Miking Techniques – Mid-Side and Decca Tree
This is a quick note for now. No sound examples either, as they are at college – documenting the basic ideas of two more useful miking techniques; Mid-Side (2 mics) and Decca Tree (3 mics).
The Mid-Side is interesting and technically confusing for some people to get there head around, as it gives a great stereo image with good mono compatibility, as it uses a centered mic set to Figure of Eight polar pattern, (patterns pointing left and right), for a stereo image. A cable splitter (Y lead) is plugged in so that two identical signals are patched to the desk.
Polar pattern for mic 1
WARNING! If you are using a condenser mic for this, that requires 48V Phantom power, ONLY power 1 cable. If you power both cables, then 96V DC will feed the mic, due to the Y adaptor connected in parallel, and it will probably fry the mic.
The second mic is placed as close as possible to the first and set to omni polar pattern. This one gives the mono image. The best way to position them is one above the other, with one upside down, so they pick up the same point in space, as best as possible:
Now for the neat bit – when you record, you will have three tracks from 2 mics. On playback, you set one side of the split channels out of phase with the other (maybe a button marked POL = polarity, on the channel somewhere). Pan these hard left and right.
This should enable you to set the faders exactly so that they cancel each other out completely. When you find this point, bring up the third mono signal, and fade out the out of phase channel. You will have a nice, slightly lop-sided stereo image with the mono channel and the in phase channel.
You will also have complete mono compatibility if you fade out the split pair signals, as you leave the omni mode on its own. This may be handy for club DJs who need to be aware of mono Nightclub PA systems, so that they can have two mixes of the same track. (A stereo mix played in a club may mean all your stereo pans disappear leaving thumping centre panned drums and bass only..!)
You can also mix the split signals, as you will get frequency dependant partial phasing between the mono signal and the out of phase signal. Experiment with it.
The next technique is the Decca Tree (yes, the record label), which is playing with the placement of 3 mics arranged in a roughly equilateral triangle shape, that roughly equates to the front mic set at your preferred distance from the source, then the R/L mics set 1m (3ft) further back and 1.5m (5ft) to the side. All mics polar patterns are set to omni. This picks up all room ambience. From above:
L 1.5m 1.5m R
You can experiment by inverting the shape, and moving it closer/further from the source. This sounded awesome on its own, recording the drum kit – a really full sound, in stereo with only 3 mics.
I will try to get the recordings for these.