broad topic.

After listening again to the songs from my previous post, I noticed that “4 Kicks” by the Kings of Leon has some interesting topics for discussion in this area.

Firstly, I notice that the electric guitars tend to be lacking much of their lower frequencies. This is more than likely designed to allow the bass guitar to stand out more in the mix without being masked by the crossover of the two instruments. This seems like a key point of this mix, as the bass guitar is particularly “weighty”, having a lot of very low frequency content (although I think this is aided somewhat by clever use of distortion, allowing harmonic content to imply more low frequency content than may in fact be present).

Aside from the sheer “weight” of the bass tone, I notice that the bass’s low frequencies tend to “bloom” up more as the instrumentation becomes sparser for short sections of the song. I feel that this exercise was in anticipation of mastering, as low frequency content needs a lot of “energy” to be perceived as being as loud as higher frequency content. As the guitars and drums fade out, there is more “room” in the mix to push up LF from the bass guitar. I feel that this “juggling” of frequency content could be useful to keep in mind during future mix sessions.

Aside from this, overall low frequency content seems “controlled”, despite its weight and tendency to bloom up in the mix. I feel that this is due to not only well informed tone sculpting through use of recording technique and EQ, but also largely due to appropriate use of compression.

To compare these findings, I searched for a more recent release that falls within the wider bracket of “Indie”. My thoughts went immediately to Arcade Fire’s latest album “Reflektor” and in particular it’s title track. Personally, I feel that this is an extremely well-produced and well-engineered track, therefore making it a good reference for this exercise.

My first impression was that the Kick drum seems to have more low frequency content; sounding a lot “bigger” in general (a logical result of the songs four on the floor beat). This has relevance to this discussion, as it will be interesting to delve into how the bass (be it guitar or synth) and the kick drum mingle in these lower frequencies without masking one another.

At first listen, it’s rather difficult to decipher these low frequency elements (especially in my far from perfect listening environment). For this reason, I thought that filters and a spectrum analyser would be useful analysis tools. As shown in the image, I used Ozone’s “Brickwall Lowpass” to concentrate my listening on the sub 120Hz range, and a 1/3rd Octave band frequency analyser with a long FFT window size to give me increased frequency content accuracy. Switching between real time and longer averaging times also aided in comparing the overall long-term LF content against the way it “pumps” in the mix.

Image

What I found was that the kick drum tends to have a lot of low frequency energy, whether the song is in a particularly bass heavy section or not. To allow for this, the bass guitar and synth elements are compressed with a sidechain from the kick to pump them in sympathy with it. This creates a lot of the energy within the track, but the relatively long release time of this sidechain would not be suitable for many songs, and therefore I feel that the thing to take away from this is that sidechaining of bass is useful for low end control and clarity, although careful attention should be paid to release times to make it appropriate for the song and/ or genre in question.

Although useful, I found that this listening session didn’t shed much light on the subtler uses of compression to control low end. Therefore, my next step shall be to research the techniques used by others in this capacity, and try them out for myself on a variety of content.

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