How To: Fix Dented Woofers on Speakers and Monitors

There are thousands of posts on the internet about fixing dented dust caps (middle part of woofer cone), so why did I write about it on my blog? Because I tried most of the methods out there, and the many of them didn't work for me. First of all, a dust cap is the cap in the middle of the woofer. It is the black circle inside the yellow woofer cone in the picture to the right. On to describe the problem..

It is fairly easy to dent dust caps and tweeters (the smaller one above the woofer in the picture). I haven't had to fix a tweeter yet, but I've heard it can be fixed similarly to a dust cap. Just make sure to be gentle and use a lot more caution, since tweeters are usually easier to rip. I bought a used pair of KRK Rokit 5 (1st Generation) studio monitors, but one of the dust caps were dented in. Since this did not make a noticeable impact on the sound and I found them at such a great deal, I bought them anyway. The dent took up over 3/4 of the dust cap's surface area, and it measured close to an inch in diameter. It had four square-like corners to it, and it was about 1/4 inch deep.

The dent didn't bother me for awhile, but it kept staring at me at my eye level a few feet away. It eventually got on my nerves, so I browsed the internet for a couple days trying different methods to fix it. Let me first say that each dent may require a different fix. I will begin with the safest method of fixing it first and work my way to the least safe method. Fixing the dent is not worth breaking your speaker's sound. Some of these methods may damage your speakers, so use caution before applying too much force.

1. Sticky Tape - This is the first thing I thought of, and it did absolutely nothing for me. It should work good on very flimsy dust caps and tweeters though. The strategy here for stronger materials is to stick the tape in the dent as much as possible without further damaging it, then quickly jerk the tape to the SIDE of the dent. For flimsier materials, such as tweeters, you may not want to jerk it quite so hard. The tape just came off on my dust caps, as they are fairly rigid. Be careful of which kind of tape you use. Some tapes may be too sticky, others may not be sticky enough, and some may leave residue or even rip! Duct tape will probably leave residue, so I would avoid it. Packaging tape (be careful of rips), masking tape, and clear sticky tape have been safe in my experience. Even though a tape may be in the same classification, its stickiness may vary.
   
   
2. Vacuum - Shop Vacs are preferred, but I did not have one. I tried a handvac and a full size home vacuum, but neither got good suction to my particular dust cap. The strategy is to use an extension tube to fit over the dent. Before turning the vac on, make contact, but don't push in. Turn it on and leave it on for a few seconds, then turn it off. After the suction has stopped, pull the tube back. Try different tube sizes. I have read where applying a hairdryer's heat beforehand might help. It did not help me though. Instead of a vacuum, you could also try an empty toilet roll, straw, or a handpump of some sort to apply suction. The first two didn't work for me, and I didn't have a handpump.
   
   
3. Push it out with your fingers - It's one of the more risky methods, since you have less control of where the dust cap bends with this method. The strategy is to gently press sideways (and in a little) towards the dent. Do this while gently pressing all the way around the dent. Focus on the corners of the dents, as this will have the most impact. You could try using two fingers at once. Hairdryer heat is suggested to help this also (see suggestion #4 for details). This method ALMOST helped me. I saw some progress, but it dented back in since I could not get all of it out this way. Be careful, if there are any small cuts or holes in the dustcap, this method may worsen them.
   
   
4. Hairdryer + Sticky Tape - This is what fixed mine. I tried it with three different tapes, and only one of the tapes worked. It was a clear sticky tape that was stickier than the cheap tapes and packaging tape, but less sticky than duct tape. First, turn the hairdryer on as hot as it goes.. let it heat up, then put it very close to the dent in the speaker. Leave the hairdryer there for around 1 minute before turning it off and setting it aside. Quickly, but gently, stick the tape to the inside of the dent and apply the same strategy as suggestion #1. The first try with the right tape worked. I just stuck it, set it there for a second to seal good, then jerked the tape to the side, and the dent popped right out! The heat causes the adhesive to stick a lot better, which allows you to pull more on the dent without the tape coming off. Pull sideways, not directly back. This may take several tries. The hairdryer may damage some heat-sensitive materials, such as thin plastic.
   
   
5. Hairdryer + CO2 - This will really put your speaker to the test. This is a method for removing dents from metal, such as in cars. This probably won't work on your dust cap unless it is metal. Nothing else was working, so I gave this a shot after the vacuum. This could be very damaging to some materials, as it could cause pressure cracks. Fortunately my dust cap could handle it (a few times). Heat up the area with a hairdryer for a minute on high, then quickly take a can of CO2 air spray (not hair spray!) and turn it upside down. Quickly spray the area for a couple seconds. The quick temperature change from high heat to ice cold may cause the dent to condense on itself and pop back out. I watched a video of this on a car dent. This didn't work on my dust cap, but it was fun and did not damage it thankfully. Be very careful, the drastic temperature change may break some speakers.
   
   
6. Hot Glue Gun - I haven't tried this method, mainly because I don't have a hot glue gun lying around, but I've seen it suggested several places. Heat glue onto the dent while applying a string, wooden dowel, or something else narrow. Let the glue dry to the dent and the object (about 30 minutes). Gently pull the object away from the dent (sideways would be the best option if you have a string, but directly away may work). If you are brave, try tugging harder or faster.. but be careful not to rip the dust cap! Once the dent is removed, tear the dried glue off. If it does not come off easily, try using nail polish remover or something similar. I've read where some people reported to superglue even, but that is too much for my liking.
   
   
7. Poke a hole in it - I don't recommend this method, but it's there if you absolutely must fix it. Bend a very fine sewing pin at a 90 degree angle and poke it into the middle of the dent. Turn the pin such that it grabs the inside of the dent and gently pull it towards you. Don't accidently poke a second hole from the inside. After the dent is fixed, work the pin back out. I've read that you may have to do this in several locations. There are a lot of mixed feelings of this method out there. If it leaves noticeable damage, you may consider using a thin layer of nail polish to paint over it. Any change in the speaker or the speaker box will change the soundwaves reflection, although you may or may not notice it. I personally didn't try this method, as I'd rather look at the dent than worry about damaging the speaker.

If none of those work, you'll just have to live with it, replace the woofer, or tear apart the woofer and hope you can repair it. You had better know what you're doing before attempting the last one, or you may end up resorting to replacing the woofer. Personally, I don't think a dented dust cap is worth replacing a woofer over. Even though I pulled the dent out, it left four very small unremovable dents where the big dent's corners were. You can only see one or two at a time, depending on how the light hits the dust cap. I tried the above methods on these small dents, but they seemed pretty permanent due to the long-term bend in the material. I hope this helps!