RMS is not a unit of measurement!

[hispls 5,000+ posts]

I'm so ******* sick of people misusing this term. I'll just leave this here:

Root mean square - Wikipedia, the free encyclopedia

Click to read more...

 

[pickup1 5,000+ posts]

(RMS) is the value of a periodic current is the DC voltage that delivers the same average power to a resistor as the periodic current.

average power.

 

[Jepalan]

(RMS) is the value of a periodic current is the DC voltage that delivers the same average power to a resistor as the periodic current.average power.

Nope. OP is right - "RMS" is not a unit of measure. What you described is RMS WATTS. You can measure RMS VOLTS, RMS AMPS, etc. But just "RMS" has no meaning.

Now don't get me started on "dB"

 

[CerwinVega_Fan 10+ year member]

Yall just some haters because my coils and amps got more rms than yours.

 

[cfox10 10+ year member]

Nope. OP is right - "RMS" is not a unit of measure. What you described is RMS WATTS. You can measure RMS VOLTS, RMS AMPS, etc. But just "RMS" has no meaning.
Now don't get me started on "dB"

square root of the arithmetic mean of the squares of a set of values, used as a measure of the typical magnitude of a set of numbers, regardless of their sign.

As defined in 2014 by the Oxford English Dictionary. AKA the most reputable English dictionary in the world.

 

[tprj82 10+ year member]

sounds like peeps mad others got more deebeez then them

 

[los33 10+ year member]

If someone mentions that there sub does 500 rms is that so bad? You guys have been around long enough to understand this is defaulted to "500 watts rms".

Now forget my post if someone was trying to setup an equation or something with just saying rms alone and not specifying what was meant by that.

 

[gckless 5,000+ posts]

So, what RMS do I need to hit 150dB's?

 

[cfox10 10+ year member]

So, what RMS do I need to hit 150dB's?

Funky Pup? fyi

Ask the writers and editors of the Oxford English Dictionary I guess? Considering they say it IS indeed a unit of measurement.

 

[Jepalan]

Funky Pup? fyiAsk the writers and editors of the Oxford English Dictionary I guess? Considering they say it IS indeed a unit of measurement.

A "measure" and a "unit of measurement" are not the same thing. Break out that oxford again. Nobody said "RMS" wasn't a measure of something. We said it is not a "unit of measurement". "Dollar" is a unit of measurement. "Volt" is a unit of measurement. "Foot" is a unit of measurement. RMS is a method of averaging typically used in physics, statistics and engineering. It is not a unit of measurement.

dB is also not a unit of measurement. it is a logarithmic expression of a ratio of two numbers and is unit less. dBV (dB relative to one volt), dBmW (dB relative to one milliwatt), etc. are units of measurement. The "dB" we typically use to measure SPL is technically "dB relative to 20 micropascals", which is roughly the quietest sound the human ear can detect.

 

[cfox10 10+ year member]

A "measure" and a "unit of measurement" are not the same thing. Break out that oxford again. Nobody said "RMS" wasn't a measure of something. We said it is not a "unit of measurement". "Dollar" is a unit of measurement. "Volt" is a unit of measurement. "Foot" is a unit of measurement. RMS is a method of averaging typically used in physics, statistics and engineering. It is not a unit of measurement.
dB is also not a unit of measurement. it is a logarithmic expression of a ratio of two numbers and is unit less. dBV (dB relative to one volt), dBmW (dB relative to one milliwatt), etc. are units of measurement. The "dB" we typically use to measure SPL is technically "dB relative to 20 micropascals", which is roughly the quietest sound the human ear can detect.

I get the first part. But I guess I don't understand how dB isn't a unit of measurement still... would it not be considered a measurement vs a reference level? I only ask because when I reference my electrical measurement tables dB is definitely one of them listed.

edit: even though it says that it's a unit of measurement specifically... it really isn't, right? It would be dBV or dBSPL? Where we are really measuring the watts/voltage/whatever we want and the dB is that number in relation to the reference level?

 

[keep_hope_alive Premium Member]

we cannot expect the masses to understand the difference, though it is important to give them the opportunity to learn.

most of the effort in answering questions is deciphering the true meaning and nature of the question since the asker is usually unable to formulate a question that accurately presents the facts.

it annoys me when amplifier manufacturers don't rate power output noting the load, THD, and supply voltage. i'd also like to see time. 1000W for 1 second is much more difficult to achieve than for 1 hour (all else equal). thermal management and long-term current handling costs money in R&D and construction.

 

[SounDrive Pro Seller]

A "measure" and a "unit of measurement" are not the same thing. Break out that oxford again. Nobody said "RMS" wasn't a measure of something. We said it is not a "unit of measurement". "Dollar" is a unit of measurement. "Volt" is a unit of measurement. "Foot" is a unit of measurement. RMS is a method of averaging typically used in physics, statistics and engineering. It is not a unit of measurement.
dB is also not a unit of measurement. it is a logarithmic expression of a ratio of two numbers and is unit less. dBV (dB relative to one volt), dBmW (dB relative to one milliwatt), etc. are units of measurement. The "dB" we typically use to measure SPL is technically "dB relative to 20 micropascals", which is roughly the quietest sound the human ear can detect.

Although this is true, dB is still properly used as a unit of SPL.

 

[hispls 5,000+ posts]

If someone mentions that there sub does 500 rms is that so bad? You guys have been around long enough to understand this is defaulted to "500 watts rms".
Now forget my post if someone was trying to setup an equation or something with just saying rms alone and not specifying what was meant by that.

It's pure ignorance and looks ignorant when people write it. People who use the term think that an RMS is something that should be compared to some "peak" number which is and has always been pure marketing bullshit and was never actually the peak to peak of the waveform, but simply a wishful thinking number that you may or may not be able to measure for one second before you see smoke.

So you're saying I should just go ahead and let people be ignorant and act stupid instead of starting this thread to try to inform people?

Funky Pup? fyi
Ask the writers and editors of the Oxford English Dictionary I guess? Considering they say it IS indeed a unit of measurement.

So if you're current is 10A RMS and your voltage is 10V RMS, your power would be 100W RMS^2? If the RMS is a unit of measurement it would need to be also multiplied.

There is a large difference between a method of measurement and a unit of measurement and since the accepted method to deal with sine waves is the root mean square, writing RMS is redundant, and not necessary.

A "measure" and a "unit of measurement" are not the same thing. Break out that oxford again. Nobody said "RMS" wasn't a measure of something. We said it is not a "unit of measurement". "Dollar" is a unit of measurement. "Volt" is a unit of measurement. "Foot" is a unit of measurement. RMS is a method of averaging typically used in physics, statistics and engineering. It is not a unit of measurement.dB is also not a unit of measurement. it is a logarithmic expression of a ratio of two numbers and is unit less. dBV (dB relative to one volt), dBmW (dB relative to one milliwatt), etc. are units of measurement. The "dB" we typically use to measure SPL is technically "dB relative to 20 micropascals", which is roughly the quietest sound the human ear can detect.

I'm glad someone actually paid attention in school. Personally I'll let dB slide on it's own since in the context here it's implied that it's referring to sound intensity.

\it annoys me when amplifier manufacturers don't rate power output noting the load, THD, and supply voltage. i'd also like to see time. 1000W for 1 second is much more difficult to achieve than for 1 hour (all else equal). thermal management and long-term current handling costs money in R&D and construction.

I think you mean the other way around. Agreed, and I'll take that a step farther and say I'd really like to see SPEAKER manufacturers add some time numbers as well. In both cases I think most people who purchase based solely on whoever puts the biggest number on the box would be rather shocked.

 

[SounDrive Pro Seller]

I think you mean the other way around. Agreed, and I'll take that a step farther and say I'd really like to see SPEAKER manufacturers add some time numbers as well. In both cases I think most people who purchase based solely on whoever puts the biggest number on the box would be rather shocked.

I couldn't agree with this any more. So many manufacturers care more about marketing than the usefulness of specifications they publish.