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Ribbon corrugating tool
Improved version (below)
Improved version with: pop filter made of non-metallic window screen fabric, acoustic cavity back wall made
of peg board material, 1:2 audio step up transformer, and brass hardware
Improved ribbon corrugating tool
The picture, above, shows the ribbon microphone on a home made stand made
of iron pipe and associated pipe flanges. Obviously, this stand is not totally consistent with the use of non-magnetic hardware
elsewhere in this project.
Above and below are pictures of the "final" version of the microphone and
its stand. Note that the wires which run between the top and the bottom of the ribbon and the microphone cable have
been shortened and twisted to minimize the area of the loop formed by the ribbon and these wires. This is important to minimize
hum pickup. You can also see the 3.2 ohm-to-1600 ohm audio step-up transformer (1:22 turns ratio) that was added between the
ribbon and the cable. The brass screws at the that hold the ribbon in place have been replaced by nylon screws.
Here is a schematic of the ribbon microphone I built. The ribbon on the
schematic is shown as being 2" long. The ribbon in my microphone is 4" long, but 2" would be better. To minimize hum pickup
(a serious problem with ribbon microphones) keep the area of the loop formed by the ribbon and the connecting wires (before
they are twisted) as small as possible. In my micropohone, the area of the loop is about 1 sq inch because the ribbon is 4"
long and the spacing beteen the ribbon and the connecting wires is about 1/4 inch.
Final version
Above and below are pictures or the front and the back of the "final"
version.
I replaced the Reynolds Wrap (R) ribbon with a piece of thinner aluminum foil (~10 microns thick),
and I used a steel spring with about 25 turns per inch, in conjunction with a mousepad, to emboss corrugations on the
ribbon.
I added a piece of 1/2" pvc pipe... that can be raised and lowered by turning two
brass screws... to make an adjustable anchor point for the top of the ribbon. This allows me to install the ribbon with a
loose tension, and then to adjust the tension for the best sound.
After all was done and said, I decided that the microphone sounded better without the pegboard backing...
so I removed that.
Overall... this was a fun project, and the microphone sounds pretty good with appropriate equalization.
The output is about 25 dB less than that of my RE-27 N/D dynamic microphone at 1 kHz.
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