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more... MicrophonesRecording TipsRecordingMarch 2009

Ribbon Microphones 101

What Are They For?
In a word: fidelity—accuracy in details, transient response, incredibly sweet and clear highs, clean mids and rich, accurate lows… probably the most natural presentation ever. Yet, they can be lush and romantic, with great warmth, and without bloat. Mic techniques coupled with the right electronics give you flexibility. Want a bit of bloat or extra warmth? Like their dynamic moving-coil brethren, ribbon mics suffer from proximity effect. Get really close, get lots of bottom. Place the mic a couple of feet away, clarity and balance start to return. Some models have a choke or high-pass circuit on board to attenuate low frequencies for close micing.

Can’t we get this level of performance with any decent mic? Nope! Here’s why: If you start with a non-linear transducer, be it loudspeaker, phono cartridge or microphone, it’s very difficult to linearize. If you start with a distorted transducer, it’s even worse. There are distortions present in all transducers—even if you think you can’t hear them. Since the electronics we’re feeding have distortion as well, the distortion is additive (actually, mathematically, it’s worse; with noise, for example, you add the squares). Many types of distortion are non-linear—they sound dissonant. If you distort the distortion coming from the mic (with electronics), you have audibly destructive fresh distortion components. If you think your chain is clean with a conventional microphone (and it might be!), with a good ribbon and transformer/ preamp, it won’t be just clean, it’ll be pristine. The ribbon microphone is the cleanest mic out there. The primary reason is the low mass of the diaphragm. Less inertia means an intrinsic ability to follow waveforms more accurately.

Figure-8 pattern typical of ribbon microphones

Cardioid (heart-like) microphone pattern
Ribbon mics ruled broadcast for years, and recording studios always have ribbons available. Besides their natural spectral balance and superb transparency, they also have great pattern flexibility. Typically, ribbon mics have a bi-directional sensitivity pattern. As you can see from the diagram, when viewed from above, you have essentially identical pickup of sound front and rear with good side rejection. If you use a pair of these correctly, you end up with the natural, open sound of the famous Blumlein Pair microphone array. In addition, many of today’s ribbons give you the option of cardioid, hypercardioid or even omni-directional patterns. Some even allow you to set almost any pattern you can dream up.

Some ribbon mics have long ribbons with a short acoustic path around the magnets, while others are the opposite. Pros select mics with these parameters in mind, but for many others purchase decisions are often dictated by pricing rather than coverage and pattern. In theory, a longer ribbon has more limited vertical pickup pattern—better for cleaner sound, as the reflective ceiling and floor surfaces contribute less coloration and reverb. There are applications, however, when you want the added ambiance.

Today’s ribbons can actually be used on stage. Combining a variable pattern with natural spectral balance and head-turning transient response can give you the very best of a good acoustic guitar—about a bazillion times better than a “quacky” onboard pickup. From oboes to piccolos, from violins to French horns, ribbons work great with acoustic instruments. No matter the music, ribbons rock.

Due to the large size of the “motor,” ribbon mics have been large from day one. Not all are large. Some look like regular hand-held, dynamic moving-coil mics, while some look like Johnny Carson’s. The old RCAs are dripping with vibe cosmetically and many companies emulate that look.