MIL-DTL-24223D(SH)
4.5.3 Dielectric strength and insulation resistance. Dielectric strength tests shall be conducted. Voice coil
circuits shall be tested while a signal is being applied as specified in 4.5.2. The voltage shall be raised gradually,
and shall be held at that value for 1 minute, ±5 seconds. The dielectric strength test shall not be applied to
electronic/electrical circuitry which uses low voltage components such a transistors, capacitors, and diodes.
Following the dielectric strength test, insulation resistance shall be tested between one voice coil terminal, and the
surrounding metal parts.
4.5.4 Polarity. A DC potential of 6 volts shall be applied across the input terminals with (-) to "MCC.COM"
and (+) to "MC+". The loudspeaker cone shall move away from the magnetic structure at the moment of
application.
4.5.5 Power input. A 70-Volt Root Mean Square (Vrms) signal warbled between the limits of 500 to 2,000 Hz
shall be applied across the "MCC.COM" and "MC+" terminals. The current drawn by the loudspeaker shall be
measured to determine compliance with the power input requirements specified in the specification sheet.
4.5.6 Acoustical performance tests. Loudspeaker acoustical performance tests specified in 4.5.6.1 through
4.5.6.6 shall be conducted with the loudspeaker positioned in a free field acoustic environment. An anechoic
chamber, where sound pressure varies inversely with distance within ± 1 dB over the measuring frequency range, is
considered a free field acoustic environment. The maximum permissible acoustic noise level of the test environment
shall be 20 dB below the nominal level produced by the loudspeaker during the test. The ambient temperature in the
sound room shall be between 68 and 86 °F (20-30 °C). The microphone used for measuring the sound pressure shall
conform to ANSI S1.15-1997, and be calibrated by the method described therein. Other types of microphones may
be used if calibrated as described in ANSI S1.15-2005. The microphone shall be positioned with its axis collinear
with the axis of the loudspeaker cone and at a distance as required by each specification sheet, between the
microphone face and the output plane (except as otherwise specified for the sound distribution test). The input
signal to the loudspeaker shall be 70 Vrms, or 95 Vrms as specified in the specification sheet.
4.5.6.1 Sound pressure output. A 70-Vrms warble signal shall be applied to the normal input terminals. The
sound pressure output levels shall be measured for each frequency band specified in the specification sheet. The
warble signal shall be such that the logarithm of frequency changes linearly with time for each frequency band. The
frequency variation in each band from the lower limit to the upper limit shall occur at a rate of 5 to 6 Hz. The output
sound pressure shall be indicated on an RMS meter. Sound pressure output levels shall meet the requirements
identified in the applicable specification sheet.
4.5.6.2 Sound pressure distribution. The sound pressure output test specified in 4.5.6.1 shall be repeated with
the microphone positioned at a distance from the center of the loudspeaker, as required by the specification sheet at
the off-axis angles specified in the specification sheets. For each off-axis angle specified in the specification sheet,
the sound pressure shall be measured at four points (two on a horizontal plane on either side of the sound axis, and
two on a vertical plane above and below the sound axis). The arithmetic average of the measured levels for each
axis shall be used as the measured off-axis sound pressure, and shall comply with the limits specified in the
specification sheet.
4.5.6.3 Frequency response. A 70-Vrms signal shall be applied to the loudspeaker input terminals. The signal
frequency shall be varied continuously over the frequency range shown on specification sheet. The frequency
response will be measured for each transformer tap option. The output sound pressure shall be measured to
determine compliance with the frequency response identified in the specification sheet.
4.5.6.4 Operation at reduced or increased input.
4.5.6.4.1 Operation at reduced input. 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 50 Vrms applied
across the "MCC.COM" and "MCX. 50V.+" terminals. Electrical input in volt-amperes shall comply with
requirements of 3.14.2. Sound pressure output level and frequency shall be in accordance with the requirements of
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