Running Distortion - Amp Risks

[LoveThatBass]

A sinewave ramps up and down realitively slowly and smoothly as compared to a square wave that is or near instantaniously on and off. Suppose the speaker was related to a person in a car. You would fare much better at a ramped take off and slow down than you would if a truck hit you a 50 miles an hour wouldn't you. Yes, speaker is not a person in a car but you get the point.

 

[Bob Lee (QSC)]

A sinewave ramps up and down realitively slowly

That depends on the frequency.

and smoothly as compared to a square wave that is or near instantaniously on and off. Suppose the speaker was related to a person in a car. You would fare much better at a ramped take off and slow down than you would if a truck hit you a 50 miles an hour wouldn't you. Yes, speaker is not a person in a car but you get the point.

No, your point is not apropos to the topic of the thread. A square wave is not like getting hit by a truck.

 

[LoveThatBass]

That depends on the frequency.



No, your point is not apropos to the topic of the thread. A square wave is not like getting hit by a truck.

No but a high wattage square wave is!

 

[Bob Lee (QSC)]

No but a high wattage square wave is!
Nuff said

No, it's not.

A square wave is just an alternating voltage. The flat part of the voltage is just a constant accelerative force on the cone. It doesn't mean that the cone tries to instantaneously traverse from one fixed position to another.

 

[LoveThatBass]

I was speaking of the rise and fall points increase closer to instantanious rather than ramping.

As far as the flat top is concerned, yes it is just current flowing constantly in one direction but also for a longer period of time than with a sinewave where it is continuously changing.

Bob, what is your take on why speakers blow? I removed the rude remark above and apologize for that.

 

[Mark Reccord]

I was speaking of the rise and fall points increase closer to instantanious rather than ramping.

As far as the flat top is concerned, yes it is just current flowing constantly in one direction but also for a longer period of time than with a sinewave where it is continuously changing.

Bob, what is your take on why speakers blow? I removed the rude remark above and apologize for that.

Keep in mind that the output signal will retain the shape of the input signal until it reaches the power supply rail voltage, so the instantaneous rise time of a true square wave isn't really applicable. Especially when you consider that amplifiers have a finite rise time and can't reproduce a wave with instantaneous rise time anyway.

 

[Bob Lee (QSC)]

I was speaking of the rise and fall points increase closer to instantanious rather than ramping.

Okay. So the cone is accelerated in one direction, and then in the other. That's how they work.

As far as the flat top is concerned, yes it is just current flowing constantly in one direction but also for a longer period of time than with a sinewave where it is continuously changing.

And what significance is that? It means that the cone is accelerating fairly steadily for that portionof the waveform.

Bob, what is your take on why speakers blow?

Overpowering or overexcursion, as was mentioned before.

 

[Jerrold Tiers]

There are some fundamental differences between clipping an amp and running a distortion pedal into it.

For one thing, the pedal probably does NOT produce a real square wave.....

The reason is that there is normally some sort of tone modification in the pedal, That generally filters high harmonics, rounding off the wave. There may also be some further tone modification, and low cutting, which turns the waveshape into a tilted, rounded-off version of a square wave. The actual average power represented by the final result is often far less than the peak.

Clipping produces a fine, clean, square, wave, how fine and clean depending on how clipped the amp is. Feedback is driving the edges to be squared up and "clean"..... And the average power represented is equal to the peak in the case of heavy clipping.

Then after the pedal comes the amp. More low cut and general EG manipulation, further scrambling the waveshape, adjusting the harmonic structure, and usually increasing the peak to average ratio.

Again, clipping is a nice clean square wave, dependent only on how much overdrive exists.

So, it is perfectly possible for a heavy pedal distortion to be VERY different from a square wave by the time it gets to the speaker.

And, it usually represents a lot less average power output than a square wave of the same amplitude. Average power is what fries speakers.

Not surprising, I'd hope, because one assumes some basic desire to be musical. A square wave is generally not the sound wanted......

 

[LoveThatBass]

Okay. So the cone is accelerated in one direction, and then in the other. That's how they work.

Yes, but at a substantially faster rate

And what significance is that? It means that the cone is accelerating fairly steadily for that portionof the waveform.

Yes, but for a longer period of time (more heat builtup on voicecoil than normal)

 

[Bob Lee (QSC)]

Yes, but at a substantially faster rate

That depends on the voltage, not on the rise time or the shape of the waveform.

Yes, but for a longer period of time (more heat builtup on voicecoil than normal)

No.

You seem to be really hung up on this. I suggest that you get some learning in how loudspeakers and amplifiers work.

 

[seamonkey]

Trust me, without even clipping, if you put in a signal with a lot of high frequency you can blow your tweeters just from the signal. Bass cabs do not make good keyboard or edrum amps. If your bass effects add just a bunch of highs - and you overpower the tweeter, it will blow - clipping or not.

Ran across this Rane paper.
[Invalid or Expired Link Removed]
It makes perfectly good sense.

This paper describes the effect at clipping as compression of the lows but the highs continue to gain db's.

A good clean amp can continue to amplify highs even while it can't push any more lows out. The paper points out clipping doesn't add as much highs as whats coming through the signal path.

Good limiting on amps prevent the lows from clipping and keep the highs and lows in proper proportions. But maybe, what people want - if they're going to clip and amp - is let the lows clip just don't let the highs grow unproportionate. Just compress the highs at high volumes. The clipping itself won't add a lot of highs, and compressing the highs of the input signal won't let it get unproportionately louder.

Of course, big amp, with no clipping, and effects, lets you do all this at different volume levels.

 

[Fuzzbass]

I don't normally post comments from other forums here, but the synchronicity is too much to ignore. Anyone care to respond?

"Well, here you seem to be saying that a 20 watt square wave will damage a 200 watt woofer, which I hope you'll agree is silly."

If a 4 ohm speaker is dissipating 20 watts continuously at a DC level, it works out to 2.25 amps going through the voice coil, it will burn it out unless it's coil is made of enormous wire. If you have a square wave going through that coil, and aside from the fact that the coil will be cooled somewhat by itself flapping in the breeze, it's still seeing negative 2.25 amps and then positive 2.25 amps with a very short amount of time between the excursions...it's called "power (or area) under the curve" in calculus parlay.
I'm done beating this horse....I'll stand by for the next great thread

 

[Bob Lee (QSC)]

If it's truly a 200-watt woofer, 20 watts of dissipation will not burn it out.

 

[Kronos]

My head with pain! (sorry, that's from another site where someone isn't very bright)

Anyway, does this mean that my speakers will be damaged by playing with distortion or not? I've played with distortion for years, I haven't had a problem, but I've never played for extended periods of time. I don't run a tweeter (they seem to be too harsh for my taste), so that's not an issue for me.

Someone please clear through the technobabble on here and can I get a yes or no answer?

P.S. I never run my amp so that my clip light turns on for more than a milisecond while basically using the strings like a strung bow and arrow. In other words, it takes a lot for my power amp to clip, and I don't run it that way.

 

[greenboy]

My head with pain! (sorry, that's from another site where someone isn't very bright)

Anyway, does this mean that my speakers will be damaged by playing with distortion or not? I've played with distortion for years, I haven't had a problem, but I've never played for extended periods of time. I don't run a tweeter (they seem to be too harsh for my taste), so that's not an issue for me.

Someone please clear through the technobabble on here and can I get a yes or no answer?

And you are saying someone on another site isn't very bright? Yet you don't belive the evidence of your own experiences unless it gets validated here on a forum in non-technical language?

And you still have not noticed that gazillions of other musicians have played with loud distortions through their rigs, which goes through PAs, through hundreds of thousands of studio monitors, home entertainment speakers, mobile systems... Better clue in, pal. Don't let some dumbasses who want to argue nonsense turn you away from what is obvious ... And in turn, you need to recognize which guys are talking trash and which are actually saying something that seems to mesh with the incredible amount of simply digested evidence out here in the real world.

Or are you just dreaming all this?

 

[The 0x]

My head with pain! (sorry, that's from another site where someone isn't very bright)

Anyway, does this mean that my speakers will be damaged by playing with distortion or not? I've played with distortion for years, I haven't had a problem, but I've never played for extended periods of time. I don't run a tweeter (they seem to be too harsh for my taste), so that's not an issue for me.

Someone please clear through the technobabble on here and can I get a yes or no answer?

P.S. I never run my amp so that my clip light turns on for more than a milisecond while basically using the strings like a strung bow and arrow. In other words, it takes a lot for my power amp to clip, and I don't run it that way.

In a nutshell, if you haven't blown your speakers by now, you'll be fine.

 

[popinfresh]

Ditto.


That must be loud as a trainwreck, though!

Indeed. My band won't let me turn up past 1-2 though =(

Oh how I yearn for the day that we play a big, loud, outdoor festival with a massive stage so I can crank it.

It still sounds great running second gain stage up and master down.. But when you turn the master up past 12 o'clock, dial in a heap of the second gain stage and the 'magic eye' closes... Oh my my =D

 

[The 0x]

Indeed. My band won't let me turn up past 1-2 though =(

Oh how I yearn for the day that we play a big, loud, outdoor festival with a massive stage so I can crank it.

It still sounds great running second gain stage up and master down.. But when you turn the master up past 12 o'clock, dial in a heap of the second gain stage and the 'magic eye' closes... Oh my my =D

Why not perform that mod where you can cut the signal to each pair of power tubes to bring the wattage down to 300, 200 or 100 watts, so you can really crank it without pissing off your bandmates TOO much? Personally, for me to get a good overdriven sound, all I need are 2x6550s, 2 15" speakers, and i'm ready to rock. Guitard's gettin a 4x12 soon though (in addition to his 4x10 combo), so I may need to double in size soon.

 

[popinfresh]

Well, i'm allready running on half power =P

Might look into it though, cheers

 

[Mark Reccord]

There are some fundamental differences between clipping an amp and running a distortion pedal into it.

For one thing, the pedal probably does NOT produce a real square wave.....

The reason is that there is normally some sort of tone modification in the pedal, That generally filters high harmonics, rounding off the wave. There may also be some further tone modification, and low cutting, which turns the waveshape into a tilted, rounded-off version of a square wave. The actual average power represented by the final result is often far less than the peak.

Clipping produces a fine, clean, square, wave, how fine and clean depending on how clipped the amp is. Feedback is driving the edges to be squared up and "clean"..... And the average power represented is equal to the peak in the case of heavy clipping.

Then after the pedal comes the amp. More low cut and general EG manipulation, further scrambling the waveshape, adjusting the harmonic structure, and usually increasing the peak to average ratio.

Again, clipping is a nice clean square wave, dependent only on how much overdrive exists.

So, it is perfectly possible for a heavy pedal distortion to be VERY different from a square wave by the time it gets to the speaker.

And, it usually represents a lot less average power output than a square wave of the same amplitude. Average power is what fries speakers.

Not surprising, I'd hope, because one assumes some basic desire to be musical. A square wave is generally not the sound wanted......

Amps don't ever produce real square waves either..... What everyone seems to forget is that in both amp clipping and in distortion effects, the portion of the input wave below the clip point is unaffected, so the output mimics the input below the rail voltage (or the artificial diode clipping point). Yes, distortion effects do tend to have filters that cut out a lot of the higher harmonics, etc. but the general mechanism is the same.

Your second last point is what I always try to drive home in these threads. The point is that the waveform in and of itself is not what causes problems, it's the average power incident on the driver.... But you know this.