true power
02-13-2011, 06:31 AM
#12
I thought the op wanted to know the power the amp was making. It should make different power into every frequency. Hense, the reason why I wrote "@ that frequency". Different frequencies cause different reactions to the "final load".
Will that frequency be where it makes max power? Maybe not... thats what testing is for. If you wanna compare it to factory specs.... they usually use a 50hz sine wave @ whatever voltage they choose to test with. If you wanted to know the amps efficiency... then ya, your going to need more equipment setup on the input side of the amp too.
I'm not here to argue with people (not in general discussion section anyway)... to my knowledge my method works fine... if someone has a different way.... to each their own.
Will that frequency be where it makes max power? Maybe not... thats what testing is for. If you wanna compare it to factory specs.... they usually use a 50hz sine wave @ whatever voltage they choose to test with. If you wanted to know the amps efficiency... then ya, your going to need more equipment setup on the input side of the amp too.
I'm not here to argue with people (not in general discussion section anyway)... to my knowledge my method works fine... if someone has a different way.... to each their own.
02-13-2011, 09:09 AM
#13
So...an amp that measures 100 watts into 4 ohms is better than an amp that gives 75 watts into 8 ohms? What if I put a real speaker load on it and not a 4 or 8 ohm resistor? What if my amp puts out 30 watts continuous but can provide 6db over that for short burts? Which is better?
What if my amp puts out 50 watts at .1%thd. Is it better than an amp that puts out 100watts at 1% distortion? How do I tell how much my amp is distorting? Please tell me for sure.. because I want just the one right answer...there is always a right answer isn't there?
oh so.. the impedance changes depending on what box the speaker is in? Yes I agree with that. Does this mean now that I need to get specs for my amp with every speaker box? Or is there one, just one.. standard way of measuring amp power that I can use to compare every amp? The manufacturers agree on this standard method right?
What if my amp puts out 50 watts at .1%thd. Is it better than an amp that puts out 100watts at 1% distortion? How do I tell how much my amp is distorting? Please tell me for sure.. because I want just the one right answer...there is always a right answer isn't there?
oh so.. the impedance changes depending on what box the speaker is in? Yes I agree with that. Does this mean now that I need to get specs for my amp with every speaker box? Or is there one, just one.. standard way of measuring amp power that I can use to compare every amp? The manufacturers agree on this standard method right?
and yes, there is a standard method to test for power. it is physics after all, and that is an exact science.
02-13-2011, 07:31 PM
#14
Its not a matter of turning things into an argument. Its a matter of making sure the OP has the correct information. As far as I know the best way to check is the way DeadlySones described. If zoomer's method works then more power to him, but we're all just trying to help. Scientists get into debates all the time, so I don't see why we shouldn't be able to. Just look at the guys on Big Bang Theory.
02-21-2011, 12:44 PM
#16
In order to make any measurement that can be used to compare different amps you have to decide on some basic measurement methods. Yes ultimately you will measure voltage and current or resistance and use the ohms law math to come up with an answer. What is missing are a few fundamentals:
1:How long do you want to measure the power? A second? A minute? 100 Milliseconds? an hour?
2:what is the voltage supplied to the amp?
3: what is the level of distortion? I suggest that simply listening for distortion is not reproducable from person to person for accurate measurments. Especially if done at different frequencies. Or if the harmonic is above the subwoofers upper response. Or if different amps behave differently when clipping.
4: what is the ambient temperature. An amp will go into thermal shutdown sooner if it is in a hotter environement.
5: what frequency and
6: what is the load impedance.
In this forum so many people nitpic about which this or that is better and will quibble about 50 watts on a 1kilowatt. It is futile to argue over this minute difference if the measurement setup is not the same for all.
1:How long do you want to measure the power? A second? A minute? 100 Milliseconds? an hour?
2:what is the voltage supplied to the amp?
3: what is the level of distortion? I suggest that simply listening for distortion is not reproducable from person to person for accurate measurments. Especially if done at different frequencies. Or if the harmonic is above the subwoofers upper response. Or if different amps behave differently when clipping.
4: what is the ambient temperature. An amp will go into thermal shutdown sooner if it is in a hotter environement.
5: what frequency and
6: what is the load impedance.
In this forum so many people nitpic about which this or that is better and will quibble about 50 watts on a 1kilowatt. It is futile to argue over this minute difference if the measurement setup is not the same for all.
02-23-2011, 06:24 AM
#18
The next thing is to get all the amp manufacturers and your car audio buddies to agree! Good Luck!
Even if everyone could agree on a test method most manufacturers would probably not want to adopt them because it would make it harder for them differentiate themselves vs competitors. They would no longer be able to make unsubstantiated claims and sell their products at exorbitant prices! Everyone would just buy the cheapest amp that puts out the most power.
Enjoy your hobby!
02-23-2011, 08:29 AM
#19
0 Watt CAFz'r
Join Date: Nov 2010
Posts: 9
The real way.
First yo use a sine wave generator and set it at 1,000 hz. for a full range amp and 40 hz. for a class d subwoofer amp. Connect the amp to a load (speaker or resistor) and connect an oscilliscope to the load. Drive the input of the amp with sine wave till the top and bottom of the wave on the oscilloscope just start to flatten. Now back off the input till the sine wave is clean again. Note the amplitude on the scope and divide the number by 0.709.
02-23-2011, 08:44 AM
#20
First yo use a sine wave generator and set it at 1,000 hz. for a full range amp and 40 hz. for a class d subwoofer amp. Connect the amp to a load (speaker or resistor) and connect an oscilliscope to the load. Drive the input of the amp with sine wave till the top and bottom of the wave on the oscilloscope just start to flatten. Now back off the input till the sine wave is clean again. Note the amplitude on the scope and divide the number by 0.709.
If you use a resistor this will give you very good idea of the power... dont forget to use V^2/R to calculate the power. However eying the clipping point is rather subjective and may not be reproducible if you wish to make exact comparisons between amps or by different people.
btw multiplying the peak voltage reading by .707 (square root of 2) will give you the RMS value. Thus giving you the power based on RMS voltage applied. The term "RMS Power" or *watts RMS* is an incorrect term for measuring power when the supplied signal is not varying in amplitude
Last edited by zoomer; 02-23-2011 at 08:48 AM.
