MIL-DTL-24223D(SH)
3.8 Terminal board. A terminal board shall be provided in the part of the enclosure that fastens to the
bulkhead. The terminal board shall provide for connecting the incoming ship s line(s), and shall be properly marked
in accordance with the specification sheets to indicate the correct connections. The terminal board will be capable
of withstanding the salt spray test specified in 4.5.11 without evidence of physical damage or corrosion.
3.9 Transformers. Transformers shall be Grade 4 or 5, Class S, life expectancy X of MIL-PRF-27, and shall be
capable of withstanding the salt spray test specified in 4.5.11 without evidence of physical damage or corrosion.
Transformers shall be mounted within the loudspeaker enclosure, except for LS-397()/SIC and LS-657()/SIC, for
which a separate transformer enclosure is permitted. Transformers shall be capable of withstanding the same testing
as the loudspeaker unit.
3.9.1 Transformer phase relation. The phase relation between the primary and secondary of the transformer
shall be such that when a potential is applied across the primary with the positive to the "MC.70V. +" or "MC.
95V.+" terminals, in accordance with 4.5.4, the voltage polarity appearing at the secondary "Full" terminal shall be
positive with the respect to the "COM" terminal.
3.10 Transformer terminals. The transformer shall have terminals that permit changing the connections without
soldering or unsoldering.
3.11 Volume adjustment. Volume shall be adjustable from "FULL" to -24 decibel (dB) in 6 dB steps in each
loudspeaker, unless otherwise stated in the specification sheets. "FULL" is defined as the use of the entire
secondary winding of the transformer.
3.12 Replaceable parts. The loudspeaker shall be designed to allow easy replacement of the transformer, the
loudspeaker unit, and, if applicable, the rotary switch. The loudspeaker unit (or driver) shall be replaceable as a
complete assembly.
3.13 Loudspeaker unit. The loudspeaker unit shall be designed to meet the performance requirements specified
herein when mounted in the loudspeaker enclosure.
3.13.1 Direct radiator diaphragm material. See the specification sheets.
3.13.2 Voice coil impedance. The total of the voice coil impedance shall be high enough to limit the power
input drawn by the complete loudspeaker to the values specified in the specification sheets.
3.13.3 Voice coil terminals. The loudspeaker unit, when examined in accordance with 4.5.1, shall have screw
type terminals mounted in a convenient location, readily accessible from the back of the unit. One terminal shall be
marked with a "+" sign.
3.13.4 Voice coil polarity. Application of a DC voltage to the voice coil terminals with positive voltage to the
"+" terminal, in accordance with 4.5.4, shall result in the cone moving outward.
3.13.5 Magnet structure. The loudspeaker unit shall have permanent magnet type structures of sufficient size to
enable the complete loudspeaker to meet the performance requirements specified in paragraph 3.14.
3.13.6 Air gap clearance. Minimum air gap clearances shall be 0.01 inch on each side of the voice coils.
3.14 Loudspeaker performance requirements.
3.14.1 Quality of reproduction. There shall be no buzzes, rattles, or other spurious sounds arising when tested
in accordance with 4.5.2.
3.14.2 Power input. The power input for each type of loudspeaker furnished under this specification shall not
exceed the values shown in the specification sheet, when measured in accordance with 4.5.5 and 4.5.6.5.
3.14.3 Sound pressure output. When tested in accordance with 4.5.6.1, loudspeakers shall produce the
minimum on-axis sound pressures identified in the specification sheets.
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