Doctorbass Show full post »
scottiej
And for those that just want power numbers for their own reference testing... dont worry to much about how you get your numbers, just do it the same way everytime and dont compare the numbers you get with the numbers others get unless you both use the same equipment and methods...
Quote 0 0
Neill Barber
Someone want to sticky this?


NeillBarber
Quote 0 0
Doctorbass
Quote:
Originally posted by scottiej:
And for those that just want power numbers for their own reference testing... dont worry to much about how you get your numbers, just do it the same way everytime and dont compare the numbers you get with the numbers others get unless you both use the same equipment and methods...
Totally agree with that in "for dummies" section, that would be easier... also called relative measurment method...

In other words, you are saying that we do not ned to border about what is the absolute exact power we have out of our amp.. but we only need to know if we have more or less between any change or mod we do on our installation... BUT if you need to compare power of an amplifier with other competitors amplifier, WE absolutly need to have a method and conditions that are indentical for each measurment.... comparing apple with apple.

Doc
Quote 0 0
Doctorbass
Quote:
Originally posted by RE-tardedF150:
Doc,


I believe your method here is wrong. Current and Voltage do not peak at the same time in AC circuits. Therefore your two peaks most likely do not occur at the same time. This would give you a false reading on power. IMO, the best way to do this without very expensive equipment is to get the RMS meters as you state, but do not put on peak hold. Burp and read the numbers at the same time. You will see that your measured power then will most likely be much less and this is because those peaks do not occur simulataneously.
Well, i dont want to debate again on that, but i need to highlight what i said:

First, the peak hold is very usefull if you want to measure the max value without having problem with the latch of digits of the dmm.. normally a dmm have around 3 samples of reading per second... and the max power may appears between 2 samplings.. BUT dmm with peak hold like HP fluke or meterman...etc have a much higher sampling rate in peak hold then others. I get normally better results with those. And believe me i know how a dmmm work and how to use it.

I understand what you mean about the difference of phase between AC current and voltage in inductive circuit... and that dmm will not see that shift and only measure the max, but it's normally around 5 to 15degree but mostly 10degree shift on the coil in usual subwoofer installations. If you measure it on a scope, you will see that the amplitude diff between 10degree shift on two sinewave is very unimportant. and when you multiply those, the difference will not be very important.

Two years ago i was thinking exactly like you and replied on some post about that inductive measurment to explain that inductive state of a coil and that it could change the real power results. But after measuring that with good instrument and acurate methode, i seen that it's very unsinificant diff... but only if you want to lost your time with: "my amp is 5W more powerfull than yours... about amp of 300W...."

Like i said, the power factor indicate this shift and is usually around 0.95...

The difference of power you can measure with and without taking account of that shift is not sinificant... let's say 10W for a 1000W amp

Remember i wrote this post with mention : FOR DUMMIES"... and dumies dont really border about 1 to 5% power difference...

All i write to inform and help dbdrag community is alway did with the best as i can and often acquired by experience and many time to measure and test stuff. I also invite other people to share their ecperiences and i'm open to compare mine to yours...

Doc
Quote 0 0
CBFryman2
What about the difference between true power and apparent power? Multiplying peak RMS voltage by peak RMS current will yeild apparent power. Real power can be much less depending on impeadance rise and degree of load change. Also, unless you have an Oscilliscope you could be clipping...if you are burping your ears should be way past their distortion threashold so oyu wont be able to detect minimal clipping. Just a thought, though this is a good way of testing the difference in power output between loads and input voltages, but not nessicarily accurately measuing the amps power output.
Quote 0 0
USAMPFREAK
All I ever do to measure power is my ac amp clamp on peak hold and dcm ac volts on peak hold AC amps * AC volts = wattage then
for box rise I use AC volts/ AC Amps

K. I. S. S.
Quote 0 0
Broken Silence - Johnny
Quote:
Originally posted by CBFryman2:
What about the difference between true power and apparent power? Multiplying peak RMS voltage by peak RMS current will yeild apparent power. Real power can be much less depending on impeadance rise and degree of load change. Also, unless you have an Oscilliscope you could be clipping...if you are burping your ears should be way past their distortion threashold so oyu wont be able to detect minimal clipping. Just a thought, though this is a good way of testing the difference in power output between loads and input voltages, but not nessicarily accurately measuing the amps power output.
You dont have your facts straight. When you are measuring the actual output of the amplifier, you do not have to take impedance into account (unless you are doing acv * acv/impedance). We are not talking about clean power here either, just power. Everyone knows that you need the power to be just a little dirty to get loud...
Quote 0 0
Contact Us | Legal Notices | Privacy