变压器用在报警喇叭上是什么作用？普通的喇叭不是这样用的

jane@2013

变压器用在报警喇叭上是什么作用？普通的喇叭不是这样用的，求大神指导，跪谢！
9 ^. _* \" i5 D* O7 X

xhy_hard

贴图出来

超級狗

此時無聲勝有聲！



A typical high-impedance system is shown in Figure 1. A transformer at the power-amplifier output steps up the voltage to approximately 70 volts at full power. Each speaker has a step-down transformer that matches the 70V line to each speaker's impedance. The primaries of all the speaker transformers are paralleled across the transformer secondary on the power amplifier.
$ P9 C: q( r0 e" c, H1 q% V
$ e* l' i$ F, s. C' |. fADVANTAGES OF 70V OPERATION
& H, T  d) o; Y/ R  v0 l+ y  r8 {As stated before, a 70V line reduces power loss due to cable heating. That's because the speaker cable carries the audio signal as a low current. Consequently you can use smaller-gauge speaker cable, or very long cable runs, without losing excessive power. Another advantage of 70V operation is that you can more easily provide the amplifier with a matching load. Suppose you're connecting hundred of speakers to a single 8-ohm amplifier output. It can be difficult to wire the speakers in a series-parallel combination having a total impedance of 8 ohms. Also it's bad practice to run speakers in series because if one speaker fails, all the speakers in series are lost. This changes the load
/ Y" D1 }) h2 e. {3 j7 wimpedance seen by the power amplifier.