Shadows, the album - The built of microphones - Part 2

Hi everyone !

In the last post, I talked about the 2 "Neumann" Clones I built. That was only two more mics to add to my gear, I needed more.

In fact, I also built 2 ribbon microphones.
For those who don't know, a ribbon microphone is a microphone which membrane is a fin aluminium foil between two strong magnets.

I never use such microphones, but I have head a lot about them, so I decided to test.

In a first time, I bought a used T.Bone RM700. I tested it, and I loved it.
Obviously, there is a serious lack of trebles, and it's very specific, but that's why I loved it.
I think that it's the kind of microphone you have to test on everything, but sometimes, you won't use it at all.

Once this mic tested, I thought that I could mod this mic, improving its building quality. At the same time, I decided to build another one.

To build a ribbon microphone, you only need three components:

- A "motor" (the system composed of the aluminium foil and the magnets)
- One output transformer, I chose the Lundahl 2912, very common for ribbon microphones. I already use some Lundahl transformers in my preamps, so I know they are good.
- A microphone body with an XLR plug in it.

The new microphone (let's call it The Blue) was the easiest to do. I ordered in China a ultra cheap microphone (sold to be a really professional one). I bought it for 30€. Once received, I threw everything inside (which really looked cheap), and I had a mic body !

I ordered the transformer at Ceres Electronique, so I had the transformers too.
For the motor, I ordered a ready one at  diyaudiocomponents.
I then had everything to build this mic. I cut the steel plate which held the old microphone membrane, and I attached the motor to this plate.
A few solders later, it was ready.

The T.Bone mod was really harder.
I already had a Lundahl transformer, and the problem came with the body.
The motor frame was metallic. This is a problem, because if you plug this mic in a preamp which has the phantom power turned on...bye bye the ribbon.
I decided to build a wood motor frame, to order magnets, and to put the aluminium foil by myself.
The wood frame was easy to do, ordering the magnets too.
Glueing the magnets on the frame was a pain in the ass. There is 5mm between them, and they were too strong to stay in place.
I had to build another wood frame, with a wedge to prevent them to attract each other.
In fact, they attracted a little each other, so the magnets are not really parallel, but it works fine, despite an awful design.

Concerning the aluminium foil, ribbon microphones usually use some 1.8 - 2.5 microns thick aluminium (the aluminium foil from diyaudiocomponents is 2.5 microns thick. For information, for chineese cheap ribbon microphones, it's usually 5 microns, and for the aluminium everyone uses in the kitchen, it's about 15 microns).
Finding such a thin foil is expansive, but I managed to find a 0.5 micron thick foil for 12€/10 foils at Charrier.
The pro is that I gained 6dB of dynamic.
The con is that 0.5 microns is really really thin, you can't breathe next to that, otherwise the foil starts to fly away...

Once the foils received, I cut one 3mm wide strap. After that, you have to corrugate the foil, so that it's able to vibrate. I built a corrugation machine with some old wheels from a video recorder.

I then attached the ribbon between the magnets, and the mic was built...

The building quality is now far superior than before, and the sound is really good.
The interesting fact about this mic, is that with the new frame design, the ribbon is no more centered in the mic body, and the mic has now two sounds, depending on which side you are.
In fact, there's a "bright" side, and a dark side. The frequency response is not the same one the two sides.
For information, a ribbon microphone is bi directional, so it takes the sound from front and rear, and it's supposed to have the same frequency response on both sides.

So how does everything sound ??
Here's a little song recorded only with these microphones.

Some technical informations:
- The clarinet and the Tin Whistle have been recorded with the modded T.Bone, "bright" side in front of the instrument.
- I did a Blumlein stereo sound take for the guitare using the two mics
- There are two Cajons, one with the snare on, and the other one with the snare off. I used the T.Bone for the front, and the Blue for the rear of the Cajon
No compression, no EQ, no effects...


See you next week !