quote:Originally posted by Gary F.: Hate to bring this back up. Did you find out anything? I think might have figured out why you are reading a higher wattage then others. I was testing my van for the upcoming 6/27 show, and I was getting some extremly high readings. Like 8000 watts out of 2 1500d's. Then I remembered something I was doing in my testing when I first got the amps, that I haven't been doing lately.
I clamped Zach's amp with my meters and got the same reading as Fred did at about 1750 watts.
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quote:Originally posted by Nightshade: I'm going to do some clamp tests of my own later on today to see if my numbers are matching up to what Fred is getting on his meter's. I know I don't have a true rms meter at all, so I will just divide by .707 to get a close estimate of power.
This is a common error, you don't need to multiply (not divide) by 0.707 since your meter will mark RMS voltage (not true RMS though). Meters actually convert the AC into DC pulsed measuring the RMS voltage.
The problem with your meter not being true-RMS is that any wave form different from a sine wave (a clipped sine wave, as an example) will measure wrong.
quote:Originally posted by Nightshade: Alright here are my test results from about 10 minutes ago. I couldn't sleep so I went to an empty parking lot to do some testing. One note I did add threaded rod to the box and all my other numbers were from before the threaded rod was added, but I don't think that will make a huge difference if any for power testing. Anyway here are my numbers:
These numbers were done using my Craftsman clamp meter that isn't a true rms meter. If you were to multiply the power by .707 to calculate for rms you would get 1448 watts. Now that sounds about right since that's what the rest of you are getting out of this amp at around the same impedence. I think that there needs to be some checking at the next NSPL event cause I thought that it was funny that each event I kept making more power when I've done nothing to increase the power at all. It may be user error since Fred doesn't clamp the cars himself, he has Mike do it for him most of the time. If this is an issue at the events then it needs to be addressed very soon since I would like to be told the correct clamp numbers. This also means that I should have quite a bit more power to go before the cap in the class. The calculated rms numbers that I got tonight are very close to those that I remember getting when Jacob put his true rms meter in my car for testing. His meter did around 1550 if I remember right. Multiplying by .707 isn't always going to be dead on, but there is no way I'm making over 2000 watts at 1.7 ohms out of a 1500d.
Your measuring problem could be clipping, that will make your meter read higher than its true-RMS measurement.
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