Additional speaker to paging system

I’m sure you can daisy chain off an existing speaker if it’s closer than the amp.
16 gauge 4 conductor is fine.
Make sure the speaker your connecting to will be in the same zone.If they have zone paging.

It dépend on the speaker if it is wire on parallel 70 there is no problem going from the other speaker but you need your total number of speaker wattage to not go over the amplifier wattage rating. If they plug in 8ohm setup you need to verify if serial or parallel and match the impedance to stay in the 8 ohms

two options from what i have done. if you have an amp, then you most likely have 70 volt speakers. can see tap on back of amp to verify. you can add speakers and one good thing is your volume is set from amp. the other way is self amp speakers from viking, requires a transformer and 2 pairs to go to each speaker added. one for paging and one pair for the power. larger transformer will do a lot of speakers but home runs back to one place is ideal for trouble shooting. but you can loop speakers. one con is that you set the volume on each speaker. 5 watt speaker is loud...... just did a 10,000 sq ft warehouse with 3 5 watt speaker and could hear anywhere is warehouse ...gauge of wire is not that big of an issue. 18 to 22 gauge will work. i have ran 4 pair 23 gauge cat 6 and just twisted pairs together for higher gauge.

At Bell Canada back in the day we used to run standard quad 24 gauge for both office and warehouse.
Then it Cat3, 4 was used.
No issues on all the above.

"but home runs back to one place is ideal for trouble shooting"
We also did home runs only.
If one shorts out, they all short out, good luck with the ext ladder to see which speaker is the devil.
Sites with just a couple or so speakers, no big deal then.

We terminated all cables to a BIX1A but used (cross-connected) a BIX Multiplying Connector to do the looping.