Everyone had probably seen the Yamaha NS10’s driver (the popular white cone speaker), mounted on a stand in front of a bass drum head. Many engineers tried this trick, and it worked so well that Yamaha decided to release a product based on it; called SubKick. The concept is very simple; they just added a drum-like housing for the driver and redesigned the electronics as a ready-to-go solution. But what is the concept behind it? Even a large diaphragm condenser microphone has a relatively small capsule to capture all bottom end frequencies produced by the kick drum. Using a speaker cone introduces some wiring complications, but it’s not rocket science since the electronic principal of dynamic microphone is pretty similar to a speaker cone, it just works another way around. You end up with a very large diaphragm dynamic microphone. I’m not going to describe all the technicalities and physics concepts behind it, just remember, that using a speaker cone as a microphone requires impedance balancing, which is done pretty easily by using a DI (Direct box).
What to use as a SubKick microphone
What can you use for a sub-kick microphone? Well, pretty much anything with a large speaker. It can be a bass or guitar cabinet, an old passive speaker, or just the driver, etc. It sounds bad on its own, so you have to mix it with a conventional microphone. Our sub-kick microphone is not going to capture any transients or mids; we just want it to translate the very low frequencies and blend them to the mix. It will require some experimentation by an engineer before a suitable driver is found. In my opinion, a car subwoofer works best with it. Its large cone and the cabinet is tuned to frequencies below 60 Hz. I suggest placing it on a solid base (I used a simple cinder block) about 10-15 cm away from the audience head of your bass drum. Some custom wiring will be required to connect it to a DI box, but it is not complicated at all.
Before the recording, you need to check the signal level and the phase. If you hear distortion or crackling from your DIY microphone, just move it further away from the head. A couple of centimetres will do. Since we did some guesswork with the wiring, make sure to check the polarity. It has to be in phase with the other kick drum microphone(s) in order to avoid signal cancellation. Record a small piece and listen to how it sounds. To hear the difference, you must have proper studio monitors set up. You need to be able to reproduce that low end in your control room; otherwise, the experiment will ruin your recording.
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