MIL-PRF-25670B
standards), the text of this document takes precedence. Nothing in this document, however,
supersedes applicable laws and regulations unless a specific exemption has been obtained.
3. REQUIREMENTS
3.1 Specification sheets. The individual item requirements shall be as specified herein and in
accordance with the applicable specification sheets. In the event of any conflict between
requirements of this specification and the specification sheets, the latter shall govern (see 6.1).
3.2 Qualification. Earphones furnished under this specification shall be products that are
authorized by the qualifying activity for listing on the applicable qualified products list (QPL) before
contract award (see 4.5 and 6.3).
3.3 Materials. All materials shall enable the parts to meet the requirements of this specification.
Materials which have measurable changes in property due to aging shall not be used, such as natural
rubber-based products or ferrite-based magnets. All metal surfaces shall be corrosion-resistant.
Cementing compounds (adhesives) which are water-soluble shall not be used.
3.3.1 Insulating and impregnating compounds. Such compounds applied shall not in any way
degrade the performance of conductor insulations to which they are applied. Neither shall they
corrode or otherwise cause the deterioration of adjacent materials (metals, plastics, etc.).
3.3.2 Diaphragm material. The diaphragm material shall be mylar, or a material having equivalent
or superior flexibility, stability and durability under specified conditions, as approved by the qualifying
activity.
3.4
Interface
3.4.1 Interface requirements. Earphone elements shall be designed in accordance with the
applicable specification sheet and the general requirements specified herein.
3.4.2 Transformers. If a transformer is used, it shall be located inside the earphone element case,
to ensure low-profile, smooth installation in headset earcups.
3.4.3 Threaded parts. All threaded parts shall be in accordance with Federal Standard H-28, to
ensure interchangeability of spare parts.
3.4.4 Finish. Final finish shall withstand the conditions cited in MIL-F-14072, type I (exposed).
3.4.5 Coil clearance. The voice coil shall not rub against adjacent parts after assembly.
Irregularities of the voice coil surface resulting from fabrication processes are considered to be a part
of the voice coil.
3.4.6 Diaphragm. The earphone elements shall be constructed to have equalization of pressure
on both sides of the diaphragm when subjected to changes in ambient pressure as low as 3.4 inches
of mercury.
3.4.7 Weight. Weight shall be as specified (see 3.1).
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