determine current needed to drive a speaker

Thread Starter

nearownkira

Joined Feb 19, 2008
20
the speaker I bought said something like 800 ohm 5W, 8 ohm 25W or 8 ohm 25W.is there a formula or something to calculate.
 

silvrstring

Joined Mar 27, 2008
159
It sounds like your max current rating would be about 1.76 A if you have a typical 8 ohm speaker. P=(I^2)R. In the same way, P=(V^2)/R. So the voltage would be around 14V. That's what your alternator normally puts out.

Are you using an amp?
 

Audioguru

Joined Dec 20, 2007
11,251
Those are very small 8 ohm speakers. The 50mm one has a max power rating of only 0.25W.
The max power might be its peak power so then its max RMS power from a sine-wave is only 177mW.

Then the RMS current at max power is 149mA RMS.
 

Thread Starter

nearownkira

Joined Feb 19, 2008
20
Those are very small 8 ohm speakers. The 50mm one has a max power rating of only 0.25W.
The max power might be its peak power so then its max RMS power from a sine-wave is only 177mW.

Then the RMS current at max power is 149mA RMS.
how do you calculate all those number?
 
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