LS-685/U Crystal Loudspeaker

NSN: 5965-01-295-1125
Brooke Clarke 2013

LS-685/U Crystal
          Loudspeaker
Background
Description
Related
Links

Background

This military speaker is designed to be light weight.  It has a plastic case instead of the normal cast metal case and a crystal speaker element instead of a classical coil and magnet type speaker (typically with an audio transformer).

Description

Back of speaker
LS-685/U Crystal
                  Loudspeaker
Front of speaker
LS-685/U Crystal
                  Loudspeaker

Close up of front of speaker
LS-685/U Crystal
                  Loudspeaker
Connector Markings
LS-685/U Crystal
                  Loudspeaker
Opened Connector
LS-685/U Crystal
                  Loudspeaker
A normal U-229 type plug has 3 pins in the metal
housing w/ 120 deg spacing, but the OCS66 shown
above has 4.  The extra pin is shown at the top center in the photo.


The LS-454/U speaker that was used with the VRC-12 series VHF low band radios used pins A (ground) and E (non standard) as does this speaker.  The common pins for an earphone or low power speaker are A and B (see U229 Pin Out web page).

The connector that looks similar to the common U-229 is in fact a PCI OCS66 that seems to be designed to NOT mate with common NATO audio connectors. 

The speaker driver seems to be made up of a sandwich of three layers: metallic cloth for one terminal, the piezo material in the center and another layer of metallic cloth.

The speaker cone is a very stiff and light weight material, maybe some type of fabric that's been stiffened, like fiberglass or phenolic.

Maybe it's the Model # MP-1103 (pdf version) speaker element?

Questions

I got two of these and they are both dead.  They are alive, but need a new connector in order to test.

If you have a working speaker:
1) what DC resistance do you see across the terminals?
    ans:  The Fluke 87 DMM shows rising resistance, i.e. a capacitor
2) what happens if you scrape a wire connecting a 1.5 Volt Alkaline cell to the speaker terminals?
    ans: At first contact there is a click, but further contacts produce no sound.
           Reversing the polarity causes one click, but no more with the same polarity.
3) What equipment does the PCI OCS66 connector mate with?
    ans:  C11561 SINCGARS Full Size Remote

TM-11-5820-890-10-8 SINCGARS Ground Combat Net Radio ICOM Manual
says:
This is the only loudspeaker that can be used with the RCU speaker connector.

Related

Military Audio Accessories
Audio Connectors
U-229 Pin Out
U-229 Audio Accessories
VIC-1 Vehicle Inter Communication
VRC-12 series radios

Links

Brooke's PRC68, Alphanumerical Index to Web Pages, Products for Sale, Personal Home, Military Information, Electronics Page
page created June 19, 2013