Burning up subwoofers what to do??? - AVS Forum
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post #1 of 13 Old 03-25-2009, 12:19 AM - Thread Starter
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I own a 2006 Ford F-150 supercrew. I bought a pioneer 12" shallow mount subwoofer and a sealed box for my truck dimensions 51"long 16"wide 6"deep. I keep burning out subs this will be my second 12" pioneer that has went out. No signs of the subwoofers going out they just stop working. I have a 800watt Phoenix Gold monoblock amp. I only use one subwoofer in my truck and the box is seperated half way so that each subwoofer has its own space. My concern is that there is not enough air space which is making my subwoofer overheat and go out.The subwoofer is rated for 250watt min and 1200watt max . Im looking for any help or advice on what i can do to stop burning out my subs. Whether it may be modifications to my box or a different type of subwoofer. Ive looked for help many other places with no results so maybe someone can help me out. Thank you
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post #2 of 13 Old 03-25-2009, 09:57 AM
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Without seeing your setup in person and checking your wiring and what settings you have on your amp it would be difficult to pinpoint one exact problem. You might be better off taking t by your local car audio dealer and asking them to have a look. Maybe take it to two places to see if they give you the same answer. They won't charge you to have a quick look at it.
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post #3 of 13 Old 03-25-2009, 03:00 PM
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With a sealed sub, you won't be able to smell the fried electronics, however, check for any air leaks anyway. Check even more carefully around the screws and speaker mounting area. When cranking the bass and checking for air leaks, there will be some turbulence from the woofer moving, so it can be a bit hard to find the small leaks around the screws.

When you install the new drivers, consider putting 1/16" weather strip (closed cell foam available at Home Depot) or a thin layer of Mortite behind the speaker to seal the mount area. It'll become a tight fit and should be a good fight to make it airtight.

Your speakers are 250watts. The 1200 max is a ridiculous up and over the ballpark and into the parking lot estimate of how much power it'll take for fry it. It sounds like your bumping the power up since there isn't enough bass. You may also be using some bass boost, which will certainly fry speakers, especially with a good beefy amp that can push real quality wattage up high. Try undoing any bass boost, set your x-over a little lower, and adjust your gains accordingly.

If the bass is still less than spectacular... then it's time to find new drivers. Find ones that are designed for the cubic footage of your enclosure. Plug the T/S parameters into the free WinISD program and have it help you decide which is best.

I'm running a small sub, 8" in a relatively smallish box ~.3 cu/ft in a very, very tiny open car, but with the help of WinISD, found the best 8" (surprizing cheap $60 JBLs) that many think is a much, much larger sub.

Best of luck.
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post #4 of 13 Old 03-25-2009, 04:29 PM
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Are you over driving the amp?

Nothing burns ANY speaker faster than overdriving and clipping the amp. When a sound wave gets clipped due to overdriving then the speaker coil must endure MAX voltage/current for the entire time that wave is clipped.... enduring a CONSTANT voltage/current even for short periods of time is not something that speaker coils are designed to do.
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post #5 of 13 Old 03-25-2009, 10:56 PM
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If your voice coil is burning up, then you are sending it too much power. The solution? Send it less power. Try to match up an amplifier that has a similar RMS output rating to the subs RMS rating. Ignore the other power ratings as they are completely useless. And as mentioned earlier, make sure the gains are set correctly.

The enclosure has more of an effect on the mechanical power handing of a sub, not the thermal power handling. You can definitely try another sub with a higher power handling. Go big enough and you could potentially run the amp fully clipped without worry of blowing the sub.
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post #6 of 13 Old 03-26-2009, 06:13 AM
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Steven is right, blown sub = too much power. How did you initially set your gains on your amp (oscilloscope, DMM, etc.)? Have you adjusted them since the original setting?

Quote:
Originally Posted by Steven Kephart View Post

you could potentially run the amp fully clipped without worry of blowing the sub.

You like bringing this debate up, huh?

Actually, I appreciate the info you passed along the last time this argument came up. I learned a lot, but I found even more info after scouring the internet trying to prove that too little power could blow a speaker (which I was obviously incapable of doing). Thanks again!
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post #7 of 13 Old 04-08-2009, 05:00 PM
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Quote:
Originally Posted by applebonker View Post

Steven is right, blown sub = too much power. How did you initially set your gains on your amp (oscilloscope, DMM, etc.)? Have you adjusted them since the original setting?



You like bringing this debate up, huh?

Actually, I appreciate the info you passed along the last time this argument came up. I learned a lot, but I found even more info after scouring the internet trying to prove that too little power could blow a speaker (which I was obviously incapable of doing). Thanks again!

If your sub is rated for 250W RMS and your mono amp is rated @ 800W then you are overdriving your sub. You would be suprised at how much power amps can deliver to a sub even @ 300-400W RMS. Lets assume your RMS rating is overrated for your sub in real world. This could decrease it's power handling capacity under 60HZ down to 120-180W RMS. Couple that with an amp that does at least 400RMS @ 12v, then you should either reduce your gains or buy 2 subs instead of 1 to match with your amps power.
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post #8 of 13 Old 04-09-2009, 12:09 AM
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Also, if you set the gain too high to the point of clipping you will blow almost any speaker regardless of how little power the amp is producing. The duty cycle of a clipped signal is huge and creates a ton of heat
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post #9 of 13 Old 04-10-2009, 08:06 AM
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Quote:
Originally Posted by DblHelix View Post

Also, if you set the gain too high to the point of clipping you will blow almost any speaker regardless of how little power the amp is producing. The duty cycle of a clipped signal is huge and creates a ton of heat

Not true. If the power output of the amplifier even fully clipped is below the power handling of the speaker then the speaker will be fine. A speaker doesn't care what kind of signal it gets just as long as it doesn't exceed it's power handling capabilities.

I've actually demonstrated this in the past. I hooked up the smallest Alpine amplifier we had to a JL W7. I turned up the gain, bass boost, etc. and turned the head unit to it's max and let it run for a while. It sounded horrible because of the head unit and amplifier were clipping the signal, but the sub handled it without a problem.
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post #10 of 13 Old 04-11-2009, 09:42 PM
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Quote:
Originally Posted by Steven Kephart View Post

Not true. If the power output of the amplifier even fully clipped is below the power handling of the speaker then the speaker will be fine. A speaker doesn't care what kind of signal it gets just as long as it doesn't exceed it's power handling capabilities.

Actually, that is not true, it doesnt matter what the power output of an amp is, or what the rated power of a speaker is, if you are clipping your amp, then you are sending DC current through your voice coil, and DC generates heat faster than huge amounts of clean audio waveform. Heat will result in a early voice coil failure.

Did both subs blow the same way? If you take them out of the box, can you move them in an out smoothly with your fingers, or do they feel like they are seized up or scratchy when you try to move the cone? If they are scratchy or seized, then you may have sent too much power to them and the voice coils got so hot they swelled. If they just feel loose like a normal new speaker, you should have the system checked out by a pro to see why they are blowing. You may have just got 2 bad subs, there is less quality control these days as all this stuff is built by robots.
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post #11 of 13 Old 04-11-2009, 11:55 PM
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Quote:
Originally Posted by Warren_G View Post

Actually, that is not true, it doesnt matter what the power output of an amp is, or what the rated power of a speaker is, if you are clipping your amp, then you are sending DC current through your voice coil, and DC generates heat faster than huge amounts of clean audio waveform. Heat will result in a early voice coil failure.

Maybe in an extremely rare case that could happen where you have a square wave at an extremely low frequency applied for a very long time. And even in this case the power level would matter. What you must understand about a speaker is it is a constant acceleration device. What that means is that it is always accelerating or decelerating as long as a signal is applied. This is true even in a square wave where the cones motion would be held in place only for a microsecond.

Or maybe you can explain why the JL sub was just fine after my experiment? After all by your account it should have been toasted.

Also note that I never said anything about rated power. I'm talking about actual power handling of the driver within the system.

If you don't believe me, all this has been discussed at length in these threads:
http://www.the12volt.com/installbay/...TID~74226~PN~1

http://www.audiogroupforum.com/csfor...clipping+blown
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post #12 of 13 Old 04-12-2009, 01:42 PM
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I could not explain why one sub in one experiment did what it did. I can tell you that I installed car audio professionally for over a decade, and I have seen many blown subs for many reasons. Usually it was the customer playing with the gains after leaving the shop.

Subs will blow in one of three ways; open voice coil, fused or swelled voice coil, or mechanical damage, which can include torn spiders, voice coils that have jumped the gap, etc.

An open voice coil can happen from too much or too little power, or just bad luck. A loud bass beat or even a bump in the road can cause a voice coil connection to fail at a terminal, or where the lead in wires meet the cone, or anywhere in the electrical path. It is not always someone's or something's fault.

A swelled voice coil means it got too hot, this can be from sending far too much power through it, but is more common from sending clipping/distortion/DC through it, and this is most common from too little power. Once again, forget rated power because a speaker's power handling depends on many things, including its enclosure, the type of signal being sent to it, crossover points, etc.

If a sub is pushed so hard that the voice coils hits the bottom, or actually jumps out of the magnetic gap, that is from too much power, but I would say that it should not come as a surprise to anyone because it would have been so loud and so distorted that they should have heard the damage coming.

To use an example, my $39 POS 10" sub has been running on an 800W RMS amp in my vehicle, and it is on its 4th year without a problem. A rule of thumb I used when installing and setting up car audio systems was that if you can hear distortion, you are doing harm to your speakers, and you can hear much more distortion with too little power. If you want to see how quickly DC can end a speakers life, you can hook up a 4 ohm sub to 36 watts of DC by connecting it across a car battery terminals. Dont try this unless you are planning to throw the speaker away, cuz it will be dead very quickly.
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post #13 of 13 Old 04-12-2009, 03:22 PM
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Quote:
Originally Posted by Warren_G View Post


An open voice coil can happen from...... too little power

That is absolutely untrue. Try reading the links I posted and you will see insurmountable evidence to the contrary.

Quote:
Originally Posted by Warren_G View Post

A loud bass beat or even a bump in the road can cause a voice coil connection to fail at a terminal, or where the lead in wires meet the cone, or anywhere in the electrical path. It is not always someone's or something's fault.

What you describe here is when the mechanical power handling of the sub is exceeded. This is greatly influenced by the enclosure. And this happens when the mechanical power handling of the sub is exceeded.

Quote:
Originally Posted by Warren_G View Post

A swelled voice coil means it got too hot, this can be from sending far too much power through it, but is more common from sending clipping/distortion/DC through it, and this is most common from too little power. Once again, forget rated power because a speaker's power handling depends on many things, including its enclosure, the type of signal being sent to it, crossover points, etc.

Exactly why I never used the term "rated power handling". But again the swelling of a kapton former is due to too much heat caused by too much power. It never happens by too little power. A speaker doesn't care what kind of signal it receives whether highly distorted, too low power, horribly clipped, or even extremely short term DC as long as the power levels don't exceed it's thermal or mechanical limits. Again, read the links to see this explained in detail.

Quote:
Originally Posted by Warren_G View Post

and you can hear much more distortion with too little power.

That makes absolutely no sense. If you have two subs playing the same signal at the same level off the same amount of power, but one sub can handle more power (as in it has "too little power" applied to it), why would you hear "much more distortion"?



Quote:
Originally Posted by Warren_G View Post

If you want to see how quickly DC can end a speakers life, you can hook up a 4 ohm sub to 36 watts of DC by connecting it across a car battery terminals. Dont try this unless you are planning to throw the speaker away, cuz it will be dead very quickly.

Your above example isn't a representation of what happens with a clipped signal. You keep ignoring my explanations on what really happens with a clipped signal. Even in the most extreme case (square wave at a very low frequency) the cone is held in place only for a microsecond before the polarity changes.

Here's some excerpts from the links I posted:

"Too much power is the ONLY thing that will destroy a well built speaker. Too high a peak power can cause it to move too far, and cause mechanical failure. Too much RMS power for too long will cause thermal failure.

A clipped signal will not damage any speaker, if it is at a level low enough so that the heat can be dissipated, and it doesn't move far enough to mechanically damage it.........

As Rob said, a square wave is not made up of positive and negative DC components. The true makeup of a square wave is the fundamental frequency signal, combined with all of the harmonics of that fundamental.The combination of the many different, but related, sine waves results in a square wave."

Mark Eldridge


"The only thing that thermally damages speakers is power... more specifically: average power over time...............

The fact that a signal is clipped does not make it inherently damaging... if the average power of the clipped signal is low it won't ever damage a speaker."

Manville Smith
JL Audio


Here's another practical experiment by a speaker engineer with an impressive resume:

"I used to work in a lab where one of our main functions was testing loudspeakers (and other audio and video gear.) I have personally placed a loudspeaker in a free-air test clamp on a square wave signal (simulating a 100% clipped signal) for extended periods of time and measured the heat build-up and can tell you with certainty that as long as the thermal and mechanical limits of the speaker are not exceeded (i.e.: as long as the power input is low enough to not deliver too much energy into the VC) the speaker will play that square wave indefinitely with no damage at all. Turn up the power, and poof goes the VC."

David Yohn
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