Why RMS?

[IDSkoT 5,000+ posts]

voltage is a term used to describe power, no?

Voltage is better thought of as "flow" or "pressure". Basically a speed in which the electricity flows.

I would only agree with you in that there ARE companies that have a fairly well defined meaning of MAX, but there is NOT a universal definition.
PEAK has a clear definition if you're talking about voltage of a sine wave (as in home electricity), but in terms of car audio Peak, MAX, Dynamic etc. all mean different things for different products. At the end of the day it's a meaningless random number chosen by the marketing department. It's not any more complicated than that.

A clipped signal (square wave, or becoming square) at the same voltage contains more RMS POWER than an unclipped wave. A perfect square wave produces 2x the power of an unclipped sine wave of the same voltage/freq. So IF a 500w rms amp were fully clipped (close to a square wave, but not perfect) a sub that can truely dissipate 1000w should not be damaged. Plus, the sound of the sub at that point would be VERY difficult to listen to. So if someone's damaging speakers because they're listening to a fully clipped amp they shouldn't be involved in this hobby anyway.

The shape of the wave (the fact that it's going from a smooth sine wave to square) has no bearing on speaker damage, only the fact that the speaker has to dissipate more power, i.e. heat.

Clipping ejumukayshen.

http://www.audiogroupforum.com/csforum/showthread.php?t=4332&highlight=clipping

I know when I'm beat *bow*. You pointed out a lot of things that I forgot about. I guess I have to read up on signal waves and the like again.

 

[FoxPro5 5,000+ posts]

RMS rated power is not average power. It doesn't work that way. If you're listening to your favorite song at a comfortable volume, do you really think your amp is putting out 75 watts to your tweeters or 1000 watts to your sub the whole time? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

What if you're listening to a very dynamic song such as the 1812 Overture that has maybe a 70dB swing. When is your 100 watt rated amp putting out 100 watts continuously? When is the amp you verified by a bench test putting out 100 watts continuously?

 

[ngsm13 5,000+ posts]

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nG

 

[IDSkoT 5,000+ posts]

RMS rated power is not average power. It doesn't work that way. If you're listening to your favorite song at a comfortable volume, do you really think your amp is putting out 75 watts to your tweeters or 1000 watts to your sub the whole time? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
What if you're listening to a very dynamic song such as the 1812 Overture that has maybe a 70dB swing. When is your 100 watt rated amp putting out 100 watts continuously? When is the amp you verified by a bench test putting out 100 watts continuously?

It's the "average" power at full volume. It's the square root of the average of the squares of all direct values of voltage / current during a half cycle of an AC circuit... so, no, it's not 100 watts CONTINUOUSLY. It's 100 watts root-mean-squared.

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Fixed.

 

[n2audio 5,000+ posts]

I know this was meant semi-rhetorically, but I'll bite anyway...

RMS rated power is not average power. It doesn't work that way. If you're listening to your favorite song at a comfortable volume, do you really think your amp is putting out 75 watts to your tweeters or 1000 watts to your sub the whole time? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Not the whole time, and assuming "comfortable" means something less than full unclipped volume - not ever.

What if you're listening to a very dynamic song such as the 1812 Overture that has maybe a 70dB swing. When is your 100 watt rated amp putting out 100 watts continuously? When is the amp you verified by a bench test putting out 100 watts continuously?

At full/high volume - for very short durations during signal peaks.

This is going to crest factor, and the rule of thumb I took from carsound a few years back is power requirements of even the most demanding music is no more than 1/3 of an amps rated/bench test power - since bench test ratings/measurements are derived from full power sine waves just before clipping.

 

[GAM3OVR 5,000+ posts]

What the hell do they mean on some of these budget amps when they say total dynamic musical RMS power or the like?

 

[JimJ 5,000+ posts]

What the hell do they mean on some of these budget amps when they say total dynamic musical RMS power or the like?

They're just blabbering, because they know suckers on forums such as this one won't know otherwise.

 

[oldschool4me 10+ year member]

voltage is a term used to describe power, no?

power is a product of voltage, current, and resistance. without any of these there is just potential. P = V2 / R = VI = I2R

 

[oldschool4me 10+ year member]

an easy way to give you an idea of what an amplifier can produce is by looking at their fuse ratings. multiply it by 10 and you will get a decent idea. if it says it is 1500w and has 80a fuse, then is bs. many dont understand. the true formula is (amps) x ( voltage) x (efficiency) so if your car voltage is at 13.8v and the amp has fuse rating of 100a and efficiency is %85 the best your going to get is 1173w and that would be a excellent amp. lol. because usually your amp will have higher fuse rating than actuall current draw.

 

[IDSkoT 5,000+ posts]

an easy way to give you an idea of what an amplifier can produce is by looking at their fuse ratings. multiply it by 10 and you will get a decent idea. if it says it is 1500w and has 80a fuse, then is bs. many dont understand. the true formula is (amps) x ( voltage) x (efficiency) so if your car voltage is at 13.8v and the amp has fuse rating of 100a and efficiency is %85 the best your going to get is 1173w and that would be a excellent amp. lol. because usually your amp will have higher fuse rating than actuall current draw.

A lot of amps don't post efficiency, but you're correct with putting the efficiency into the formula. But I've found that most of the time, it isn't necessary... and as for taking the fuses and multiplying them by ten, that's silly. Almost all modern cars run off a 12> volt current, so multiplying the fuses by 12 would be more logical. This doesn't factor in efficiency, but that's really dynamic based on the amp and the resistance.

 

[oldschool4me 10+ year member]

A lot of amps don't post efficiency, but you're correct with putting the efficiency into the formula. But I've found that most of the time, it isn't necessary... and as for taking the fuses and multiplying them by ten, that's silly. Almost all modern cars run off a 12> volt current, so multiplying the fuses by 12 would be more logical. This doesn't factor in efficiency, but that's really dynamic based on the amp and the resistance.

not silly, it is about as close as your going to get without factoring efficiency, actual voltage, and actual current draw. like i said, if the amp is fused at 100a more than likely its not going to draw 100amps.

 

[FoxPro5 5,000+ posts]

power requirements of even the most demanding music is no more than 1/3 of an amps rated/bench test power - since bench test ratings/measurements are derived from full power sine waves just before clipping.

Should we also spill the beans and tell them that the avg radiating driver wastes at least 95% of that as heat?

Knowing this, what about RMS speaker ratings?

Amplifier efficiency?

Power compression?

Lack of a proper baffle, install mistakes, or off axis listening effects?

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[FoxPro5 5,000+ posts]

They're just blabbering, because they know suckers on forums such as this one won't know otherwise.

Marketing always works better when people are confused.

 

[bigred572005 10+ year member]

ya everyone said the same shit. so here it goes.

you have a sub that is 1000w rms and a amp that is 1000rms. Bullshit. they way companies test there products are at totally different frequencies that what you listen to normally. This gives them the ability to say the push 1000w rms. this rms rating is ran at a much higher hertz probally around 80 to 100hz. most subs enthusiasts like the clean sound of a 40hz tune. they way u can tell how good the sub is is to look at the magnet, flex range, and depth of the sub. the bigger the more powerful. (most of the time anyways) when u look to buy a rms amp look at the fuses on the side of the amp. this is the most important thing that many people don't know because they are stupid. AND WALMART LIES!!!

This is the real way how to tell what rms you amp is. look at the fuses on the side of the amp. add them up and times them by how many volts you are running. So lets say that you have no secondary battery, you are probally running around 12volts average. if the fuses on the side of the amp add up to 80 (keep in mind there may only be one fuse) take 80X12=960 THIS IS YOU TURE MAX POWER BUT NOT YOUR AVERAGE RMS. to get your rms just take 75% of the 960, this gives you your amp efficiency. so again 75% of 960watts = 720 AND THIS IS YOU RMS.

back to the actual question its as simple as this. dont ever buy walmart quaility junk. always have an amp that will overpower your sub. this allows less strain on you car electrical system. learn how to wire you subs to certain ohms, so you can get the most out of you sub and amp. if you do this CLIPPING will never be an issue. AND I HOPE SOME RETARDS AT BEST BUY DIDNT TELL YOU TO DO THAT. TAKE YOU SHIT TO A REAL CAR AUDIO SHOP AND STOP LISTENING TO WHOEVER TOLD YOU THAT.

 

[terra 5,000+ posts]

........This gives them the ability to say the push 1000w rms. this rms rating is ran at a much higher hertz probally around 80 to 100hz. most subs enthusiasts like the clean sound of a 40hz tune. they way u can tell how good the sub is is to look at the magnet, flex range, and depth of the sub. the bigger the more powerful. (most of the time anyways)......

Um...what? The size of the magnet and flex range and depth of a sub tells you how good it is? ****, I've been wrong all these years..//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif