Sign in with
Sign up | Sign in
Your question

Suggest- is music power = rms power

Last response: in Other Consumer Electronics
Share
June 21, 2011 9:14:19 AM

Hello,
i have a 12" subwoofer.it is written that it has a maximum music power of 550W. i want to know what is its RMS power and how strong amp to run it properly.
June 21, 2011 5:41:49 PM

RMS isnt an exact number.

because a ported box might run a little bit more power than a sealed box if/when the voice coil is running cooler.

kind of stupid to say, some might think/feel/say.
because a sealed box will see the air temperature inside go down if the room is cooled.
and with enough time and heat, the air temp inside will go up.
usually it isnt much about time, but a lot of the heat that doesnt really get warm enough to heat up the air in the box.

those coils are designed to work with a few different variables.
current is one variable
voltage is another variable
heat is another variable

current is more likely to be suggested as the RMS value.
but as reality has it, voltage is what gives you all of the transients and extra details.
in combination, they can change the way the speaker plays audio.
some speakers might not care at all.. and the differences arent audible, you would need lab equipment to hunt for any changes.
but then again, just because you dont hear any difference.. that doesnt mean the voice coil isnt generating any more or less heat.
a coil can be designed to resist electrical fluctuations that are far and few between.
other coils can be designed to heat up (or it is the lack of design that they heat up)

in the end, it is going to be the heat that destroys the voice coil (unless the copper starts to unwind).
a maximum power wattage could mean quite a few different things.
but generally..
if you are operating the voice coil at the recommended temperature.. the maximum number should mean all of the extra little spikes of voltage that would be acceptable without causing the heat of the coil to rise.


an example..
say you have a four door vehicle and want to know how low the car can be, because each time a person gets inside the vehicle the car lowers.
so if the manufacturer of the vehicle says the car has an RMS value of 3 inches lower ... they would also give you a maximum number of inches for the bumps in the road.
not talking about a pot hole because a pot hole goes down.. a bump is a rise in the road.
so if the maximum value was 4 inches.. that means you can put in as many people or as much weight as you want until the vehicle drops 3 inches.
and the maximum a bump in the road can push the tire upwards is 1 inch.
that means you have to drive around the larger bumps to avoid them.

you have the option to carry one less person = 2 inches
and that means you can run over a bump that is 2 inches tall.
take out another person and the car only dropped 1 inch.
this means you can run over a bump that is 3 inches

the whole point of the example is... 4 inches is the maximum.. and if you do 5 inches the tire is going to slam up into the wheel well and the car's frame is going to get bent (and that is like one tire pointed slightly left or right.. and the rest of the wheels are pointed straight)
if you do this with a speakers voice coil.. the speaker is going to cook itself and you will fry the voice coil, usually meaning the speaker will stop playing audio and there will be smoke coming from the coil.



so look at it like this..
if your voice coil has a maximum temperature of 200 degrees F
how many watts does it take to reach 200 degrees F (or 180 if you want to be safe.. or even 150)
then.. the maximum number for peak wattage means the voice coil will accept the extra electricity for a brief moment and ignore it by not getting any hotter.

how brief of a moment are we talking about?
well imagine a sparkler for the fourth of july... ONE spark, as you watch it leave the stick until the spark dies out and you cant see it anymore.
that is probably longer than the electricity peaks that are going to the speaker.

watch a video of a persons eyeball blinking.. the audio peak is probably something closer to that length of time.
if all you have is a maximum rating.. it does you or me no good.
maybe they want you to stick around with one of those laser thermometers pointed at the voice coil.. and raise the power until the speaker blows.
then go buy another one.
chances are, it is put there so you go buy another one.
or
it was put there to prove you didnt know what you are doing.

nobody cares about such a general value.
people shouldnt care completely about the RMS value.
because if you run your amp at 100 watts RMS .. you could be seeing blinks of 150 watts ... or blinks of 300 watts.

amplifier designers/makers need that number to know how much their amp can spit out peaks to make the speaker sound its best.
so if your amp is only spitting out peaks of 150 watts .. the speaker might sound like it is worth $40
and when your amp spits out 300 watts.. the speaker might show itself as being worth $175


nothing we can do for you except tell you to not use the speaker if you dont want to break it.
sure, you could try to start low and work your way up.
but
75 watts RMS and you are feeding it 100 watts RMS .. the speaker might appear to be okay for a couple months and then suddenly die.
m
0
l
July 18, 2011 7:26:33 PM

basically there a couple of common sense things here , any time a speaker is distorting or clipping you run the chance of ruining the speaker if prolonged , second if you have clean power and you over power a speaker you will have thermal issues at the voice coil .i have seen often rms being about half of the peak rated power


i would say the number that says nominal power is your rms power or if you wanted to try half of the peak rated power maybe that would be a good place to start.
m
0
l
July 19, 2011 3:55:40 AM

the reason you generally see the RMS rating as half of the peak rated power is because of the casual production of the metal used for the voice coil.

maybe not the same exact factory, but those factorys are using the same general recipe to make the metal.

the difference between RMS and peak power has proven to be different.
sometimes the peak is way too high and will never be seen or used.
other times the peak is way too low and causes distortion or damage early.

to work as a team requires the RMS and peak numbers to be a standard, and the amplifiers to provide RMS and peak powers that match - as a team effort.
this allows the audio industry to literally flood the consumer market with products that could fill homes as swift as a large river dam breaking and flooding the land downstream.



another question may be.. how long is a peak?
can a peak last 1 second? 1/8th of a second?
perhaps 3 or 5 seconds?

kinda cute to match your amp with the peak of a speaker, you can get more out of it.
and if you are lucky, those peaks could be throwing the cone in and out more.. and that can equal to a bit more air cooling the coil.

getting that close to the edge, you need to know the audio being played to know if there is going to be enough peaks to cool the coil enough to add another ____ watts.

most people dont really need to care about it unless they are using some attack or sustain in their audio rack.
m
0
l
!