The invention discloses a high-
loudness vehicle-mounted alarm. The high-
loudness vehicle-mounted alarm consists of an alarm
machine box and a high-power speaker, wherein the high-power speaker is formed to a compressive sounding head by a W-shaped basin frame, an annular magnetic conducting cavity, an annular strong permanent
magnet, a W-shaped
sound film, a skeleton sound ring and a W-shaped end cover; a reflective horn is mounted on the compressive sounding head; the W-shaped
sound film is equivalent to one sound ring to push two sound films, so that the effective vibrating area of the
sound film is enlarged; a conical structure of the W-shaped sound film is excellent in rigidity and light in weight; the sound ring of a
center tap is directly matched and connected with an
audio power amplifier output circuit; an improved
magnetic circuit system is simple in structure, strong in
magnetism and light in weight; in the
audio power amplifier circuit, upper and
lower field effect tubes are connected to A and B type push-pull output circuits having
common drain; the
negative feedback is deep; the
amplifier tone quality is improved; the amplifier stability is improved; the
field effect tubes are high in output current and low in loss; a vehicle power supply with
low voltage of 12 V is only used for generating an electroacoustic power above 500 W; and the high-power speaker is driven to give a high-
loudness alarm sound.