Tag Archives: DIY

Austin Ribbon Mic Completed

The completed Austin ribbon mic. This one will be given away at the Producer’s and Engineer’s Summit at Welcome To 1979 in Nashville, coming up in November.

Here’s a look at my Austin ribbon mic, I completed it yesterday. Building this mic certainly was actually really easy, except for one part… installing the ribbon in the frame. I had to do this several times… six, to be exact. I  had various problems. One, for example, didn’t show it’s ugly head until I’d completed an installation… tiny tears all along the edge of the ribbon. I learned they were caused by the ruler I was using, which had a cork backing that was set slightly behind the ruler’s edge. This small unsupported space allowed the foil room to stress and tear. I corrected this by using a length of rectangular aluminum as a straightedge, this pressed down on the foil right at the cutting edge.

Another problem I had was corrugating the ribbon. I was trying to protect the ribbon by corrugating it with the release paper on the top and bottom, but doing so a) causes the ribbon to curl up, and b) makes the corrugations shallower. If the ribbon isn’t sufficiently corrugated, it is extremely difficult to get it tensioned properly. The tension is important… the ribbon can neither sag in the frame, nor should it be too tight. I had the latter problem, and the ribbon developed a longitudinal curl, so scratch that ribbon.

But thanks in no small part to Rick’s patient support via several emails, I finally got one in. It wasn’t perfect… it could be centered just a hair better… but it looked ok, so I closed it up and finished the mic.

And considering everything, it sounds quite lovely. The last time I used a ribbon mic was 25 years ago, when I did my thesis recording using a pair of RCA TK77’s that the university owned, so I don’t have much of a frame of reference, but it seems to have a nicely balanced frequency response. From what I understand, construction errors show up as poor highs or lows. I don’t have a frequency analyzer set up yet so I can’t give any numbers, but my subjective analysis says “nice.” Now, like all ribbons, the output is rather low, and I did my testing using a rather crappy mic preamp. On voice, one has to crank the gain up quite a bit, and this gave me a lot of preamp noise. For someone who is a low talker, this wouldn’t work. But I got a rather useable level on my acoustic guitar.

Again, I can recommend Rick’s kit quite highly, especially if you’ve never built a mic before. He’s done everything that can be done to insure a good outcome, and the one I built certainly worked out well. That’s not to say it’s simple… you need patience, and good, steady hands will help as well. But I’ve already got parts here to build four more for myself!

The Austin Ribbon Mic

I recently received an Austin Ribbon mic kit from Rick Wilkinson (Rickshaw Records) out in California. Unfortunately, I can’t say I’m the proud owner… this mic is going to be built and given away as a door prize at the DIY panel at the Producers and Engineers Summit at Welcome To 1979 in November.

I haven’t finished the build yet, so I can’t give a complete review of the mic, but I can make some comments about the kit and the resources that come with it. Building a ribbon mic is not that complex- IN THEORY. It’s just a thin metal ribbon suspended between two magnets. There isn’t much electronic inside the mic, just a transformer. The design has been around since the 30’s.

The theory is simple. But like most things, it’s the Devil in the details. You can find articles and instruction on the web for free. And that’s what I started to do years ago. I got halfway through the project and shelved it… there wasn’t enough detail for me to be successful.

Or you can spend some money and increase your chances. Rick sells plans for ten bucks, or his ribbon kit for $275 with a Cinemag transformer. (There is a less expensive version with a stock transformer, and I understand the stock transformer is exceptionally high quality. It’s sold out right now, but should be available again shortly) Rick sent me a kit with a Cinemag transformer, so that’s the version I’m reviewing here.

The kit itself is extremely well done. The mic tube is powder coated brass, 1 1/2″ diameter, and exactly machined. All the holes are already drilled, so you don’t need a drill press. The motor frame (a critical part) is a machined piece of plastic. The fit was perfect. I especially liked his design… I designed my own once, and it was a cumbersome mess. Ricks is elegant, simple, strong, and works well. (some folks claim that metal frames are superior. Perhaps they are… I’m not sure… but I think that at least part of the reason behind this claim is that’s what is available from China.)

The greatest value for me, though, is Rick’s instructional materials. When you buy a kit (or his plans), he sends you a link where you can download  PDF instruction manual and several videos where he goes through the process of building a mic. These videos are really helpful, especially when it comes to corrugating and installing the ribbon.

Commercial mics use ribbons that are anywhere from 5 microns to 1.8 microns thick. The ribbon material that Rick supplies is about 0.8 microns. (Thinner ribbons increase high-freq sensitivity.) This is similar to “imitation silver” guilding leaf, it’s readily available on the internet. I’ve bought some from Hobby Lobby before and tried to cut a ribbon from it. I can say without hesitation that it ain’t easy. But that’s the beauty of these videos. Once you see someone doing it, you understand the method better… much better than just reading about it. And you can see that it is possible to make a well-functioning ribbon from scratch, but understand that it’ll take some practice. Even breathing can cause a cut ribbon to fly off your bench. So be ready to make several practice ribbons before you get one correctly made and mounted in your mic frame. And if you just can’t get it, there is an internet source for commercial ribbon foil now. A company called Lebow sells pure aluminum foil in a variety of thicknesses, including 1.8 and 2.5 microns. This would be vastly easier to handle, but it’s also vastly more expensive at $25/sheet. (There may be other sources as well, but this was the only one that I could find. I ordered two sheets to use in my own mics, but they aren’t in yet.)

Ribbon-making details is a big advantage of his instructions, but it isn’t the only one. For example, I learned that you can use a brass footrail cap on the bottom of your mic to hold the XLR connector. These things are nice, solid castings, and if you shop around, you can find them at about $5 apiece. (I wish I’d thought of that.) Circular Switchcraft connectors fit well in these caps.  This would be a good solution for any tubular-bodied homebuilt mic.

The videos do have a slight downside. You have to remember that Rick has built a lot of mics, so some of the things he does in the videos look easier than they will be to folks like you or I. It’s really difficult to explain the things that practice teaches you. But I’m pretty sure that I’ll have a working ribbon mic once the dust settles… I’ll keep you posted.

UPDATE: I finally got up the nerve to install the ribbon today. It worked on the second try, which really isn’t bad. I’m pretty sure that my success with this is pretty much due to Rick’s instruction. Like I said previously, I’ve tried this before and failed miserably. Seeing it done (in a video) makes all the difference.

A just-placed ribbon in the motor frame. This job requires lots of patience, but it can be done.

That is not to say, however, that it was easy. The foil is the definition of flimsy… if it were any thinner I think it’d fly off my bench because of the rotation of the earth. Using the more expensive 2.5 micron foil should be easier (though I expect still no picnic), and that’s what I’m planning for my own ribbon motor frames. (I figured this one should be made as a stock kit, in order to give a fair review.) There will be some slight differences, like slightly thicker magnets… I’m still in the design and prototype phase. But if they work, it’ll be fun to try some design variations like waffle plates (resonators) and silks.