Amp Manufacturers are LIARS!

Originally Written May 5, 2011
by Shane Martin
The Wholie Shop

Okay so maybe the title of this article is a bit extreme, however; the truth is amplifier wattage ratings can be very misleading as to what type of performance you can actually expect to see when it's connected to the electrical system on your ride.

There are tons and tons of amplifiers on the market today and they all have different power ratings and very different price tags.

I'm sure we've all met that guy who claimed he had a "2000" watt car stereo in his car... Problem was it still sounded terrible right?
Chances are his amplifier(s) might have had 1000 watts or 2000 watts written right on the top of it. In reality he had nowhere near that much power.

The reason for this is the rules governing how wattages are measured by manufacturers are very very lax. Home audio and car audio rules are very different. If you go buy a home amplifier and it says its 150 watts, it's really cranking out 150 watts.. In the mobile audio industry however we're not so lucky..

A less than honest company can take their new amplifier, put it on a test bench, pump liquid nitrogen over it to cool it down, then run 40 volts through it on a dummy load and if that amplifier produces 500 watts for a millisecond before it fries they can slap a sticker on it that says it's rated at 500 watts maximum.

In real life with music and speakers and a 12 volt charging system you're never ever going to get anywhere near 500 watts out of that amplifier.

For example: Lets take an inexpensive amplifier that is commonly used in the construction of home brew ATV audio tubes.. The Pyramid PB440x, this amplifier claims to be rated at 240 watts x 2 channels or 440 watts total...

We can use the following formula to figure out how close to that we can actually get.

Watts = Volts x Amps

If our battery is healthy and fully charged it should have 12.5 volts in it. If our engine is running, a healthy electrical system should put out about 14.4 volts.

We can use the size of the fuse in an amplifier to approximate what the maximum current draw could possibly be (any more and it would blow the fuse). The PB440x has a 10 amp fuse in it.

So 14.4 volts x 10 amps = 144 Watts.. or 72 watts per channel MAXIMUM. That's much much less than the 440 watts they claim or even the 240 watts they claim one channel can run at..

To actually get 440 watts out of the little pb440x amplifier would have to consume much more current (amperage)
Assuming 14.4 volts:
440 watts / 14.4 volts = 30 1/2 amps!!
There's no way in the world that the pyramid is going to draw anywhere near 30.5 amps before it goes up in smoke, clearly the ratings are grossly inflated.

Using an ammeter could give us a better idea of what the amplifier is actually putting out. Running a pb440x with the gain at 75% and the volume up to the maximum it was drawing less than 3 amps when checked with a digital ammmeter.

Therefore;
14.4 volts x 3 amps = 43.2 watts TOTAL or 21.6 watts per channel, this is a little more power than you are going to get out of a normal car stereo head unit.

Pyramid most definately is not the only manufacturer guilty of claiming physically un-obtainable power ratings on their products. On the flip side there are plenty of them out there that do not over-inflate their wattages to sell products. Typically you'll find that a much lower wattage rated amplifier costs quite a bit more than the inexpensive amps that claim so much power.

Wetsounds offers a marine amplifier that is small in size but packs a massive punch. It's power is rated a couple of different ways;

Stereo @ 4 Ohms 75 x 2 watts RMS
Stereo @ 2 Ohms 125 x 2 watts RMS
Mono @ 4 Ohms 250 x 1 watts RMS

See the words RMS up there? It stands for Root Mean Square or in the context of this article the average power output of the amplifier. This is a much better way to gauge the given power of an amplifier but even then please do not just take the manufacturers word for it.

You'll note that there are several different ratings depending upon the Ohm load (resistance) of the speakers connected to it, the lower the ohm load the less resistive it is and the easier it is for the amplifier to flow more current to it. This does not mean you should strive for 2 ohm loads everywhere, yes your amplifier will produce more power but it will also produce more heat.. Something that can cause your amplifier to shut down or worse burn up. Heat is a very real factor when you have an amplifier sealed up inside a pvc tube with zero outside air passing over the cooling fins.

For the sake of this example we are going to use the 4 ohm stereo rating which according to wetsounds is 75 watts.
To actually produce 75 watts @ 14.4 volts it would need to draw about 5.2 amps. This amp is also equipped with a 30 amp fuse in the side of it and at maximum volume 5.2 amps is no sweat for this amplifier.
14.4 volts X 5.2 amps = 75 Watts

On the other extreme to produce the full 250 watts it would need to draw nearly 17 amps! While possible i've yet to see one of these amps pull much over 12 amps.. Which can be limited to the size of your power and ground wires. They can only flow so much current and the amplifier can't produce it if getting it from the battery is a problem.

14.4 Volts X 12 Amps = 172.8 Watts
This much more power than the wimpy 21 watts from the previous example, and our speakers will surely appreciate the extra power they have to re-produce music with cleanly, without distortion.

What all this actually means is that using the maximum rated wattage (or basing your decision soley upon price) when you decide if one amplifier is superior to another is not a good idea.

When talking about atv's where space is such a premium our choices are very limited when it comes to which amplifiers will even fit inside a section of 6" PVC, that being said; please don't expect a 500 watt amplifier that costs $40 to compare to a 300 watt amplifier that costs $300. There will be major differences in the sound quality as well as usable power.

In a 2 speaker setup the 2 channel cheapo amps may produce ample power to play your music with acceptable volume provided they're set up right and the amplifier has the option to set a crossover to keep the heavy bass out.. If you start looking at adding more than 2 speakers or want to play it loud enough, and clear enough to entertain your buddies behind you, you'll need to look into higher quality amplifiers that will produce more power.
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