Have you ever wondered how your electronic drum pads work? No! Stop! Don’t hit the back button! This might be something which could be useful. Honest!
Hopefully a little bit of knowledge in this area could work wonders in the future when you are on stage sitting behind your electronic drum kit and wondering why things are behaving strangely.
Those of you who have taken a drum pad apart (which I'm guessing wont be many of you), will have found a small brassy coin-sized disc inside your drum pad. This is called a piezo transducer. The piezo transducer is the heart and soul of 99% of all drum pads. It’s very simple - it’s a small disc of brass, with a smaller circle of a white papery material on one side. The brass and the papery stuff will have a lead soldered onto them and its these two leads which take the signal off down a few cables to your drum module.
The white papery stuff is actually a very thin slither of piezo crystal, and its this crystal which makes the transducer work.
Piezos (or piezo transducers) actually crop up all over the place. You’re probably quite close to a load of them right now. Piezos are used in electric devices when they are required to either buzz or beep. My fridge bleeps at me when I leave the door open, and this bleeping is all thanks to a piezo transducer.
So why are we talking about fridges in a column which should be about electronic drums? Well, piezo transducers have a couple of very interesting characteristics. The first one, and this is where fridge comes into it, is that when voltage is applied to one, it buzzes or beeps (depending on the signal that is sent to it). But also, when you hit or shake a piezo transducer it generates a small electrical signal. And that is what we are here to talk about.
So, like we were saying, inside pretty much all electronic drum pads is a piezo. When you hit your pad, and it may be a rubber pad, a mesh pad, silicon pad, or even riot shield plastic (older readers will be nodding at this point and rubbing their elbows), the piezo transducer converts the sound of your stick hitting the pad into a little voltage spike. This voltage spike travels down the cables to the module (or brain) of your kit and causes it to make a sound, making the drum pad sound like a 1930's Ludwig Black Beauty, 15” Gamelean gong, or Moog Taurus bass pedal, or whatever.
Piezos are actually quite good at acting like microphones. If you attach a piezo to the bottom of an empty tin can and yell into it you can use that as a basic microphone into a PA. It won’t sound very good as piezo's don’t have very much low-end (or bass) to them, but it would still sound like a thin, trebley voice.
So piezos work by vibration - if they are bent or hit they create a little voltage signal. But how they work is also the very thing that makes them really frustrating to us electronic drummers.
I’m sure you have experienced hitting one drum pad and the one next to it also making a noise, even though you didn't hit it. This is called cross triggering and it’s caused by the vibration of you hitting one drum pad going through the stand or rack and setting off another pad. It is incredibly frustrating and has happened to all of us at one point or another, and will continue to do so as long as drum pads have piezos inside them.
So, the very thing that makes piezo transducers work is also the thing that makes them behave badly - vibration.
This is why getting your settings correct is so important.
As I said in the very first Seriously Wired article, we all play very differently. Every single drummers plays differently. We all use different sticks, we are all different weights, different heights, and have different influences. However, the electronic drum makers have to produce kits which we can all sit down and play straight away. But, the five thousand dollar/pound/euro electronic drum kit you are playing doesn’t know whether you are a 72-year-old granny with massive drumsticks or a 17-year-old playing with knitting needles. Therefore, electronic drum manufacturers have to make compromises.
These compromises are very obvious if you have never played an electronic drum kit before and you are used to playing acoustic drums only. The first time you play an electronic kit, it might not be very obvious, but there is actually very little dynamic range available to you (and when I talk about dynamic range, I mean the volume range from very quiet to very loud). When your electronic kit is new to you, you probably don’t even realise, as it such a novelty to play, but the more time you spend with electronics, the more you realise that it’s not actually very much like an acoustic drum kit in how it responds to you hitting lightly and hard.
The whole subject of setting up your pads to work perfectly for you we will look at in another article, but one thing we can do right now is just make sure thats the cross triggering is down to a minimum - in other words, the pads only make a noise when we want them to make a noise.
If you think about it, an acoustic drum kit has a certain amount of cross triggering in it - when you hit your snare drum, the toms probably resonate in sympathy. A well set up electronic kit may well also cross trigger very slightly, it just wont to be so noticeable.
So what we got to do? Well if you look in the manual of your electronic drum kit, you’re probably find something which talks about 'threshold'. Threshold is the level at which your electronic kit starts to think “Hang on, I’ve been hit. I probably should make some noise “. The module ignores any vibrations or hits from the pads which are below the threshold but as soon as a hit is the same as the threshold level or bigger, the module will make a sound.
The threshold inside a drum module is like the seawall at the seaside – its crude, but you know its stormy when the waves start to come over the top of it. Threshold in an electronic kit is exactly the same - any pad hits, or knocks, or vibration which don’t come over the threshold is completely ignored, but everything which comes over the threshold is acted upon. When it is correctly set up, this will make your kit much less likely to accidentally trigger when the bass player jumps onto the drum riser.
To do this properly, you need to adjust every single pad. And every single pad will have a different setting, so don't set them all the same, as it wont work as well as it could.
Hit each pad as quietly as the quietest hit you'll play in a gig situation. There is no point pretending you play with feathers instead of drum sticks, and theres no point you pretending you are the hardest hitting drummer in the world – you need to be realistic here. So hit each pad quietly and bring up the threshold until your kit stops making a noise. Then just back off the threshold (in other words lower it again very slightly) and that’s it, you are done! If you repeat that with all the drum pads in your set up, you will end up with a much cleaner triggering drum kit. Oh and remember to save it!
As with all things it might need a little more tweaking, to get totally correct, but it will be a great place to start.
So next time, lets have a look at the gain and the curves (“The wha...?”)