Something most people have heard but never seen

[Doug3004]

The place I work at was doing some remodeling, and I saw a ceiling speaker sitting in a trash cart so I took a couple pictures. The inset photos are both sides of the transformer labeling.

(picture should be below)

Save this photo if you like it--it may disappear at any time.

 

[davenn]

There are pretty standard 70/100V speaker line speakers

I used to work for an audio video company where we install 100's and 100's of these in supermarkets, shopping malls and other large shops within malls

the ideal is to be able to run higher voltage out to the speaker system thereby drastically reducing losses
At each speaker where the input voltage of the system could be selected, commonly 25, 50, 75 or 100V ... 75 and 100V lines being the most common
the secondary of the transformer has taps to determine what wattage that speaker was to be set at, commonly 2.5W or 5W

these are the typical ones I would use in installs or repairs

https://www.altronics.com.au/p/c2125-redback-200mm-8-inch-5w-100v-twin-cone-fastfix-speaker/

 

[Audioguru]

100V was used in stores and shopping malls but 25V was used is schools so that the little kids running around in the ceiling did not get electrocuted.