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[Stelios Mac]

Is the distorted signal tweeter stressed more than the other?

If both setups were driving the speakers within their RMS & peak power limits there wouldn't be a problem with either.

But if you're "on the edge" I'd say it depends on how you measure "X".
Clean vocals have a good deal of dynamics, distorted vocals have less dynamics.

If "X" is peak power then undistorted vocals would be "safer" material, as their RMS power would be lower than that of distorted vocals.
If "X" is RMS power, then distorted vocals would be "safer" material, as their dynamics are much less than the dynamics of clean vocals and thus their peak power would be lower.

[David Allred]

If both setups were driving the speakers within their RMS & peak power limits there wouldn't be a problem with either.

But if you're "on the edge" I'd say it depends on how you measure "X".
Clean vocals have a good deal of dynamics, distorted vocals have less dynamics.

If "X" is peak power then undistorted vocals would be "safer" material, as their RMS power would be lower than that of distorted vocals.
If "X" is RMS power, then distorted vocals would be "safer" material, as their dynamics are much less than the dynamics of clean vocals and thus their peak power would be lower.

My "equal total energy" requirement eliminates fluctuations and what-ifs (I think) regarding RMS vs peak vs a male or female voice.  Lets say the mic is picking up a 5khz sine tone.
One mic is over-driven.  The distorted signal gains harmonics, but level is reduced to have equal "energy".  Same as the undistorted mic.

[Bob Leonard]

ANY DIFFERENCE BETWEEN THE INPUT WAVEFORM AND OUTPUT WAVEFORM IS DISTORTION.

Clipping is a form of distortion but not the only form of it, but SUSTAINED AMPLIFIER OUTPUT CLIPPING is bad for speakers because it's happening at the FULL OUTPUT CAPABILITY OF THE AMP.

I don't think I can make that any clearer.

Correct on all counts as usual.

Dave,

Those compression drivers are failing because they are being driven past there electrical capabilities, not because of the distortion.

ANY amplifier driven to clipping can and will generate as much as 10x the rated output of the amplifier. And even though this power is generated for moments in time the end result is a destroyed driver in every case. You need to look at the voice coil as if it were a FUSE. The capability of that FUSE is measured by the amount of voltage/current it will handle. Too much generated current and the FUSE faults. Bye, bye voice coil.

Want the speakers to last. Stop driving them into clipping.

From the Mackie manual;

6. LIMIT Indicator
The SR1521z has a built-in limiter that prevents the amplifier outputs from clipping or overdriving the transducers. The LIMIT indicator lights when the limiter is activated. It's okay for the LIMIT indicator to blink occasionally, but if it blinks frequently or lights continuously, turn down the level control until the LIMIT indicator only blinks occasionally.

Max SPL for the cabinet is 127db. Don't expect miracles.

[Stelios Mac]

My "equal total energy" requirement eliminates fluctuations and what-ifs (I think) regarding RMS vs peak vs a male or female voice.  Lets say the mic is picking up a 5khz sine tone.
One mic is over-driven.  The distorted signal gains harmonics, but level is reduced to have equal "energy".  Same as the undistorted mic.

In that case, as long as the "X" is within the speaker's power limits it'll be no problem with either. You could feed pink noise into it and it would be exactly the same.

Think of it this way; The tweeter's diaphragm is just making a movement that corresponds to what sort of signal you feed it.
It doesn't matter what that movement looks like, as long as short & long term power as well as frequency content (high-pass) are kept within certain limits to prevent over-excursion, over-heating and long-term fatigue.

[Ivan Beaver]

Here is a good way to think about it.

Speakers die from 2 causes, to much heat over time and overexcursion.

I won't talk about the excursion issue here.

It is ALL about the time AND the level.

Think of it this way.  What if I asked you what the maximum temp your body could withstand.  Let's call it a "rating"-a nice simple number.  You know what happens with "simple numbers".

Most people would say around 120*Fahrenheit.  But what if I told you I could easily withstand 1500*F.  I can, and can easily prove it any time.

All you have to do is to run your finger through a candle flame.

If you do it fast, you won't burn.

So put a candle on the ground.  Hold your hand above it about 6' off of the ground.  How long can you hold it without pain?

Now lower it to 3' and the time becomes much shorter.

And so forth.

So it is not just the "power" but ALSO the time the power is applied that is the problem for most loudspeakers.

Peaks are fine, as long as the average level is well below the peak.

When an amplifier is clipped, the peaks are not any higher, but the AVERAGE LEVEL goes up quite a bit, and causes the burning.

[Bob Leonard]

OP/ interested others,

Please take the time to read the documents at the links below;

http://www.jblpro.com/ProductAttachments/spkpwfaq.pdf

http://www.jblpro.com/ProductAttachments/lowpower.pdf

http://www.jblpro.com/ProductAttachments/pssdm_1.pdf

http://www.jblpro.com/ProductAttachments/pssdm_2.pdf

[Paul G. OBrien]

If a guitar pedal adds distortion to the direct channel sound of the guitar, and the output from the mixer is set at a specific amplitude, and the wave form is captured, then sent to the amp and speaker.  The affect on the tweeter is "X".

X = Higher average power dissipation.

If a guitar (less pedal) is plugged into a channel, can the channel or main bus be over-driven to match the waveform (previously) going to the amp?.

Exactly match it? Probably not but will it be close enough to produce a similar result.. yes.

Did the affect to the tweeter change?

Not appreciably.

What if the matching waveform is only achieved in the amp's input circuit or the output circuit due to clipping?

Now you are getting into very dangerous territory. Overdriving an upstream preamp stage can be done without over powering a speaker because there is always another gain control downstream that can adjust for the increased signal level.. this is how guitar amps live to see another day. But over driving a power amp  is almost always a guaranteed path to blown speakers because you have no control over the output.

[Ivan Beaver]

 Now you are getting into very dangerous territory. Overdriving an upstream preamp stage can be done without over powering a speaker because there is always another gain control downstream that can adjust for the increased signal level.. this is how guitar amps live to see another day. But over driving a power amp  is almost always a guaranteed path to blown speakers because you have no control over the output.

Actually a lot of guitar amps get their sound from overdriving the output stage, and the compression that comes along with it.

Especially for the LOUD players.

The speakers survive because they are typically only reproducing one instrument-NOT a whole band.

With a full band, there is a lot more energy, even though the peak levels between a guitar and a full band are the same, the average levels would be higher with a full band.

It is the "total power under the curve" that does the heating/damage

[Paul G. OBrien]

My "equal total energy" requirement eliminates fluctuations and what-ifs (I think) regarding RMS vs peak vs a male or female voice.  Lets say the mic is picking up a 5khz sine tone.
One mic is over-driven.  The distorted signal gains harmonics, but level is reduced to have equal "energy".  Same as the undistorted mic.

Problem is speakers can be blown by any one of several different methods so you can't distill several different scenarios down to one common denominator. Your typical 1" exit compression driver may have a peak power rating of 100w but only a 25w rms rating.  A powered speaker like this Mackie has a 100w amplifier feeding the CD, that means this amp has 4 times more power than than this driver can handle in certain situations. That may sound stupid but providing less would really hurt output potential. This works fine with all kinds of music but a sustained tone at the right frequency could melt the driver. People blow tweeters with mic feedback all the time.

[Paul G. OBrien]

Actually a lot of guitar amps get their sound from overdriving the output stage, and the compression that comes along with it.

OK.. but in that case it is a 15w or 25w amp driving a 50w or 75w driver, and the manufacturer has designed the device to operate this way so maybe it wasn't a good example as it's pretty much the opposite amp/speaker relationship that a PA speaker has.

[ProSoundWeb Community]