In the US, you can get most of the parts at www.digikey.com - in Europe, consider www.conrad.de (cable, all other parts) and http://www.schlotzhauer-versand.de/ for mic capsules.
- 2 miniature electret microphone capsules (get the best ones you can find - your selection will have a major influence on the sound quality - recommendation: Panasonic WM-60/61, Monacor MCE-2000/4000/4500). (article about directional vs. omni-directional mics)
- 3.5 mm (1/8") stereo plug with cable, preferably angled and shielded
- a few cm / inches of heat shrinkable tubing, slightly larger diameter than the capsules
- soldering iron + solder
- hot melt glue + gun
1) Skin and solder the cable to the capsule, the shield to the outer shell of the capsule, keep soldering time as short as possible. Use some sort of heat sink where available.
mini_R0015250.JPG 54.23KB 1463 downloads mini_R0015207.JPG 42.28KB 1613 downloads
2) Bend the cable and add some hot melt glue. (heat)
mini_R0015224.JPG 50.22KB 1159 downloads mini_R0015227.JPG 56.61KB 1184 downloads
3) Cut suitable pieces off the heat shrink tube (about 1/2 inch) and put it over the capsules.
mini_R0015229.JPG 75.64KB 1027 downloads mini_R0015233.JPG 42.83KB 959 downloads mini_R0015231.JPG 74.01KB 870 downloads
4) Heat it with a lighter or similar tool for a short time just until it doesn't shrink any further, remove leaking glue as long as it is fluid. This process requires some experience. You may want to practice first on other objects before ruining your capsules. Never apply excessive heat to a single spot, keep the heat source moving. Constantly cool the capsule by blowing against it for a few seconds directly after heat has been applied. Do not touch the hot glue with your fingers.
mini_R0015244.JPG 37.77KB 1014 downloads mini_R0015247.JPG 78.49KB 1037 downloads mini_R0015245.JPG 36.85KB 943 downloads
When using omni-directional microphones, for a realistic stereo image it is important to separate the mic elements about 6-8 inches (15-20 cm) and preferably have a separator in between, which is ideally your head. You can attach the microphones to the rim of eyeglasses using the same heat shrink tube method, put them into eye glass retainers (croakies) or just use black electrical tape. Don't mount them too far up front or you'll loose a great part of the head's separating characteristic. Having them as close as possible to your ears is ideal.
mini_P1010193.jpg 76.05KB 881 downloads mini_P1010201.jpg 47.44KB 928 downloads mini_P1010194.jpg 73KB 882 downloads
If you want to make sure to have no significant channel differences, you need to match the capsules before assembly. As with any electronic part, no two capsules are exactly the same, but you can minimize the differences by picking a pair with close to identical characteristics.
To do so, solder a random pair of mic capsules to the plug with cable. Download the test tones here: test_tones.zip 76.92KB 36 downloads
Play the tones through a Hi-Fi loudspeaker at a moderate volume. Hold the mic capsules very close together and monitor the level indicator on your recorder while slowly moving the capsules back and forth from the loudspeaker. Both channels should read about the same, otherwise try different capsules. The test tones are 100Hz and 1000Hz (1kHz) sines in mp3 format.
Edited by greenmachine, 11 May 2009 - 01:10 PM.