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Purchasing a Battery and Inverter to Run My PA

Hello Forum!

I've not posted before but am in need of some guidance and hoping I might find it here . . .

I am preparing to purchase a deep-cycle battery, along with a pure-sine power inverter, to run a pair of Yamaha MSR100 speakers during outdoor performances. I've done a good deal of research but I'm concerned that I may not full understand the power consumption of the speakers.

Both are 100w speakers, and the specs say that they each have a power consumotion of 70w.  At a total of 140 watts, I caculated that the speakers consume ~ 12 amps, and that a 50 amp-hour battery could therefore power these speaks for ~ 4 hours (without factoring in % efficiency of the power inverter).

Is 70w correct, or is it only the "idle" power consumotion?  Do they draw more than 140 watts when in use? 

I'll need to know this in order to purchase the right battery and the right power inverter.  Thanks so much if any one you can offer some input!

-Lou




bklouis
2 responses Add your response
glennewdick's avatar
glennewdick
1,666 posts
 
I think you have calculated incorrectly if each speaker is 70w power usage at its max power ( it should be rate max power) then the amps consumed would be (70w=115v X amps) so 115/70= 1.64 amps, note your speakers require 115v AC and draw 70w max each so your amp draw cal should be based off the 115v ac not the 12v dc so each speaker will draw 1.64 amps at 115vac.

 you will need min 140w power inverter then add a safety net - power on inrush protection so double or triple that. you could easily run this off a 300w inverter i'd think. 

now yes your inverter will draw more current from your battery as its available voltage is 11-14 vdc but the power is the same, well add in the power to run the inverter. So yes your inverter will draw more amps at less voltage from the battery but out put less amps at a higher voltage into the 115vac. 

some one check that please
dangerousman
3 posts
 
Make sure your inverter is *Pure* sine wave - not modified sinewave. To avoid nasty buzz noise, and for better efficiency. The power needs of music amps are usually massively over-stated https://invertero.com/ I have a client that is a "track" singer and his PA is a 200 watt head with two 12 inch speakers. He uses a deep cycle marine battery and a 500 watt inverter and can run his PA for right at two hours when he does an outdoor street gig.
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