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Old 11th June 2007, 10:00 AM   #1
mehrdad is offline mehrdad  Iran
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Default How Much Power There Is In Car Amps?

Hello

I Have Some Questions:

In commerical Car Power Amplifiers In The Shops how much power Is Usually Available?
And How Much Power Is Most Desired?
100? 200? 300? ...

And How many Channels Are Usually Desired?

Thanks.
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Old 11th June 2007, 10:26 AM   #2
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As a rule of thumb, whatever the power says on the amp, divide by 5 to find the real power.
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Old 11th June 2007, 10:41 AM   #3
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A lot of higher power amps actually deliver close to rated power and sometimes even more, provided you can deliver the current. But almost 100% of the cheaper models NEVER deliver even close to specs sadly. When it comes to insane power rating of 3kW and above I am not sure who well specs match actual performance.
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Old 11th June 2007, 10:41 AM   #4
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Quote:
As a rule of thumb, whatever the power says on the amp, divide by 5 to find the real power.
Finally we get to the truth about car amplifier ratings.

About 16 yrs ago when on the bench we tested some high power car amplifiers both on the bench and in the car. With a bank of 6 fully charged batteries and a 250 amp charger piggy backed to the batteries the car amplifiers didn't come even close when driving a 1K sine wave. In the car setting we got about a 1/5th of the rated power into the dummy load also.

I guess it has to do with the ability to say to your friends that you have 1000 watt amplifiers and watch them as their jaws drop. In reality you would have to be really lucky to get 200 watts out.
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Old 11th June 2007, 10:47 AM   #5
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Forgot you question about channels. I prefer active crossovers which means one channel per driver. At least subs/midsubs can kick insanely if you use a very steep band pass crossover. I once tried a 12" PA midbass speaker in a 50l sealed box. I had a power amp that gave me roughly 600WRMS @ 8 ohm and crossover ~50-125Hz. I am currently experimenting with an active 2-way design with fairly small amps for my car. So far I have modified the built in crossover from 15-300Hz stock to somewhere around 3kHz and it seem to be working great.
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Old 11th June 2007, 11:08 AM   #6
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Quote:
Originally posted by burnedfingers


Finally we get to the truth about car amplifier ratings.

About 16 yrs ago when on the bench we tested some high power car amplifiers both on the bench and in the car. With a bank of 6 fully charged batteries and a 250 amp charger piggy backed to the batteries the car amplifiers didn't come even close when driving a 1K sine wave. In the car setting we got about a 1/5th of the rated power into the dummy load also.

I guess it has to do with the ability to say to your friends that you have 1000 watt amplifiers and watch them as their jaws drop. In reality you would have to be really lucky to get 200 watts out.
The amplifier I use to drive my sub and my two front channels can easily deliver ~2x135WRMS + 1x500WRMS @ 8 ohms pink noise all channels driven simultaneously.
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Old 11th June 2007, 11:23 AM   #7
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Quote:
Originally posted by burnedfingers


About 16 yrs ago when on the bench we tested some high power car amplifiers both on the bench and in the car.
I would guess that there has been some progress in the last 16 years.
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Old 11th June 2007, 11:26 AM   #8
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The amplifier I use to drive my sub and my two front channels can easily deliver ~2x135WRMS + 1x500WRMS @ 8 ohms pink noise all channels driven simultaneously.
I assume you used test equipment as opposed to someone's finely tuned ear?

Quote:
I would guess that there has been some progress in the last 16 years.
Either that or some truth to the actual power ratings.
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Old 11th June 2007, 02:50 PM   #9
mehrdad is offline mehrdad  Iran
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Would Companies Fool People With PMPO Watt Instead Of RMS?
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Old 11th June 2007, 05:42 PM   #10
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Quote:
Originally posted by mehrdad
Would Companies Fool People With PMPO Watt Instead Of RMS?

Done all the time.

I recall repairing one guy's "high power" 2 channel amplifier. Fancy chrome chassis, this baby even had a large fan built in !! Must be a lot of power.

So I go into the amp to replace a shorted BJT. In the process of firing it up and performing checks, I discovered the power supply rails were +/- 45V.

Now someone please tell me how I can obtain a rating of 1000W into 4 ohms (bridged or not) with 45V rails? I see no more than 250W, with no doubt some ugly distortion.

The best part of it was, the actual power supply itself was essentially nonexistent in capacitance reservoir, telling me this would be peak watts, and certainly not rms. And the fan? HAHA, no need for it, the thing ran cool, because it wasn't really drawing high watts under load.

The marketing genius of car audio (and home audio, for that matter, is no different).
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