MIL-DTL-24223/3B(SH)
Description: The type LS-657()/SIC loudspeaker shall be designed for deck mounting. A maximum of eight
driver units shall be employed.
Dimensions and weight: See FIGURE 1 for dimensions. Weight shall not exceed 60 pounds.
Cable entrance: See FIGURE 1. Cable shall be installed using a stuffing tube. The stuffing tubes will be size 2
in accordance with ASTM F1836M. Stuffing tubes are not required unless otherwise specified. The type
LS-657()/SIC shall be designed to accommodate cables entering the transformer enclosure via a
shipbuilder-installed stuffing tube.
Degree of enclosure: Except for the opening required for acoustic radiation, the enclosure shall conform with
the "totally enclosed" requirements of MIL-STD-108. The opening for acoustic radiation shall be covered with
mesh or perforated metal not less than 0.032-inch thick. Mesh openings or perforations shall not be larger than 9/32
inch. Where required for servicing internal assemblies, the mesh shall be removable.
Enclosure construction: Mounting base shall be aluminum sheet 6061-T4 in accordance with ASTM B209-10.
Enclosure shall be aluminum sheet 5052-H32 in accordance with ASTM B209-10. The edge at the opening shall be
double thickness. Wire connections shall be closed lug on a threaded terminal. At least one rear drainage hole is to
be provided for internal drainage. Exterior surfaces shall drain when level. Application is shipboard, exterior, and
unsheltered. The horn enclosure shall contain required driver(s) and terminal board (if required); the transformer
enclosure shall contain the transformer assemblies and terminal board (if required). Both enclosures shall be
provided with a removable cover (or horn assembly) to give access to all interior parts and the enclosure mounting
holes. The enclosure covers shall be secured by means of screws engaging in tapped holes provided in the
enclosure. Removing the cover shall not involve disturbance of incoming cables and terminal tubes. Part mounting
fasteners shall be secured so as not to require demounting of the enclosure for part replacement. Parts shall be
mounted so that their terminal markings are visible with the enclosure cover removed.
Coatings: Aluminum and aluminum alloy parts shall be pretreated and painted. The pretreatment shall be
either anodized in accordance with MIL-A-8625, or chemically pretreated in accordance with MIL-DTL-5541. It
shall then be primed with a single coat of epoxy primer conforming to MIL-PRF-23377, a second coat of epoxy
paint formula 151 in accordance with MIL-DTL-24441, and two top coats silicone alkyd in accordance with MIL-
PRF-24635. The color shall be haze gray, color No. 26270, in accordance with Fed. Std. 595C.
Input enclosure: Transformer and wiring terminal block shall be in a separate water tight enclosure.
Application is shipboard, exterior, and unsheltered.
Speaker drivers: Speaker driver assemblies shall not exceed eight.
Horn assembly: No plastic material is allowed in the horn assembly, except for acoustic gaskets.
Mounting: All acoustical testing shall be performed with the complete assembly mounted on 4-foot by 8-foot
by ¾-inch sheets of plywood to simulate the deck mounted environment.
Marking: Internal marking shall be in accordance with FIGURE 3 herein.
PERFORMANCE REQUIREMENTS:
Power Input: Volt-ampere input specified in TABLE I shall provide at least sound pressure output, indicated in
TABLE I.
Sound pressure output: Sound pressure output shall be measured at the distance identified in TABLE I.
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