Check this out.
Now you can see what them "Legacy" Or Pyramid amps are really putting out for wattage.

I am going to go check my amp right now.

Check this out
http://www.conceptconcept.com/download/measurwatts.pdf

 

I tested two of my amps
The THUMP! amp..
600RMSx1 Bridged at 4OhM is what advertised.
I got 361 Peak LOL Which is about 250~ RMS.

Then I tried my CONCEPT amp.
Its 500RMS x1 AT 2OHM.

But I only had 1 sub so I could only test the CONCEPT amp for its rating at 4 OHM
250RMS @ 4ohm Bridged.
I got 400 Peak Watts which is about 280RMS.

Stupid Thump! piece of crap!

 

one MAJOR flaw with measuring it that way....you simply CAN'T measure the power of an amp playing music. There is a reason why when mag's test an amp they use sine waves and resistors (or reactive loads like Car Sound).

The voice coil of a speaker does not have a constant impedence, it varies with frequency. You will never get a constant voltage when playing music. You HAVE to do it with a sine wave of known frequency and you HAVE to measure the impedence of the speaker at the freq (and no a multimeter can't do that, it justs measures dc resistance which is useless for this).

Another flaw with that is that when you measure with a volt meter you ARE getting rms (or constant) not peak.

 

i agree, from an engineering perspective, that's not a real accurate way to measure. if you did an averaged sampling over a time period, and had a dynamic impedance measurement of your speaker, you could get a much better rough guess.

the reason they use resistors and sine waves is to test the electronics of the amp in a consistent way. if amp A puts out 500W peak @ 60hz to a 4ohm resistor and amp B puts out 300W to the same setup, you can bet that for music frequencies in the 60hz range amp A will be more powerful than amp B.

also, most companies cheat measuring the peak outputs by testing right to the edge of FCC allowed standards. they'll take a peak over a ridiculously short time period, with an power supply input of about 18 volts, and run the whole thing at 50° below zero. very few companies run them at real conditions, because it makes no sense from a marketing standpoint, but i wish they would....

i actually wrote to pioneer to complain about this issue over the last receiver i bought. it's a nice piece of equipment, had all the digital stuff way ahead of its time, but was rated at 5x100W RMS. the input power on the back is rated at like 400W. now i know the laws of conservation of energy, and you're not getting 500W RMS out of 400W input, let alone 500W because of losses. so while it's hard to do that for car audio, looking at the power supply rating is a good way to estimate real power from home stuff.

 

This is NOT at all an accurate way to measure wattage from your amp! Any number you come up with WILL be total BS! You can NOT “measure” the AC voltage coming out of your amp with any old AC voltmeter! You’re run of the mill DMM or VOM (DMM stands of digital multi meter and VOM stands for Volts, Ohms, and Amp measured in mA) is ONLY accurate at 60 Hz. The audio frequency range is 20Hz to 20,000Hz (or 20KHz). So your DMM CAN NOT ACCURATLY measure the voltage out, it’s not at a steady 60Hz. So any number you get from the Equation would be calculated using inaccurate numbers from the start. And I’m not even getting in to dynamic resistance, or the other five variable and inaccuracies in this plan, like load/no load voltage output from an amp. BS!

 

What if you get a bass CD with a constant 60 hz bass line??? You said if it's constant it'll work. You could just get an IASCA test CD.

 

One big flaw that nobody here has addressed yet (unless I didn't read well enough) is that you're measuring the voltage into a purely resistive load when you use a DMM. Nevermind the fact that you're measuring it into an impedance in the mega-ohm reason, which is going to be miles away from the optimal bias of the output fets.

But anyway... back to what I was saying. An amp will react differently to a reactive load than it will to a resistive load. Most cheap amps make LESS power into the more difficult reactive load than they do into a purely resistive load. This means that your Pyramid, which only makes 1/2 of its rated power into a resistive load, is going to do EVEN WORSE when trying to push a real speaker. There are a few good amp designs out there (the older Rockfords come to mind) that actually make MORE power into a reactive load than a resistive load. This is yet another thing that doesn't show up on paper that separates the good from the junk. A 1000 watt Pyramid, that actually makes 100 watts into a 4 ohm resistive load, probably makes 50 or 75 watts when pushing a speaker. Take a 1000 watt Rockford, make 1200 into a 4 ohm resistive load, and 1300 into a speaker.

 

If you play a 60Hz sine wave then yes you will eliminate that error. But you still need to know the impedence of the speaker @ 60Hz...which in a box will most likely be really large (depending on the sub and where its res freq is at in the enclosure).

 

330hp_91RS, That would eliminate that error, but not dynamic resistance, or that a speaker voice coil is a partial inductive load, or load/no load differences (using a DMM is like using no load) or the tempter of the amp, the distortion levels at different power levels. I just chose to rant about one thing at a time. Another thing that has not been brought up is distortion. One amp may put out 100 watts and anther 70 watts. If the second one is a “cleaner” 70 watts which would you want to power your mids and highs? I’ll take the “cleaner” 70 watt amp.