Adventures In Audio
Doppler phasing - extreme creativity in the studio

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.

Thursday March 10, 2011

Phasing and flanging effects are most commonly achieved using either rack mounted effects units, stomp boxes or digital plug-ins.

But the original phasing technique was done by tape manipulation and required no equipment other than the tape recorders that were standard in the studios of the day.

These days, tape recorders are a rarity. So is it still possible to produce phasing effects without special equipment? The answer is yes...

The Doppler phasing technique requires no equipment other than a source of sound - a guitar combo amp is handy - and a microphone. It's easier if the microphone is mounted on the boom section of a mic stand, without the floor part, so you can easily hand hold it.

Christian Andreas Doppler is the scientist we have to thank for discovering that if a sound source moves, then when it moves towards the listener its pitch is apparently raised. When it moves away its pitch is lowered. The same applies if it is the listener who is moving.

Here, we are going to play the signal to be phased through the amp, and move the microphone backwards and forwards in front of the speaker. It also works if you move the mic in circles, or even random patterns.

As the mic approaches the speaker, the pitch of the signal is raised, as it moves away the pitch is lowered.

But this isn't phasing - it is just a cyclic pitch change that will be heard as vibrato.

Now consider the reflections of sound in the room, particularly from the wall opposite the amp. As the mic moves towards the amp, it moves away from the reflecting wall. So as the pitch of the direct sound rises, the pitch of the reflection falls.

This gives an amazingly rich and vibrant sound - very different to what you get with effects units, particularly digital effects. And don't forget that there will be many reflections, all treated slightly differently, adding to the richness.

For stereo, two people can move two mics independently.

In the 1960s, recording used to be all about creativity. Now it seems to be a matter of selecting a preset. But with Doppler phasing, you'll get a sound that no preset can match.

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