Dr. Shoen’s girlfriend at the time found this microphone in a dumpster behind a church. What did he really find, and could it be more than a theatrical prop onstage? The Unbrokenstring Crew goes to work!
Shure Brothers built this iconic microphone at the factory in Evanston, Illinois in the years between 1951 and 1961. The art deco design is recognized around the world as “The Elvis Microphone.”
The 55S is a smaller version of the Model 55 Shure Brothers microphone first produced in 1939.
Unidyne is a term coined to reflect that a single (unitary) microphone diaphragm is employed. The moving coil technique employed to convert sound pressure into electricity makes this a dynamic microphone; Thus we have the word “Unidyne.”
Units with the ON/OFF switch were produced after 1961
The silk wind screen is badly deteriorated. The microphone makes a loud ‘clunk’ noise when it is moved. We need to look inside.
Four screws allow the halves of the microphone body to be separated.
Inside the microphone, we see the element at the top and a multiple-impedance transformer on the bottom.
Two screws hold a bracket that retains a foam vibration dampener in place, which has long since deteriorated and crumbled away. This is the source of our ‘thunk.’
Two more foam vibration dampeners hold the bottom of the element. They are also deteriorated. More ‘thunk.’
The microphone element lifts out easily once the top bracket is removed.
Some of the foam isolation dampeners remain on the bottom two microphone element supports. These are end-of-life and no longer available from Shure.
It is easy to see places where the silk wind screen is missing.
The matching transformer is mounted along with a couple of boxes that retain the now-deteriorated foam vibration dampeners.
Two screws hold these parts in place.
We see the back side of the impedance selector switch in the background, and some set screws in the foreground. What do these do?
The bottom set screw is supposed to hold this spring sheath around the green and orange wires in place.
The top set screw holds the impedance selector switch in place.
We need to take everything out.
The spring sheath runs through the base of the microphone and protects the wires as the microphone is flexed at the joint.
Inside the top of the microphone case we find this sticker, which records the patent numbers employed in the design of this microphone.
The pivot between the microphone and base needs to come apart for cleaning and adjustment.
This screw can be adjusted to set the stiffness of the microphone head relative to the base.
Graphite washers ride between the moving parts for lubrication.
A dent in the body of the microphone needs to be removed. Yes, I’m using my luthier’s hammer to pound out the dent.
Can you see where the dent was?
The old silk wind screen was glued inside the case of the microphone.
Acetone will dissolve the old glue. It will also dissolve silk, turning this cleanup step into a blue sticky ‘hot mess.’
But a little patience and perseverance yields a clean microphone case.
Warning – Skeleton Shot! I’ll betcha that you have never seen a microphone like this.
We found some sheer blue silk fabric for the wind screen. This brighter blue is not historically correct, as ‘Victoria Blue’ (Pantone 2756) was specified by the factory. However, this blue matches the Shure nameplate and badge.
This is a test.
Fabric is glued to the top and bottom as well as sides of the front half of the microphone enclosure. We will now fabricate a soft pillow to allow the fabric to be ‘blocked’ into place as the glue dries in the front half of the microphone enclosure.
This soft pillow will be fabricated from Oomoo. Yes, the silicon mold-making resin will be just the thing.
Equal parts by volume are mixed.
The mix is poured into the front half of the microphone. A plastic sheet protects the microphone shell from the casting material. The Oomoo silicone mold material won’t hurt the microphone shell, but I don’t want to risk contaminating the microphone shell and possibly compromising the glue adhesion later.
And here is our pillow!
We don’t want the pillow to deform the fabric, so these high points are removed by hand with an Exacto knife.
Here is the finished pillow inside the microphone shell.
And here is the fabric, glued and blocked into the microphone shell.
Time to reassemble. The moving joint is reassembled and the cable from the base to the enclosure is reinstalled.
The spring around the cable is held in place with the set screw, as we discovered earlier. This is a nice view of the fabric in the back shell of the microphone. This piece is just a flat rectangular sheet stretched across the back, so it’s easy to glue in place by hand without a block.
The joint is back together. No lubrication is necessary as the graphite washers are doing their job.
A smooth, firm grip at the joint is established before installing the lock nut.
This is what the spring protecting the wires is supposed to look like.
The microphone element works, but I couldn’t resist taking a look at the technology behind US Patent 2,237,298. The hemispherical shell on the back of the element helps establish the cardioid pickup pattern of the element.
I fabricated new foam vibration dampeners, which are installed in three places. The matching transformer assembly goes back where it belongs.
The microphone element is reinstalled where it belongs and wired in. This is now a working microphone. The covering on the microphone element is actually the same material used for vintage silk stockings a.k.a. nylons.
A set of four matching screws are fitted and finished to hold the two halves of the microphone enclosure together.
Thanks for reading all the way to the end!
CONTACT – David Latchaw EE