Connecting ceiling speakers to amplifier

You can use the 70v pin on the speaker out connect. So you'll have the common and 70v pins connected.

You don't need 4 sets of wires brought back for parallel wiring. Still just 1 set of wires. It may actually be wired that way. Either way with the 70v connection it shouldn't matter. It matters more with the low impedance connections (the 8 ohm pin on the speaker output).

When wiring speakers in parallel you divide the ohms by the number of speakers for your total impedance (so 4 8ohm speakers nets 2 ohms). For wiring in series you multiple (ends up being 32 ohms). For low impedance connections this can be an issue - too much impedance on the speaker side means the speakers cannot get the full power from the amp - they won't get as loud. Likewise with a lower impedance the amp can deliver more power to the speakers, but go below the rating of the amp and it can damage the amp or speakers (or both).

The reason the "high impedance" setups exist (these are the 70/100 volt speakers) is for stores and other facilities where many speakers are driven by a single amp, it makes connecting many speakers less of a headache.

The reason I brought up the wiring scheme (parallel vs series) is because I've never seen high impedance systems run in series. I don't think it'll cause any issues (especially with so few speakers), but it may - so if you're finding something doesn't work it could be how it's wired. Also, it could actually be wired in parallel, but the electrician might not have used the correct terminology.