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# What does RMS mean in terms of speaker output?

How loud is it? Give me comparisons please.

### 10 Answers

- 1 decade agoFavorite Answer
Speakers generally have an average or nominal wattage (power) rating and a peak wattage (power) rating.

Power is energy per time. It is measured in watts. Power delivered by an amplifier to a load (speaker) is normally determined by dividing the voltage (V) squared by the impedance (Z) :

Power = V² / Z

The resulting type of power will depend on what voltage we use. If peak voltages are used, then the result is peak power. If RMS voltages are used, then average power is obtained. RMS (root-mean-square), is only a mathematical method to extract the mean value of an alternating signal (one with negative as well as positive values).

Average or nominal wattage: Often wrongly referred to as "RMS" power, since it is derived from RMS voltage readings. RMS (root-mean-square) only makes sense on variables that have negative as well as positive values. Power is only positive (goes from the amplifier to the speaker, not the other way round), so does not need the "root" and the "square" of the RMS process (which just extract the sign out of a number), just the "mean" (average). Average power is therefore that which uses RMS voltage for its calculation.

Peak power. Corresponds to the calculation of power based upon peak voltages.

What all that means in the real world is that a speaker RMS wattage is what you want to use when you match it with an amp.

Example: You have a decent bookshelf stereo that is rated at 100 watts per channel PEAK power at 8 ohm impedance. Surfing ebay you find a great deal on speakers that have a 50 watt, 8 ohm impedance, RMS rating. Since it's an RMS rating, as a general rule of thumb, their peak power rating would be twice the RMS rating. In this case 100 watt peak power, the same as your bookshelf system, so your stereo wouldn't blow these speakers out.

Conversely if your stereo is rated for 100 watts RMS at 8 ohms and the speakers you find are rated at 100 watts peak, then the RMS rating for the speakers is probably only 50 watts and your stereo will blow them out.

Keep in mind through all this that more power doesn't always = louder or better sounding.

- 1 decade ago
RMS stand for root mean square. in electrical terms it applies to the average value of a signal. for example the main voltage is usually rated at 110v rms or 230v rms occasionally spikes can cause the voltage to shoot up significantly or given drop.

RMS usually reflects the true power handling capacity of the speaker.

in recents years the term PMO is also used this is peak music power.

it does mean much only to impress comsumer with the larger number.

thus a 100 watt rms speaker would be able to handle more power that a 100PMo speaker, a 100rms amplifier would give more power than a 100PMO amplifer.

This extract from wikipedia explains it all

The term sine power is used in the specification or measurement of audio amplifiers or loudspeakers. A meaningful and reliable measure of the power output of an audio amplifier, or the power handling of a loudspeaker is continuous sine wave power, or more strictly 'continuous average sine wave power'. Such a figure will often be found in advertising literature referred to as "true RMS power", but this is quite incorrect. Although there is such a thing as RMS (Root Mean Square) power, it is neither useful as a measurement nor what is intended by those who use the term. The sine wave power is found by averaging the instantaneous power output over a long period of time (or one complete cycle), so it is actually the average power or mean power. The term RMS is used mistakenly due to the fact that the mean power is calculated from the RMS voltage and current (or one of them and the impedance); power being proportional to the square of voltage or current.

- Anonymous4 years ago
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To start off, high-end car audio systems are comprised of three main things: Speakers, Headunit, and Ampilifier. The sound starts in the head-unit as a cd or ipod connection. From there it travels to the amplifier. The amplifier takes that "small" signal and makes it REALLY BIG! Think of it like a popcorn kernel. The un-popped kernel comes from the headunit and the amplifier blows it up and makes it bigger. Then, the signal travels from the amplifier to the speakers which make all of the glorious sound waves we hear! To answer the rest of your question: Subwoofers are used to produce sound waves with a frequency of about 80hz or lower. They fill out the low-end of your music and can add Boom-Boom if you would like. Peak wattage refers to the amount of power (supplied by the amplifier) that the speaker can take before ruining the internal components. It is best to stay just below that number. 1, 2, and 3 channel amps vary based on the number of outputs they have. A one channel, or mono amp is used to power a single output, usually a subwoofer. A 2 channel amp has two outputs, usually left and right, that is used to power either two subwoofers of a Left and Right speaker set. There are amps that go all the way up to 5 channels to power 4 sets of speakers and a sub. You do not NEED a sub in your car, but they will make your system sound better. Subwoofers fill our your music and add the low-end that you would typically miss with just stock speakers. Take at look at the manufacturers web-site to find the specs on your headunit. Then take a look at your speakers spec sheet to see what the RMS and max wattages are. Most of the time, after-market speakers will require an amplifier, plus, using an aftermarket (not in Headunit) amplifier will make your system sound better. The difference between two and three way speakers is the physical number of drivers combined into one unit. A two way speaker has a main woofer cone and a tweeter in one unit. A three-way speaker has a woofer cone, a mid-range driver, and a tweeter all in one enclosure.

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- 5 years ago
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RE:

What does RMS mean in terms of speaker output?

How loud is it? Give me comparisons please.

Source(s): rms terms speaker output: https://tr.im/4HzDT - Anonymous1 decade ago
RMS means Root Means Square

this is the messurnment way for sound in wattage

- 1 decade ago
RMS means Root Means Square... its the "true power in wattage that the speakers can output.

- Blunt HonestyLv 71 decade ago
Russ Martin Show. Great radio show. Comes out of the speakers. How loud depends on how loud I turn it up. It's the #1 afternoon show in DFW. That's how it compares.