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Overpowered/Underpowered Sub Woofers


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After reading some of the other posts I think I may have dove into shark invested waters. Maybe Ill slowly back out of this one before I start a shit storm all over again lol....

 

Nope, no reason to repost accurate and factual information all over again. If you want to believe the BS shoveled your way by your local "professionals" which uses metaphors that don't even apply instead of trying to understand the actual physics of it, then be my guest. As they say, ignorance is bliss and by my estimation there is an abundance of people living in their own utopia.

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So by what you've said, I can't hurt a sub rated at 400w RMS with an amp that's rated at 200w rms

 

Yes, entirely possible, but it wouldn't be from underpowering the speaker. It would be from overpowering it. Perhaps if you removed your head from where you have it placed most of the time you could see why that is the case.

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Fact is, underpowering (in and of itself) isn't bad... the problem is, most people over-drive the low-powered amp, which results in distortion, which can damage the sub.

 

On the other side, over powering a sub continuously can also damage the sub, if it's done continously. Of course, the specs on the sub are provided with a margin of safety, so 500W to a 400W sub may be ok... then again, it may not.

 

So, simplistically, "underpowering a sub is bad"... but the real reason is because of amplifier distortion when the amp is driven too hard.

 

The bottom line is, don't distort... you should be able to hear what distortion sounds like, and then make sure you're below that level, for a given amp. Beyond that, you can overpower the subwoofer's rating a bit... but I still prefer to stay at or below it - because I can hear when I'm distorting, and have the sense to turn it down before it damages the speaker.

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Fact is, underpowering (in and of itself) isn't bad... the problem is, most people over-drive the low-powered amp, which results in distortion, which can damage the sub.

 

On the other side, over powering a sub continuously can also damage the sub, if it's done continously. Of course, the specs on the sub are provided with a margin of safety, so 500W to a 400W sub may be ok... then again, it may not.

 

So, simplistically, "underpowering a sub is bad"... but the real reason is because of amplifier distortion when the amp is driven too hard.

 

The bottom line is, don't distort... you should be able to hear what distortion sounds like, and then make sure you're below that level, for a given amp. Beyond that, you can overpower the subwoofer's rating a bit... but I still prefer to stay at or below it - because I can hear when I'm distorting, and have the sense to turn it down before it damages the speaker.

 

 

Totally wrong. Distortion doesn't kill speakers. The only two things that can destroy a speaker is too much instantaneous power or too much power over time. If distortion kills speakers, how do guitar amps survive? They are full of distortion.

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Guitar amps survive because they are amps. The drivers attached to those amps blow all the time.

 

It's wonderful that you can copy and paste from Msmith, but what you've posted really doesn't have anything to do with most of this thread... except for what you've brought to it. You can't even read my posts right to make a proper response.

Edited by mwiener2

(Updated 8/22/17)

2005 Outback FMT

Running on Electrons

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So by what you've said, I can't hurt a sub rated at 400w RMS with an amp that's rated at 200w rms

 

Why is that so hard to believe? Your hypothetical 400wrms subwoofer can dissipate the heat from a 400wrms signal, and it has the excursion to handle a 400wrms signal... so why do you think a 200wrms signal is going to exceed any of that sub's limits?

 

If you blow a 400wrms sub with a 200wrms amp, then it wasn't a 400wrms sub, and/or it wasn't a 200wrms amp.

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Wow. Finally some fireworks.

 

I have to admit that Mike and I don't always see eye to eye on electronics/stereo set ups.

 

But....

 

He is 100% correct in this matter.

 

Amps too weak for the amount of volume requested by the user will keep trying to drive to the point of clipping/distortion. This distortion being fed to the speaker will cause the motor windings to overheat. If nothing else you take the chance of melting some adhesive or copper and causing a loose voice coil wire (sounds like scratching as the cone moves). At worst you will completely melt the voice coil and seize the motor. Speakers are electronic motors driving a cone to reproduce sound. Too much power can over heat them, too much dirty power (small amps pushed too hard) is just as dangerous.

 

IMHO, I prefer more power than needed, used at safe levels. I currently push 750 watts continuous into each of my 10w6V2's. They are rated at 600 max. The warranty is void. I am not worried. I know how hard I can push them, I can hear distortion. As long as I don't over drive them for too long they are fine.

 

More Power, proper set up and balance, learn how to listen, learn how to use the volume knob.

 

 

And I admit that is much harder to melt down a woofer than a small 1/2" tweeter with distorted power from an overworked amp. But, I too have voice coils for reference and lots of large magnets from the backs of blown woofers that were driven with cheap crap overrated amps.

Edited by m sprank
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M sprank, Both "sides" have correct info. "distortion" in this case is the "200w" amp providing more than 200w. The amp rating is NOT the max distorted power output. The rating is the max undistorted power output! The distance from there to the voltage rails is unknown from a basic data sheet, and in addition one distortion starts occurring, if you look at the power curve of the waveform, you're going up in power significantly. 20v peak to peak sine wave contains less power than a 20v peak to peak square wave.

 

Bottom line, unless the sub is rated for more than the total (nondisclosed distorted) power output of the amp, you can overheat and melt the voice coils. (This statement assumes no margin on the rating, which with reputable brands, such as Msmith's JL Audio, will have.)

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Bottom line is both work, both could be dangerous. Heck even a manufacturer recommended pairing of amps and speakers could be pushed to meltdown. Anything and everything is breakable. Nothing is indestructible. Forget who is "right" about the electrical engineering side of things and just be practical. :)

 

You CAN do either. You WILL be fine. Just use common sense with the gains and volume knob. ;)

 

Now if anyone needs to get out that pent up frustration, I am willing to build an 8 foot high 12 foot chain link cage in my back yard for you to settle your differences. I will even split the video rights with you. :spin:

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Just because it is written on the internet doesn't make it true;)

 

The ONLY two things that can kill a speaker are too much power over time and too much instantaneous power. Period. End of story. No further exlpanation needed.

 

It is very easy for me to disprove any of these myths in this thread with real World experiments with items I have sitting at my house or work.

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biz77, I did notice that the link pretty much agrees with what you said...

 

This is absolutely false:

 

"5.21 What's worse for a speaker, too much or too little power? [iDB]

Problems occur (in everyday operation) when distortion is fed to a speaker. This occurs MUCH more often when you are dealing with an underpowered system -- typically the owner will turn up the volume too much or set the amplifier gains too high to try and get more volume from the system. These introduce distortion to the signal -- this will destroy *any* speaker. (See section 5.22 Why is distortion harmful to my speakers? [RK].) "

 

The explanation beyond this is okay, but the statement that distortion kills speakers is absolutely untrue:

 

I can take an old Panasonic shelf system I have sitting at home rated for ~ 15 watts per channel and hook one channel up to the subwoofer system I use in the car - a single Polk Audio SR124 subwoofer. It is rated for 700wrms and 1,400 watts peak per the manufacturer. I can then crank that 15 wpc Panasonic shelf system up so that it is clipping non-stop with very audible distortion. I will be able to do this indefinately and that speaker will not be harmed. The speaker has more than enough thermal capacity to dissipate the power that is being fed to it. Furthermore it can only reproduce the signal that it is fed. It doesn't know the difference between a clean signal, a distorted signal and a clipped signal. That right there disproves that "distortion kills speakers" and also that "clipping your amp kills speakers."

 

So now the question becomes would I be comfortable performing the same test with a decent quality 400 watt rated amplifier? No I would not. Now who knows why I wouldn't?

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Amps too weak for the amount of volume requested by the user will keep trying to drive to the point of clipping/distortion. This distortion being fed to the speaker will cause the motor windings to overheat.

 

Why do you believe that 200 watts from an amp will create more heat than a 400-watt subwoofer can handle? An honest subwoofer manufacturer will not rate their subwoofers with a number higher than the amount of power (read as: heat) that the subwoofer can dissipate. It doesn't matter if the signal is a sine wave or a square wave, a signal at a given amount of power will create a proportional amount of heat.

 

I still believe that if you kill a 400w sub with a 200w amp, it wasn't a 400w sub or it wasn't a 200w amp.

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NSFW, ratings are ratings, and a "200w" amp is a 200w amp at a certain frequency creating a sine wave. That does not say what the "200w" amp can do if over driven.

 

The case biz77 states is true, but that isn't what we see in practice. In practice, the underpowered sub woofer is over driven by an amp that is capable of distorted power higher than the rated power of the sub or the undistorted rated power. This is done because the user wants more volume, and just turns things up.

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