sBASSdrum: The Making of a Snare Drum

I will admit: I’m not very good at making snares yet. But perfection can wait for v0.2. 🙂

I’ve been reading over the very excellent Synth Secrets set of articles and learning about all the amazing ways engineers have figured out to make passable drum sounds with electronic equipment. I needed this information because I had never really thought of what a snare drum is and how to recreate one with synthesis. Worse yet, I’m basically working with simplified waveforms and envelopes. So, this insight from Gordon Reid’s writings is really helping.

OK, so what is a snare drum?

It is:

  • A wood shell (blue in the picture)
  • Metal rims
  • A top flexible membrane and a bottom flexible membrane (top head, bottom head)
  • A bunch of snares strapped to the bottom (springs)

How does it work?

  • You hit the top drum head (the “batter” head)
  • The air bounces around and forces the lower drum head
  • The bottom head slaps the snare springs
  • The snares pop off the back and then slap down, each part of the snare wires coming back into contact with the head again at different rates creating thousands of tiny popping sounds

And you know the result: a “tssshhh” snappy sound with possibly a little tone under that sound.

Let’s take a look at some of my favorite snares:

blog_snares_real2_1a

blog_snares_808_1a

blog_snares_real_1a

Simulating this in a drum machine is pretty amazing. If you were to physically model this it would probably take quite the computer to model each of the parts of the springs and the crazy reflections of the tiny snare slaps bouncing off of the sides of the drum head and reflecting back, further rippling back onto the snares themselves, … and so on.

But engineers have figured out a much simpler way of doing this in hardware:

  • The top head and bottom heads can be simulated with just simple triangle waves
  • And a noise generator can be used to take place of the snares

The resulting wave form looks like the typical diminishing funnel shape with a strong carrier tone and some noise throughout.

Then, there’s what I decided to do:
blog_snares_renoise
Breaking this down:

  • The 2 left columns are filtered and shaped white noise
  • The 2 right columns are shaped triangle waves

The first channel is plain white noise with a low-pass that falls off about 8.6KHz so its color is a thick “psshhh”. This is meant to simulate the snares longer ringing against the bottom head. The second channel is also white noise but it is a band-pass that peaks around 2.8KHz and its Q lets in both high frequencies up to maybe 12KHz and down to 300Hz. This one has a much quicker volume decay. The net effect of the two shaped noise waves is there’s a fairly gutteral “kshhh” around 3KHz (which is like the initial slaps of the snares against the bottom head) and has a pretty full frequency range so it sounds crisp. But since the first channel’s noise lasts longer than the second channel’s, it sounds as if someone were slow cranking down a low pass filter over time.

Next, the two triangle waves are tuned similarly to Reid’s tutorial: 180Hz and 330Hz. I make the 330Hz fall of quick and the 180Hz fall off slower. The effect of this that the 330Hz acts like the initial hit of the drum stick against the top head and the 180Hz acts like the main resonant tone of the snare drum.

Let’s check out how this all sounds:

And let’s see how it ended up looking:
blog_snares_mine_1a