Would a 1000 watt amplifier do this?

[Speedskater]

All you need to know about 70 Volt speaker systems:

RaneNote 136
Constant-Voltage Audio Distribution Systems
Dennis Bohn, Rane
25, 70.7 & 100 Volts
U.S. Standards
Just What is "Constant" Anyway?

Constant-Voltage Audio Distribution Systems: 25, 70.7 & 100 Volts

Use a transformer to step-up the power amplifier's output, drive long lines, and use another transformer to step-down the voltage at each loudspeaker.

www.ranecommercial.com

* * * * * * * * *

70/ 100V Audio Distribution Systems
By Rod Elliott (ESP)

High Voltage (70/100V) Audio

Elliott Sound Products - Commercial audio, 100V, 70V line systems, transformers, amplifiers and ancillaries.

sound-au.com

 

[TLS Guy]

Yep, just mount a small 70V transformer on each speaker.
A large hi-fi power amplifier will drive a 70 Volt system without a special output transformer.

For his application he does not need a high powered amplifier. That is the crazy part of this post.

 

[Speedskater]

True, but in a 70 Volt system, a lower power hi-fi amplifier would need a 70V output transformer.
Without the transformer, it's about voltage swing not power.

 

[highfigh]

Now four or eight identical 4 or 8 Ohm speakers can be wired in a series~parallel arraignment to provide a good 4 or 8 Ohm load for the 1000Watt amplifier.

And the OP wrote that this was intended for moderate output, so 1000W is unnecessary.

 

[highfigh]

Because it is the best, cheapest, easiest and most reliable solution to his problem. This is out side for low powered speakers over some scenic construction. So, it will be mono.

One 70 volt amp will do the job, like I specked. Then he only needs one run of bell wire to the small 70 volt speakers. He sets the tap he needs, and runs the bell wire from one speaker to the next.

This is quick, easy cheap and reliable. That is the most optimal solution for his plans.

I know how it works! I don't know how many times I have recommended 70V but the fact remains- a low impedance amplifier CAN be used for this if the system is designed properly. I didn't see any mention by the OP that he was looking for speakers, so I didn't assume he is and that means the ones he has aren't for 70V.

Also, volume controls for a 70V system are more expensive than the lowZ version. If budget is a factor, 70V could end up being more expensive.

40W isn't much for an indoor system- it would be inadequate outdoors and with the need to maintain 20% headroom, that puts the usable output at 32W.

 

[fmw]

Not if they are all in parallel. What sort of system is this? If you are building a system like this you must have a plan for handling the impedance issues. If you connected seven speakers together, even if they were 8 ohms, you would have an impedance of just over 1 ohm and blow the amp.

So with that many speakers, you need to go with a 70 volt speaker system, or use impedance balancing auto transformers.
It sounds to me that you are already out of your depth.

The impedance is manageable by wiring small groups in parallel and then wiring the groups together in series. I'm reminded of the old sweet 16 systems that were wired that way. They had workable impedances but weren't all that sweet.