sBASSdrum: The Making of a Kick Drum

What’s in a good kick drum? If you ask me, I think it’s:

  • At least 100ms, probably no more than 200ms
  • Light, sharp impact sound on the attack
  • Beefy sustain
  • Lowering of frequency over time

Let’s take a look at the raw waveforms some of my favorite kick drums:

blog_kick_1a

blog_kick_1a3

blog_kick_1a2

So, they all have similar traits. If you look up a spectral graph of one of the kicks it might look like this:

blog_kick_spectral-1a

As you can see, the first 0.05 seconds there’s a lot of business going on in all the frequency ranges. After that it seems to hover around somewhere between 100hz down to 50hz in a slow descent. I think why most people do this is because a natural bass drum works pretty similarly:

  • You step on the pedal
  • The pedal swings and slaps the bass drum head hard
  • You get an audible “smack” as the pedal contacts the head and a lot of energy is transferred into the drum
  • The air bounces around and pushes both the drum head and the drum front back and forth in a big slow oscillation
  • Then over time the energy is lost and the oscillation slows down along with the volume

Even when synthesizing a bass drum manually it just seems more natural to follow these rules.

So here’s how I made my bass drum. First, this is what it sounds like:

Let’s break this down into the components:

  • The click: this is faked out slap of the drum pedal against a drum head. Obviously, synthesizers don’t have a pedal or a drum head, but we’re so used to hearing it that it feels weird without it. Plus, it makes it audible on crappy computer speakers. Here I recorded the sound of me punching (yes) a receipt from Target with my LS-12 field recorder.
  • The initial reverberation: I like to do this with a sine wave that rapidly falls from a high frequency to 0hz. It makes a “pew” sound if it’s slow, or something more like a long “click” if it’s slightly longer. When mixed with the click it makes a nice audible “smack”.
  • The body: Again this uses a sine wave that falls but it does it slowly. I start it around C4 (261Hz) and let it fall down to C2 pretty quick (131Hz) and then trail off from there.

I made the sine wave in Adobe Audition (just a pure 261Hz wave) and then set it as instruments in Renoise:

blog_kick_renoise

I know most people can’t read Renoise format, but it goes like this:

  • Each vertical column you can think of as an instrument
  • The left two columns are grouped together
  • The far left is the “click” with a sine wave at C6 (~1Khz) and rapidly falls to 0Hz linearly
  • The middle is the “body” with a sine wave at C4 (~261Hz) and initially falls a bit probably down to about 150Hz then slowly falls after that.
  • The receipt sound is on the 4th track.

The two sine waves’ outputs are further modified by a parametric EQ which tries to accentuate the 100-200Hz range. One thing I’ve learned from testing: you never know what kind of speakers your listener will have and if you have a sine wave that is accentuated in the 60-150Hz range and the frequency is falling through that range, then you’ll most likely get a decent “whomp” out of it. The corollary is that that “click” and “receipt” sounds are much higher in the frequency range (above 300Hz) so on tiny cell phone speakers that have no bass response you will still at least get a small “pop” sound.

Anyways, let’s take a look at the wave form the 3 instruments made together:

blog_kick_2a

Lots of high frequencies in the front, an expanding “whomp” in the middle covering a big spectrum, and most of the energy is out by 0.25 secs.