The classic X-Y technique has uses beyond stereo pickup duties, but what are they and why should we consider them? We discuss…

For many, nothing beats the involving sense of size and realism that a stereo recording brings to the mix, with almost any source that possesses some amount of physical width benefitting from the treatment. Any of several different techniques using two microphones may be employed to achieve panoramic nirvana, with some of them possessing favourable qualities that can be employed for recording situations other than stereo.

Capturing Stereo

Stereo recording relies on there being a difference of some kind between the two channels conveying the sound captured. If both channels are the same then sounds will appear to be centrally placed to the listener. These differences can either be in the form of level differences, time differences, or both.

Level difference techniques employ directional mics mounted close together and angled so as to capture different parts of the soundstage at different levels. In the case of time difference techniques, mics (often omni pattern) are spaced apart so as to capture different parts of the soundstage at different times. When using directional mics, a fusion of both techniques can be employed by spacing the mics slightly.

X-Y stereo is a level difference technique which sees two cardioid mics placed as close to each other as their bodies will allow, angled apart by 90 degrees. There are variations on this combination, and contrary to popular belief, changing these parameters does not ‘break’ the sound, and indeed should be changed when the situation calls for it.

X-Y For Mono Sources

With both techniques employed to capture two discrete channels of information, with some imagination, these channels can be things other than left or right, such as source A and source B. This way, any ‘stereo’ array to be pointed to capture discrete sources.

We can work on the understanding that an X-Y stereo array works better in mono (owing to the fact that both mics essentially hear everything at the same time) than a spaced array does. We can then use X-Y to capture two different mono sources that are physically close to each other (which can be panned to the same position in the mix) such as a pair of horns or a singing acoustic guitarist, simply by using the array on its side for the latter. This can be especially useful for when the talent is moving around a lot in relation to the array, where the constantly shifting path lengths can make ‘phasing’ especially audible. While we might not have quite the same control as that afforded by spaced spot mics, what we do have is a setup that behaves well in a mono or stereo mix, forgoing spaced mics’ potential for phasiness.

In the video we demonstrate how using X-Y for two simultaneous mono sources (vocal and acoustic) can solve the problems that using a conventional spaced mic approach can cause.

The acoustic guitar is mixed higher than would be used for the final mix. For this example the raised level best demonstrates the phasing artefacts that can be heard when two spaced mics are used.

Not Just For Stereo

Filmmakers often talk about capturing images ‘in-camera’ as opposed to getting them in post production. While phase related issues can to an extent be dealt with using techniques such as phase rotation, taking the ‘in-camera’ approach to recordings is always quicker, can improve audio quality, and can be more rewarding for both engineer and artist who prize authenticity. Using a level difference technique such as X-Y comes into its own for separate sources, where pure, phase-free capture is the aim.