A Decca tree stereo recording setup involves three mics that mix together to give a pleasing, accurate stereo image. Half of the name came from the Decca recording label, who invented the technique, and half came from the how the setup looks - kind of like a tree.
The first part of the Decca tree stereo recording setup is two omni-directional microphones, in a spaced pair configuration. They are usually placed between one and six feet apart. This provides the foundation of the stereo image for the recording.
The second part is a third omni mic, placed in the middle of the first two, and slightly front. This mic adds clarity and a lot more placement information in creating a soundstage in the mix.
The general rule of thumb for placing the third mic is not hard. Exactly in the middle between the outer two mics, and slightly in front. To determine how far front, take the distance between the two side mics, and divide by two. For example, if the left and right microphones are two feet apart, put the center mic one foot in front.
This configuration looks and works a lot like a simple AB spaced pair stereo recording mic setup. The difference of the third mic adds precision in pinpointing the "location" of sounds when you listen over a stereo system.
When you mix a the tree stereo pattern, pan the outer mics to hard left and right, and leave the center mic panned to the center. Remember, the rules are not absolute - you are free to modify as needed to suit your purposes.
As with any spaced pair stereo recording pattern, you don't want to let the mic spread get too big. The further apart the omni mics are, the more "gaps" you will notice in the final product. If the microphones are just too far apart, the mix won't sound unified - it will seem disjointed and far apart.
What microphones work best with a this recording setup? The only requirement is that they be omni-directional. You can use cheap ones, or you can use expensive ones. I use a pair of Earthworks QTC-40 omnis for the sides, and an Audio Technica AT4050 for the center. The AT4050 is switchable between omni and cardioid, so that works well for me.
I really like the quality of recording that these mics give me when working in a Decca tree format. The stereo image is superb, and overall, it's just a lot of fun!
In recap - the Decca tree stereo recording setup uses three omni mics, two sides, and one center, slightly in front of the sides. It offers a precision stereo image, and works with all kinds of omni microphones. Keep the setup close enough together, and you'll have great results. I love the sounds I get from my Earthworks QTC40s and Audio Technica AT4050.
Lee started his career in recording with an auspicious goal - record tracks of his own voice singing in harmony. As a hobby project, it didn't have the funding to go to a studio and pay for someone to do it for him. Like many of you, he pulled himself up by the bootstraps to learn the art of recording.