Tag Archives: Optimum Stereo Signal

Jecklin Disk: Optimum Stereo Signal Recording in a Few Hours

Too much acoustic isolation, too many decisions deferred for the mix, too much editing, and not enough commitment to the moment, the space, the mistakes, the excitement, and the humanity of people playing music together. That’s how I feel about the modern multi-track computer centric recording process. It drove me away from a career as a recording engineer but also towards my love of realistic stereo recording.  Working for entities like the Arizona Opera Co, the Tucson Symphony and the Tucson Chamber Artists opened my eyes to the possibilities of musical performances inextricably linked to the acoustic spaces they inhabit.  And the virtue of capturing sounds using barebones yet high quality stereo recording techniques. Especially in comparison to close mic’ed, multi-tracked, heavily edited and processed methodologies.

With that said I have been gathering the necessary components to create that kind of barebones high quality stereo recording rig. With the intention of capturing sounds that are linked to a space and moment in time.  There are the mics, the mic preamps, the analog to digital converters, the flash recorder, the laptop with appropriate software, etc. All checked off the list.  But a key piece to this compact rig is a baffle placed between the two microphones  that creates what Jurg Jecklin called the Optimum Stereo Signal.  This baffle is generally known as a Jecklin Disk.  The disk mimics the effects of the head with the two omni directional mics being the ears.  This creates a stereo signal with both time and frequency dependent amplitude differences between the left and right channels. Those differences are the cues our brains use to place sound sources in 3-dimensional space.  So upon playback the recording can accurately reproduce the space where it took place. Commercially manufactured Jecklin Disks are available but they’re relatively expensive (~$250) and relatively easy to build if you have all the necessary materials and tools.  A few weeks ago I weaved this project into a Saturday full of chores and errands.

Jecklin Disk Build

The basic shape was cut out of 1/2″ birch plywood with a router & circle cutting jig. The notches for stand mounting and mic placement were cut on the band saw.  A dado was cut into the handle and  a hole was drilled to mate with the threaded part of a standard mic clip. The mounting handle was coated with Plasti Dip to make it durable and comfortable to handle.

Jecklin Disk Mounting Point

The rectangular pieces of 1″ foam were attached to the plywood using a spray adhesive.  Then roughly trimmed with scissors to match the diameter of the disk.  Later I took the disk to the router table and more accurately trimmed the foam to the edge of the disk with a pattern maker’s bit.

Jecklin Disk Foam Adhesive  (2)

Jecklin Disk Roughed Out Resize

The stand mount is based on a very simple stereo mic bar and the bottom section of a mic clip.  The steps to mount the stereo bar, disk and mics are illustrated below.

Jecklin Disk Tripod Mount

Including drying times for the Plasti Dip and spray adhesive the project only took a few hours.  Luckily I had all the materials and tools on hand and had the design bouncing around my head long enough that it all just fell together.  I did some test recordings around the house to get an idea of the general sound, mic placement and gain settings. But the real test would be to take it out into the field and record a live performance.  So I reached out to a musician friend of mine Tom Walbank to see if he wouldn’t mind being a guinea pig.  He has a weekly gig at a local coffee house/art gallery/bar here in Tucson called Cafe Passe and told me to come on down the next Friday.

Walbank Passe Jecklin Disk Recording 11-22-2013

I think the recording came out great.  It captured things that so many modern recordings lack: the spontaneity of the moment, a feeling for the acoustic space it was recorded in, the mistakes, the excitement, and the humanity of the people playing and interacting with the music.

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