How are subs power ratings calculated?

[ado 10+ year member]

Looks like you learned a little from our convos. But efficiency isn't .707. Efficiency deals more with the power required to make the output desired.

.707 is a standard number to calculate RMS. If you look it up, you'll get a better definition.

 

[rc10mike 10+ year member]

Looks like you learned a little from our convos. But efficiency isn't .707. Efficiency deals more with the power required to make the output desired.
.707 is a standard number to calculate RMS. If you look it up, you'll get a better definition.

I think he did that meaning that the average class D amp is ~70% efficient.

 

[muskyhunter567 10+ year member]

im pulling 40-60 amps on a 1606D amp, at between 40-60 volts? why is yours so low? i can easily draw mid 20s on normal music? am i missing somthing and, p.s. i thought it was car input volts x amps, like 12v stuff?

 

[JimJ 5,000+ posts]

Efficiency is not calculated on the output side...when you're talking about efficiency, it's on the input side of things, it's a comparison of how much power is being consumed to generate the output power.

 

[ado 10+ year member]

Efficiency is not calculated on the output side...when you're talking about efficiency, it's on the input side of things, it's a comparison of how much power is being consumed to generate the output power.

Exactly. It would not drop the RMS rating of his amp at all. The .707 is the number used to calculate your RMS when multiplying by your Peak value.

 

[Dak446 10+ year member]

in your OP where do you get "in reality it's only 510w"?
I have no idea how mfg's arrive at their speaker ratings, but would bet a lot that it varies pretty widely.

I think most speaker ratings are intended to identify the size of the amp that should be used, not necessarily the actual thermal power handling capability of the speaker.

The average speaker rated for 100w rms is intended to be driven with a 100w amp.

The 100w amp, in turn, will deliver roughly 20w (actual, average) to the speaker due to the crest factor of music.

Setting your gains with a DMM at the amp's rated power using a 0dB tone only assures the amp will never clip, and almost assures it will never reach full rated ouput, even dynamically, because of the way music is recorded.

really well put. by going off of an equation, one cannot be certain that it is "true" rms, even if they think they have it all figured out. everything isn't perfect, and boxes rise impedence, among other things, and there are many more factors that come into play. some companies will run their subs at x watts for x amount of time, until they get to the point where the sub blows after that time, and that's how they get thermal handling power. the 13w7 runs for like 8 hrs straight at 1000 wrms...that's how they rate theirs. i read that somewhere, may be wrong, but i was using as an example. im not following you with the .707 though, that seems like a terribly inefficient amp //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[IDSkoT 5,000+ posts]

i may be wrong but not all amps put out the same power at 40 volts??? what amp??

He said 40 volts at 1-ohm... so, yes, yes they do.

God, I hate you.

I think he did that meaning that the average class D amp is ~70% efficient.

Actually, the average Class D amp is ~80%. People use Class D amps due to their efficiency. 70% efficiency isn't really efficient.

 

[Lakota 5,000+ posts]

Over time you will learn that most manufacturers stated RMS doesn't mean shit.

 

[Atimm693 10+ year member]

Keep in mind the box plays a pretty big role in a drivers efficiency.

 

[scarolinablazin 10+ year member]

He said 40 volts at 1-ohm... so, yes, yes they do.God, I hate you.

i bet you're wrong there mr think you know everything but really don't know shit. i have a bazooka amp that is 1 ohm stereo stable. $1000 says it's not putting out the same power as his amp x 2 seeing as it's only 600 watts total.

 

[n2audio 5,000+ posts]

Just wanted to add - dmm's already account for rms value of a sine wave. You dont have to multiply by .707 again if thats what you were doing.

 

[lincolntc690 10+ year member]

i may be wrong but not all amps put out the same power at 40 volts??? what amp??

40 volts at a given resistance is the same no matter what amp//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[audiolife 5,000+ posts]

I do not think every company rates the same way with woofers, some will go thermal others may go mechanical while others yet mix the two together and take 40% off the top to stop warranty issues LOL

 

[microhaxo 10+ year member]

im pulling 40-60 amps on a 1606D amp, at between 40-60 volts? why is yours so low? i can easily draw mid 20s on normal music? am i missing somthing and, p.s. i thought it was car input volts x amps, like 12v stuff?

Im not sure why mine is so low..

Just so we are on the same page im clamping the AC current from the speaker wire in my trunk..

NOT the power wire from my battery, my clamp doesn't do DC current.

 

[.::DuD3::. 10+ year member]

I know that people go by the general rule of thumb W = v^2 / ohm
But that is not true W != v^2/ohm

The last few days have changed my views of car audio installation for ever.

True rms is

Watts = Amperage x AC voltage

and

Ohm = AC Voltage / Amps

So my question is how do companies determine the RMS rating of their subs?

Currently im running a hifonics amp that is giving my sub 40v at 1 ohm, thats 1600w rms to a lot of you guys but in reality its only 510w RMS...

My sub is rated to take 600w RMS but i believe that this is not quite true..

If i give my sub 600w TRUE rms it would go beyond its excursion limits by a great deal.

No bass boost all flat.

Sorry for the confusing jargon, i just want to be more educated.

Just so you know, there are different ways to calculate power. Power is defined by the voltage * amperage: P=VI (its probably best to refer to it with a P instead of W, since W is synonymous with Energy, not power) . You can also use Ohm's law to substitute in for V or I and get P=(V^2)/R or P=(I^2)R. There is no such thing as 'true-rms.' RMS is RMS, do a google search and read up (its root-mean-squared because of the sinusoidal signal). Also, Ohm's law stands true for both DC and AC, however in AC resistance is referred to as impedance and given the variable Z instead of R (V=IZ).

I'm not really sure how they determine the power ratings, but I'm sure they have a mathematical method rather than Billy-Bob throwing an amp on a speaker and waiting until it smokes.