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Why subwoofers blow: slam, bang, pop, and sizzle

Too much power or distortion damages subwoofers

A blown up subwoofer

An exploded view of the parts of a speaker. This particular example is the woofer from a set of Focal component speakers. (click the image to enlarge)

In a perfect world: the music sounds great

The sine wave below represents a signal that an amplifier sends to a subwoofer as a variation in voltage over time. The vertical axis represents voltage, the horizontal axis represents time. In AC (alternating current) signals, like music, the voltage swings between positive and negative values. Point A represents the point in time when the amplifier is telling the sub's voice coil and cone to be as far forward, toward the front, as that particular voltage (+V1) tells them to be. Point B is where –V1 voltage positions them toward the rear. Traveling back and forth rapidly, the cone pushes air and makes sound — and it's musical.

Clean sine wave

Overpowering your subwoofer – Slam and Bang

First we'll cover what happens when you give your subwoofer too much power. It's great to turn it up, but that extra volume starts to distort the music. Not only does it sound bad, but it can damage your speakers and subs, especially if you do this all the time.

Slam: The incoming signal tells the cone to move too far forward

Let's say that points A and B (and +V1 and –V1) are the maximum ratings of our subwoofer. If we increase the volume of the signal, the higher voltage (+V2) now tries to move the cone even further toward the front (C). The signal is still a clean signal, but now it is trying to move the cone and voice coil much further than they were designed to go, tearing the cone, spider, and surround apart, destroying the subwoofer.

Clean loud and louder sine wave

Bang: The signal tells the coil to move too far backward

On the other side of things, when the signal (-V2) tells the voice coil to move too far toward the rear (D), the voice coil crashes into the back plate of the magnet assembly, cracking the coil and its former (the tube it coils around), and probably jamming it in the voice coil gap.

Underpowering your subwoofer — Pop and Sizzle

Underpowering a subwoofer isn’t inherently bad for the sub. Not giving it enough power just means that the music will sound weak and lack detail.

The danger is when that power is coming from an amplifier that's being overworked and sending out a clipped signal. The clipped signal tries to make the sub do things it's not designed to do, which leads to it tearing itself apart or overheating and burning out.

First, what’s a clipped signal?
Clipping a signal, or squaring its waveform, occurs when the volume of a source signal exceeds the electronic capability of a circuit. Let's say our amplifier can't play a signal more powerful than what voltage V1 can produce. If we tried to increase the volume at the source, the amplifier wouldn't produce more voltage, it would distort the signal, eventually into the form of a square wave.

Square wave distortion

Pop: A clipped signal tries to move the cone too quickly

You will notice that the sides of the clipped signal are vertical. That means that the signal will try to move the sub's cone from all the way forward (point E) to all the way to the rear (F) in zero amount of time, travelling at the speed of infinity. Nothing travels that fast, and the sub either tears itself apart trying, or the flapping cone wobbles just enough to jam the coil in the magnet's voice coil gap, killing the sub.

Sizzle: A clipped signal also tells the voice coil to hold still and heat up

The other parts of a square wave, the top and bottom, are horizontal lines that represent the times the signal is telling the cone to stay all the way forward or all the way back. Current flowing through a stationary coil only heats up the coil, which doesn't even benefit from a cooling breeze due to movement. The coil usually burns through one or more of its windings, or heats up enough to deform its shape so that it jams in the magnet's voice coil gap.

There's another, more complex reason voice coils burn when subjected to over-driven, clipped signals. A square wave carries twice the RMS power of a sine wave of the same amplitude (height). So not only is the signal telling the voice coil to pop into a position and sizzle, it's doing it with almost twice the power of the sub's maximum capacity. Usually, it's the glue holding the coil wire to the former that first melts under all the heat, and the coil crashes in its gap.

Distortion is the sub killer

Low power and low volume will not hurt a sub – but distortion will. A clipped signal is a sub's worst enemy. It isn't loudness that destroys an under-powered sub, it's trying to get bass volume by turning up a distorting signal that does it.

How to not blow your subwoofer — match the RMS power ratings

Ignore all "peak" and "maximum" wattage ratings, and use only RMS ratings. They may be harder to find, but RMS ratings are the only power ratings you should use. To safely drive a subwoofer, use an amplifier that can give it no more than its highest RMS power rating.

It's also crucial you set the amplifier's gain correctly. If you don't know how, you can check out Tuning Your Subs or Using Test Tones to Set Amplifier Gain for some helpful tips. And remember, if you want to run two or more subs, you've got to supply enough power for each and every one of them.

JL Audio W3v3 exploded view
  • Scott (Hometheaterguy) from Phoenix

    Posted on 5/4/2023

    The Basket was not mentioned, howeverthe pic of it is shown-but I guess it is self-explanatory it holds the components of a driver together. Google gave me this: "Conventional drivers use the loudspeaker basket to which all moving parts as well as the motor system are mounted. The basket is also used to mount the driver to the cabinet so that unwanted vibrations can travel freely from the driver to the cabinet and vice versa, influencing and deteriorating the speakers performance." [link removed] Loudspeaker Basket Design - Audio Physic Loudspeaker

  • Dominic T Tone from Lake Worth

    Posted on 2/23/2023

    I am having an issue with Yamaha RX-V675 receiver and a Kenwood SW-32HT subwoofer. The sub intermittenly works. The light on the back turn from red to green. Sometimes it works all day, other times it won't even produce sound. Many times, I hear a click in coming from the sub when it stops producing sound. I've tried using YPAO setup. That seemed to work for day. Then, nothing the next. I also tried adjusting the levels and again, seemed to work one day, but not the next. Any thoughts?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/23/2023

    Dominic, It sounds like a loose connection, a bad wire, or a malfunctioning subwoofer amplifier. Check the wiring first.
  • Andrew from Ham Lake

    Posted on 10/2/2022

    I have; 2 Skar audio SVR 12" subs connected to a RP1200.1 amplifier ( Subs are 800 RMS per & AMP is 1200watts @ 1ohm). The wattage is below the rated RMS when combined. Running a 4AWG wiring kit & a standard kicker LOC. at higher volume my subs make a "whack" noise (especially with low notes). Almost like hitting a pen against the cone of the woofer. This will happen regardless of installing other subwoofers so it's not the subwoofers. Can the LOC cause this? Any ideas? I checked my connections several times, I don't expect wiring issue. Please do let me know, I'd appreciate it. Ohh, car is a 2013 Kia Optima. OEM Infinity system. LOC is running off the rear deck subwoofer

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/3/2022

    Andrew, The sound you're hearing is due to clipped, square-wave signals hitting your subs. There could be many sources for this. Start with taking your signal from a full-range source, like rear speakers not the factory sub channel. Another issue may be your amplifier's gain is not set properly, allowing clipped signals to be produced at the amp's input stage.
  • Barbara Carson from Fort Collins

    Posted on 4/18/2022

    Intending to improve our home theater, last month we purchased three ELAC shelf speakers from Crutchfield: a center and a pair of stereos. Since then a low volume rumble began emitting from our Definitive sub woofer. The grumble comes and goes in a series of five to fifteen at a time. Music, news and films sound fine. However, the little rumble can be heard even with the Yamaha amp on mute. We have the gain set relatively low (~8o'clock~) and the low pass crossover is dead center. The TV volume is on but is set inaudibly low. Even though I've read this article I am not able to identify what could be wrong. Can you help?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 4/19/2022

    Barbara, A subwoofer making rumbling noises indicates a malfunctioning sub amp. If you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system.
  • Johnnie b from Temple Hills

    Posted on 4/7/2022

    Can anyone help my dc lvl5 m4 3.5 12 (3500rms) was sounding gd parked went in store came out and now its constantly popping every second with bass knob all the way down what can cause this and what can fix this issue system was connected with smd dd1 and cc1

    Commenter image

    Buck Pomerantz from Crutchfield

    on 4/7/2022

    Johnnie, That sounds like a loose connection or the sub amp malfunctioning.
  • ed from Levittown, pa

    Posted on 2/20/2022

    hi im running a brand new jvc head unit. 8 inch touch screen in a 17 chevy cruze ltz. for last year i had my system rigged up with a 10 dollar adadpter that hooked into the factory speaker harness converting signal to a rca. last week updated everything in the car. new subs, wiring, amp, headunit, appropriate wires, harnesses, relays etc. now that i have replaced my factory touch screen with the jvc aftermarket i am getting a constant thump, every 1.5 seconds through my subs. i have tried replacing the rca cables, the remote wire, re locating the ground to 3 diffrent grounds 1 of which being the battery terminal itself. speakers in the car sound amazing and have 0 issues but the sound coming to the subs its non existent. went from 2000 watt power accoustic 1500 rms mono chanel 2 ohm amp to a boss 1500 max 1000 rms 2-4 ohm dual output bridgeable to 1 chanel amp to drive these animals of subs massive kilox122's these things absolutely knocked 20 blocks away while "rigged" up but now hooked up properly im getting OOHHGATZ. broke down today and ordered a more powerful amp 3000 watt peak 2000 rms 2 ohm mono output by soundstream. but i am wondering what else to troublshoot while waiting for new amp to arrive thursday. any help is appreciated

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/21/2022

    Ed, Even without knowing exactly what system you have - there are six different options for your vehicle - "getting a constant thump every 1.5 seconds" is indicative of an ANC (automated noise control) reacting to your aftermarket sub. Disabling the ANC module will be your best option. You can find out how from your car dealer or maybe in an online forum about your vehicle.
  • Stout from Siler City

    Posted on 2/11/2022

    Can I push my (2) Kickers rated at 150 watts RMS each with an Orion Cobalt CB1500.1 amp that is 360 watts RMS at 2 ohms without any problems? I know I'll be over 60 watts over but I seen somewhere that going over the rated RMS by 15% would be ok.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/14/2022

    Stout, It seems you have the logic of this exactly backwards. Sending a subwoofer more than its rating is bad - it could get damaged and will not be warrantied.
  • Maurice from TUAKAU

    Posted on 12/6/2021

    Hi hope you can help as I cannot find any answer to this on the net! I'm using mains L - R out on my mixer to send line out signal to a PA 15 active sub woofer which ha own level control ! We Question if I use my mains out level control it raises and lowers volume through the PA to the active speakers! Can I damage the sub woofer by using the mains out level control as this raises the line out gain!

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/7/2021

    Maurice, As with any piece of gear, your subwoofer can get damaged due to abuse. You need to set the sub's volume so that when the PA is playing at its loudest, the sub is not distorting.
  • Gustavo Herrera from Mexicali

    Posted on 12/2/2021

    My subwoofer starts making a strange sound when I turn it up [thump/crack], the amp levels/gain are at minimum and it still happens. It should be noted that this problem did not happen before. my components are as follows: -Stereo without filters or effects, EQ Flat. -Amplifier. KW XR901-5 -Box: Dbox 1X10XPC -Sub-bass: JL Audio 10w3v3-4

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/2/2021

    Gustavo, Your sub may already be damaged. Playing distorted music, even with the amp gain turned down, can still burn-out a subwoofer.
  • Michael from Bellport NY

    Posted on 10/2/2021

    is a 600w RMS amp with 600w RMS subwoofer safe?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/11/2021

    Michael, Yes. That's what those ratings are for: safety.

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