Instructables
Picture of Loudspeaker Rescue
An singular loudspeaker on the side of the road was enough to make me turn the car around, retrieve the treasure, and leave behind just the plywood "free" sign as I drove away with fixer-upper of vintage speaker. Three feet tall, and sporting four woofers, a port, and some mystery crossover/loudness adjustment, this worn warrior was a few easy and inexpensive steps away from re-living its glory days:

             1) Un-denting the dust caps

              2) Re-foaming the woofer

              3) Repairing paper cones

In order to complete these steps we need the following materials:

-sewing needle or safety pin

-speaker re-foam kit that fits the woofer in question (I got mine from SpeakerWorks.com http://www.speakerworks.com/foam_surround_sizing_s/63.htm)

-coffee filters

-source of cotton fibers (cotton swabs, cotton balls, yarn, or whatever you have)
 
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Step 1: Un-denting the dust caps

Picture of Un-denting the dust caps
Saftey pin.JPG
Rescued cap.JPG
The dust cap in the center of the speaker protect the voice coil and motor that drive the speaker, so when a toddler pokes in a dust cap like it was bubble wrap, keep in mind the dust cap is just doing its job and keeping the crucial (and more expensive) parts underneath safe. It is also much easier to un-pop a dust cap than replace a motor structure.

This is where the sewing needle or safety pin comes in handy. Poke the  tip of the needle or pin into the dent in the cone, and position the needle sideways so as to allow one to pry/pull the dent out. Using the needle/pin to get inside the cap, one can push out smaller dents and wrinkles.

Alternatively, a vacuum cleaner hose can be carefully placed over the cone, and the vacuum may pull the dents out. This works for larger dust caps.

The dust cap won't look like new, there may still be creases in it and a small pin hole or two, but it will be in much better shape than it was.
andrea biffi7 months ago

well done! I just posted a similar instructable, I found my speakers on the side of the road too, mine are smaller, but still very hard to carry on my bicycle... LOL! Did you have to let the speaker play some time before hearing a good quality sound?

Robert Cohn (author)  andrea biffi7 months ago
I didn't have to let it play for long, it sounded great right after the repair, though typically new surrounds take time to break in completely. At this point in time the speaker has been seeing regular use for a year and all the repairs have held up very well, and it still sounds great!
Great! Thanks :-)
thanks for posting I never knew that the subs could be refoamed
Great post, restoring free stuff is my favorite. Curious if the ohms match up to what the box says. I've got a pair that look similar and one has a toasted x-over that is on the repair list.
pattiemelt1 year ago
Several years ago I traded a hybrid waterbed for a pair of Bose 901 Series IV speakers. They were in excellent condition, or so I thought. After using them for a while I decided the sound just wasn't right so I took the grill covers off only to find the foam on almost all the speakers was disintegrating. Luckily everything else was still in good shape. I bought a repair kit (set of foams & glue) off Ebay & replaced them & the speakers still sound like brand new. It was an experience that took about 2 weeks, scraping the old foam & adhesive off with an exacto knife (there are 8 speakers in each unit), but was well worth the effort.

Nice that you saved another old speaker from certain death. Good 'ible!
sconner11 year ago
Nice job saving these from the landfill.
Speakers are easy to fix if you have a source for the new surrounds.
It's more important to have patience than skill to do this.
sconner11 year ago
Methyl Ethyl Ketone (MEK) will loosen the glue used on the original surround and dust cap making it unnecessary to cut them off. You can get this in the solvents area of the paint dept of your favorite hardware store or home center. Do this in a well ventilated area, this goes for the new glue too. Don't breathe the fumes.
If you're replacing the midrange drivers, make sure to get ones that have a sealed back, especially if it's a sealed enclosure. Otherwise the pressure developed by the woofer will blow them out.
Guilty as charged! did that with 500 watt tube amp once!
RikJamez1 year ago
Does anyone here know how to test voice coils to check if they are ' blown ' or burnt out ? I assumed the way to do it was to check the resistance of each ( Voice coil ) with a DMM to see if it matches the stated spec. And does it have to be exactly the stated resistance, or is there a range, as in 2 ohms ( 1.8 - 2.2 )
Thanx...
RikJamez
Robert Cohn (author)  RikJamez1 year ago
If the voice coil was burnt out, I imagine the resistance would be orders of magnitude higher than spec, or there would be no electrical connection at all, and wouldn't be readable. It does not have to be exactly spec, there will likely be an acceptable deviation range, and if the spec is for impedance (also measured in ohms) the measured resistance of the coil will likely be lower. If there is a raspy or metallic scraping sound when the woofer plays, there is likely physical damage to the motor structure, (or a cone/coil misalignment).
blanchae1 year ago
They actually are not dust caps but reflectors for the mid range frequency sound. On speakers, only the lowest frequency sounds propagate to the outer edges. The mid frequencies loose too much energy to reach the outer edge. They use the center cap to improve the dispersion of the mid range frequencies. The best sound location for speakers are corners of a room - where the two walls and a floor or a ceiling meet. The room acts like a horn to boost the bass and focus the sound in one direction.

Thanks for posting the instructable.
Robert Cohn (author)  blanchae1 year ago
Very interesting, thanks for the info!
miscbs1 year ago
Great instructable! Besides straight pins I have also use a bit of good sticky tape to restore dust caps.
Yes, blanchae, believe it or not, the industry refers to it as the 'dust cap'. One time I was able to fix a dented dust cap with a vacuum cleaner. As you might expect, I put the end of the suction hose up to the dust cap until the suction grabbed hold and then pulled. The dust cap has to be fairly big, though. The best solution though is to install a heavy metal grille so it doesn't get dented in the first place.
reuben81 year ago
I use a vacuum cleaner to pop out the speaker cones. Kids always press them in.
onemoroni11 year ago
Good instructable! I did the same thing with two huge vintage Pioneer speakers that I bought for $5 each at a thrift store and they rock the house. Love those speaker kits. They make them for all sizes if you want to do the smaller ones and sell the dust caps separate if you want to replace the crushed ones, or just cut them off, push out and reattach and an alternative.
AuralVirus1 year ago
I've always used a loop of sticky tape, wrapped sticky side out, around my finger to "pull" a pushed dust cap out. Also blue-tack, if manipulated / kneaded enough so that it is as sticky as possible, will also work.
Seems unnecessary to pierce the cap with a pin.
Doyle Farr1 year ago
When my son was little he thought it was funny to poke at the Dust Caps. I always used a piece of Scotch Tape to pull them back out.
uhclem1 year ago
I've heard you can also pop the dust caps back out with a vacuum cleaner.
jrigvd uhclem1 year ago
tried it, sucked up the dustcap from my nephews usb speaker stand
jrm8069 uhclem1 year ago
Yes, just as he stated in this well done instructable. I am glad to know there are kits available. This had never come up in my research.
robhybrid1 year ago
Before poking a hole in the dome, I usually try putting some duck tape on there and pulling it off quickly.
sbiickert1 year ago
Thanks so much for posting this! I have a set of "classic" speakers that the foam rotted away on. I had assumed the speakers were garbage. Now I know better.
Try to get foam surrounds that were designed for your particular woofer so the compliance is correct. Frequently the places that sell new surrounds for the woofer have new dust covers as well. Sometimes they sell them together as kits.
For the tweeter, they are touchy, remember it vibrates at up to 20,000 cycles per second, if you add the weight of the coffee filter and glue to one side it will affect the sound to some degree. It is up to you if you can hear this or if this bothers you or not. If you look around you might be able to replace the tweeter with a new exact replacement one quite economically.
Also while the woofer is out of the speaker you might want to look inside the cabinet and clean the contacts on any crossover controls and consider replacing any electrolytic capacitors in the the crossover. It may or may not have any. If the speaker is old enough for the foam to rot, it could be old enough for the electrolytic capacitors to go bad too.
OmeJozz1 year ago
Thanks for the info. I didn't even know you can buy those foam surrounds.
Now i can fix my old speakers (never had the guts to throw them away ;o).
Robert Cohn (author)  OmeJozz1 year ago
Thanks for reading! Feel free to message me if you have questions on fixing yours!
CarpePM1 year ago
ONE woofer, two mids, and a tweeter.
Robert Cohn (author)  CarpePM1 year ago
Very true, I miss spoke. I'll be more careful next time!
bayo121 year ago
w
That free speaker is a nice score. Good ible, comprehensive and detailed.
Awesome tip.

I was thinking CPR, but this works too.
Thanks for posting. I have had success using a vacuum cleaner to pull the dents out of the dust caps just find a tube that fits over the cap and suck the dent out. The old hi fi stuff sounds so good its a shame to dump it
great instructable