Click here to purchase the entire book in PDF format. ES There are many occasions where you will want to add some extra microphones out in the hall to capture reverberation with very little direct sound. This is helpful, particularly in sessions where you don't have a lot of sound-check time, or when the hall has problems. (Typically, you can cover up acoustical problems by adding more microphones to smear things out.) Many people like to use VERY widely spaced omni's for this, but this technique really doesn't make much sense. As we'll see later, the further apart a pair of microphones are in a diffuse field (like a reverberant concert hall) the less correlated they are. If your microphones are stuck on opposite sides of the hall (this is not an uncommon practice) you basically get two completely uncorrelated signals. The result is that the reverberation (and the audience noise, if they're there) sits in two discrete pockets in the listening room - one pocket for each loudspeaker. This gives the illusion of a very wide sound, but there is nothing holding the two sides together - it's just one big hole in the middle. So, how can we get a nice, wide hall sound, with an even spread and avoid picking up too much direct sound? This is the goal of the ES (or Enhanced Surround) microphone technique developed by Wieslaw Woszczyk. The configuration is simply two cardioids with an included angle of 180$^\circ$ degrees (placed back-to-back) with one of the outputs reversed in polarity. Each microphone is panned completely to one channel. This technique has a number of interesting properties. It was initially developed to make a microphone technique that was compatible with the old matrixed surround systems from Dolby. Since the information coming in the centre of this pair is opposite in polarity between the two mic's, this info would come through a 2-4 matrix and wind up in the surrounds. Therefore you had control over your surround info in the matrix, with a smooth transition from surround to left and right as the sound came around to either side of the pair from the middle. Also, if you sum your mix to mono, this pair gives you the same output as if you had a bidirectional mic in the same location. Since the null of that bidirectional is probably facing the stage, you get reverb, and very little slap delay from the direct sound. Of course, it could be argued that you want less reverb in a mono mix, to keep things intelligible... but that's a personal opinion. If you do want to try this technique, I would highly recommend implementing it using a technique borrowed from an MS pair. Set up a coincident omnidirectional and bidirectional with the null of the bidirectional facing forwards (so the mic is facing sideways). Send the two signals through an standard MS matrix where the bidirectional is the M channel and the omni is the S channel. The result will be a perfectly matched ES pair with the benefits of negatively correlated low frequency (thanks to the low-end response of the omni).