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Square Wave damaging speaker/driver

post #1 of 14
3/7/08 at 4:49pm
Thread Starter 
I know a fair amount of stuff on speakers and audio and such, but I was just inquiring about this.


I was in a makeshift studio today working in pro tools. I added the "signal generator" insert and fooled around with it.

When I put the "wave type" to square, and when i oscillated the frequency up and down around 20-70hz, the tweeter would make a few REALLY loud pops, like the tweeter was exploding.

Is this normal when oscillating, or was the speaker getting destroyed?
Hopefully it makes sense, thanks for any thoughts or insight.
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post #2 of 14
3/7/08 at 4:55pm
Ummm... yes it can be very harmful.

You are going from positive voltage to NO voltage. It is just like being yanked violently!
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post #3 of 14
3/7/08 at 4:57pm
You're simulating clipping. The top of the square wave is a constant DC voltage. Not the normal sine wave from audio.


Yes the speaker was being destroyed.


Mitch
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post #4 of 14
3/7/08 at 5:28pm
At 20-70 Hz, it probably wasn't the tweeter being destroyed. It was whatever driver is doing bass.
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post #5 of 14
3/7/08 at 6:20pm
Quote:
Originally Posted by guzziguy View Post
At 20-70 Hz, it probably wasn't the tweeter being destroyed. It was whatever driver is doing bass.
square waves WILL destroy a tweeter.

the leading and trailing edges of the wave appear to be a very high frequency signal to the crossover to the tweeter, so it "opens" and allows signal through. by the time the crossover "closes" the flat-top of the wave is sneaking through and your tweeter goes "poof."

bigg drivers for bass are generally much more robust than tweeters. as long as the maximum power handling is not exceeded I would only worry a little about the bass drivers.
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post #6 of 14
3/7/08 at 6:31pm
Even if your speaker can handle a bit of a square wave, it will overheat the voice coil eventually. You get heat with the movement, and it often doesn't take much for that to destroy a speaker.
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post #7 of 14
3/7/08 at 6:35pm
Basically, you're feeding it DC voltage instead of AC, which is a VERY bad thing for speakers so I wouldn't try it again.
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post #8 of 14
3/7/08 at 6:49pm
Thread Starter 
im glad I decided it was a bad idea after the first pop and started a thread. So theoretically if someone made a CD (uhh U2 for example) and as a prank one of the tracks had a huge assortment of oscillating square waves going from a good deal of current to no current, it would heavily damage all the speakers of those who listened to it?
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post #9 of 14
3/7/08 at 7:23pm
Quote:
Originally Posted by sackynut View Post
im glad I decided it was a bad idea after the first pop and started a thread. So theoretically if someone made a CD (uhh U2 for example) and as a prank one of the tracks had a huge assortment of oscillating square waves going from a good deal of current to no current, it would heavily damage all the speakers of those who listened to it?
If they had headphones on it could make their head implode. Not funny.
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post #10 of 14
3/7/08 at 7:38pm
Quote:
Originally Posted by sackynut View Post
im glad I decided it was a bad idea after the first pop and started a thread. So theoretically if someone made a CD (uhh U2 for example) and as a prank one of the tracks had a huge assortment of oscillating square waves going from a good deal of current to no current, it would heavily damage all the speakers of those who listened to it?
Theoretically, yes.

Realistically, who knows? It's very easy to write a program that outputs a square wave that jumps from maxmum to minimum amplitude constantly. A friend of mine has done this, actually, with several overlaid square waves. And burned a CD.

It behaves differently on different cd players, oddly enough. and of course speakers aren't getting maximum amplitude unless you turn it up, and some systems strip out some of the audio as clipping.
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post #11 of 14
3/7/08 at 10:09pm
The reason the tweeter is popping is because when a square wave of 20-70Hz is fed to a multi-driver speaker, the tweeter will only see an impulse. In most good multi-way speakers (certainly in a studio), the tweeter will usually not see any DC input due to good crossover design.

My studio monitors get fed square waves all week and have never had any issues. As long as the volume is kept within reason, there won't be any problems, regardless of what signal your software produces. In all likelihood your soundcard will filter it before it even reaches the crossover.
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post #12 of 14
3/7/08 at 11:08pm
Quote:
Originally Posted by b0dhi View Post
My studio monitors get fed square waves all week and have never had any issues.
Just out of curiosity, what do you do?
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post #13 of 14
3/7/08 at 11:49pm
I produce various electronica (and chiptunes, hence the abundance of square waves).
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post #14 of 14
3/8/08 at 12:02am
I just generated a 70Hz square in Adobe Audition and I don't hear anything out of the ordinary. As b0dhi says there is nothing inherently dangerous about square waves if you have sanely designed equipment.
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