Power requirements of sound system

Desert Rat

I'm installing a small solar electric system that will power a PA system. Another guy is supplying the sound equipment, and we are having a disagreement.
Here are the published specifications of a powered speaker that will be used in the system (there will be two of these speakers).

Amplifier
    Low frequency range  Max output power    700W
    High frequency range  Max output power   300W

Power supply
    Voltage (fuses)
          120V, 60Hz (T6.3A H 250V)
    Power consumption    Max 110W

What I'm concerned with is the electrical draw of the speakers. Looks straightforward to me:  Max 110W as stated in the specifications.
He says they can draw 12.6 amps @ 120 volts, but I think he's confusing the fuse size with actual power draw. He also says that "if the speakers can put out 700 watts, they can draw 700 watts". I think he's comparing apples and oranges. Comments?

Brock

Yes 700w is 700w, the thing is most sound systems are rated at a true peak, the most they could possibly output before blowing the speaker.  So imagine that loud screech of feedback, that might pull that much for that second or two.  Most likely you are running 1/10 that during a loud song and 1/100th of that for speaking again unless your running white noise flat out.  I would make sure you get a true sine wave inverter of a minimum of 1000w, but I would guess realistically your going to pull 100w average with a "loud" song.  If you get a mod sine wave you will get a lot of buzz and the amps will get a lot warmer and burn out.

Honestly for a system like that you might look at 12v system from a good auto setup and avoid the inverter.  The other option would be a powered speaker with a battery / amp built in, far less picky about the power you feed it and the amp and the speakers are matched for each other.  But it all depends on what you intend to do with the system.

BB.

From what little I know--Audio power output ratings are basically "lies".

Your best bet is to get a Kill-a-Watt type meter and measure the actual loads (rough peak wattage), and kWH per session/day/etc... Even if the audio system can output 110 Watts--It would be unusual for the system to output that power level continuously--Real audio is going to have high and low volume output running. You need the total power usage under field conditions.

http://www.solar-electric.com/kiacpomome.html

Note that audio systems can also be pretty efficient or very inefficient (i.e., AC power consumed may have little to do with the level of audio output). Again, the Kill-a-Watt meter will tell you a lot.

-Bill

Dave Angelini

A sales brochure tells lies?  Bill, are your sure?  Hee hee.

The other thing is that some of the new gear automatically goes to stand-by and draws very little power. The subs will shut down and the system can be very efficient. I know the nice Yamaha unit that Costco sells is so efficient that you see mostly audio power on the
 K-Watt.

H2SO4_guy

Depends on how it is played.  If the bass is pushed hard, the Kill-A-Watt meter will have trouble picking up the peaks and sharp fast peaks (Like thumping bass) can take a battery down quicker than the numbers would imply.  Also depends on the headroom of the inverter to handle the peaks too.  The Peukert effect is a factor on the large quick power draws to charge the transformers and caps on the amps. 

Bottom line, if it is loud, it will last a lot less time than expected. 

westbranch

Dave, which Yamaha units are you referring to?  I looked and only see exterior speakers on the .Ca site. Are they only in the US?

Dave Angelini

Just saw it again yesterday on my monthly costco run out of the mountains. Gawd I hate the civilized world of city life.
Some items are not on-line and they had a Sony unit also. I think the Yamaha had 2 billion watts in 7 speakers.

I found this link but I do not know which model I saw.... sorry.

http://www.avsforum.com/forum/90-receivers-amps-processors/2185057-costco-receivers-yamaha-rx-v775-vs-yamaha-tsr-5790-a.html