Acoustic phasing and acoustic EQ in

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 Record-Producer.com.

Tuesday February 5, 2019
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If you haven't seen the movie Bohemian Rhapsody yet, then you should. As well as telling the story of the band Queen up to their appearance in Live Aid in 1985, it offers interesting insights into their studio recording process.

Of course it is a dramatization and it would be unreasonable to expect every detail to be correct, but I have some examples here that are very realistic and would be useful to musicians, producers and engineers today.

Acoustic phasing

The first example is of acoustic phasing. Take a look at this - it's a very short segment in the movie so I've repeated it a couple of times in slow motion. There's no sound because the soundtrack of the movie plays Seven Seas of Rhye rather than the actual sounds of the events depicted. You'll get a better view if you click into full-screen mode.

What you see in the clip is Brian May (of course, the actor who plays Brian May, but for simplicity I'll use the names of the band members) playing electric guitar into a combo amplifier. The amp is suspended from the ceiling and swung from side to side. Freddie Mercury chases the amp with a microphone on a boom.

What you would hear if you tried this yourself is acoustic phasing. Because the mic chases the speaker, the direct sound of the guitar is more or less the same as if the amp and mic were static in the normal way. However the mic will also pick up the ambience of the room.

Because the amp is swinging towards one wall of the room, the Doppler effect will cause the reflections from that wall to rise in frequency. Similarly because the amp is swinging away from the opposite wall, the Doppler effect will cause the reflections from that wall to fall in frequency. The movement of the microphone also creates a similar Doppler effect.

This creates a thickening effect in the natural reverberation of the room, and also a swirling effect because of the movement. I strongly suggest you try it, but be careful not to cause injury or damage.

Acoustic EQ with phasing

This clip shows John Deacon spinning a cymbal before striking it, which would be an interesting effect it its own right. Prior to that, Brian May and John Deacon place a metal trash can over a microphone (it looks rather like an RCA 44-BX which would be a very valuable mic to risk damaging).

This creates an acoustic EQ effect where the resonance of the volume of air inside the trash can accentuates certain frequencies, and also the trash can itself will probably resonate.

But further than this, as John Deacon hits the cymbal, Brian May moves the microphone, inside the trash can, past the cymbal. This causes an acoustic phasing effect similar to the first example.

Clearly there is a comedic element in this clip - perhaps it happened naturally during filming, but the acoustic EQ and acoustic phasing effects depicted are genuine.

Once again, I recommend you try this effect, preferably with a cheaper microphone.

From the trailer

Here are two clips from the movie's trailer that I didn't see in the film - maybe I saw a different cut. Again there is unfortunately no audio for the same reason as the first two examples. The clips are VERY short in the trailer so again I have included slow-motion versions. Firstly some more acoustic EQ...

In this we see the band singing through cardboard tubes. Again this will create interesting acoustic equalization. It's also worth noting that Brian May is aiming his tube exactly towards the side of the mic. This mic appears to be an RCA 44-BX which is a ribbon mic and therefore entirely insensitive towards the sides.

The last example is a little more weird and it takes a bit of peering into....

What I think I see is a loudspeaker suspended by its own cable, presumably playing back a track that was recorded previously (as would have been done in real life, remembering that this is dramatized).

Now what about the plastic wrapping around the front? Look closely... It is holding a tambourine in front of the drive unit! Oddly enough I have done something like this in the past - I once had a singer (the under-appreciated Danielle Dax) sing through a rototom.

Have a go

Now you have seen how it's done, and I'll remind you that these are all genuine real-life techniques, I'd like to invite you to have a go, taking care of all aspects of safety of course.

If you come up with something interesting, let us know via the contact page and we may be able to feature your work in the newsletter.

By the way...

Acoustic EQ is covered in the Audio Masterclass Professional Course in Equalization. Acoustic phasing is covered in the Audio Masterclass Professional Course in Reverb and Effects.

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