measuring watts??

[Mass Car Audio 10+ year member]

No. bigger the impedance load, bigger the resistance of flow of power to the subs = less power.
no resistance means the most power.

8 ohms of resistance restricts the amp more than 4 ohms does and thus you double the power by cutting the resistance in half

ok I see what you were talking about now, make complete sense. The amp will run just above the short protect with no impedance load.

 

[WOT]

Best thread Ive read in a while

Anyone care to explain imp rise in english? Like I wired my (4) DVC 4ohm subs to a 2ohm load on my amp. What actual load would my amp be seeing? Not likes theres any way I can wire all 4 of them to a lower load if the imp rise is to much. But Id like to know

 

[midnightg35x 10+ year member]

ok I see what you were talking about now, make complete sense. The amp will run just above the short protect with no impedance load.

No impedance load implies infinite resistance, not zero resistance. Zero resistance is a short.

Checking the AC voltage of an amp with no load USUALLY works, but not always depending on the topology of the amp. To find the actual power out, as said before you need a clamp ammeter, a voltmeter, and a test tone. That gives you the true power by multiplying amps x voltage.

 

[audioarsonal 10+ year member]

Best thread Ive read in a while
Anyone care to explain imp rise in english? Like I wired my (4) DVC 4ohm subs to a 2ohm load on my amp. What actual load would my amp be seeing? Not likes theres any way I can wire all 4 of them to a lower load if the imp rise is to much. But Id like to know

Impeadnce rise only matters when burping.Music is transient so the actual impeadnce is constantly changing.

You could wire down to .5 ohm if your amp is stable at that.

 

[Mass Car Audio 10+ year member]

No impedance load implies infinite resistance, not zero resistance. Zero resistance is a short.
Checking the AC voltage of an amp with no load USUALLY works, but not always depending on the topology of the amp. To find the actual power out, as said before you need a clamp ammeter, a voltmeter, and a test tone. That gives you the true power by multiplying amps x voltage.

yes i know this, I stated his before that If he wants to calculate the power going to his speakers he needs to leave them hooked up so he gets a reading with the impedance load from the speakers. If he unhooked the speakers he would get the maximum rms the amp will produce if it has a non regulated output, he has a impedance load that he should take into effect. He is not trying to measure the full potential of the amp, he is trying to figure out the power going to his speakers when they are hooked up.

 

[audioarsonal 10+ year member]

Without the speakers being connected you won't be able to get the amps reading either.

 

[Mass Car Audio 10+ year member]

Without the speakers being connected you won't be able to get the amps reading either.

That's what I've been trying to say this whole time..lol

 

[midnightg35x 10+ year member]

yes i know this, I stated his before that If he wants to calculate the power going to his speakers he needs to leave them hooked up so he gets a reading with the impedance load from the speakers. If he unhooked the speakers he would get the maximum rms the amp will produce if it has a non regulated output, he has a impedance load that he should take into effect. He is not trying to measure the full potential of the amp, he is trying to figure out the power going to his speakers when they are hooked up.

Fair enough.

On another point on the OP's question: When playing regular music any number you got would be swinging wildly. Only a test tone would give you a consistent number.

 

[gunz4me 10+ year member]

In all of this ohms law BS, EVERY SINGLE ONE of you missed another vital piece of the puzzle. One better have an oscilloscope to watch the waveform (eta on a constant test tone) otherwise there is no way to determine clipped power from clean power.

Otherwise one will be saying "ZOMG, muh 1,000 watt amp produces 1,700 watts RMS. Look at muh proofz!"

 

[audioarsonal 10+ year member]

In all of this ohms law BS, EVERY SINGLE ONE of you missed another vital piece of the puzzle. One better have an oscilloscope to watch the waveform (eta on a constant test tone) otherwise there is no way to determine clipped power from clean power.
Otherwise one will be saying "ZOMG, muh 1,000 watt amp produces 1,700 watts RMS. Look at muh proofz!"

Clipped or clean its still power.If you know what your doing you will get fairly accurate results without an Oscope.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[gunz4me 10+ year member]

Clipped or clean its still power.If you know what your doing you will get fairly accurate results without an Oscope.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

What exactly is that distortion percentage where most humans start to determine signs of clipping on subwoofers again?

Oh that is right, you know what you are doing and can obtain precise mesurements with only part of the puzzle.//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[Mass Car Audio 10+ year member]

Clipped or clean its still power.If you know what your doing you will get fairly accurate results without an Oscope.//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

x2... I always use my oscilloscope when testing the output power of a amplifier that I have just repaired or bought. I also use it when setting the gain. As long as you know your divisions and your equations when using the graph on a oscilloscope you should get a very accurate reading.

 

[Mass Car Audio 10+ year member]

What exactly is that distortion percentage where most humans start to determine signs of clipping on subwoofers again?
Oh that is right, you know what you are doing and can obtain precise mesurements with only part of the puzzle.//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

The human ear can only pick up about 10% t.h.d and above.

 

[SlowLoudNBangin 10+ year member]

x2... I always use my oscilloscope when testing the output power of a amplifier that I have just repaired or bought. I also use it when setting the gain. As long as you know your divisions and your equations when using the graph on a oscilloscope you should get a very accurate reading.

now when you say " i always use my O'scope when testing the output..." are you just talking about the setting the gain part...as in checking for clipping...or actually finding the constant output of amp by only using scope?

cause i want to do the same thing, measure the RMS output of my amp, but i only have a o'scope, im gonna get the clamp and DMM soon though, whats crazy is i got a EZdigital 5060a 60MHz 2channel scope in perfect working order for 10bucks from my school, and i know it works cause i tested it myself. im in my 7th quarter at ITT tech for electronics...love it

so im pretty sure im not going to be able to do this since im going to need a clamp meter for current, and a DMM for impedance,

cause P=IV, but what about the equation P=(V^2) / ®.... which is the same thing, could i square my voltage and divide by my sub load...anyone ever found it that way?

or am i SOL and theres no possible way to measure RMS wattage with only an O'scope...

thanks in advance for any advice.

 

[Haunz 10+ year member]

It sounds like you want to measure actual power to the speakers with music. Put your meters on average responding and play your music. This will give you apparent power, finding actual power would be quite difficult without a powermeter. You can use a program like speakerworkshop to measure % THD if you are so inclined.