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Overpowered/Underpowered Sub Woofers


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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.

 

It is both true and what we see in practice. Let's go back to my example and examine why I would be less than comfortable running an amp rated for 400 watts into my 700 watt rated sub under the same conditions as the little 15wpc Panasonic shelf system.

 

Let's say our 400 watt amp is capable of producing 400 watts as a pure sine wave across it's entire bandwidth. A sinewave has a crest factor of 3db, which means that the average power is half of the peak power. Running this particular amp in this fashion should pose no problem to my speaker rated at 700 watts.

 

Now we take the same amp and run it into clipping. This produces what approaches a square wave. Unlike a sine wave, a square wave has a crest factor of 0 db, which means the average power is equal to the peak power. This 400 watt amplifier is now providing power to the speaker that is identical to that of an amp that is running a clean sine wave at 800 watts. But wait! The subwoofer was rated for only 700 watts continuous power. I'm now exceeding the thermal capabilities of the speaker by 100 watts. It probably won't last long under those conditions. So am I underpowering the speaker? Is distortion killing the speaker? Is the clipping killing the speaker?

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I love this sh**. :) biz77, I don't think anyone is really disagreeing with you. The conversation is getting too technical, that's all.

 

Clipping/distortion/exceedingly high continuous power, what ever anyone wants to call it.

 

We agree that it is killing speakers and it is doing so with a small amp and higher "rated" speaker.

 

So what if audiophiles (who are not engineers) call it distortion. Thats what they hear. Distortion, and they know that lots of it kills the speaker.

 

Clipping, that's what techies call it. They know it by the distortion they hear or the dummy lights on the amp. Either way, they know it kills speakers

 

Power in a square wave form and delivered at higher than "rated" continuous amounts. If the engineers want to debate semantics, so be it. They know it kills speakers.

 

So we all agree that you can kill speaker that is "underpowered". Speakers are just motors after all. The science of it was not the original question. In the end we can all agree to disagree on what is doing it, and agree that is does happen.

 

This thread should now be moved to another forum. :lol:

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Don't try to spin it so you look semi-correct. You are confusing actual cause/effect with symptoms. The only two things that kill speakers is too much power over time and too much instantaneous power. Distortion does not kill speakers. Clipping does not kill speakers and too little power does not kill speakers. I've shown how I can provide a speaker with all of those nasty things and how it will survive indefinately through all of them. It's not semantics. It's ignorance.

 

It would be like me telling you that my friend died from a headache. As it turns out he had a brain aneurysm, but he said he had a bad headache and then within a couple of hours was dead. I'm going to say that he died from a headache because it is just semantics and that's what I want to say. Do you ever get a headache? Are you dead?

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:soap_box:

 

You are taking this WAAAAAAAYYYYYYY too far. If you walked into 99.97% of hi end car stereo and even home audio shops and asked this question they would give you the clipping/distortion story. Even if they understood the actual electrical and physical properties of what was happening. Why? Because it is good enough and why make someones head spin.

 

Not everyone wears a hat with a propeller like you. Not everyone needs to know the EXACT cause down to electrons. If your friend dies of an aneurysm is a clinical study and meeting held to explain exactly how it happened down to the molecular level? NO. So yeah if he says he has a headache and then he dies, I guess it hurt real friggin bad.

 

Get a life man. Its darn hard to melt a woofers voice coil from an underpowered amp anyways. Most of the real world examples of melted voice coils are from tweeters and mids. I might not have an engineering degree but I am pretty smart. I just don't feel the need to convince everyone else of it all the time. If you need this much mental stimulation join a MENSA forum.

 

I feel better now.

Edited by m sprank
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Just because it is written on the internet doesn't make it true;)
The RAC is not just another internet site. This is a group populated by tournament competitors, winners, etc. What's more, it's based on info from the Usenet system, which has been around far longer than web-based forums and such. These people know their stuff... and should carry far more weight than some unknown person posting on a forum. (In other words, I don't know your knowledgebase.)

 

Anyway, as others have said, this has gotten very technical. The bottom line, as msprank said is totally valid for the overall case:

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. ;)"

 

I'm happy to continue the discussion (propeller-head on this end) if you wish, but I think we are essentially saying the same thing. The only reason I harp on distortion is because you can actually hear it, whereas you cannot "hear" overheating voice coils. This is why I always underpower my subs.

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I'm happy to continue the discussion (propeller-head on this end) if you wish, but I think we are essentially saying the same thing. The only reason I harp on distortion is because you can actually hear it, whereas you cannot "hear" overheating voice coils. This is why I always underpower my subs.

 

Logical answer and an easy way to identify a problem.

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:soap_box:

 

You are taking this WAAAAAAAYYYYYYY too far. If you walked into 99.97% of hi end car stereo and even home audio shops and asked this question they would give you the clipping/distortion story. Even if they understood the actual electrical and physical properties of what was happening. Why? Because it is good enough and why make someones head spin.

 

Not everyone wears a hat with a propeller like you. Not everyone needs to know the EXACT cause down to electrons. If your friend dies of an aneurysm is a clinical study and meeting held to explain exactly how it happened down to the molecular level? NO. So yeah if he says he has a headache and then he dies, I guess it hurt real friggin bad.

 

Get a life man. Its darn hard to melt a woofers voice coil from an underpowered amp anyways. Most of the real world examples of melted voice coils are from tweeters and mids. I might not have an engineering degree but I am pretty smart. I just don't feel the need to convince everyone else of it all the time. If you need this much mental stimulation join a MENSA forum.

 

I feel better now.

 

Well m sprank, I appologize for physically dragging you into this discussion and making you participate against your will.

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Still not getting the point?

 

KISS.

 

We all get it, your smarter than everyone else and the internet.

 

 

 

For what its worth, I like more power and properly set gains. Then of course I have to refrain from the temptation to turn the volume to 11, lol. But I guess the "bigger is better" theory might just be the red blooded American in me. Its been over 15 years since I popped a woofer (even in competition). Been even longer since I popped a mid or tweet. But, from about the age of 14 to 20 I was real good at doing it.

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Still not getting the point?

 

For what its worth, I like more power and properly set gains.

 

This is the bottom line for this thread and it’s been said at least every 3rd post in one form or another.

 

Set your gains kiddies. Learn to listen to your drivers (speaker, woofer), learn to hear them reaching their mechanical limits then back off. If you do this your speakers will last a long time.

 

I still have my JL10w3 subwoofer from 12 years ago, bumping away, its been in 3 generations of Legacy's. "OVERPOWERED" by the same amp the ENTIRE time. Anecdotal? Yes. But if I go outside and push that woofer beyond its mechanical limits (by feeding it too much power: cranking the gains) I will be replacing it by the end of the month.

I'm only saying this again because beyond all the technical info and arguing, it's all you need to know. Set your gains.

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JL site re how to 'set your gain' (pdf file - download)

 

http://mobile.jlaudio.com/pdfs/gainSetting.pdf

 

Download Test Tones

http://www.ronelmm.com/tones/

http://www.eminent-tech.com/music/multimediatest.html

 

More on Clipping

http://www.bcae1.com/2ltlpwr.htm

 

What I found in SoundSolution site ...

Most audio equipment dies for one simple reason. Most people push their equipment beyond its limits. Whether it is the amplifier, subwoofer or full range speakers, clipping is the number one cause of failure. To prevent clipping, use this tutorial.

 

To figure out what voltage you should set the gains to, multiply the RMS power of the amplifiers output by the impedance of the speaker, then find the square root of that number. If you are using an amplifier that has an RMS rating of more than your speaker(s) can handle/rated for, then use the RMS rating of the speaker (instead of the RMS of the amplifier) to determine the voltage to set your amp to. This is also referred to as gaining down.

 

Gain Setting Equation

 

 

 

 

 

Voltage of the output = sqrt(RMS Power X impedance of the speaker)

 

  • Example
    Say the amp provides 100WRMS into a 4 ohm speaker:
     
    Voltage = sqrt(100W X 4 ohms)
    Voltage = sqrt(400W*ohms)
    Voltage = 20V
     
    Again, that was only an example, use the ratings of your amp to figure that out.

Setting the Gain(s)

 

 

 

 

 

To set the gain(s), you need two things:

 

  • 1. A DMM (digital multi-meter) that is capable of measuring AC voltage (needs to be able to measure up to a range of 200V).
    2. A test tone CD to use to set the gains at the correct setting.

Now, to set the gain(s):

 

  • 1. Start the vehicle, and pop the test tone CD in the head unit.
    2. DO NOT hook up the sub(s) or speaker(s) to the amplifier while doing this, just leave the outputs unused at this time.
     
     
     
     
     
    3. Now, time to set up the head unit.
    • a. If the loudest you listen to your music at on a regular basis is 22/35 with bass @ +3 and treble @ 0 with MX (or any other sound processor) on, use those settings. NEVER turn the headunit above 3/4 of the maximum volume.
      b. Remember to have the car turned on.
      c. If you want to use bass boost on a sub amp, set it prior to setting the gains on the amp and use the center frequency of the bass boost (45 Hz for most amps) as your test tone.
      d. Please remember that if you have a subwoofer volume control on the headunit and/or a bass knob for the amplifier, set it to the maximum before you set the gains on the sub amp.

    4. Take the leads from the DMM and but them on the outputs from the amp.

    5. Set the gain so that the outputs of the amplifier equal the voltage you found above. This is a MUST.

     

****************************************

I think this is an easier / more generic way to adjust your sub ...

 

If you just bought it, you'll want to break it in. From what I've been told, the gain is usually set around 2/3. Play at medium volume for 20-40 hours till they're broken in (usually takes a week or two). Then you turn your stereo up till its as loud as you'll play it and turn the gain up til you hear some sort of distortion of the sub then turn it down till it's back in control then turn it down a little more to be safe. That should ensure you keep your sub in good working order. Someone correct me on this if I'm wrong.

 

****************************************

 

More on HOW TO SET GAIN

http://www.the12volt.com/installbay/forum_posts.asp~TID~85479~PN~1

 

****************************************

 

How to Set Your Amplifier's Gain Correctly (sounddomain.com)

http://forum.sounddomain.com/ubbthreads.php/ubb/showflat/Number/65167/page/1/fpart/2

 

****************************************

 

Youtube - Car Audio Amp Tuning

[ame=http://www.youtube.com/watch?v=doWVsaU0ydI]YouTube- Car Audio Amplifier Tunning : RMS Test and Gain setting for Sub Woofer with DMM[/ame]

 

****************************************

 

Youtube - Adjust Your Gain Properly

[ame=http://www.youtube.com/watch?v=aG-KU_LYypM]YouTube- How to adjust your gain propperly[/ame]

Edited by bigdadi
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This was a good read. Its unfortunate that false information is so plentiful that when someone who does know what their talking about tries to explain things they get ridiculed.

 

It is, however, entertaining to see certain peoples responses to a technically sound argument...

You're taking two apples and trying to tell them apart by using an orange.

:lol::lol::lol:

 

The main point from this thread is: 99.999% of people on forums think they know what they're talking about. And 0.001% of people on forums who do know what they're talking about will be ridiculed by the other 99.999% following a logical and well reasoned argument.

 

Thank you for the detailed explanation, biz. Unfortunately trying to reason with an entire forum is more difficult than the many years of schooling / experience that you obviously carry under your belt.

lol
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  • 7 months later...

Some (not all) of you people have no idea what you are talking about and should understand how audio systems work before attempting to give advise. Some of the statements given are false. "running DC power to a voice coil". A speaker cone operates off of alternating current. Don't believe me? Hook up the speaker terminals to a battery and watch the cone move in only 1 direction. Next hook the terminals up to an AC wall plug(fun to do but the speaker won't last long)and you will get a 60HZ tone--50HZ overseas.

The gain control thing "just turn up/down the gain on your amplifier". The sole purpose of the gain control is to match the input level of the amplifier to the head unit's voltage pre-output. The gain control is not a volume knob. If you have a higher end head unit with a full 4 volt pre-out, then you would set the gain on the amp to 4 volts(which would mean all the way down, or close to it depending on the manufacturer). "But then it won't be loud enough" Get a bigger amp! That's what those little numbers on the gain control are there for.

As far as "blowing speakers" are concerned, someone did get it right by stating "there are only 2 ways to blow a speaker". Mechanical failure, possible yes, likely no. Most frequently the voice coil's tiny wire burns because it's thermal limit has been exceeded.

Edited by stevenva
RIP 96 Legacy 2.2 4EAT lost reverse @ 374,000 miles
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  • 3 months later...
Don't try to spin it so you look semi-correct. You are confusing actual cause/effect with symptoms. The only two things that kill speakers is too much power over time and too much instantaneous power. Distortion does not kill speakers. Clipping does not kill speakers and too little power does not kill speakers. I've shown how I can provide a speaker with all of those nasty things and how it will survive indefinately through all of them. It's not semantics. It's ignorance.

 

It would be like me telling you that my friend died from a headache. As it turns out he had a brain aneurysm, but he said he had a bad headache and then within a couple of hours was dead. I'm going to say that he died from a headache because it is just semantics and that's what I want to say. Do you ever get a headache? Are you dead?

 

I wish I was a member here when you guys started this whole debate. It sucks that I'm only getting the ass-end of it now. Hopfully this thread will stay active since I'm only 2 months since the last posting hehehehe.

 

Now to light the fire (if i can)

 

I think the main thing alot of people should do is look at how they define the state of distortion.

 

The 15wpc shelf system can not damage the 700w speaker which sounds distorted. This is because the shelf system can not overdrive the speaker beyond 700w of heat/power or even come close to it. However, overvolting the 400w amp to reach its max at 800w constantly can damage the speaker since we are exceeding the 700w rms mfg rating.

 

In both cases, you can 'hear' a form of distortion. 1 type is from overmodulated sound from the shelf system to the speaker which is not damaging. The other is mechanical malfunction of the speaker itself which is damaging.

 

Therefore, if anyone says to me that distortion damages a speaker then I have to question exactly what they are referring to when they say distortion.

Edited by OblivionLord
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