How many microphones do you need?

AKG 426 Mid Side Microphone

One of the more common questions we are asked when bidding for recording work is how many microphones will be used for the recording?   Without wishing to sound off hand about it, the usual answer is however many we need!

To some extent I can understand the reasoning behind a potential customer asking this question.  There are a lot of people out there who claim to offer location recordings and in fact turn up with a stereo pair of microphones and a portable recorder.    Sometimes this is all you need.  Aside of working with 4 Part Music, I also run a number of choirs.  In order to help people learn the songs I will often record rehearsals.  For that purpose a small hand held recorder and a pair of microphones is perfectly adequate.

But when you are trying to make a professional recording, whether that’s of a Primary school Choir, a Community Choir or an award winning Silver Band, then you will often need considerably more than a stereo pair of mics.  Ultimately however, it is not so much about the quantity of microphones, but the quality of each microphone and then most importantly the placement in the recording venue.

How many channels are needed?

When we got out on location our default position is to take 16 channels.  This is usually more than enough for most types of recording. However, it doesn’t always mean there will be 16 microphones placed in the venue.  Some microphones, Soundfield microphones for example require 4 channels.  You then have mid-side microphones which require 2 channels.  And some channels need to be reserved for DI (Direct Injection) for example if recording an electric guitar, keyboard or taking a feed from a backing track. Taking all that into account then it is quite easy to use up 16 channels whilst only having 8 or so microphones in the space.

When determining the number of microphones / channels to be used consideration also needs to be given to the final mix.  Certainly when recording a choir, the intention is to capture the sound which a listener might hear.   Yes of course you need to capture the detail but you do not need so much that the final sound is confused.  Regardless of how many microphones / channels are used in the recording session, in the majority of cases the final output will be a stereo image.  This image is the result of all these multiple channels being carefully combined in post production.

What happens in Post Production?

Once you have successfully captured the recording on location, using as many or as few channels as necessary, it then becomes a matter of ‘post’.   Of all the aspects of recording, this is the bit which is often least understood.  With experience and careful mic placement, usually most channels are used in the final output.  However, sometimes it is useful to create options.   Consequently we may put up more microphones than strictly necessary, to make decisions after the session.  This is the main advantage of a multi-mic setup.

Audio post production is a huge topic.  However, the most important thing for any sound engineer is to start with a decent quality recording. As far as possible it is always best to keep each channel as ‘clean’ as possible.  Each channel needs to be carefully labelled in the DAW to establish it’s ‘purpose’ in the mix.   One of the first things to consider is mic placement in a stereo image.   Usually, within the software each microphone can be positioned into it’s own space on a virtual stage which represents its location in the field.  This is critical to get right otherwise you will get an incorrect image.

From that point balance needs to be considered.  In very simple terms this is the level or crudely volume from each microphone which is added into the final mix. Sometimes even a very small amount from just one microphone can make a lot of difference.

Ultimately, this is barely scratching the surface of what is involved in post production. But even these two basic elements can absorb a lot of time.  Almost every tweak means listening to the entire song again.  Ignoring making production decisions and the editing process, which itself can take many hours, on average every track will be listened to at least a dozen times during the course of post production.

Is there a right or wrong?

Ultimately in music recording and music production, even for the most skilled engineers, there is a lot of trial and error.  Nowhere more than location recordings.  Every location is different and as such every set up is different. There are basic parameters which are followed and a few ‘rules’.  But ultimately microphone placement, and the number of channels used is a decision based on many years of experience, a degree of intuition and above all relies on listening both on location and afterwards.

About the Author: Jules Addison is  Director of 4 Part Music, a Sound Engineer and Choirmaster with many years experience both running and recording choirs all over the UK.

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