True RMS question

[bjfish11 5,000+ posts]

anyone?

 

[bjfish11 5,000+ posts]

come on guys, someone must know how to do this....

 

[Raisedin305 5,000+ posts]

hmm. odd. i would think you would be getting 34V, 34A.
just for fun -- this is the output current and output voltage right? make sure you aren't measuring output voltage and input current.

I thought the same thing

 

[bjfish11 5,000+ posts]

well apparantly im doing something wrong, so if someone could like walk me though the steps i would greatly appreciate it.

 

[Johnny Drama 5,000+ posts]

ok, here is what i got now:13.8 amps with clamp meter around positive speaker wire running to subs

43.7 volts with dmm connected to speaker wires with subs unhooked.

What am i doing wrong?

Could someone please walk me through the process?

Clamp shoud be around + speaker wire...

DMM should be on INPUT voltage (you will need to read the LOWEST number during the note to find what the power drops to when current is drawn.

Clamp# x DMM# = wattage

 

[bjfish11 5,000+ posts]

imput voltage?

Thats around 14.6 volts. That means i will need approx. 82 amps to get anywhere around 1200, that doesnt sound right.

 

[SuperJETT 10+ year member]

You also need to do both measurements at the same time. Play your test tone, check steady amps and steady voltage on the output to the sub(s). It doesn't matter which wire, positive or negative, but make sure you're only around one because if you're around both they will cancel each other.

Power = current * voltage, however this is assuming a purely resistive load, which speakers are not. There is reactive power in the circuit which creates the magnetic field around the voice coil, but doesn't do any real work which is power.

 

[bjfish11 5,000+ posts]

can anyone walk me through the steps of this?

 

[thch 10+ year member]

i get 603 VA as the apparent power. this is a impedance magnitude of 3.16 ohm. that may be correct. if the equipment allows, try testing at other frequencies.