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Can't blow a speaker by under powering it.......

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#81
makohund said:
I thought the question itself was answered fully by the second post. The third was really awesome though, by adding "why the question gets asked" in the first place.
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The premise is "underpowering a speaker CAN (or can't) blow a speaker", not "underpowering a speaker WILL blow a speaker."

Post #2 uses facts to show the latter is incorrect (which it obviously is). Post #3 addresses the former which is a much different statement.
 
#83
mech said:
Can anyone show me that there is no DC component to the two waveforms in this pic or that a speaker will act other than described? This is a decent 100Hz square wave on the top with over 99% DC duration and a clipped 100Hz sine wave with about 50% DC duration on the bottom.
ClippedSinewave_zps368e3422.jpg


mech
Click to expand...
I suppose this is after the fact, but HOW do you get that bottom output by simply clipping a sine wave? Until I read the text, I assumed the bottom waveform was just a cap charge/discharge circuit.
 
#84
This usually gets a lot of traction. What I would do is go talk to your local tech and ask him.

If you want a chance to watch people engage in some of the most useless digging in to their positions. If you want to see a great display of Non Sequiters, cannards, and sopholism you have hit the right button.

I suggest you self learn about things like OHMs law. And what happens when an AC current tends towards DC. Which happens during clipping.

You'll learn more opening abook about this subject than reading these posts.

As far as it being true? Please.

two fingers said:
Wait! No flames! I get it. I just can't explain it.

I was talking to a friend earlier and he was throwing the old conventional "wisdom" at me about blowing a speaker by under powering it. And I have seen posts on this forum dozens of times that say it isn't true. But I couldn't explain to him WHY it isn't true. Now I am only a few month into an electronics degree. I understand some terminology but not the most complex (and he is about the same). Help me explain this in the simplest terms you can come up with other than "It's true so shut up."

Please and thank you.

(builds fort to block many sharp objects being hurled in his direction currently)
:hiding:
Click to expand...
 
#85
Well I would not say I am an expert on speakers and amps, but in my car I have a 25 watt stereo system. I put speakers in it that are rated at 150 watts. Now I am not saying that I am not burning them up but after 10 years they sound like brand new and just keep playing. I think that is under powering them. Oh by the way the stereo itself is also 10 years old and it doesn't seem that the higher wattage speakers have pulled enough power through the amp to burn it up either.
 
#86
mech said:
Are you saying a DC voltage will not make a speaker move and stay in that position? If so hook up a 12 VDC car battery to a speaker, leave it for a while and see if the coil doesn't get hot or burn open, depending on the ratings of the speaker.

mech
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But the current available from the amplifier has to be sufficient to damage the speaker. You wouldn't need to "leave it for a while" because a while will be far more than what's needed. A car battery will kill a speaker damn near instantaneously and I have seen speakers that were "tested", by being connected to a car battery. There are very few amplifiers that will kill a speaker that fast, but some will definitely drive high current loads.
 
#88
i feel a little sheepish jumping in here, but my understanding is that a square wave that had long enough "tops" to actually hold a speaker still at the end of its travel would by definition be one that was way too low a frequency for the cab the speaker was in, thus blowing the speaker by overexcursion.

so it's still just too much power and/or too low a frequency that blows speakers, regardless of the shape of the waveform.
 
#89
1958Bassman said:
But high frequency clipped signal is close enough for government work. Still not DC but it will heat up the voice coil.
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Any signal will.

>90% of the power into a loudspeaker converts to heat instead of acoustic energy. If the transducer doesn't reproduce the signal, that becomes 100%. There's not a big difference.
 
#90
CL400Peavey said:
Mech the point is, what you have pictured is not what the speaker is really doing.There is some level of acceleration where the driver has to slow down and move the other direction. Its not really stationary.
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Any time period where there's no change in amplitude, it's staying in one place and that clipped sine wave shows that the amplitude doesn't change after it leaves the curve.
 
#91
Baer said:
The premise is "underpowering a speaker CAN (or can't) blow a speaker", not "underpowering a speaker WILL blow a speaker."

Post #2 uses facts to show the latter is incorrect (which it obviously is). Post #3 addresses the former which is a much different statement.
Click to expand...

Ah, very nice. Broken down that way, I must agree, and happily concede. :cool:
 
#92
1958Bassman said:
A car battery will kill a speaker damn near instantaneously and I have seen speakers that were "tested", by being connected to a car battery.
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A 12V car battery (or other 12V DC source) will dissipate about 25 to 28 watts in a typical 8Ω driver. That could kill a low-power loudspeaker or a mid/high-frequency driver but probably not a typical one used in a bass rig.
 
#93
1958Bassman said:
Any time period where there's no change in amplitude, it's staying in one place and that clipped sine wave shows that the amplitude doesn't change after it leaves the curve.
Click to expand...

No, it's not. The little flat top is a constant acceleration, not a "staying in place."
 
#94
1958Bassman said:
Any time period where there's no change in amplitude, it's staying in one place and that clipped sine wave shows that the amplitude doesn't change after it leaves the curve.
Click to expand...
the voltage may be staying in one place, but the speaker is still zooming along trying to get to the spot the voltage is demanding it go, pushing air the whole way; unless the frequency is too low for the cab, that voltage will flip the other way well before the speaker ever gets there.

(edit: or, whut bob sez)
 
#96
To the OP:

As is noted, this is a much debated question. But realize many of these responses are addressing two different questions.

"Can a speaker be blown because of underpowering it?"

"Will a speaker be blown because of underpowering it?"

If there is ONE situation where this CAN happen despite MANY situations where is DOESN'T happen, the answer to the first question is yes and the answer to the second question is no.

As the minority points out, there are situations (see Post #3) where speakers have been blown because of underpowering them. As the majority points out, there are many examples where underpowering does not blow a speaker.

It's like asking the following ...

"Can a person have an accident if he is driving too slowly?"

... and then getting lots of people telling you "Hey, I drive slowly all the time without having accidents. So no, you can't have an accident if you are driving too slowly."

It's incorrect logic.

Think about it. It can happen. Then realize that even though it can happen, the odds are very high that it won't happen.
 
#97
Even if the speaker DID move perfectly, and "stayed in one place" for each half period of a 20Hz square wave, it would only be in one position for 25ms. If you can overheat a speaker within 50ms under normal operating voltage, it seems like a pretty crappy speaker.
 
#99
Baer said:
As the minority points out, there are situations (see Post #3) where speakers have been blown because of underpowering them. As the majority points out, there are many examples where underpowering does not blow a speaker.
Click to expand...

Here's the thing- even in post number 3, the speaker is blown because it received too much power. The overpowering is caused by clipping of the amp. The fact that the amp is clipping is only due to the fact that it is operating beyond its capabilities, and has nothing to do with the fact that the amp is rated for a lower voltage than the cab.

To say that you can under power a cab, you must give a circumstance where a higher wattage cabinet will fail but a lower wattage cabinet would survive. Otherwise, the cabinet failure is NOT due to"under powering".
 
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