Mercenary Audio - WTF are Ribbon Mic's? by David Satz from the rec.audio.pro Usenet Group

Could someone please enlighten me as to

What a Ribbon Mic is?
How they differ from other types of mic?
What are their advantages and disadvantages?
and typical uses for them.
"Ribbon" is one general type of microphone mechanism, as contrasted with "dynamic," "condenser," "piezoelectric," "carbon", etc. Each of these categories defines a physical method by which a microphone can convert sound waves into a varying electrical current or voltage.

In ribbon microphones, a narrow strip of (generally) aluminum is suspended within the field of a strong permanent magnet. When sound waves cause the ribbon to vibrate within the field, the motion of the ribbon cuts the lines of magnetic force and causes a current to be induced in the ribbon. Since aluminum conducts electricity, this rather small current is available at the ends of the ribbon, and can be sent down a cable and amplified.

Of the different types I listed, ribbons and condensers have one important thing in common: the object which the sound waves must set in motion can have relatively low mass, and can be built so that any resonances in the audio band are either damped or absent in the first place.

This gives ribbon and condenser microphones the best chance at being sonically accurate transducers, if that's what their designers would like them to be.

Ribbon microphones do not require external powering, which is a definite advantage over condenser microphones, but they have much lower sensitivity (= output for a given sound pressure level) than condensers, which puts more of a requirement on the preamp or recorder to which they are connected, to amplify their signal without adding too much noise in the process. Other problems include the fact that the permanent magnet assembly in some ribbon microphones is large, heavy, and a potential danger to any tape recordings placed within several inches of the microphone, and the fact that the ribbon can be destroyed in an instant if some bozo decides to test the microphone by blowing into it.

Ribbon microphones were the high quality type of radio broadcast microphone in the U.S. until the end of World War II. You've undoubtedly seen many photographs of "diamond"-shaped microphones and of microphones that look like greatly enlarged vitamin capsules (cylinders rounded on both the top and bottom)--those are mostly classic RCA ribbon microphones. Entire decades of well known singers and pop instrumentalists were recorded and broadcast through ribbon microphones; ribbons determined the essential sound of records and radio in this country for a whole generation.

Now, I happen to use condenser microphones, and the ones I use are predominantly neutral-sounding, but I'm in the small and ever-shrinking classical recording field. The condenser mikes used most often in pop and jazz recording are mostly brighter sounding than reality, which has led many people to the false conclusion that "condensers sound bright because they're condensers." (No, condensers sound bright because people buy bright-sounding condensers, so the companies that sell condensers keep making bright- sounding ones. Duh.)

But given that widespread, false belief, the accompanying belief is that "ribbons sound warm and natural without the false brightness of condensers." Reality: condensers can be warm and natural without false brightness, and ribbons can be harsh and grainy sounding--but a market exists primarily for condensers that are bright sounding and for ribbons that are warm and natural without false brightness, so that's a lot of what's out there. Which means that some very useful, nice-sounding ribbon mikes exist.

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