Lspade69

iTrader: (2)

holy crud. Did you go to college for this stuff?

BigRedGuy

iTrader: (11)

Hmmmmm.....

.707
X.707
=.499849

square root of 2 is actually 1.4142135....

now what?....

Sorry to nitpick, but mathematical errors make me nuts....my kids hate it when I offer to help with their homework.....

Folk128

iTrader: (1)

sorry, root2 is going to peak from rms. it would be 1/root2 to go from peak to rms.

Tom.F.1

iTrader: (1)

It definitely sounds like he went to college. I also went to college, specifically for audio electronics and I’ve forgotten most formulas.

You'll find out, if you really want to test it, that music has very little to with the math. The math only works for sine waves, like from a real test generator. And don't ever put real sine waves into your speakers. They'll generate more heat than sound.

The real test for an amp would be with a good generator and a linear resistor for a load. The problem there is high power resistors are very expensive.

How about a more practical test, i do it for setting up my own stuff. I have a true RMS voltmeter. Really it only works up to 1000 Hz, but that’s good enough. I also have an Audio test CD. It has 75 tracks, with various sounds and sweeps, but the one you want is white noise (so you don't damage speakers).
I measured speaker voltage (trusting that they're really 4 ohm) to set the left and right, front, rear and sub levels the same. I didn't set anything for max spl. I don't ever want to hit clipping, nor do I ever want to overdrive a speaker. I've tweaked levels for preference since then, but at least I started with a level playing field.

Sassmaster

iTrader: (2)

Measuring output voltage is only valid if you're using a true RMS meter, otherwise your meter will fudge it up depending on the voltage and frequency at that moment

Lspade69

iTrader: (2)

What is white noise? I downloaded some tones and put on a cd and tested my subs. There was some frequencies comin outa the speakers. Now everyso often I hear a split second crackle on the low bass notes, it may be possible that it is my inline crossovers (400hz's I think) that I put in. I heard that in a few installs they make wierd noises.

Haunz

iTrader: (3)

white noise is collection of random tones with equal power distrobution.. for audio testing you should use pink noise which approximates music and has equal power distrobution between octaves... (although for continuous power output testing using 1khz or some specified frequency is quite common)

as far as multimeters go your average cheapie already takes the peak voltage and multiplies it by .707 to give an RMS voltage.... but they will only be accurate around 60Hz....

as posted for a good approximation of continuous output you should use an RMS voltmeter, and RMS ammeter, a test tone, and a non-inductive load resistor.... (although what is really needed is a power meter)

fyi- high power load resistors are expensive but a 10watt submerged in distilled water or oil will work just fine... another hint is to use a piezo tweeter in parallel with the resistor when testing a full range amplifier to detect harmonics created by clipping....