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Old 08-14-2009, 09:46 AM   #1
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Default converting Watts max to Watts Rms

I need to know what wattage I'm running on my system. I have a JC Power M800D Mono-block amp and a Kicker 12" DVC rated 800 Watts max wired to 1 ohm. What is the wattage RMS on this setup?

Second, is there a specific formula to convert Max Wattage to RMS Wattage or is RootMeanSquare the formula? The reason I want to know is that while my Pioneer Deck (See my garage for the exact model number) is rated at 50 watts max, the RMS rating on it is only 22 watts but by the RMS formula, it should be rated at about 35 watts rms...

See my problem?
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Old 08-15-2009, 04:37 AM   #2
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Default Re: converting Watts max to Watts Rms

There is no easy conversion, since amps do not produce pure sine waves and the load is impedance, not pure resistance. If the output is a pure sine wave, you get the following simplified expression for a purely resistive load:

Peak = 2^(1/2)*RMS
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Old 08-17-2009, 11:10 AM   #3
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Default Re: converting Watts max to Watts Rms

umm.. yea i'm starting to think that some companies are just making up max power now, its ridiculous, i remember a few years ago rf started making there 301s amps (300w rms) and putting 900w max on the amps outer casings, they have really stooped down.... max power is BS
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Old 08-17-2009, 12:17 PM   #4
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Default Re: converting Watts max to Watts Rms

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Originally Posted by twentyhurtz View Post
umm.. yea i'm starting to think that some companies are just making up max power now, its ridiculous, i remember a few years ago rf started making there 301s amps (300w rms) and putting 900w max on the amps outer casings, they have really stooped down.... max power is BS
Well if you see 900watts on the casing that's just the MAXIMUM the Amp can put out. Truth be told, you will NEVER see that peak for more then a second at best, that's why the RMS is the more important number, becuase that's the output of the amp on a consistent basis.


So we'll use mine as an Example..

My Amps put out 2000watts Max, but I have 1400rms..that means that it's normal output consistently, while playing is about 1400watts. RMS is the number to base your build off of, and will ensure your putting out what u want. So if you want 900watts out of your amp, you should look into copping something with roughly double that on it's max, as the RMS number will probably be the output ur looking for.
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Old 08-17-2009, 01:59 PM   #5
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Default Re: converting Watts max to Watts Rms

yea... i know that, i was only making a stink about rf doing that ****, trust me i been competing a long time, i have most amp/sub spec memorized, or i used to.. don't keep up with the new stuff just 05 and older.
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Old 08-18-2009, 12:18 AM   #6
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Default Re: converting Watts max to Watts Rms

Quote:
Originally Posted by twentyhurtz View Post
umm.. yea i'm starting to think that some companies are just making up max power now, its ridiculous, i remember a few years ago rf started making there 301s amps (300w rms) and putting 900w max on the amps outer casings, they have really stooped down.... max power is BS
I've always viewed max power ratings as pointless BS, which explains why that calculation for converting from max to rms is often so far out it isn't funny.
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Old 08-18-2009, 02:29 PM   #7
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Default Re: converting Watts max to Watts Rms

really the ratings on an amplifier dont mean crap. How an amplifier company chooses to rate their amplifier is all over the place.

A good rule of thumb I use is take the current used by the amp and multiply by the voltage

example
30amp*14.4V=432W assuming 100% efficientcy.

Most class AB amps are 30% efficient =129Watts which is a reasonable figure.
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Old 08-18-2009, 06:03 PM   #8
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Default Re: converting Watts max to Watts Rms

Quote:
Originally Posted by nsxxtreme View Post
really the ratings on an amplifier dont mean crap. How an amplifier company chooses to rate their amplifier is all over the place.

A good rule of thumb I use is take the current used by the amp and multiply by the voltage

example
30amp*14.4V=432W assuming 100% efficientcy.

Most class AB amps are 30% efficient =129Watts which is a reasonable figure.
That being said, most "consumer-friendly" sub amps, and a good percentage of 4channel amps these days are class D.
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Old 08-18-2009, 10:13 PM   #9
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Default Re: converting Watts max to Watts Rms

i would much rather take my fluke clamp meter and a good O scope and find out exactly how much power my amp puts out at a given voltage.... to hell with ratings
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Old 08-18-2009, 10:26 PM   #10
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Default Re: converting Watts max to Watts Rms

Quote:
Originally Posted by nsxxtreme View Post
really the ratings on an amplifier dont mean crap. How an amplifier company chooses to rate their amplifier is all over the place.

A good rule of thumb I use is take the current used by the amp and multiply by the voltage

example
30amp*14.4V=432W assuming 100% efficientcy.

Most class AB amps are 30% efficient =129Watts which is a reasonable figure.
i have always generally done this too for mystery amps, it is a good rule of thumb i agree.. except for the usamps hc100, which is rated at 800w rms yet usamps suggest an inline 225a fuse, ha..
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Old 08-19-2009, 08:45 AM   #11
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Default Re: converting Watts max to Watts Rms

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Originally Posted by twentyhurtz View Post
i have always generally done this too for mystery amps, it is a good rule of thumb i agree.. except for the usamps hc100, which is rated at 800w rms yet usamps suggest an inline 225a fuse, ha..
so thats the only under rated amp ever? lol
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Old 08-19-2009, 12:39 PM   #12
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Default Re: converting Watts max to Watts Rms

it was an example.... !
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Old 08-21-2009, 10:36 AM   #13
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Default Re: converting Watts max to Watts Rms

Quote:
Originally Posted by nsxxtreme View Post
really the ratings on an amplifier dont mean crap. How an amplifier company chooses to rate their amplifier is all over the place.

A good rule of thumb I use is take the current used by the amp and multiply by the voltage

example
30amp*14.4V=432W assuming 100% efficientcy.

Most class AB amps are 30% efficient =129Watts which is a reasonable figure.
so..........the 30 amps you get is how much current you measured or are you taking that from, say, for example, the 30 amp fuse you may have installed on your amplifier. Mine has two 30 amp fuses installed on the side and I assume that makes 60 amps max. so...

60 amp(max) * 14.4V * 30% efficiency = roughly 260 watts???

^^^This at 100% efficiency (assuming my calculations are correct) would be roughly 860 watts MAX, and the RMS would be the 260 watts, right???

or am I still confused?
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Old 08-21-2009, 10:49 AM   #14
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Default Re: converting Watts max to Watts Rms

RMS wattage is half peak wattage if I'm not mistaken. But that 22w you see on radios is usually continuous power not just RMS. It is the actual power you would expect to see over time. RMS doesn't take time into account.
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Old 08-21-2009, 05:20 PM   #15
 
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Default Re: converting Watts max to Watts Rms

This article will help you: http://www.crutchfield.com/S-fA9OU9V...fer_power.html
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Old 08-24-2009, 05:46 AM   #16
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Default Re: converting Watts max to Watts Rms

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Originally Posted by XstreamRocker View Post
so..........the 30 amps you get is how much current you measured or are you taking that from, say, for example, the 30 amp fuse you may have installed on your amplifier. Mine has two 30 amp fuses installed on the side and I assume that makes 60 amps max. so...
Just to confuse you further. Fuses don't necessarily blow at the current stamped on them.

There is a multiplication factor applied to the fuses current rating to find out it's minimum tripping current. It varies widely between different fuse styles and manufacturers, so unless you test it, or score the data sheets for the manufacturer, well, you are basically just guessing.
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Old 08-25-2009, 08:18 AM   #17
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Default Re: converting Watts max to Watts Rms

So, basically, the RMS compared to the MAX is different for every amp/sub manufacturer and there is no set formula. I guess I need to research my **** and figure it out on my own?
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Old 08-25-2009, 08:23 AM   #18
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Default Re: converting Watts max to Watts Rms

Ok, I think I figured it out. I found their website (http://www.jcpoweraudioteam.com/products/monsiry.html) and saw that my amp is not rated at 1ohm!!! haha!!!
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