Speaker wattage definition

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Jerboy

Banned
Oct 27, 2001
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Are these Logitech speakers really 400W?? Their subwoofer is supposedly 188W and four satellites fills up the balance. How likely is it that they can actually take that power continuously?

Let's talk about it's subwoofer. We'll assume that it's resistance(imp.) is 4ohms.

V^2/R=W, R x W=V^2. 4 x 188=752, sqrt 752=27.4V.

Now we know that this speaker will be drawing 188W at 27.4V input voltage.

Let's hook it up to a Variac connected to 120V AC and adjust it's output to 27.4V.

Will the speaker survive until next morning?


The power company's power can easily handle this kind of power level without any clipping and very low distortion.
 
B

Bozz

Senior member
Jun 27, 2001
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That speaker system actually looks quite chunky.

Many woofers are tested using RMS power at 400Hz sine wave (well of course its sine wave because you can't get calculate RMS with other waveshapes) and usually its the maximum power the driver can continuously sink without overheating, failing or distorting.

One more thing to consider, most class-b amplifiers are about 30-40% efficient so 400WRMS equates to about 1000 watts drawn from the power point. If you have doubts about it's capacity simply check the mains fuse rating, it very often gives a fake away :)

Cheers
 
H

Heisenberg

Lifer
Dec 21, 2001
10,621
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<< That speaker system actually looks quite chunky.

Many woofers are tested using RMS power at 400Hz sine wave (well of course its sine wave because you can't get calculate RMS with other waveshapes) and usually its the maximum power the driver can continuously sink without overheating, failing or distorting.

One more thing to consider, most class-b amplifiers are about 30-40% efficient so 400WRMS equates to about 1000 watts drawn from the power point. If you have doubts about it's capacity simply check the mains fuse rating, it very often gives a fake away :)

Cheers >>



Just to clarify, you can calculate RMS for other waveforms. It's just not the same (2^.5)/2 relationship between peak-to-peak and RMS as it is for a sine wave. If what logitech reports is a true RMS figure, then the sub should be able to handle it, although I'm still not sure why anyone would want to do this to a new subwoofer.
 
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