I am doing research on installing a small constant-voltage speaker system using a ten year old TOA BG-115 Integrated Amplifier, and I am trying to determine what the reason is for the existence of 25 volt wiring for distributed audio background music / announcement building speakers.
Speakers, with integrated multitap transformer and 25/70v voltage selection: http://www.specotech.com/index.php/products/audio/speakers/surface-mount/item/572-wb86t
And what this is for anyone who is not familiar: https://en.wikipedia.org/wiki/Constant-voltage_speaker_system
The more common distributed audio design is to use 70 volts. The only specific answer I have been able to find so far is that "some building safety codes require the use of 25 volts". Yes, but why, exactly?
As far as I understand the main benefit of 70 volt is operating at a higher voltage allows audio signals to travel much further through the distributed wiring network to the speakers.
25 volt will apparently have a correspondingly shorter operating distance for the same amount of line losses, and will lose more signal to resistance. How much this matters is unknown.
Apparently 70 volt can give you quite a shock even compared to 120 volt AC due to the high frequency components of audio signals. That is why a plastic cover is over the audio transformer output terminals of this amplifier, to reduce the risk of shock.
Is this part of the reason for the use of 25 volt systems, less or no shock hazard?