1、1 METRIC 1 31 Mav 1995 Superseding 22 May 1985 A- A- 5 9 O 02 MIL-L-24223 COMMERCIAL ITEM DESCRIPTION LOUDSPEAKER, SHIPBOARD ANNOUNCING SYSTEMS The General Services Administration has authorized the use of this commercial item description as a replacement for MIL-L-24223 which is canceled. 1. Scope.
2、 This Commercial Item Description covers requirements for enclosed permanent magnet loudspeakers for use in 70.7 volt distribution systems on Naval ships. 2. Salient characteristics. 2.1 Specification sheets. The individual item requirements shall be as specified herein and in accordance with the ap
3、plicable specification sheet. In the event of any conflict between the requirements of this Commercial Item Description and the specification sheet, the latter shall govern. 2.2 Restricted materials. The material listed below shall not be used in the construction of shipboard announcing system louds
4、peakers. Flammable materials Asbestos, asbestos compounds, and asbestos-filled molding compounds Lithium and lithium compounds Magnesium or magnesium alloy Zinc or zinc alloy Carcinogens Radioactive material Polychlorinated Biphenyl (PCB) Polyvinyl Chloride (PVC), except where used for component lea
5、ds Mercury or its compounds and amalgams Cadmium Chloroflourocarbons 2.3 Inert materials. All materials shall be fungus inert or shall be suitably treated to retard fungus growth. The manufacturer shall certify that all external materials are fungus resistant or shall test the material in accordance
6、 with ASTM G21. There shall be no evidence of fungus growth on the surfaces of loudspeaker components. I Beneficial comments, recommendations, additions, deletions, clarifications, etc. and any other data which may improve this document should be sent by letter to: Commander, Naval Sea System Comman
7、d, Attn: 03R42, 2531 Jefferson Davis Hwy., Arlington, VA 22242-5160. AMCC N/A FSC 6320 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A-A-59002 m 999997V 03683b5 3T3 m
8、 A-A-5 9002 2.4 Reliability. Speaker units shall have a MTBF of 10,000 hours, with failure defined as inability to meet the requirements of this specification. 2.5 Maintainability. Construction shall be such that no special tools are required for installation, disassembly or reassembly. The followin
9、g components shall be accessible by opening the enclosure for removal or replacement using common tools without disturbing any other parts: (a) Speaker driver (b) Speaker cone or horn (c) Transformer (d) Volume switch 2.6 Enclosure construction. Loudspeaker enclosures and horns shall be manufactured
10、 of metal, with sufficient guage to withstand all applicable tests described in this document. The enclosure and horn shall sustain no visual deformation after enduring these tests. 2.7 Visual conformance. The presence of any of the following defects shall be cause for non-acceptance: (a) Mounting d
11、imensions incorrect. (b) Defective or missing parts which could cause failure of function, systemoverload or personnel hazard. (c) Marking missing, illegible, or incorrect. (d) Any loose internal foreign object or particles that may interfere with loudspeaker movement or switch operation. (e) Connec
12、tions, electrical parts missing, oxidized, or inaccessibly located. (f) Wiring with incorrect connection, frayed and broken strands, melted or burned or cut insulation. Incorrect color code, interference with assembly or operation of the loudspeaker, excessive bare wire, ordeteriorated insulation. E
13、nclosure with poor coatings, dimensional defects, water does not drain. Bending, cracks. Prohibited material or parts. 2.8 Foreign object protection. The opening for acoustic radiation shall be protected so that any particle having a dimension greater than 2.0 mm will not penetrate to the operating
14、components of the speaker, unless otherwise stated in the applicable specification sheet. 2.9 Coverage angle. The specified sound coverage angle is the angle at which the sound pressure output has decreased 6 dB from the zero-degree on-axis value. This angle shall be as specified in the applicable s
15、pecification sheet when tested as follows: Measure the on-axis sound pressure as specified in the Minimum Sound Pressure Output Test while the speaker is verticallymountedto a rotatable fixture. The speaker shall be rotated about an axis perpendicular to the sound output axis that intersects the sou
16、nd output axis within O to 76.2 mm of the front face of the loudspeaker. Record the angle of rotation from lton-axisl to the angle where the sound level is 6 dB below the llon-axis“ value. Repeat the measurements in the opposite direction. Rotate the loudspeaker 90 degrees about its output axis (hor
17、izontal mount) then repeat the above two measurements. The microphone shall be located at the distance required in the applicable specification sheet. The 800 to 1250 warble band shall be used. The arithmetic average of the two measured angles is the “coverage angle. II 2.10 Finish. Metal surfaces s
18、hall be finished with a corrosion resistant powdered epoxy coating, in the specified color, in accordance with best commercial practices. (9) 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A-A-59002 I 9999974 Olb83bb 23T A-A- 5 90 02 Composite mat
19、erials shall be finished in the color specified in the contract. 2.11 Cable entrance. Enclosure cable entrance shall be as specified in the applicable specification sheet. 2.12 Grounding and bonding. Metallic enclosures shall be provided with a stud for grounding and bonding. Resistance between the
20、stud tip and any point of the enclosure or any exposed metallic components shall be O ohms when measured with a high quality ohmmeter. The stud shall be placed on the side of the enclosure. 2.13 Electrical isolation. All electrical components shall be electrically isolated from the enclosure or any
21、exposed metallic components. Electrical isolation shall be 100-megohm or greater when measured with a high quality 500 volt megger . 2.14 Loudspeaker input. of accepting an input from a 70.7 volt line. 2.15 Input terminal block. A terminal block shall be provided in the part of the enclosure that is
22、 mounted. The terminal block shall provide for connecting the incoming ships lines and shall be marked to differentiate the Common terminal from the +70V terminal. Loudspeakers built to this specification shall be capable 2.16 Volume control switch. When the specification sheet requires external vol
23、ume selection, a switch meeting the requirements of EIA-520F000 shall be used. The counterclockwise end of rotation shall be llOFF1l. The clockwise end of rotation shall be iiFITLLE1 volume. Six positions with approximately 30-degree spacing are required. The switch shall connect one lead from the v
24、oice coil to various taps of the line-to-voice coil transformer, with the taps emanating from the full transformer output and successive 6 dE3 decrements. If required by the specification sheet, internal volume control need not be a switch, but must be adjustable by hand. Internal volume control sha
25、ll connect one lead from the voice coil to various taps of the line-to-voice coil transformer, with the taps emanating from the full transformer output and successive 6 dB decrements. 2.17 Polarity. The loudspeaker shall be configured such that when a positive voltage is applied to the positive inpu
26、t terminal (relative to the common terminal), the loudspeaker cone shall move away from the magnetic structure at the moment of application. 2.18 Transformer dielectric withstanding voltage. The loudspeaker transformer shall prevent electrical breakdown such as corona (defined in ASTM 18681, flash-o
27、ver (surface discharge), spark-over (air discharge), or breakdown (puncture discharge) when subjected to the dielectric test of ETA RS-186-4. A dielectric withstanding voltage of 600 volts (rms) for one minute at 60 Hz, with more than 20 megohms resistance to core and between windings, will be used.
28、 The dielectric withstanding voltage shall be applied from transformer terminals to core and from primary to secondary terminals. 2.19 Circuit diagram. A printed schematic interior wiring diagram of the loudspeaker shall be securely affixed inside the enclosure where it will be easily readable with
29、the cover open. The circuit diagram shall show wire color coding, terminal designations and volume selector switch connections, where used. The circuit diagram shall show the proper connections for different lines and the means for adjusting volume. 2.20 Stray magnetic field and materials permeabili
30、ty. The loudspeaker stray magnetic field and materials permeability shall meet the limits set in the applicable specification sheet when tested in accordance with the following procedure: The stray magnetic field produced by the loudspeaker shall be measured in a horizontal plane O. 762 m below the
31、center of the loudspeaker magnet. The measuring probe shall be oriented to measure the vertical component of the magnetic field. Sufficient The loudspeaker shall be mounted with the magnet axis horizontal. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IH
32、S-,-,-A-A-59002 = 999997Y 0168367 176 W A-A- 5 9 O 02 measurements shall be taken to determine the peak value of the stray field in the horizontal plane. The test shall then be repeated once with the loudspeaker tilted forward 10 degrees (magnet axis 10 degrees below horizontal) and once with the lo
33、udspeaker tilted 10 degrees to the rear (magnet axis 10 degrees above horizontal). The permeability of material after fabrication shall be determined by placing the indicator (inserted with a 2.0 slug) in contact with each part of the loudspeaker required to be non-magnetic. 2.21 Fundamental resonan
34、ce. The fundamental resonance of the loudspeaker element shall not vary by more than 5 percent when measured in accordance with EIA RS 276. 2.22 Impedance. The 1000 Hz loudspeaker rated impedance shall be 8 2 1 ohms when tested as follows: Measure the voltage drop across the speaker element for a 10
35、00 Hz signal. Measure the DC resistance of the coil. Compute the reactance and impedance at 1000 Hz. The direct current resistance shall equal rated impedance divided by 1.15 15 percent. 2.23 Peak volt-ampere capacity. The loudspeaker shall meet the requirements of this commercial item description a
36、fter carrying a 10 percent duty cycle at the peak volt-ampere capacity required in the specification sheet for 15 minutes. 2.24 Total harmonic distortion. The total harmonic distortion of the loudspeaker shall not exceed 5 percent when tested as follows: Input a constant amplitude sinusoidal signal
37、with less than 0.2 percent distortion to the normal assembly input terminals. The voltage level shall be as required for rated output power. Measure the percent harmonic distortion of 200, 1000, 2000, and 4000 Hz output sound pressure waves. Determine the percent total harmonic distortion by the fol
38、lowing formula : P, = Fundamental sinusoid P, = Harmonics of P1 2.25 Minimum sound pressure output. The loudspeaker shall produce at least the minimum rms on-axis sound pressure specified in the applicable specification sheet when tested as follows: A 70 Vrms sinusoidal warbled signal shall be appli
39、ed to the normal input terminals. The sound pressure output levels referenced to 0.0002 dynes/cm2 shall be measured for each of the bands required in the applicable specification sheet. The warble shall be a logarithmic frequency change calibrated in frequency decades per unit of time. The output so
40、und pressure shall be measured using an ANSI S1.4 standard sound level meter with either a “Cl scale response or linear scale response. A 5 minute warm-up of the speaker coil is required prior to start of this test, if the speaker was in a room temperature environment for approximately 1 hour prior
41、to turning on the speaker. The microphone shall be located on axis at the distance required in the specification sheet, except when doing environmental tests in an environmental test chamber. Measure and record volts and amperes input during each warble band test. The input frequency in each band sh
42、all be warbled. The warble frequency shall be 5 to 6 Hz. Set meter movement to slow speed setting. 2.26 Frequency response. The frequency versus sound pressure output response shall fall within the limits shown on the applicable specification sheet figure when tested as follows: A 70 Vrms single fre
43、quency sinusoidal signal shall be applied to the input terminals. The signal frequency shall be varied in accordance with accepted operating procedures for the test equipment. For test equipment incapable of continuous sweep measurement, the signal frequency shall be varied in steps approximately eq
44、ual to 10 percent of the signal frequency over the range required by the applicable specification sheet. Record the output sound pressure at each 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A-A- 59002 step using a 200 (or lower) to 9000 (or hig
45、her) band width plus or minus 1 dB system. For test equipment capable of continuous sweep measurement, the frequency response shall fall within the specification sheet limits over the bandwidth shown. 2.27 Operation at reduced output. The sound pressure output shall be within 1.0 dB of the indicated
46、 value below iiFULL1l output at each adjustable level when the frequency response test of paragraph 2.26 is conducted with the loudspeaker volume set to minus 6 dB, minus 12 dB, minus 18 dB, and minus 24 B as applicable. 2.28 Endurance. The loudspeaker shall meet the requirements of this commercial
47、item description during and after undergoing the following endurance test for 72 hours at an ambient air temperature of 65OC: A warbled frequency in the 800 to 1250 Hz band at 70.7 Vrms shall be applied to the assembly input terminals. The signal source shall be rated 4 times the loudspeaker “rated“
48、 continuous power. The loudspeaker shall meet the resonance test requirements of EIA RS-276 before and after the endurance test. 2.29 Humidity. The loudspeaker shall meet the requirements of this commercial item description whil e exposed to a relative humidity of 95 percent when tested in accordanc
49、e with IEC 68-2-30Ca (modified to require 21 days testing). 2.30 Immersion. The loudspeaker shall meet the performance requirements of this commercial item description after being totally immersed in 35 parts per 1000 salt water for 30 minutes, removed, and allowed to drain for not more than 15 minutes (assuming the tested loudspeaker was previously subjected to the shock test). 2.31 Salt spray. The loudspeaker shall satisfy the visual inspection requirements of 2.7 and meet the performance requirements of
