Velvacs double reflex horn style alarm incorporates a patented speaker designed to provide the high output sound levels of a large speaker with the efficiencies of a smaller speaker. Given that a larger horn is more efficient, Velvacs double reflex design allows a 24 inch horn to be folded into a standard size back-up alarm. The highly efficient horn requires less electrical power to drive the horn. A more efficient horn means less power consumption, less generated heat and increased alarm reliability. A conventional alarm that draws 600 mA of current dissipates about 7 WATTS of power and mostly in the form of heat. Velvacs double reflex horn can develop the same sound level output with about half the current draw and only 3.5 WATTS of power, resulting in a cooler running alarm with more reliability. Velvacs design incorporates a self-cleaning feature that pumps out contaminates from the sound chamber. This results in increased reliability and longer life in adverse conditions. The folded horn design projects the sound to the rear of the vehicle, not all around the vehicle like a typical speaker type alarm, making it harder for dirt to collect inside of the alarm and affect the sound level produced. Meets requirements of SAE J944, CE, e-Mark and UL, OSHA, MSHA, and IP67