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Figure of 8 as Mid in Mid/Side

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Figure of 8 as Mid in Mid/Side

Postby Bob Bickerton » Wed Jan 11, 2017 11:07 am

A post beer curiosity ramble.....

We've discussed a number of times the usefulness of using two figure of eight mics for recording singer guitarists, pointing the null of the pattern at the opposite source to attenuate it.

Recently I've been experimenting with M/S recording on instruments like guitar and have been well pleased with the results from using an MKH8040/MKH30 combo.

So I've been thinking that it may be useful to use an M/S technique when recording singer guitarists. The theory being that if the mid mic was figure of eight with the null pointing at the voice then the side mic would, by default, have it's null pointing at the voice as well.

I've just tried it with a Naked Eye ribbon as the mid and the MKH30 as the side and using a U87 on the voice. Plenty of attention of opposite sources, but I'm finding the guitar sounds pretty phasey when the side is kicked in.

Haven't spent much time on it and really just messing around, but I was curious to know if this was a recognised technique and if it's workable.

Bob
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Re: Figure of 8 as Mid in Mid/Side

Postby John Willett » Wed Jan 11, 2017 12:59 pm

Hi Bob,

Two fig-8 in MS is the way Blumline originally did it.

Read this paper by Wes Dooley and Ron Streicher which will explain it all (link is to a PDF).

But the mid fig-8 points towards the voice - only the side has the null to the voice.

The paper includes some very good diagrams which show what happens with various level differences between the mid and side mics - excellent. :thumbup:

Some of the nasties you hear may be due to having a switchable-pattern mic. in fig-8, rather than using a second MKH 30.

I hope this helps.
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Re: Figure of 8 as Mid in Mid/Side

Postby Bob Bickerton » Wed Jan 11, 2017 7:58 pm

Thanks John.

I probably wasn't clear, but was talking about an M/S array on guitar PLUS a figure of eight on voice.

Bob
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Re: Figure of 8 as Mid in Mid/Side

Postby Sam Inglis » Wed Jan 11, 2017 8:10 pm

I wonder if the problem here is that the Sides mic on the guitar is basically off-axis to everything. So, although the vocal is in the deepest part of the null, actually the guitar is also in the side null. I'd imagine the separation in the Sides mic is not as good as it is in the Mid mic, and that any vocal it does capture is fairly nasty.

For me this is a situation where you're nearly always better off with the more artificial stereo picture you get from two separate guitar mics in different places, both positioned so the guitar is on-axis and the vocal in the null.

In theory the M/S approach might offer a more 'realistic' picture of the guitar, but then who listens to guitars from a foot in front of the neck joint anyway?
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Re: Figure of 8 as Mid in Mid/Side

Postby Kwackman » Wed Jan 11, 2017 8:13 pm

Bob Bickerton wrote: I'm finding the guitar sounds pretty phasey when the side is kicked in.

How close to each other were the Mid & Side capsules?
If you zoom in to waveform level, can you see if the two mic tracks are totally in phase?

Last year, thanks to a discussion you & the Elf had, I experimented with MS recording of an acoustic guitar. I hadn't the capsules terribly close together, and delaying the M mic track (or advancing the S mic track) to make the waveforms match up, helped get rid of some oddities I was having.
I discovered (2nd recording) that making a sync "clap" before playing the tune, makes aligning tracks so much easier!
The above may, or may not be relevant to your situation..
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Re: Figure of 8 as Mid in Mid/Side

Postby Hugh Robjohns » Wed Jan 11, 2017 8:57 pm

Bob Bickerton wrote:I've just tried it with a Naked Eye ribbon as the mid and the MKH30 as the side and using a U87 on the voice. Plenty of attention of opposite sources, but I'm finding the guitar sounds pretty phasey when the side is kicked in.

So the idea of using fig 8s on voice and guitar, angled so that their nulls reject the opposite source, is an established technique (and one I described in SOS nearly 20 years ago!)

The idea of using an MS array to record acoustic guitars is also well known and, as you say, the side mic null can be angled towards the voice very easily too.

The MS array on its own shouldn't sound phasey, because it's a coincident array. Of course... If the capsules aren't tightly coincident anything is possible...

But if it sounds phasey when you fade up the side mic with the vocal mic (U87) is because they are both hearing the same thing, separated by a short time delay.

So, either the side mic null isn't rejecting enough of the voice (picking up chest resonances, maybe), or it's picking up vocal sound reflected off the walls/floor/guitar body etc.

H
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