True Wattage????

[jvk5o1 10+ year member]

CAN ANYONE ANSWER?

HOW IS TRUE WATTAGE DETERMINED?

I'VE HEARD THAT THE AMP FUSES DIVIDED BY ALTERNATOR TIMES THE BATTERY. IS THIS TRUE, OR NOT?

HOW IS THIS PROCESS DONE / CAN IT BE DONE WITH DIGITAL VOLT METER?

THOUGHT THIS MIGHT HELP ME AND ALL NEW COMERS INTO THE AUDIO WORLD

Click to read more...

 

[FurbiesAndBeans 10+ year member]

What are u talking about?

Max wattage you can pull is amps of the fuse(s) X volts (most cars are either 13.8 or 14.4). That's if you have 100% efficiency, which no amp does.

 

[IDSkoT 5,000+ posts]

Generally, you can find the RMS (or close) by multiplying the volts of your car by the amount that the fuses add up to, by the efficiency of the amp.

I.E. 12 volts with 2x 40 ampere fuses with 80% efficiency would produce about 768 W-RMS.

But, you have to clamp it to actually find the real RMS.

 

[jvk5o1 10+ year member]

Example Of The Meaning "clamp It''?

 

[DidUHearThat? 10+ year member]

The only way to accurately determine the true RMS wattage is with an osolloscope and calibrated test tone/source so you can determine the THD. RMS is rated at a specific THD. Usually either .1%, 1% or 10%. Max voltage is about twice this number.

With a standard meter, clamp Ampmeter, or calculations based on current draw (deducting for efficeincy) you're actually reading Max wattage. The true RMS wattage is about half that, but again, no way to know without an osolloscope and calibrated input source.

ETA: I forgot you also need a calibrated dummy load, 4 ohm, 8 ohm, 2 ohm, etc.

 

[UndercoverPunk 5,000+ posts]

You Take The Fake Wattage And Multiply By 12.

 

[DidUHearThat? 10+ year member]

Example Of The Meaning "clamp It''?

A type of meter with the ability to place a clamp probe over the main positive power lead and it measures the amp current flowing thru the cable without having to make direct contact with the copper.

This will tell you how much power the amp is drawing, or even how much power it's outputting, but this is max watts, not RMS.

Looking at input fuses is helpfull at spotting amps that the manufacturer is lying thier *** off if it's physically impossible to output that many watts with that small of a current input, but it will not give you exact RMS numbers.

 

[jvk5o1 10+ year member]

Where Could I Get An Osolloscope And How Much?

 

[Ronmeister]

For an oscilloscope it's going to cost a lot.

Mine was just over 800 bucks about 8 years ago.

Ron

 

[JimJ 5,000+ posts]

Ebay, couple hundred dollars.

 

[IDSkoT 5,000+ posts]

There are a few for $300 or so. They're not cheap, at all.

 

[jvk5o1 10+ year member]

Anybody Have One Close To Shreveport,la?

 

[quest51210 10+ year member]

its on the box when you buy

 

[DidUHearThat? 10+ year member]

O-scopes are expensive and complicated to operate. You also need a calibrated input source and calibrated dummy load. It's much cheaper to just buy amps from a company that can be trusted with thier claims. Your likely to get a better, more reliable product as well.

For example:

JBL/Crown = True RMS watts

Pyramid = lying