[quote user="JazzHands"]
Hi guys, joined the forum after seeing so many helpful replies to other peoples' posts. I'm wondering if you can help me understand RMS.
[/quote]
All numbers are merely indicative.
That should be a standard disclaimer printed in all manuals of AV equipments
Oh well, you asked about RMS.
RMS - is an acronym for Root Mean Square. As such Root-Mean-Square is a general concept in school level mathmetics. If you insist much on theory here is it: http://en.wikipedia.org/wiki/Root_mean_square
To keep the matters simple, RMS is used to express the power handling capability of an amp or a loudspeaker system. Notice the phrase loudspeaker system. The RMS value is expressed, generally, is of the whole loudspeaker system and not of a single driver. That makes it easier for consumers to understand the whole system as a whole. Otherwise, an end user will have to know maths and physics to calculate the RMS value of a loudspeaker system.
When a manufacturer says, this loudspeaker's power handling capacity is 20 wrms, he means to says, this loudspeaker (system) is capable of handling 20 watts of power (again, thats a complex calculation, if a load lets 1 ampere of current pass thru given 1 volt, it is said to be a 1 watt consumer, save for loudspeaker load). Simply put, the RMS value is an indication of how much currenton a long-term basis a loudspeaker can take. Notice the phrase long-term basis. Usually, the voice coil of a transducer will be able handle a lot more power on a short-term basis than it can on long term basis. Why? Because, that will be an instantaneous attack (order of a 1000th of a second or so).
[quote user="JazzHands"]If a speaker system says something like "20W RMS", what is it actually telling me it can do?[/quote]
It is saying, it will be able to handle power equivalent of 20 watts on a long-term basis (implies, it will perform best with an amplifier that generates 20 on a long-term basis)
[quote user="JazzHands"]
Also, what if an all-on-one iPod speaker system sort of thing has two 10W speakers, does that mean it outputs 20W?[/quote]
Depends on the what exactly manufacturer wrote. If he said - 10 watts per channel and it has two channels it means 20 watts equivalent. But if he didn't indicate clearly, it may well mean the system has 10 wrms of output.