AudioBanter.com - View Single Post - Help me understand what is too much volume.

(John Atkinson) wrote:

(Nousaine) wrote in message
.net...
"normanstrong" wrote:
Let's suppose your speaker is rated up to 100 watts, and it crosses
over from woofer to tweeter at 2000Hz. Since music contains very
little content above 1000Hz it is unlikely that a 100W signal will
contain enough power above 2000Hz to damage your tweeter, which might
very well be limited to about 10 watts.

Now imagine a change: a 1000Hz note is played at full output. That
will be 100W, most all of it going into the woofer. Now we continue
increasing the input so that what comes out of the amplifier consists
of a 1000Hz square wave having the same peak value as the original
100W output. The amplifier is now outputting a 200W signal, half of
which is the original 1000Hz sine wave, and the rest consisting of all
the odd harmonics (3000, 5000, 7000, etc.) What you have here is 100
watts worth of signal being fed directly to the tweeter. Since the
tweeter itself cannot handle anything like 100 Watts, it burns out.

This scenario contains some interesting assumptions doesn't it? First
it assumes the power supply of the 100 watt amplifier can deliver 200
watts simply by driving it into clipping?

Only if the sinewave is so overdriven that a completely square waveform
results.

So exactly how does being driven into clipping make the output devices and
power supply capable of delivering power that is un-tappable under other
operating conditions?

This may be unlikely but it is not impossible. And for the same
output voltage the squarewave does indeed offer twice the power.

In
reality, the clipped amplifier will be giving out more power for the same
output voltage, the amount of which depends on the degree of clipping.

But you're assuming it ALL goes to tweeter frequencies. What are the
frequencies at which amplifiers are driven into clipping?

And it assumes that the harmonic structure of clipping distributes
equal energy above the fundamental.

For a fully squared waveform, I believe this is the case. For a clipped
but not fully squared signal, all that can be said is that the extra power
represented by the harmonics in the scenario that Norm was referring to
is indeed fed to the tweeter,

Maybe.

which might not be able to handle it.

That's the prime issue here. Tweeters are cooked by too much power over a given
period. What clipping, as you call the party effect, does is raise the average
power level over time. It doesn't, by itself, represent a danger to tweeters.

Having seen speakers with tweeters blown by relatively low-powered
amplifiers driven continuously into clipping (the so-called "Party Test"),
I think it not improbable.

John Atkinson
Editor, Stereophile

Drive the speaker to the same SPL level with a larger amplifier and you'll fuse
that tweeter in exactly the same time.