What Watts are What?

tombuur

tombuur

New member
Talking about live P.A. (couldn't find a more appropriate forum than this).

Manufacturers state all kinds of Watts for their equipment. Speakers sometimes 3 different, sometimes one for peak and one for longer duration I guess. Also concerning amps, I understand the difference related to speaker impedance, when it is the same as internal impedance you get maximum Watts. Yet, they still specify all sort of Watts, making comparisons difficult.

Can anyone direct to a site explaining the different standards, or tell me Watts it all about?
 
The most meaningful is RMS (Root Mean Square) which takes into account the average level of the playback. Anything else is "tastes richer" or "makes women look at you" hype.
 
tombuur said:
Talking about live P.A. (couldn't find a more appropriate forum than this).

Manufacturers state all kinds of Watts for their equipment. Speakers sometimes 3 different, sometimes one for peak and one for longer duration I guess. Also concerning amps, I understand the difference related to speaker impedance, when it is the same as internal impedance you get maximum Watts. Yet, they still specify all sort of Watts, making comparisons difficult.

Can anyone direct to a site explaining the different standards, or tell me Watts it all about?
Click to expand...



RMS Voltages and Watts:
The square root of the average of the squares of a variable quantity.

In terms of voltage, the root mean square voltage is called the effective voltage, as opposed to the peak voltage which corresponds to the maximum AMPLITUDE of the voltage variations. RMS power (in watts) is similarly called the effective power, since for an AMPLIFIER, for instance, it represents its real POWER.

The following relationships hold between peak, rms and average voltage. Note that the so-called peak-to-peak voltage is twice the peak voltage.

rms voltage = 0.707 peak voltage
rms voltage = 1.11 average voltage

peak voltage = 1.414 rms voltage
peak voltage = 1.57 average voltage

average voltage = 0.637 peak voltage
average voltage = 0.9 rms voltage

I hope this helps you. You can apply the math to the spec(s) of the amplifier you are considering to get the "real" power figure you are looking for.
 
Here are some specs for a subwoofer:

Recommended amplifier W rms 1600

Long term power (AES) W 800

Short term power (IEC 268-5) W 3200

Thanks for telling me what RMS is. What's the other stuff, AES for example.
 
tombuur said:
Here are some specs for a subwoofer:

Recommended amplifier W rms 1600

Long term power (AES) W 800

Short term power (IEC 268-5) W 3200

Thanks for telling me what RMS is. What's the other stuff, AES for example.
Click to expand...




The AES measurement is a defined standard in which a band of pink noise from 125Hz to 8Khz, with +6dB peaks, is applied to the input of the loudspeaker for a period of two hours. A loudspeaker that has its power rating in AES watts can handle (for a short time) peaks of about +6dB above the AES rating.

The maximum output level at 1 meter away from a loudspeaker can be found from the following formula:

SPLmax-AES = sensitivity + 10 log (AES power rating)

SPLmax = sensitivity + 10 log (AES power rating) + 6

Hope this helps.
 
Thanks, I am getting wiser.

The +6dB for short term explains why those Watts often is 4 times max level of the continously applied Watts.

Now I just wonder how RMS relates to AES.
 
You can search on Google and find lots of pages that deal with WATTs and related matters. The FTC standards for amplifier power rating are very effective for comparison between brands.

The default for most amps is 8 ohms. However many can drive low impedance loads, and generally produce higher output. Be sure your amp can handle small ohm loads before you connect them.

Ed
 
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