JBL演出音箱　SR4733A

SR4733A－两路全音域音箱
　　SR4733A为两路双15寸全音域音箱，在不选配超低音时，适宜作为中型场所之工程。双15寸低音提供低至35Hz的低音，雄厚有力。亦适宜作为流动演出系统中使用。
■ 频率响应：35-18kHz
■ 承受功率/ 连续粉红噪声：1200W
■ 峰值粉红噪声：4800W
■ 整组音箱阻抗：4Ω
■ 灵敏度(1W@1m)：99dB
■ 峰值声压级(1m)：136dB
■ 覆盖角度(水平x垂直)：90°×50°
■ 分频点频率：1.2kHz
■ 扬声器单元/ 低音单元：2206H(×2)
■ 中/高音单元：2447J
■ 中/高音号筒：2381
■ 推荐分频点频率：1.2-1.4kHz
■ 低音单元功率/阻抗：1200W/4Ω
■ 高音单元功率/阻抗：150W/16Ω
■ 尺寸(高x阔x深)毫米：1219×622×432mm
■ 净重：65.7kg

  James Bullough Lansing was born James Martini, 14 January 1902, in Macoupin County, Millwood Township, Illinois. His parents were
Henry Martini, born in St. Louis, Missouri, and Grace Erbs Martini, born in Central City, Illinois. The elder Martini was a coal mining
engineer, and his work required that the family moved about quite a bit during Lansing's early years. Lansing was the ninth of fourteen
children, one of whom died in infancy. For a short time, Lansing lived with the Bullough family in Litchfield, Illinois. He later took their
name when he changed his from Martini to Lansing.
Not much is known about Lansing's early days, and we are indebted to Bill Martin, one of three surviving brothers, for providing most
of the information presented here. Lansing graduated the eighth grade at the Lawrence School in Springfield, Illinois. He also attended
the Springfield, Illinois, High School. Later, he took courses in a small business college in Springfield.

As a young lad he was very interested in all things electrical and mechanical. At about the age of 10, he built a Leyden Jar which he used
to play pranks on his playmates. He also constructed crystal sets, and at one time, probably about the age of 12 or so, built a small radio
transmitter from scratch. The signals from this set were apparently strong enough to reach the Great Lakes Naval Station in Illinois; naval
personnel determined the source of these signals and later supervised
the timely dismantling of the young Lansing's radio transmitter.

For a while Lansing worked as an automotive mechanic, specializing in fine engine repair work. He attended an automotive school for
mechanics in Detroit through the courtesy of the dealer he worked for in Springfield.

Lansing's mother died 1 November 1924 at the age of 56, and at that time Lansing left home. As best we can determine, he went directly
to Salt Lake City. Mrs. Lansing, the former Glenna Peterson of Salt Lake City, tells of meeting Lansing in 1925 in that city. At the time he
was working for a radio station as an engineer. In addition, he worked for the Baldwin loudspeaker company in Salt Lake City for a time.
He also met his future business partner, Ken Decker, in Salt Lake City.