W RMS ??

[Inferno]

hello there...
i ve asked before what s W RMS ??( for audio applications )...
how can i calculate it ?? is there any formulas ???
how is it related with the intensity and voltage of the power source ?? :?:

 

[chemelec]

Watts RMS: Is typically RMS Volts times RMS Amps.
But Numerous Manufacturers Screw this around very much and come up with outragous figures.

Statistics don't lie, but liers DEFINATELY make statistics.

 

[Nigel Goodwin]

hello there...
i ve asked before what s W RMS ??( for audio applications )...
how can i calculate it ?? is there any formulas ???
how is it related with the intensity and voltage of the power source ?? :?:

To measure the output of an amplifier you feed a sinewave input that gives an output just before the onset of clipping into the load you require. You either measure the RMS value of this with a suitable AC millivoltmeter, or measure the peak to peak value with a scope, and convert to RMS volts by dividing by 2.828. You then square the RMS voltage and divide by the speaker impedance - this gives the RMS output power in watts.

 

[Inferno]

well i ve made some measurments on the output ... it s going between 0.3 V and 3 V so when dividing by 2.828 i would get betwenn 0.11 and 1.1 ... when squaring it would be 0.01 and 1.21 ... when dividing by 8( speaker impedance ) it would be 0.00125 and 0.126 W RMS ??? is that possible ???
so i dunno if i m making false mathematics here.. but all i want to know is that when i m using like u said a 8 Ohm speaker ... with a battery of 12 V and a sinusoidal sound on the output with high frequency ( about 3 to 10 Khz) i want that the intensity do not cross the 0.5 A on the power input ( the battery ) what is the maximum power of the amplifier that i can use ???? i mean which amplifier can i use for this maximum ??

 

[Nigel Goodwin]

well i ve made some measurments on the output ... it s going between 0.3 V and 3 V so when dividing by 2.828 i would get betwenn 0.11 and 1.1 ... when squaring it would be 0.01 and 1.21 ... when dividing by 8( speaker impedance ) it would be 0.00125 and 0.126 W RMS ??? is that possible ???
so i dunno if i m making false mathematics here.. but all i want to know is that when i m using like u said a 8 ohm speaker ... with a battery of 12 V and a sinusoidal sound on the output with high frequency ( about 3 to 10 Khz) i want that the intensity do not cross the 0.5 A on the power input ( the battery ) what is the maximum power of the amplifier that i can use ???? i mean which amplifier can i use for this maximum ??

How are you measuring the output of the amplifier?, you can't use a normal multi-meter, you need either an AC Millivoltmeter, or an oscilloscope - an oscilloscope is probably preferred, so you can check for the onset of clipping. It's usual to perform these tests at 1KHz, but also at other frequencies as well to check for full power across a wide range.

0.5A at 12V is 6W consumption, an amplifier outputing 4W into a 4 ohm load will probably be using about 0.5A. With 2W into 8 ohms it should be about half of that.

 

[Inferno]

i used an AC millivoltmeter and i got these results..
so anyway .. is there anyway that i can measure the impedance of the tweeter |???
and u think that with a 2 W amplifier and a 8 Ohm tweeter .. the internsity should be 0.25 on a 12 V battery ??
so is it logical that with a 4 W amplifier and a 8 Ohm tweeter....... it should be 0.5 ??
and what if the tweeter is 4 Ohm ??
10x a lot for ur usefull replies ... just need a final one plz answer all the questions if that is possible .. 10x a lot again and sorry for my stupid questions

 

[Nigel Goodwin]

i used an AC millivoltmeter and i got these results..
so anyway .. is there anyway that i can measure the impedance of the tweeter |???

Use the AC millivoltmeter to measure the voltage across it, and the current through it (measure the voltage drop across a series resistance to do this), then apply ohms law.

and u think that with a 2 W amplifier and a 8 ohm tweeter .. the internsity should be 0.25 on a 12 V battery ??
so is it logical that with a 4 W amplifier and a 8 ohm tweeter....... it should be 0.5 ??

No, you will only get 4W with a 4 ohm speaker from a 12V supply, if you wanted 4W with an 8 ohm speaker you would need a higher supply rail.

and what if the tweeter is 4 ohm ??

See above!.