About Ribbon Microphones

Ribbon microphones have legendary status in the industry. Back in the ‘40’s, ‘50s and even ‘60s, ribbon mics were quite popular. Since that time, they have fallen into disuse, because many of their virtues were acquired by the dual large-diaphragm condenser microphones, with comparatively few of the operational problems that ribbon microphones presented.

Naturally, such mics are steeped in an aura of retro superiority, and there is a cult of users who swear by (a) ribbon microphones in general and (b) old ribbon microphones in particular, such as the RCA 77DX mic and/or the Bang & Olufsen 200 stereo ribbon mic. Such mics are alleged to have extraordinarily “natural” sound quality, which is to say that some engineers really like the way they capture the timbre of instruments and voices in the studio.

It’s useful, in light of this, to consider how ribbon mics actually work. To quote from my new book, Total Recording (what a trip! - to be able to quote myself! – not hafta get permission!!!):

The ribbon microphone lies somewhere between the condenser and the dynamic microphone in terms of attributes. It also has a specific and particular directional behavior that makes it special.

The ribbon microphone consists of a comparatively large, compliant metallic diaphragm suspended in a strong magnetic field. As the diaphragm moves in response to the motion (velocity, actually) of the air, its passage through the magnetic field causes an electrical current to be generated, creating the audio signal.

By the nature of the design, the ribbon diaphragm is open to air on both sides. As a result, sound artifacts arriving from the sides of the microphone diaphragm exert equal pressure on both sides of the diaphragm, so that it doesn’t move. The result is that the electrical output of the microphone varies as a function of the angle of arrival of any given sound artifact. More specifically, sounds arriving from the side are not picked up, while sound from the front is picked up strongly and sound from the back is picked up equally strongly, but with the polarity of the electrical output from the microphone reversed.

This bi-directional, or “Figure 8”, directional behavior is of great importance to understanding general microphone usage, a variety of stereo microphone techniques, and the derivation of the so-called “cardioid” directional behavior of microphones.

What I didn’t say in the book, and probably should have, is that one of the virtues of the ribbon microphone is that the ribbon itself, being so compliant and low in mass, floating in space as it were, has really excellent transient response to the velocity (and direction) of the air molecules. Because the ribbon is essentially free-floating, it can really provide a quite accurate rendition of the changing state of air velocity at the mic. This is also, of course, an operational hazard. The ribbon is extremely vulnerable to air motion (you NEVER blow into a ribbon to see if it’s working) and suffers from an extreme case of proximity effect. I suspect that these are some of the reasons ribbons have fallen into disuse – they have been a little too fragile for the rigors of rock’nroll life.

The Royer R-121 Microphone

With all that said, I was pleased to find that Royer Labs has come out with a new ribbon mic, the R-121, using some updated technology for both the ribbon itself (a 2.5 micron thick aluminum ribbon) and for the neodymium magnets (there are two magnets in each R-121, one on each side of the ribbon). Royer also offers a stereo ribbon microphone, the Royer/Speiden SF-12. The SF-12 is not simply a stereo version of the R-121, it’s an altogether different microphone with some common tonal charisteristics. Such a pair of ribbon elements in a coincident array constitute the so-called “Blumlein Pair” and can be used in either XY or MS configurations for immense fun and profit. Really tasty.

Whatever. I got Recording Mag (Metlay, actually) to put the bite on Royer at NAMM to send me some mics, which they kindly did (two R-121s). The mic is really nice-looking. It is a carefully fabricated metal structure exhibiting excellent build quality, with typical “ears” sticking outside of the cylindrical mic housing that are in fact the magnets. Note: you’ve gotta be careful around magnetic tapes and the like - the permanent magnets in a ribbon mic are quite strong, and they will partially or fully gauss and/or degauss DATs, credit cards, cassettes, etc. Each mic comes in a rugged wooden case, and a spring-loaded mic clip is provided. You can get a really nifty windscreen with it, as well as a shock mount. Both accessories are highly recommended. Oh yes, the price. $995 MSRP. Not cheap, but not outrageous, either.

Like all ribbon mics, the Royer is bi-directional in pickup pattern (the so-called “Figure-8” pattern). Happily, my measurements confirmed that the pattern is pretty much constant across the audio spectrum. Royer claims a frequency response of 30-15,000 Hz. and the mic easily does that (see the sidebar about measurements, however, for an interesting tale). Sensitivity was rated at -54 dBV for a 94 dB SPL input, which is typical for any reasonable unpowered microphone. Royer recommends that you operate the microphone into a load of greater than 1 kilohm. Not a problem, most of the time. The maximum level that the mic is rated to endure is “> 130 dB SPL.” I probably wouldn’t stick the Royer into a kick drum, or right in front of a stack of Marshalls playing Goth. Royer doesn’t publish an Equivalent Input Noise (E.I.N.) spec, but I informally measured it to be around 23 dBA SPL. Decent. Interestingly, Royer offers a lifetime warranty to the original owner. Nice touch.