question about wattage

[partridge_88]

on my infinity speaker box it has two rating, one is 225 WATTS PEAK POWER and the other is 75WATTS RMS.

wot does this? does this mean that the most power you could put thru the speakers with an amplifier is 225 wats?

[Martin]

wrms = watts mean, root sqaured.

watts are AC, meaing they (on a graph) go up and down in a curve.

To answer your question, wrms is basically, 'average'. the peak is what it could do, for a very split second, before (possibley) breaking/failing. Not working ever again.
This is why we match wrms, and ignore the peak figures.


that's only a basic explanation btw

[partridge_88]

ok thanks martin, so i should be looking at an amp to match my front comps, which are 75watts RMS?

[Martin]

yes, 75wrms.

some say, if you cant match spot on, get slightly higher wrms amp
others say, if you cant match spot on, get slightly lower wrms amp

Howeverm 75wrms is a common wrms IMO on amps :thumbs:

[partridge_88]

cool so there should be a setting on an amp i get to put 75 watts through each front speaker yeah. thanks martin sorry about all the questions im pretty new to ice, and i dont want to botch it because botched electrics is a life or death matter

[Martin]

cool so there should be a setting on an amp i get to put 75 watts through each front speaker yeah. thanks martin sorry about all the questions im pretty new to ice, and i dont want to botch it because botched electrics is a life or death matter

i suppose you could get an electric fire, but from 12 volts, you wont die. But if you buzz your self out its bloody annoying :lol:

look at 2 channel amps, and look in the technical specification to say 2 x 75wrms.
ignore PEAK figures. They are useless in this instance.

[purecarsound]

For a more in depth explanation....

http://www.classictruckshop.com/clubs/earlyburbs/projects/stereo/systems.htm

Watts Voltage times current. Simple as that. Example: 12 volts x 5 amps = 60 watts... 120 volts x 0.5 amps = 60 watts. And here's where some of the horse puckey claims come in. An amplifier feeds more or less alternating current to the speakers. The audio wave form isn't pure AC, but is a modulating and changing wave form. DC Ohm's law doesn't really cover speakers because AC is measured in impedance and reactance. Because of the reactance of the moving coil through the magnet, it gets a bit complex to figure out amplifier and speaker watts via formulas. Since most of the power in music is in the low frequencies, (bass) this is what is typically used. The formula for power is: P=EI Cosine Phase Angle. P (power) = E (voltage) x I (current) x phase angle in degrees. Simple ain't it? A good MOSFET 100 watt amp running a 4 ohm speaker at the full 100 watts, that's 4 ohms Impedance, not DC ohms, will put about 24 volts AC at about 5 amps into the speaker. Phase angle is pretty much everywhere in the music's AC wave, so it's hard to calculate, and is usually considered 90 degrees. As you can see, the little cigarette pack sized "200 watt" amp really isn't possible with just a 12 volt supply, and no inverters. A good amp will have inverter circuitry to get the AC voltage up where it's needed. And, that's why a REAL 200 watt RMS amp will need welding wire from the battery, cooling fans, and is the size of a small suitcase. Most amps are rated total power, so divide the watt rating by the number of channels it has. i.e. A 200 watt, 4 channel amp is 50 watts per channel... A 100 watt, 2 channel amp is 50 per channel... etc.


RMS Root Mean Square. The equivalent DC 'work' value an AC voltage can produce. The 120 volts RMS AC at your house outlet, is actually about 170 volts peak to peak. This is a measurement that's only seen on an oscilloscope, and is the actual peaks of the wave form on the scope's screen. A useless measurement, as the extreme upper and lower parts of the AC wave doesn't do any work. The RMS value draws a line at the 0.707 part af the wave form, and this is where the current has actual work value. BUT, this peak to peak measurement is what a lot of auto sound amps use as it's power rating!! It won't anymore move the speaker cone at this peaked value, than the HP number on a dyno caught at the end of it's swing will turn your Suburban's tires against the ground. If an amplifier doesn't rate itself on the box in RMS numbers listed as to what they used for a test load, keep on shopping. (i.e. 40 watts RMS into 2 ohms) And, most cheap amplifier makers use a higher frequency into a 1 or 2 ohm test COIL, and not necessarily a speaker, for the watt ratings. That's their flimsy way of getting it past the Federal Trade Commission.

[Martin]

:lol: we can all copy and paste. I try to explain in a breif understable level, keeping it relevant.

I'd recomend http://www.bcae1.com

it coveres EVERYTHING about car audio. I havent once left that site without finding out what i wanted to know :)

[ST_C0R5A]

For a more in depth explanation....

http://www.classictruckshop.com/clubs/earlyburbs/projects/stereo/systems.htm

A audio explained website very useful Very Good for beginners