4. Electro-technical contexts
Once more: With 100V PA systems, we are dealing with a fundamentally different concept than the traditional music and voice transmission systems. The audience of 100V PA systems will simply never remain static in a single position, a situation which would be appropriate for stereo transmission. With 100V PA systems...
| 1. | ... transmission is therefore always mono. |
| 2. | ... only a single amp is required (minimum). |
| 3. | ... as many speakers as the amp allows can be hooked up. |
| 4. | ... separate amps for every programme to be transmitted are required. |
| 5. | ... sound can be transmitted over greater distances than other PA or HiFi systems. |
| 6. | ... relatively low wattage (e.g. 120 W) is involved. |
Technically speaking, we achieve the longer transmission distances by employing transformers, which step the signal voltage up or down, convert impedance (alternating current resistance) and then adjust it again.
I have explained the circuit principle above.
We can therefore do without greater currents and the concomitant larger cable diameters.
The speakers' output is often less than 10 W and may even be halved or quartered. This also means that the volume, or sound pressure, is reduced. Halving the output means a reduction by 3 dB. By adding the output values of all the speakers, we arrive at the system's total output value.
Ten Watt may not deliver great volume, but to supply a restaurant of 80 square meters with background sound, for example, 40W is actually sufficient.
Furthermore, in such a system we can switch all speakers in parallel without any problems, since their input transformers supply the necessary impedance. In low-ohm circuits (4 Ohm / 8 Ohm) this does not work, since the total impedance quickly reduces to a degree which is dangerous for the amp (this continually overloads the amp and can lead to its destruction).
