Calculating RMS

[scypher]

I'm asking if there is a standard way for ALL amps to calculate real RMS out of the amp....so if i waz to tell u partial specs of my amp without tellin u d brand or wat the stated RMS waz, would u b able to tell me accurately how muc RMS my amp can give with the following info?

250A fuse & stable at 0.5 Ohm

[pay1093]

input voltage maybe needed..


I think its, Watts=Volts X Volts/Resistance, not 100%

[tuner361]

......

[SR]

P=IV

so say your input voltage is 13.5 your max current draw is 250 amps

so that gives you 3375 watts
then you have efficiency say tis a class d amp and assume 80% efficient
gives you 2700 watts of actual power going to the speakers

then using the formula for rms (root mean square) which is .707
which gives you 2079
so your amp theroetically puts out 2000 watts rms as a good guestimate

[ruffneck_12]

you can bench test it too
hook up a speaker at the lowest impedance possible and play a test tone... measure the voltage of the output

(V^2)/R = v is voltage, r is the impedance of the speaker(s) in what ever config it's in....

just square the voltage and divide it by the impedance

(V^2)/R= ???W
----------------------------
If you have an AC ammeter you can clamp the speaker wire and check the voltage separately with a voltmeter,,,, just multiply both values to get the wattage
---------

SR has a good method also

[MONGO]

but remember without doing a bench test, using the fuse rating and efficiency to calculate the power is just a estimation..or guestimation..

[Coppershot]

Check out performance auto & sound magazine or website http://www.pasmag.com/car-audio/test-reports
They have rms specs for a couple of amps across various different brands. Bench tested results for RMS ratings at 12.6V and at 14.4v as compared to manufacturer ratings.

If your amp brand and line is tested, the results is a good estimation for other amps in the series.
Except if its an AB 4 channel, and they tested a mono class d amp in the same brand and series.
Estimation will be off.
Also the results for an alpine mrx 4 ch will not be the same as an alpine pdx 4ch cause its a different line but same brand.
The very popular brands have bench test results on various forums as well.

Scroll to bottom of these links for an example.
http://www.pasmag.com/car-audio/test-reports/1883-test-report-alpine-mrx-f30
http://www.pasmag.com/car-audio/test-reports/1812-test-report-rockford-fosgate-t1000-4ad

there is also a german site (translate with google) for older amps, but I cant find it now. Its bookmarked on my home machine.

[scypher]

P=IV

so say your input voltage is 13.5 your max current draw is 250 amps

so that gives you 3375 watts
then you have efficiency say tis a class d amp and assume 80% efficient
gives you 2700 watts of actual power going to the speakers

then using the formula for rms (root mean square) which is .707
which gives you 2079
so your amp theroetically puts out 2000 watts rms as a good guestimate

sum1 once told me all u do is take the voltage multiply by fuse rating then multiply by 75% efficiency.....so i did 14v * 250A * 75% = 2625 assuming <--that figure was more or less the actual RMS ratings...anyhow i attached the manual specs now, im lookin for a calculator/formula without having to do actual physical tests, such as tests tones etc if possible that is.

[3stagevtec]

^ Purchase a reputable amp and you wouldn't have all that stress...

(all you'd have to do is change your avatar.. lol)

[scypher]

nah i'll nvr change, & its not stress its interest. my 4 12" will run on it with ease. hope u didnt mean change to d usual that most Trini i shud say, does use like US amp, PA, Hi-F, Lanzar & all dat non sense....i like JL audio but they dont look fancy...gotta look pretty too 4me 2b interested. Its 2b expected by almost all amps that u dont get the rated RMS but its how big of d difference is wat matters & SS in most cases arnt off by much compared to alot of amps u see in trinidad. i need about 2200RMS & i bought a amp stated 2600RMS i aint worried at all. It would b stress if i had bought another brand tho.

But tnx anyway 3stagevtec

[scypher]

P=IV

so say your input voltage is 13.5 your max current draw is 250 amps

so that gives you 3375 watts
then you have efficiency say tis a class d amp and assume 80% efficient
gives you 2700 watts of actual power going to the speakers

then using the formula for rms (root mean square) which is .707
which gives you 2079
so your amp theroetically puts out 2000 watts rms as a good guestimate

Simple & understandable,thanks SR

[Gladiator]

nah i'll nvr change, & its not stress its interest. my 4 12" will run on it with ease. hope u didnt mean change to d usual that most Trini i shud say, does use like US amp, PA, Hi-F, Lanzar & all dat non sense....i like JL audio but they dont look fancy...gotta look pretty too 4me 2b interested. Its 2b expected by almost all amps that u dont get the rated RMS but its how big of d difference is wat matters & SS in most cases arnt off by much compared to alot of amps u see in trinidad. i need about 2200RMS & i bought a amp stated 2600RMS i aint worried at all. It would b stress if i had bought another brand tho.

But tnx anyway 3stagevtec

Most of the time, manufacturers disguise poor build and design with a fancy cover. "Looks" should be the last thing to determine the quality of an amp.

If you want to see the REAL BEAUTY of an amplifier, crack open the cover of a true high end amp and appreciate the heavy copper bus bars, the beautiful symmetrical design, the oversized torroid, the high capacity capacitor bank, the long rails of mosfets, the 5 band resistors, I can go on and on....but you get my drift!!!

Sound Stream is considered very low end and cant even compare with entry level stuff by JL Audio. (with the exception of their "old school" amps which deserves much respect among audiophiles).

JL AUDIO


SOUND STREAM

[ChristianRD]

nah i'll nvr change, & its not stress its interest. my 4 12" will run on it with ease. hope u didnt mean change to d usual that most Trini i shud say, does use like US amp, PA, Hi-F, Lanzar & all dat non sense....i like JL audio but they dont look fancy...gotta look pretty too 4me 2b interested. Its 2b expected by almost all amps that u dont get the rated RMS but its how big of d difference is wat matters & SS in most cases arnt off by much compared to alot of amps u see in trinidad. i need about 2200RMS & i bought a amp stated 2600RMS i aint worried at all. It would b stress if i had bought another brand tho.

But tnx anyway 3stagevtec

what de hell i reading here?

ENT

Best I start buying power acoustik crypt series with the skulls on it. It does look rell cork dan.

And here I thought my sundown woulda do rated

[scypher]

Hey it looks flashy so it must be good

pioneer u really need 2 stay out of this almost every post u in , u always hating or sayin sumtin negative 2 sum1 get a life & stop always acting like u d best ting out there....& stupid ppl read carefully, no1 said lookin good means its a good amp think smarter nah....my personal thoughts are that i also take looks in2 consideration jeez simple English so hard for alyuh trini. i cah always b breakin it down to baby mode 4 ppl like alyuh yuh know. & 4d nex 1 that assumin he know it all, no1 said fuse rating means the power it means u can use it as a estimate guide. lawd backanal everywhere so.

[scypher]

cya really argue wid dem nah, they assume fuse rating = power output

so dem 3000W boss an ting...real powah puttin out

shame on allyuh JL men who have 1000/1 n ting...more so dem ole US Amps an dem...man put it in de same line with power acoustik yes

again read carefully i didnt put JL in d same class, take ur time, try baby steps u'll get it.

[scypher]

Most of the time, manufacturers disguise poor build and design with a fancy cover. "Looks" should be the last thing to determine the quality of an amp.

If you want to see the REAL BEAUTY of an amplifier, crack open the cover of a true high end amp and appreciate the heavy copper bus bars, the beautiful symmetrical design, the oversized torroid, the high capacity capacitor bank, the long rails of mosfets, the 5 band resistors, I can go on and on....but you get my drift!!!

Sound Stream is considered very low end and cant even compare with entry level stuff by JL Audio. (with the exception of their "old school" amps which deserves much respect among audiophiles).

JL AUDIO


SOUND STREAM

anyways yet again please read b4 u post ty...i did not say looks waz d 1st ting i consider infact it is d last ting & unlike some ppl where looks doesnt matter , i does 2me so jus bcuz i take it in2 consideration & u dont doesnt mean u u should post random amp pictures 2prove a point that i care noting about...i guess u missed that part where i said "I like JL" just doesnt look too fancy....take it easy nah alyuh gettin on so hype 4notin, everybody want 2 act like they no it all.

[Gladiator]

Most of the time, manufacturers disguise poor build and design with a fancy cover. "Looks" should be the last thing to determine the quality of an amp.

If you want to see the REAL BEAUTY of an amplifier, crack open the cover of a true high end amp and appreciate the heavy copper bus bars, the beautiful symmetrical design, the oversized torroid, the high capacity capacitor bank, the long rails of mosfets, the 5 band resistors, I can go on and on....but you get my drift!!!

Sound Stream is considered very low end and cant even compare with entry level stuff by JL Audio. (with the exception of their "old school" amps which deserves much respect among audiophiles).

JL AUDIO


SOUND STREAM

anyways yet again please read b4 u post ty...i did not say looks waz d 1st ting i consider infact it is d last ting & unlike some ppl where looks doesnt matter , i does 2me so jus bcuz i take it in2 consideration & u dont doesnt mean u u should post random amp pictures 2prove a point that i care noting about...i guess u missed that part where i said "I like JL" just doesnt look too fancy....take it easy nah alyuh gettin on so hype 4notin, everybody want 2 act like they no it all.

Padna.... Don't take it personal, just wanted to advise you to buy a good product and share a little bit of info at the same time. At the end of the day it does not affect me or Pioneer if you acquire High or Low end gear.

[scypher]

Most of the time, manufacturers disguise poor build and design with a fancy cover. "Looks" should be the last thing to determine the quality of an amp.

If you want to see the REAL BEAUTY of an amplifier, crack open the cover of a true high end amp and appreciate the heavy copper bus bars, the beautiful symmetrical design, the oversized torroid, the high capacity capacitor bank, the long rails of mosfets, the 5 band resistors, I can go on and on....but you get my drift!!!

Sound Stream is considered very low end and cant even compare with entry level stuff by JL Audio. (with the exception of their "old school" amps which deserves much respect among audiophiles).

JL AUDIO


SOUND STREAM

anyways yet again please read b4 u post ty...i did not say looks waz d 1st ting i consider infact it is d last ting & unlike some ppl where looks doesnt matter , i does 2me so jus bcuz i take it in2 consideration & u dont doesnt mean u u should post random amp pictures 2prove a point that i care noting about...i guess u missed that part where i said "I like JL" just doesnt look too fancy....take it easy nah alyuh gettin on so hype 4notin, everybody want 2 act like they no it all.

Padna.... Don't take it personal, just wanted to advise you to buy a good product and share a little bit of info at the same time. At the end of the day it does not affect me or Pioneer if you acquire High or Low end gear.

ok kool no scn dere...it doesnt affect me wat i buy either, at d end of d day it waz my money & my choice.... pioneer on d other hand does have issues with any & everybody from wat i see. know it all ppl like him who always tryin 2 bring down others jus annoys me. i'd like it if he stays out my posts. I hear ya tho Gladiator

[scypher]

Point out my non proper words that waz too hard 4u to understand or waz my abbreviations too muc 4u? lol...if u cant keep up not my fault i not gona break down & recheck & make sure everytin perfect 4u 2understand , too bad. sry i make u out dere. stop always goin on ppl posts always lookin 2make trouble nah, u ha nun better 2do?

[goalpost]

is 'muc' an abbreviation of 'much'? is it really that hard to write the extra 'h'?

[scypher]

is 'muc' an abbreviation of 'much'? is it really that hard to write the extra 'h'?

got a problem wit how i choose to type then go cry sumwhere else...cuz it aint gona change. u knew the wrd waz "much" so mission accomplished.

[ruffneck_12]

US amp, PA, Hi-F, Lanzar & all dat non sense

Besides the PA, those are some of the most reputable brands on the market yo

[silent_riot]

It's one thing to calculate output, its another to measure it and see what it actually does.
Calculation involves assumptions about efficiency and current draw, which can vary widely from real world scenarios.

[scypher]

It's one thing to calculate output, its another to measure it and see what it actually does.
Calculation involves assumptions about efficiency and current draw, which can vary widely from real world scenarios.

as u mentioned that i was trying to research the efficiency % for my amp but didnt get a figure to work with.....& how do you go about getting that figure....so that's something you have to guess a figure huh? does class D amps have a efficiency range to go by tho if u know?

[silent_riot]

The rule of thumb efficiency figure was given in this thread - about 80% for Class D amps.
Measuring the actual efficiency would be a case of measuring the unclipped output of the amp with meters, a stable load and an O-Scope, while simultaneously measuring the power input with more meters.

Read up some amplifier power reviews and they tell you how they measure the output.

[scypher]

oh ok thanks man.