[ARC5] Weird headphones.

[Richard Knoppow]

    The ANBH-1A is essientially identical to the commercial
Permoflux DHS-15B. They are moving coil headphones of very
good quality. They were used in aircraft and elsewhere. They
came in two kinds of headbands and as plain capsules with a
short cable to be installed in flying helmets. The headbands
were either a type for aircraft use with a fixed width
headpiece covered with a removable canvas cover with a
leather lining on the side that rested on the head, the
other had two adjustable bands covered with leather (later
ones were covered with plastic), this is the HB-7 type.  The
impedance is approximately 300 ohms each so a pair connected
in series is 600 ohms.  The frequency response is about 100
hz to about 10,000 hz with no resonances.  Permoflux
supplied these in a "binaural" or stereo form as well as the
standard mono form. The ANBH-1A has diaphragms made of
phenolic impregnated cloth. The earlier ANBH-1 has metallic
diaphragms (not sure of the material) which have a less
smooth frequency response but are still quite high quality.
    The ear cushions supplied were oval to fit over the ears
with rubber backing and pads made of light leather (drawing
a blank on the name of the stuff) filled with kapock. Old
cushions are often found with cracked leather parts and worn
out pads. One often finds cushions cut out of flying
helmets. These are slightly asymetrical and are marked FRONT
on one side. The tilt the phones slightly toward the ear
when oriented correctly.
    The military evidely continued to use this type of
headphone into probably the 1960s with some changes, the
earlier ones IMO are of better quality.
    These phones were very common on the surplus market
after WW-2 but are hard to find now.
    Some ANBH-1 phones have round cases, the ANBH-1A has a
squared off section in the rear, I think to clear an
internal transformer. The commercial Permoflux phones have
the flat sided section. The commercial version of the
headband has a long cord on it, the military version has a
short cord with a break-away connector.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "ARC5" <arc5 at mailman.qth.net>
Sent: Tuesday, July 01, 2014 11:44 AM
Subject: [ARC5] Weird headphones.


> Hello again, Gents:
>
> I have been using a set of headphones for the past several
> years that
> have always intrigued me.
>
> The outsides are a thin bakelite, tear-drop shaped housing
> with nice semi-
> hard rubber pads fitted over them.
>
> Inside of each ear-piece is an element with the following
> marks on them:
>
> ANB-H-1A, then in paint PRD1
>
> The headband is engraved HB-7, appears to be made of
> stainless steel, and
> has leather coverings over the two adjustable spring
> "loops".
>
> When I found them in my junque, they were missing the
> cords, so I wired
> them in series, properly phasing them in the process.
>
> They have always worked well for me, although I do have to
> replace the
> cords periodically since the wire I use is thin and easily
> broken.
>
> My questions are 1) what is the likely impedance of these
> (I have assumed
> 600 ohms), 2) doesn't the PRD1 indicate that they were
> probably used with
> either a radiation meter of some sort or perhaps a
> mine-detector. 3) how
> old might they be?
>
> I have never seen a set of military headphones with
> tear-drop shaped
> housings before.
>
> Ken W7EKB