
COMPRESSION DRIVERS
FOR ELECTRONIC SIREN LOUDSPEAKERS
FEATURES 
• Choice of 58 or 100 Watt Power Handling for High Intelligibility and 
 Sound Penetration
• Heavy-Duty Weatherproof Construction
• Specifically-Designed for Electronic Siren and Signaling applications
• Accommodates Most Horns and Reflex Horns with Standard 
 13⁄8" – 18 Thread Pattern
APPLICATIONS
Depend on SD Series compression drivers for elec tron ic siren and 
signaling needs on emergency and law enforcement vehicles, as well 
as for use in stationary and mobile public address systems. Models 
SD-70 and the patented SD-370A (U.S. Patent #7,760,501) provide 
maximum power conversion with low-amplifier output to fulfill highintelligibility and sound-penetration requirements. Model SD-70, rated 
at 58 Watts RMS, is recommended for medium-power systems such 
SD-70
SD-370A
as commercial and industrial warning systems. Model SD-370A, rated 
at 100 Watts RMS, is recommended for high-power systems in public 
safety, civil authority, military, or emergency medical applications. 
Either unit can be used with most horns or reflex horns equipped with 
the industry standard 13⁄8" – 18 thread pattern.
GENERAL DESCRIPTION
SD Series 58 and 100 Watt compression drivers are standard 
components of the Atlas Sound electronic siren loudspeaker 
assemblies. Weatherproof units are ideal for use in police, fire, 
ambulance, and utility vehicles. Model SD-70 is recommended for 
medium-powered systems; SD-370A for high-powered systems. 
Drivers are equipped with a non-fatiguing, self-aligning sound chamber 
assembly containing a 23⁄4" phenolic diaphragm with a nominal 
impedance of 11 Ohms. Replacement head assembly, Model K-70GB 
is available for field replacement of Model SD-70; Model K-370A for 
SD-370A. Product series is suitable for use with matched amplifier 
and control equipment in systems requiring AMECA (Automotive 
Manufacturer Equipment Compliance Agency, Inc.) certification to 
General Services Administration spec i fi ca tions (KKK-A-1822C). The 
SD-370A is constructed using an ALNICO magnet.
SD-70
SD-370A
SEVEN
  POWER  IMPEDANCE  PLANE WAVE  LOW FREQ. LIMIT  SOUND       
MODEL  RATING    FREQ. RESPONSE  @ FULL POWER  LEVEL***  DIMENSIONS   WEIGHT
 SD-70  58 Watts*  11 Ohms  100 - 2,900Hz  200Hz  115.8 (avg)  4 
    (nominal)  (±5dB)  80-2,900Hz (±5dB)  (111 x 90mm)      (2.3kg) 
 SD-370A 100 Watts**  11 Ohms  100 - 2,500Hz  200Hz  117 (avg)   4 
    (nominal)  (±5dB)  100-2,500Hz (±5dB)  (118 x 102mm)      3.5kg) 
* 25V into 11 Ohms = 58 Watts  ** 33V into 11 Ohms = 100 Watts  *** Measured on a plane wave tube at 1mW
1601 JACK MCKAY BLVD. / ENNIS, TEXAS 75119 U.S.A. 
TELEPHONE: (800) 876-3333 / FAX (800) 765-3435
 © 2006 Atlas Sound LP  Printed in U.S.A.    ATS002453 RevA 8/06  SL7-1546
SPECIFICATIONS
Specifications subject to change without notice
Specifications subject to change without notice
Specifications subject to change without noticeSpecifications subject to change without noticeSpecifications subject to change without notice
AtlasSound.com
3
⁄
8
" Dia. x 3
5
⁄
8
" Dia. x 3
9
⁄
16
" H  5 lbs.
1
⁄
16
" H  7.7 lbs.
343

ARCHITECT & ENGINEER SPECIFICATIONS
Siren loudspeaker shall be Atlas Sound Model (SD-70, SD-370A) or 
approved equal. Assembly shall have a full-range power capacity of 
______ Watts RMS. Rated frequency response range shall be ____ 
____________ Hz ±5dB when measured on a plane wave tube at 1 
mW. Unit shall have a sound pressure output of ______dB at rated 
SD-70 Impedance
power when measured on a plane wave tube at 1 mW. Driver shall be 
capable of standard indoor/outdoor use and be fully-weather resistant.  
Units shall terminate in the industry standard 1 
Diaphragm material shall be high-temperature molded phenolic.
SD-70 Plane Wave Tube Response
3
⁄8" – 18 thread pattern. 
SD-370A Impedance
NOTE: Plane wave tube measurements provide resistive loads to test drivers. Actual frequency 
response of a driver / horn combination will vary depending on the horn used with the driver. Consult 
individual horn specification sheet for typical horn frequency response.
Specifications subject to change without notice
1601 JACK MCKAY BLVD. / ENNIS, TEXAS 75119 U.S.A. 
TELEPHONE: (800) 876-3333 / FAX (800) 765-3435
 © 2006 Atlas Sound LP  Printed in U.S.A.    ATS002453 RevA 8/06  SL7-1546
SD-370A Plane Wave Tube Response
AtlasSound.com