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Hello, I have a question about speakers. If the speakers are 3 OHM and I have a Sony STR-K740P receiver which I think is rated at 8 OHM. Will this hurt the speakers or the receiver? This is for my parents surround sound system that I threw together. Just average use, not turn up too loud or anything? HELP...lol


Thank you,

Robert Smith
 

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Short answer: probably


Long answer: P=V^2/R so let's say for instance your amp outputs 40V nominally with a 8 ohm speaker you would get 200W of power if you go to 3 ohms the power goes to 533.3W.


Current is the killer of electronics and it is P=I^2R so since you know what power would be dissipated you can figure the current which would be 13.3A for the 3ohm and 5A for the 8 ohm. This would be harmful if the amp is not designed for that current capacity Ie big power supply and proper wire/ trace sizes.


Now we know speakers have variable resistance depending on frequency and that amps have some built-in resistance and really you need to do a voltage divider formula and long speaker cables add to this as well but I have rambled enough
 
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