Out of nowhere, your subwoofer starts to play at the low end or even too loud. Sometimes it will produce scratchy sounds and distorted vibrations. Many subwoofer owners begin to wonder how to tell if a subwoofer is damaged. It is easy to recognize physical damage on a subwoofer, but interior damage is hard to realize.
When a subwoofer blows is when interior damages happen. Too much power is the leading cause of blown subwoofers. Moreover, many distorted signals or clipped signals can also damage a subwoofer. This article has comprehensive information on how to tell if a subwoofer is damaged. These methods are trial and error until you find the source of the damage.
How Do You Tell If a Subwoofer Is Damaged?
1. Do a Sound Test
A good sound test is the first and best way to tell if a subwoofer is damaged. And the sound test will tell you if the subwoofer is wholly damaged or partially damaged. With the sound test, you will get several results, indicating the degree of damage. Here are some of the main results from a tough sound test.
a) No sound
This indicates that the subwoofer is fully damaged. But before you run to that conclusion, ensure the audio cables are connected well and in perfect condition. Also, check the audio source; maybe it is not working or corrupted. It is good to do the sound test using the radio side of the subwoofer.
b) Partial sound
This is a clear sign that your subwoofer is partially damaged. Sometimes the partial sound can have some distortions and weak vibrations. You can also receive some scratching sounds at any volume; you have to look at the cone.
2. Do a Cone Test
A cone is built to move freely because of the suspension technique. Remove the protective screen over the cone and place your two hands on the cone; apply slight pressure. By doing so, you might get one of the three results below.
No movement: This clearly shows that your subwoofer is completely damaged. And most likely, the subwoofer is blown.
Wobbly cone: this is when the cone is too weak and irregularly moves around. This means the suspension technique is not working hence not doing the intended purpose.
Scratching sound: try to move the cone with your hands; if you get some scratching sound, the whole cone is damaged. In such a case, the cone needs replacement.
3. Do a Voice Coil Test
A voice coil is a tube with winding wires attached to the cone. It is the part that generates the motive force for the cone. The motive force is released when the current passes and causes a reaction with the magnetic field around. A voice coil has positive and negative ends and can easily blow.
You need a multimeter to test if the voice coil is damaged. This device measures the electric resistance, and a good voice coil should have a resistance of above 1.0 ohm. The reading must be steady on one figure; the voice coil is damaged if it shifts abruptly, changing figures. And no resistance result is the clearest indicator of a damaged voice coil.
Some subwoofers have two voice coils; in this situation, measure the resistance separately for each voice coil. Here is the procedure for using the multimeter on the voice coil.
Step #1. Unplug the subwoofer from the power and disconnect all audio cables and input from the subwoofer.
Step #2. Remove the woofer from its enclosure and identify the voice coil attached to the cone.
Step #3. Turn on the multimeter and connect the red probe to the coil’s positive terminal and the black probe to the negative terminal of the voice coil.
Step #4. Immediately the multimeter will measure the level of electric resistance.
Leading Causes of Subwoofer Damage
1. Clipped or Distorted Signals
All subwoofers have the maximum output rating. And clipping occurs when you push the amplifier over the recommended output voltage. This signal distortion will make the subwoofer deliver above its capability. An average signal is supposed to be in the waveform, but a clipped one is flat at the top.
The clipped signal will make the voice coil overheat, and eventually, the adhesive on the coil will melt, and the whole voice coil will expand. When the coil grows, it detaches from the tube. Sometimes it will produce some gasses and bubbles around the tube, and you will get some rattling sound.
Ensure you know the signal’s voltage from the audio source, and you will avoid clipping. Identify the source of the distorted signal and level up the amp for better signals.
2. Overpowering the Subwoofer
Your subwoofer can be playing with unclipped signals, but they are too high than it can handle. This is now overpowering the subwoofer. It will lead to physical damage like tearing the cone and detaching the voice coil from the cone most of the time. Make sure you note the RMS of the subwoofer to avoid overpowering it.
DIY Repair Of Stuck Voice Coil and a Tear
A Stuck Voice Coil
Step 1. Gently press on the cone and see if the voice coil moves back into position.
Step 2. If the coil does not move back, ensure the wires are still in place and try again to push it into position.
Step 3. Lastly, push both sides of the con, and the coil will readjust itself. And test the speaker before screwing it back in place.
Step 1. Take a paper towel and cut a perfect piece that fits the tear size. The piece should be average size, enough to cover the tear but not too big. Cut two pieces of paper towel.
Step 2. Apply Elmer’s glue on one piece of paper towel and patch it on the torn part. Apply the same glue and patch it on the other side of the tear.
Step 3. Use a flat tool like a butter knife to press the pieces on the tear so that they are firmly attached.
How To Repair a Damaged Voice Coil In a Subwoofer
You can repair the voice coil after measuring the multimeter’s electric resistance and ascertaining that it is damaged. You can buy a new voice coil from a retail store but save that money and repair it with simple tools and short steps. Use the following steps to have your damaged voice coil working again.
– Copper wire (insulated)
– Conduct adhesive
– Masking tape
– Clean cloth
– Epoxy resin (slow-drying)
– Wooden sticks or pencils
– X-ray films
– Heat gun
– Winding machine
– Aluminum foil
– A tube with the same size as your voice coil
Place the tube on the winding machine and wrap the X-ray film on it. The X-ray film will help you when you want to remove the aluminum foil.
Use a measuring tape or ruler to measure the width of the lousy voice coil. Then cut an aluminum foil with the exact measurements but give an allowance of 2mm.
Use the thin wooden sticks to bend the aluminum foil, make sure the silver or shinny part faces inwards. Then wrap the curved aluminum foil on the tube and tape it down.
Prepare the epoxy resin on a small plate and add epoxy solvent for a perfect solution. Then apply the epoxy resin over the aluminum foil, make sure it covers the whole foil before you start winding the copper wire. Make the first layer of winding copper wire and leave an allowance at the beginning.
Start using the winding machine after the first layer of copper wire. Also, apply the epoxy resin after every layer. The device will ensure perfect turns and no spaces in between the layers. The second layer also should have a protruding wire like the first one.
Give the whole system 24 hours to dry or use a heat gun to accelerate the drying process. Use a piece of cloth to remove bubbles as the system dries up.
Use sandpaper or a lighter to remove the insulation on the two protruding wires. The wire for the first layer is positive, while the second layer is negative. You can confirm this using a digital voltmeter.
With the help of the X-ray films, remove the new voice coil from the tube. And measure the size of the voice coil collar, apply the adhesive contact on that surface, and allow it to dry.
Apply solder on the two terminals and weld them respectively. Use a cell battery to test the new voice coil. A perfect voice coil will move upwards when you connect positive to positive and negative to negative.
When you confirm the voice coil is working, then reassemble the whole system back together, and your subwoofer will be up and loud again.
Care and Maintenance Tips For Subwoofers
1. Place It at a Strategic Position
Do not place your subwoofer in an enclosed space or directly in front of a wall. Sound vibrations are powerful energy and can quickly bounce back to destroy the cone and voice coil. Experts recommend at least two feet of free space around the subwoofer. Also, a good space will make you receive the best acoustics.
Avoid high traffic areas like along the corridors, and when a subwoofer looks excellent in a place, it does not mean it is supposed to be there.
2. Clean the Subwoofer
Cleaning is the first maintenance tip for any electronic device. Always wipe the exterior with a wet rug, including the power cables and audio cables. Dirt and dust can quickly accumulate on the cone and exert extra pressure breaking the suspension. You can also clean the inside using compressed air. Alcohol and bleach can damage the subwoofer’s exterior.
3. Set To the Recommended Signal and Volume
If you do not pass the authorized volume and signal strength, your subwoofer will have a longer useful life. Capped signals force the voice coil to overheat and expand, detaching from the tube. Do not turn up the volume to maximum, but just about 75% is the best for human enjoyment and better acoustics.
4. Do Not Leave Children and Pets Unattended
Pets and children also love the good sound from subwoofers, but you have to watch them when using the subwoofer. The best solution is to train your children on the subwoofer’s appropriate ways. Do not allow them to play around with the subwoofer because they can physically hit it. Teach them to unplug from the power source after using it.
5. Always Get Professional Help
Whenever your subwoofer is damaged, call a professional. An expert can quickly tell if a subwoofer is damaged and give you the best solution available. Always a multimeter near to help you measure the electric resistance before you call a professional. Also, try to use DIY methods to repair a damaged subwoofer.
6. Keep the Subwoofer Off Metals and Magnets
Do not place your subwoofer near metal and other magnetic materials because they can affect the internal magnetism of the subwoofer. The crossing magnetic fields can damage the internal electromagnet hence poor sound quality. Static electricity is also bad for subwoofers; as a result, do not walk on the carpet and touch your subwoofer.
7. Keep the User’s Manual Nearby
Ensure you read and understand the user’s manual before using a new subwoofer. Always refer to the manual in case of any challenge. Keep in mind the maximum amount of voltage and power your subwoofer can handle. Call customer care services for better resolution if the issue is too technical.
It is not easy to tell if a subwoofer is damaged, but you can conclude with simple trial and error methods. Start with a good sound test to gauge the level of perfectness, and no sound is a clear indicator of a damaged subwoofer. Next, do a cone test and ensure the suspension technique is still in place and the cone is not wobbling.
The final way to tell if a subwoofer is damaged is by doing a voice coil test using a multimeter. A good voice coil should have a steady reading over 1.0 ohms. The voice coil is the biggest suspect for a damaged subwoofer. However, you can use the ten steps above to repair a voice coil.