Stereo techniques in music recording – part I

Posted on June 27, 2010

All right, gather round folks.  This shall be the first in a likely series of posts about recording music, intended for people who don’t really know what they’re doing yet.  My bona fides:  I don’t really know what I’m doing either, but I have a lot of experience making mistakes, and that is the essence of learning recording.  So let’s talk stereo.  You’ll find many other such references elsewhere on the net, but what the hell…

If you have two functioning ears then you hear in stereo – that is, each of your ears hears the same sound slightly differently, which allows you to triangulate the sound, in a way, and give it depth and location.  Imagine a sound directly to your right, say a cat meowing.  The sound travels from the cat to you and hits your right ear sliiiiightly before your left ear, and the sound your left ear hears is slighly muffled because the sound isn’t going directly into it.  The sound also echoes off of the wall on your left and comes back to your left ear first, and so on and so on.  This is very subtle, but the result is that each ear hears the sound with numerous variations, and your brain is wired to interpret those variations in meaningful ways (you know where the sound is, how loud it is, how close it is, et cetera).

To see this in action you can do something very simple:  find a room with a slight echo (nothing crazy like a stairwell) and have a friend clap.  Fine.  Then plug one of your ears and note the difference – the clap sounds deadened and flat.  Why?  No stereo image.  Simple.

So how is this relevant to recording?  Well, creating stereo images in recordings can go a long way toward making interesting or pleasing sounds, and is a simple technique you can use to bring out a part in a song.  Additionally, you can abuse this technique to make very interesting effects.  When a lot of beginners record sounds they take a microphone, point it at the source and press record.  Fine.  I should be clear:  there is NOTHING wrong with this approach.  It works just fine and yields excellent results.  However, a single microphone is only one “ear” so to speak; it only picks up a single, mono image of a sound – just like our example of plugging one of your ears.  As a result, the sound – especially if close-mic’d (i.e. close to the sound, without picking up natural reverberations from the room) – will sound a bit flat.

And this leads us to our first, general stereo technique:  use two microphones.  In order to recreate a stereo image on a recording the most direct method is to simply use a pair of microphones, which in effect mimics how we hear.  The key in doing this, though, is to make sure that the microphones are picking up different versions of the sound by placing them in different positions.  This applies to pretty much anything – a xylophone, a violin, a voice – but the most common application is guitar amplifiers, so I’ll use that in what follows, but these ideas are by no means limited to electric guitars.  To put together a stereo setup you can be painstaking or you can be very haphazard.  Many recording geek sites will have you testing the phase alignment of your mics for three hours before starting and experimenting relentlessly to find the perfect sound.  Rubbish!  It’s not that this is a bad approach, but by NO means need you do all of these things.  I prefer to simply set up a mic and go, and work with whatever sound I happen to get.  So if you like my guitar sound, follow my advice.  If not, do the opposite.  I set up mics this way partially because I’m lazy, partially because I’m eager to get on with things, and largely because I enjoy the challenge of working with non-standard sounds.

I usually use a Shure SM-58 or a Beta-57, positioned an inch or two away from the speaker, at a 30 degree angle or so.  Sometimes less, sometimes more.  This is probably what you do too, more or less.  To this I add an Audio Technica 3035 condenser mic which I primarily use for vocals.  The trick here is that the AT sounds completely different than the Shures – it’s much brighter and clearer, and (being a condenser mic) is much more sensitive.  This is essential for generating an interesting stereo image.  To further the differences in the sound I will also place the second mic two to five feet away from the amp, and sometimes I’ll even point it away from the amp completely.  Many people suggest mic-ing the back of an amp and other things and these are good ideas.  The point is that you can get interesting sounds by not trying to capture one perfect image of a sound, but rather by capturing two imperfect images and blending them together.

Here’s what it looks like:

Stereo microphone setup

Two microphones, one amp

You want to tweak the levels so that the volumes from both mics are more or less balanced, but don’t sweat it if they’re not perfectly aligned.  You could adjust it later or you could just leave it.

So I recorded a little demo for educational purposes.  It consists of two guitar parts, both recorded exactly as you see above (guitar:  Gibson SG, amp:  Carr Mercury).  I added a cheapo mono drum part just for the hell of it too, and that’s it.  No effects, no compression, no nothing.  So first off listen to the demo with just the SM58 mic, with both parts in the centre of the spectrum.  I highly recommend doing so with headphones, or decent speakers – i.e. not your laptop’s speakers – in order to get the most out of this.

mono – this is the demo in mono, using only the SM58 mic.

full stereo – this is the exact same thing, except both parts use both mics.  For each part (both of which consist of two tracks) one mic is panned hard left, and the other hard right.  I reversed the pannings of each part, so that for Part 1 mic 1 is left and mic 2 is right, and for Part 2 mic 1 is right and mic 2 is left.  This is important when blending similar parts.

It looks like this in ProTools:

Each part is in two tracks (the same performance recorded through different microphones at the same time).  Note the volumes are more or less equivalent.

blend – and finally a cool technique, using mono and stereo.  This is the same demo as above, however it starts in mono and then expands into stereo.  This is an easy way to add some dynamics to your track without really doing, well, anything!

Hopefully this has been useful, and remember that guitars are just an example, you could do this for anything.