Jecklin disks are one of our favorite stereo or binaural micing techniques. It creates a more natural stereo image by adding some amount of isolation between the two microphones being used. We're essentially simulating the dampening that a human head exerts on sound arriving to our ears.

There are a handful of companies selling discs, most notably Josephson Engineering's TN5. We've built our own in house with a 12" round piece of plywood and some acoustic foam. Not nearly as good as a TN5, but we've been very happy with the results.

We'll usually use a pair of Gefell M930s, which is a large diaphgram cardioid, when using a jecklin disc. We've also mixed mics, for example, when recording acoustic guitars and we wanted a "crispier" mic pointed at the neck. This is one of the fun things about jecklin discs: you get to experiment a really hear the differences between the two microphones.