Ribbon Microphones

Yet another type of microphone! ....... This is the last, I promise.

The advent of the "wireless" (radio) in the 'twenties saw the development of microphones suitable for reproducing both the human voice and musical instruments with appropriate fidelity and clarity for the home listeners.  The old carbon and crystal types just wouldn't do:  frequency response and ease of use had to be drastically improved, especially in the new motion pictures with sound.  Enter the ribbon microphone.

This is a famous example from the 'thirties from RCA.  Used in studios and on location by countless commentators, newsreaders, talent and musicians throughout more than four decades, and still going strong in many commercial music studios today, if you can afford one, that is.
Compared to, say, a typical condenser mic., ribbon microphones tend to be classed as "warm", "smooth", "un-hyped", etc.
Because of their construction, they pick up sound from front and rear sides, nearly always equally, but not from side sources.  More on pick-up patterns at some point in the future.
As moving-coil (dynamic) microphones improved in sensitivity and frequency response, ribbon mics were used less often, especially in announcing roles.

 Recent years have seen growing interest in ribbon microphones, with many manufacturers designing and producing variations of this type of mic.

Why "ribbon" ?

These two photos of the "motor" of a typical ribbon mic. show a magnet assembly on each side of a piece of crimped or folded aluminium foil, the two ends of which are connected to a miniature matching transformer (not shown in the photos).  The foil strip is typically 4 or 5 millimetres wide, anything from 50 to 80mm long and only about 2 microns thick - about the same thickness as the "silver paper" often serving as a wrapper around you favourite chocolate bar.
The magnets are strong, but the ribbon is very flimsy - never blow into a ribbon (or condenser) microphone to see if it is working!

Sound causes the ribbon to vibrate in sympathy between the poles of the magnet(s), causing a weak electric current to flow along the length of the metallic ribbon.  A small transformer in the microphone body provides the correct voltage and electrical impedance ( Never mind!) for the microphone preamplifer.  Some versions of ribbon mic. include a preamplifier in the microphone itself:  they are termed "active" ribbon mics.  A fair bit of "gain" is needed for the low-output ribbon mic., even more than is required for dynamic types.  High gain, low noise preamps are mandatory.

I must admit that some of my favourite microphones are ribbons.  So far, only three - a Royer stereo type, a custom long-ribbon type from O.P.R. in Wiiliamstown, and a modified MXL R144 (see top of page), improved by replacing the ribbon and transformer.  Thanks, Mark at O.P.R..

Don't forget, if you have any questions or comments, please feel free to contact me via email, or through the comments box.

Thanks for reading!

Rob.