[MRCA] VN-era speaker unit question

WA5CAB at cs.com WA5CAB at cs.com
Wed Aug 21 23:18:28 EDT 2013


LS-7 and LS-11 were originally for use with SCR-284.  They were carried 
over for use with SCR-694-C and later with AN/GRC-9.  LS-11 was also used with 
AN/TXC-1.  They may have been used with SCR-178 and SCR-179.

Both are WW-II vintage and have stamped steel cases and stamped steel front 
covers.  All originally had metal nameplates affixed.

LS-7-A, LS-11-A and LS-166/U are Korean War vintage and all have cast 
aluminum cases and a cast aluminum front plate.  The transformer is mounted to 
the case instead of to the loudspeaker.  Input impedances are 4000, 250 and 
600 respectively.  LS-166/U has a switch on the side with positions labeled 
Vehicle and Pack.

The first four all have a cord terminated in either PL-55 (WW-II) or 
PJ-055B (Korea).  LS-166/U's cord is terminated in U-77/U.

The Vietnam vintage LS-454/U is the same as LS-166/U with two exceptions - 
connector is U-229/U and no switch.

Another much rarer loud speaker is LS-590/U.  A combination of LS-7-A and 
LS-11-A, it has a cast aluminum case and cover, a PJ-055B and a tapped 
transformer and selector switch to select either 250 or 4000 ohms input impedance. 
 It was used with AN/GRC-9(*), AN/VRC-34 and AN/TXC-1.

All of the cast aluminum case units have the nomenclature cast or engraved.

Robert D.

In a message dated 08/21/2013 14:30:46 PM Central Daylight Time, 
jeepp at comcast.net writes: 
> On 8/21/2013 8:23 AM, Rob Flory wrote:
> >Hi,
> >I am preparing a public demonstration of a TBX set where it would be 
> >desirable to have audio that people standing around the set could hear.
> >
> >Do I have it right that the iconic VN-era speaker, which has a switch 
> >on the side for "Field or Pack Set Use" or "Vehicle Set Use" has an 
> >impedance through a transformer of hundreds of ohms in one of those 
> >positions?
> >
> >I don't know the nomenclature for the speaker, as the example I have 
> >doesn't have a tag.  Can someone tell me the nomenclature?
> >
> >Unfortunately I don't have the TBX set to just hook it up and try it.
> >
> >Thanks, Rob
> >
> >
> 
> Rob,
> 
> The impedance of the LS-166 and LS-454 are both 600 ohms, of course.    
> Both these speakers look the same and both have the nomenclature 
> engraved on the side.   I'm curious as to the one you might have?  The 
> LS-7 and LS-11 stamped metal speakers (with louvers) usually have 
> painted-on nomenclature or a metal tag and are nom. 4000 ohms.  They 
> were, of course, for the GRC-9, et al. but do not have the selector 
> switch.  What connector is on the one you have?
> 
> Jeep - K3HVG

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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