Ok, so I was just wondering what the difference is between RMS, PEAK, and PROGRAM, and what they are.
Thanks
Thanks
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Whats the difference?
- Thread starter Bass_masta16
- Start date
My understanding is (take it for what it is worth):
RMS = Root Means Square or average. The average load that the speaker can take. This assumes a constant input at a constant frequency.
Peak = Highest level the speaker can take. This the the absolute peak during very hard passages and dynamics.
Program = Probably same as RMS but calculated as some type of average over time or a band of frequencies.
Use the RMS.
Ox.
RMS = Root Means Square or average. The average load that the speaker can take. This assumes a constant input at a constant frequency.
Peak = Highest level the speaker can take. This the the absolute peak during very hard passages and dynamics.
Program = Probably same as RMS but calculated as some type of average over time or a band of frequencies.
Use the RMS.
Ox.
I wouldn't always believe it though..
Brands tend to .. whats the word I'm looking for.. Lie.
Use RMS as a guide and then use your ears to make sure.
Brands tend to .. whats the word I'm looking for.. Lie.
Use RMS as a guide and then use your ears to make sure.
"RMS" is a misnomer, but typically refers to the average output power when feeding a clean sinewave into a resistive dummy load. There is some wiggle room in this spec, because different makers define "clean" in different ways. The best specs accompany the RMS power rating with a corresponding distortion rating. For speakers, "RMS" is the average input power that the speaker can handle, with an input signal that does not drive the cone to over-excursion.
"Peak" has no widely accepted or believable definition, and can range from a number that is roughly twice the RMS value, all the way up to the stratosphere.
"Program" typically refers to speakers, and the reputable driver makers appear to define it as exactly twice the RMS rating. For speakers, the RMS rating and the excursion limit are the things that are actually measured by the driver maker.
It's worth noting that many speakers can handle much less than their rated input power if the signal is a pure sine wave at low frequencies. This is not a huge concern if you play with a tone that contains a reasonable mixture of harmonics, so long as the speaker is well designed. A poorly designed speaker can be driven to over-excursion without exceeding its rated power, and extremely bass-heavy EQ can cause the same thing to happen even with many good speakers.
"Peak" has no widely accepted or believable definition, and can range from a number that is roughly twice the RMS value, all the way up to the stratosphere.
"Program" typically refers to speakers, and the reputable driver makers appear to define it as exactly twice the RMS rating. For speakers, the RMS rating and the excursion limit are the things that are actually measured by the driver maker.
It's worth noting that many speakers can handle much less than their rated input power if the signal is a pure sine wave at low frequencies. This is not a huge concern if you play with a tone that contains a reasonable mixture of harmonics, so long as the speaker is well designed. A poorly designed speaker can be driven to over-excursion without exceeding its rated power, and extremely bass-heavy EQ can cause the same thing to happen even with many good speakers.
These guys like fdeck know what these terms really mean from a technical standpoint. For practical purposes use the RMS rating, or whatever the lowest wattage rating is. That usually indicates how much power the coil can take over an extended period of time (like a gig). The higher numbers may indicate what it can handle in a short burst of high power but not what they can take consistently. Also keep in mind the wattage or power handling rating of a speaker is a measurement of how much heat the voice coil can take before is gets too hot and melts, many bass speaker reach their mechanical limit with a lot less input than this. This means that although the voice coil can take 250 watts of power before it melts, it may take a lot less than that to make the speaker jump back and forth further than it's designed to, that would be mechanical limits. For example you could have a 500 watt bass cab that could start to fart out with 200 watts of input. That's doesn't mean you can't pair a 1000 watt amp with it, as long as you don't crank it to 10.
Peak is in fact very well defined. It is the highest value measured during a period. Like RMS, it's really only useful when talking about simple waveforms, usually a sine wave. RMS (Root Mean Square, as someone almost said earlier) is the quadratic mean of a signal. For a sine wave, V(RMS) = V(PEAK)/SQRT(2)
It (*edit: peak) can, of course, also refer to the absolute maximum power a speaker can take for a very short period without breaking, but that's not something to rely on. For example, if you have a 100W amplifier, and a speaker rated at, say 60W but can handle as much as 150W in short bursts with rest in between, your amplifier is still fully capable of delivering a signal that may ruin your speaker element(s), even if it rarely happens during normal use.
Which brings us to "Program", which is pure marketing ********. It has a very vague definition that results in a higher rating (somewhere between the continuous power rating and the absolute maximum) which makes the stuff sell easier. It's based on the fact that music typically is dynamic and rarely uses the full power of the amplifier, at least not for long times. So the program rating is basically the amplifier power rating that the speakers should be able to handle if the signal is an average piece of music (whatever that is).
Peak instantaneous power is a good definition. However, I have seen more abuse of this rating than the others. Once in a while someone dumps a pile of cheap no-brand amps on eBay, with truly stratospheric power ratings. Right now there is a guitar amp rated at "20 Watts RMS 100 Watts Max."
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
- 278
- 76
- Disclosures
- Owner, Bill Fitzmaurice Loudspeaker Design
RMS = Honest
Program = Stretching the truth
Peak = Really stretching the truth
Peak Program Music Power = Our amps suck
Since RMS is the most conservative rating it's also the most useful, and the only one you should use for comparison purposes.
Haha
Maybe it has very large caps in the power supply?
Or maybe it's a 100W amp with no heatsinks?
On a more serious note, a peak instantaneous power rating any greater than the RMS rating times the square root of two indicates that a) the seller is trying to screw you over, or b) the manufacturer doesn't know what he's doing. For an amp, that is.
- Mar 24, 2003
- 809
- 2,523
- Disclosures
- Robert A. Gallien, President Gallien-Krueger
Any signal has distortion which is contained in the harmonics of the fundamental. So a 1kHz signal will have energy at 1kHz, 2kHz, 3kHz, 4kHz ... and so on. The power contained in the signal is the total power contained in the fundamental and all the harmonics. The way the total power is calculated is to square all the harmonic values (including the fundamental) add them up and then take the square root of the total. RMS stands for Root Mean Square or the square root of the total of the squares. This is the only real definition of power. All other terms such as program and peak have no real meaning. To be accurate a power rating should specify the frequency it was measured at the total harmonic distortion.
RMS may be sometimes labeled as "continuous". Whatever it is, go by the lowest number and then listen to your speakers. Distortion, farting or a "stressed" sound means it's time to back off either the volume or the bass knob, or some combination of both. Some schools of thought say you should use an amplifier that can provide twice the power that the speaker load is rated at. That doesn't mean hit it with all that power, that means headroom, or, your amp isn't working as hard as it can to produce what you need. In other words, your amp has some power left in reserve that it doesn't need all the time which results in a cleaner sound and is not as taxing on your equipment. This isn't a hard and fast rule, just means you don't need to worry about using a 500 watt amp with a 300 watt cab, etc. Again, as long as you don't crank everything.
