The large diaphragm of this microphone will pick up more of the low frequencies when recording a kick drum or bass guitar.
Sound recording engineers have been using this trick for years, and Yamaha has also made a commercial speaker microphone called the SubKick, that usually retails for around USD$300.
I was able to build this mic for under $20 by "scrounging" various parts out of old junk. Even if you need to buy all the components, you should be able to build this mic for a fraction of the price of the retail version.
This design goes slightly beyond the SubKick, as far as electronics are concerned, with a dual coil design, and internal direct injection (DI) box.
You should be comfortable using a power drill and a soldering iron, and be able to read a schematic diagram. There is a little sewing, but it isn't too difficult.
Step 1: Materials and Tools
- 6.5" dual coil woofer speaker (4ohm). I pulled this one from an Altec Lansing multimedia system that had a blown amplifier.
- 10" drum. Cheap is okay, but you'll want something with lugs that screw into the shell, not springs or T-rods that screw into couplers. I found this one for $2 at a second hand store.
- Two miniature bungee or elastic cords. I got a 4 pack for $2.50
- Crimp on terminal rings. I paid $2.50 for a dozen
- Adjustable hose clamp (the same diameter as the magnet of your speaker). This was about $1.50 at the hardware store.
- Female mounting flange for 3/8" microphone stand and small bolts to mount it. I got this at Parts Express
- 2 sq. ft. of speaker grill cloth. Also at Parts Express
- Male XLR 3pin panel mount connector and mounting screws
- Two 1/4" TS (mono) female phone jacks (at least one needs a tab for a normalling connection)
- A six-pole four-throw rotary switch (I scrounged my switch from a 4-way printer "data" switch box), or you can use Mouser part no. 105-SR2921F-34S
- 100 ohm potentiometer, also called a variable resistor
- two knobs (for pot and rotary switch)
- Two DPDT toggle switches (on-on)
- A SPST toggle switch
- Resistors: 100k ohm, two 10k ohm, 10 ohm
- 100nF capacitor
- 1:1 ratio audio isolation transformer (pulled from a second hand 270-054 I got for $1)
- metal container to hold and shield transformer, and mounting hardware
- heat shrink tubing or electrical tape
- connecting wire. 22ga or 24ga is fine.
- short microphone stand (another second hand store find)
- Small adjustable wrench
- Soldering iron and solder
- Wire stripper/crimper
- Sewing needle
- Small hack saw
- Ruler, or other measuring device
- Sharp hobby knife
- Marking pen
- Rotary tool
- Drum key
- Pliers, tweezers, or other soldering aids
- Adjustable calipers
- Cutting mat
- label maker