joswald21
Minor Hero
"Makes much more sense to live in the present tense." - McCready, Vedder
Posts: 53 
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Post by joswald21 on Oct 15, 2017 8:39:23 GMT -5
Can anyone explain how to determine the amount of current there is between an amplifier/receiver and a pair of speakers?
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Post by 405x5 on Oct 15, 2017 9:05:26 GMT -5
Can anyone explain how to determine the amount of current there is between an amplifier/receiver and a pair of speakers? Question too vague....what is it you are trying to determine? Bill |
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Post by Boomzilla on Oct 15, 2017 9:35:29 GMT -5
Crudely - Yes, you can measure with a volt-ohm meter. Play a white or pink noise signal at a volume that you want to know the current of. Measure the AC volts across the +/- speaker terminals with your VOM. You'll also need the "nominal impedance" of your speakers (from the manufacturer's spec sheet).
Now use Ohm's law. Measured voltage divided by nominal impedance = current in amperes. So, for example, if you measure 2 volts across the terminals, and you have 8 ohm speakers, then 2/8 = 0.25 amps.
This is rude and crude, but better than nothing.
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Post by geebo on Oct 15, 2017 9:36:14 GMT -5
Divide volts by resistance. But those two vary wildly with music and frequency so good luck. I guess if you played a steady tone and knew the resistance of your speakers at that particular frequency you could get a good approximation. Why would you want to know this if I may ask?
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Post by bluemeanies on Oct 15, 2017 10:37:05 GMT -5
Crudely - Yes, you can measure with a volt-ohm meter. Play a white or pink noise signal at a volume that you want to know the current of. Measure the AC volts across the +/- speaker terminals with your VOM. You'll also need the "nominal impedance" of your speakers (from the manufacturer's spec sheet). Now use Ohm's law. Measured voltage divided by nominal impedance = current in amperes. So, for example, if you measure 2 volts across the terminals, and you have 8 ohm speakers, then 2/8 = 0.25 amps. This is rude and crude, but better than nothing. SMARTY pants😂😂 |
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joswald21
Minor Hero
"Makes much more sense to live in the present tense." - McCready, Vedder
Posts: 53
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Post by joswald21 on Oct 15, 2017 12:05:23 GMT -5
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Post by Boomzilla on Oct 15, 2017 13:55:50 GMT -5
Maybe you got the amps and ohms mixed up?
4 amps at 4 ohms is 16 volts. 16 volts @ 4 amps = 64 watts
5 amps at 8 ohms is 40 volts. 40 volts @ 5 amps = 200 watts
But if it was:
5 amps at 4 ohms = 20 volts and 20 volts @ 5 amps = 100 watts
4 amps at 8 ohms = 36 volts and 36 volts @ 4 amps = 144 watts
The latter seems more plausible than the former.
And unless you're trying to fill a stadium with LOUD music, the switch is more than adequate for home use (where almost all listening is done at 1 watt or less).
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DYohn
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Post by DYohn on Oct 15, 2017 14:54:20 GMT -5
Speakers don’t work that way. They are AC reactive loads with continually varying impedance depending on signal frequency. You cannot measure this with a VOM nor can you base estimates on rated impedance. Plus unless you are playing test tones or noise signals amplifier power continually varies as well.
Bottom line is use 16AWG or larger speaker wire and don’t worry about it.
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Post by Boomzilla on Oct 15, 2017 14:56:34 GMT -5
Speakers don’t work that way. They are AC reactive loads with continually varying impedance depending on signal frequency. You cannot measure this with a VOM nor can you base estimates on rated impedance. Plus unless you are playing test tones or noise signals amplifier power continually varies as well. Bottom line is use 16AWG or larger speaker wire and don’t worry about it. ^^^ What I said. |
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joswald21
Minor Hero
"Makes much more sense to live in the present tense." - McCready, Vedder
Posts: 53
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Post by joswald21 on Oct 15, 2017 15:16:34 GMT -5
Maybe you got the amps and ohms mixed up? 4 amps at 4 ohms is 16 volts. 16 volts @ 4 amps = 64 watts 5 amps at 8 ohms is 40 volts. 40 volts @ 5 amps = 200 watts But if it was: 5 amps at 4 ohms = 20 volts and 20 volts @ 5 amps = 100 watts 4 amps at 8 ohms = 36 volts and 36 volts @ 4 amps = 144 watts The latter seems more plausible than the former. And unless you're trying to fill a stadium with LOUD music, the switch is more than adequate for home use (where almost all listening is done at 1 watt or less). Broomzilla...you are correct. The latter is what I should have typed. Thanks for the help. |
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Deleted
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Post by Deleted on Oct 16, 2017 12:26:43 GMT -5
R= DC resistance
Z= AC resistance, dependent on frequency.
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Post by mgbpuff on Oct 16, 2017 13:25:34 GMT -5
Put a small resistor (.5 ohm maybe) in series with the speaker. Play some music through the system. View the wave form across the resistor on an oscilloscope. This is both a voltage wave form and a current waveform. The value of current is I = V/R.
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