MIL-DTL-24223D(SH)
4.5.6.4.2 Operation at increased input. For type LS-657()/SIC loudspeakers, power input, sound pressure
output, and frequency response measurements shall be made as specified in 4.5.5, 4.5.6.1, and 4.5.6.3, except that
the input shall be 95 Vrms applied across the "MCC.COM" and "MC 95+" terminals. Electrical input in
volt-amperes shall comply with the requirements of 3.14.2; sound pressure output level and frequency response shall
4.5.6.5 Operation at reduced output. Sound pressure output measurements shall be in accordance with 3.14.7
when tested in accordance with 4.5.6.1 for the 800 to 1,250 Hz band with the transformer secondary tapped at "-6
dB", "-12 dB", "-18 dB", and "-24 dB".
4.5.6.6 Frequency response and sound pressure output. The verification requirements of 4.5.6.1 and 4.5.6.3
apply. These tests may be accomplished under anechoic conditions or, at the option of the contractor, the testing
may be accomplished using a non-anechoic test chamber, provided that the relationship between the anechoic
response and the response in the particular non-anechoic chamber used is known and verified in a manner acceptable
to the procuring agency.
4.5.7 Immersion. The loudspeaker shall be immersed in sea water (specific gravity 1.025) in the normal
position with the top edge of the loudspeaker enclosure 3 feet below the surface of the water for 1 hour. After
removal and drainage in the same position, the loudspeaker shall meet the requirements of 3.14.1.
4.5.8 Endurance. A warble frequency signal of 800 to 1,250 Hz at a voltage of 70 Vrms shall be impressed
across the normal input terminals of the loudspeaker for a continuous period of 100 hours. The loudspeaker shall
then be operated for 1 additional hour with the input voltage raised to 99 Vrms, except for types LS-397()/SIC and
LS-657()/SIC, which are excluded from the test at a raised input voltage. The loudspeaker volume adjustment shall
be set to "FULL" for loudspeakers with volume adjustment. The ambient temperature of air around the loudspeaker
shall be 149 °F (65 °C) throughout this test. Loudspeaker performance following the endurance test shall be in
accordance with the requirements of 3.17.
4.5.9 Humidity. The loudspeaker shall be subjected to the humidity test in accordance with Method 507,
Procedure II of MIL-STD-810, except that the temperature shall be 149 °F (65 °C) in lieu of 140 °F (60 °C). This
testing requires periodic operational checkout. Operational checkout shall conform to the requirement in 3.14.1.
4.5.10 Temperature. The loudspeaker shall be subjected to the high temperature test of MIL-STD-810,
Method 501, Procedure I for storage, and Procedure II for operation. The loudspeaker shall also be subjected to the
low temperature test of MIL-STD-810, Method 502, Procedure I for storage, and Procedure II for operation. For the
storage test, after stabilizing at room temperature, operational testing in accordance with 4.5.6.1 shall be conducted.
For the high and low operating tests, operational testing shall be conducted at the temperature extremes. If test
equipment cannot be found that operates at these extremes, qualitative listening by a government representative is
acceptable.
4.5.11 Salt spray. The loudspeaker shall be subjected to a salt spray test performed in accordance with Method
101 of MIL-STD-202. The salt solution concentration shall be 20 percent. Length of the test shall be 96 hours.
Following the salt spray test, the loudspeaker shall conform to the requirements of 3.19, the terminal board to the
4.5.12 Vibration. The loudspeaker shall be mounted on a simulated bulkhead or deck, as applicable, and
subjected to the vibration test for vital equipment as specified in MIL-STD-167-1. The loudspeaker shall be
energized with a 70-volt signal warbled from 800 to 1,250 Hz during the test. Following the vibration test, the
4.5.13 Shock. The loudspeaker shall be mounted on a simulated bulkhead or deck, as applicable and subjected
to the Grade A, Class I, Type A, lightweight high intensity shock test specified in MIL-S-901, with the loudspeaker
energized as specified in 4.5.12. After being subjected to the shock test, the loudspeaker shall conform to the
requirements of 3.22.
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