Ribbon microphones: what are they and how they work

Hello everyone and welcome to this week's article!

Today were going to talk about ribbon microphones.
Ribbon microphones are a a particular type of microphone that use a thin ribbon of a conductive material (for example aluminum) between the poles of a magnet to record the sound, and this particular construction allows it to sound very pleasant, round and sensitive to certain frequencies, but at the same time makes it quite fragile, therefore it needs to be handled with more attention than a regular dynamic mike.

Ribbon microphones were first introduced in the early '20s of the past century, and they were praised to be the type of microphone more suited to reproduce the whole spectrum of human hearing (20hz to 20khz), and with the time, as per the other types of microphones, technology evolved and today we can count on microphones that are less fragile than before (although it's still importato to observe caution when handling them), made with more solid and durable materials, with various types of sensitivity pattern (cardioid, hypercardioid, variable, uni-directional, bi-directional and so on), active and passive.

The active ones work more like condenser microphones, meaning that they need an energy source in order to work (never use the phantom power on a passive ribbon microphone or some internal component will break!!), while the passive ones work like dynamic mikes, and are used often to microphone brass instruments and guitar amplifiers.

Speaking of guitar amplifiers, there are 2 main techniques which are very popular in recording studios, and that involve both a ribbon microphone (such as the famous Royer R-121) and the omnipresent Shure SM57: the most famous is the one in which the ribbon microphone is in vertical in front of the center of the dustcap, next to the speaker grill (to take the high end of the tone, since it doesn't sound too brittle or harsh), and with the SM57 pointing towards the edge of the dustcap, so it's slightly off the center and this way it captures a bit more the body of the tone.

The second technique is the other way around: the SM57 points towards the center of the speaker, essentially capturing the high end of the amp, and the ribbon mike is slightly away from the speaker grill (we're talking around 15cm) and off-center, so it will take more the low-mids part of the guitar tone.

Either way, it's essential to check out the position between the two microphones to minimize phase cancellation, so if you notice there are a lot of phase issues try moving one of the 2 microphones in order to align the phase, plus if the guitar amp volume is extremely high, it could be also a good idea to tilt slightly the ribbon mike off axis in order to prevent the sound pressure to hit the ribbon too frontally.

Obviously these are just a couple of the thousands of possible mic placements, but they are a good starting point when trying out a ribbon microphone.

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