Instructables
Picture of re-foam your old speakers
speaker44.jpg
In last years it happened to me to run across ruined speakers more often than we would think. I love those old heavy and huge black speakers typical of '90 years. I obtained this pair for free, I decided to repair it and this time I supported the process with a full photographic documentation and a detailed instructable for your pleasure ;-)
The re-foam process is the same for squawkers and subwoofers, but since I fixed both you can see the entire repairing dynamic for both cases. I also documented myself before planning my first speaker refurbishing attempt, and I found a good guide on decware.com. After some successful realizations I can tell that's a useful reading.
 
Remove these adsRemove these ads by Signing Up

Step 1: Is it really to trash?

Picture of is it really to trash?
speaker03.jpg
speaker04.jpg
As you noticed from the first image the speakers appeared in a very bad situation. Actually you wouldn't tell, but this is an ordinary situation for a 20 years old woofer, indeed the edges (made of foam or rubber), after many years crumble. The tweeter's cone doesn't need to move as much as the woofers so there is no edge which could break. A speaker in this state usually emits a very low sound, and it's practically useless, many people throw it away, since a refurbishing professional service could be expensive. I will explain how to bring them back to life with a 15$ investment. 

Step 2: The replacements

Picture of the replacements
speaker07.jpg
All you need are the substitutes for your speaker's surrounds. You can choose either foam or rubber edges from eBay. To choose the right size unfortunately is not so simple as to choose between S, M or L. You have to measure the external diameter of the cardboard cone, and the inner diameter of the steel frame. Practically you need the exact inner and outer diameters of the bumping central stripe of the surrounds. The inner and outer diameters of the full rubber/foam piece could vary a little bit. Measures are usually specified in inches, so if your meter uses metric system, I suggest you to convert it in imperial units. Some surrounds sellers let you choosing between flat and sloping cone border, so choose that feature after inspecting your speakers, that will affect the slope of the surround's inner stripe. I bought these and these replacements for my speakers.

Step 3: Cleaning process

Picture of cleaning process
speaker11.jpg
speaker09.jpg
speaker10.jpg
Once obtained the replacements, first action is to remove old surrounds and clean cone and frame, so to obtain a smooth surface. As tool you can use a flat blade cutter, scratch out the foam and glue remains, ant pay attention to not cut the cardboard cone. 

Step 4: Removing big domes

Picture of removing big domes
speaker13.jpg
To center the cone during the gluing, wee need to obtain access to the central steel core. Since it's usually covered by a convex cardboard plate which protect the core from the dust, we have to take it off. 
Dust covers have to be removed AFTER cleaning the surfaces from any dust and especially any iron filing remained after scratching the frame. Indeed magnet of the speaker will attract those filing, and they will obstruct the gap around the magnet, contrasting the cone movement.
With a cutter, paying attention to NOT CUT THE CONE, detach the dust cap from the cone. In the case of the subwoofer this parts are glued to the cone and with a small pressure they could be detached. We'll see that it's not so simple for the midrange speakers. You can try to leave a small hinge attached so to insert caps in the exact initial position.

Step 5: And little ones

Picture of and little ones
speaker15.jpg
Indeed for these smaller speakers, the dust caps are glued much more tighter, and I learned that trying to unglue them could ruin the cardboard cone surface. So I decided to cut them at an inner circumference, as you can see in pictures. But please try not to cut the power wires which lay at the bottom of the cone.

Step 6: Centering the cone

The paper sheet is needed to form some paper stripes, so that they can act as spacer to isolate the cylindrical core from the metal tube connected to the cone. This thickness is not constant for every speakers, and you have to try with more sheets and lengths.
I made a mistake here since with my 80 g/m2 sheets I had to make one and half turns to reach the exact thickness. That results in a not centered cone, because the spacer on one side is double than on the opposite side. By the way this mistake doesn't affect the speaker functioning in my case, but choose a different sheet thickness if you encounter in a similar circumstance, or use four shims, trying different thickness.

Step 7: Pour glue

As glue any vinylic glue is good, but I suggest you to check that it will become completely transparent, some of them remain white after drying. With the paper cylinder well into position place the foam surround over the cone, so to see if it fits right. You can also remove the speaker from their wood case, but I find useful to have a so handy stand.
Add glue all around both frame and cone, try to pour the right amount of glue and to diffuse it uniformly.

Step 8: Gluing edges

Now add the foam edge pushing it gently over the glue. Avoid forcing the cone on one side or the other, since it has to remain centered. With your finger spread the excess glue, don't worry if it appears to be too much.

Step 9: ...glued

Picture of ...glued
speaker24.jpg
Indeed when the glue will dry any excess will magically disappear. You can now remove the inner paper spiral. Now make a constant pressure on the cone with your hand and check that there is no friction at all between core and metal ring. If you feel friction, and you are sure it's not due to an unbalanced pressure from your hand,  you can unglue the external stripe of the surround, and glue it again letting it free to position.

Step 10: Gaskets

Picture of gaskets
speaker26.jpg
Now set up all the foam gaskets cleaning them from any glue remains, by the way if your work is not accurate nobody will notice that ;-)
These gaskets are supposed to keep the front cover far from the surrounds, and to protect these from any accidental bump, anyway they are not essential.

Step 11: Gaskets glued on subwoofers

Picture of gaskets glued on subwoofers
speaker28.jpg
Add some vinylic glue on the outer stripe of the surrounds and also on the metal frame circumference, then place the four parts of the gaskets so that they match with the holes and between themselves. Push them over the glue and let them drying. 

Step 12: ...and on squawkers

Picture of ...and on squawkers
speaker34.jpg
speaker35.jpg
As you notice the foam gaskets for the midrange speakers are too tight and the make an interference with the new surrounds. This could be easily fixed cutting away a stripe of gasket from the inside circumference. 

Step 13: Dust caps...

Picture of dust caps...
speaker30.jpg
If you arrived to this step with no mistakes you can be proud of yourself, since the worst is left behind.
Gluing back in place the dust caps is not easy but could not affect the behavior of the speaker, so proceed serenely ;-)
I used a pair of adhesive tape to handle the domes better, but use paper tape, since in my case this ruined a little bit the cardboard.
Place some glue all around the disc border, don't leave any interruption along the glue trail.

Step 14: ..glued on subwoofers

Picture of ..glued on subwoofers
speaker32.jpg
Place the cone in his original position, push it gently trying not to leave big lacks of glue, and leave it drying. Any small split  which appears without glue will be filled spreading glue with your finger. Place a weight (not too much of course!) over the cardboard dome until it's dry. Any further split in the gluing will be filled after.

Step 15: ...and glued on squawkers

Picture of ...and glued on squawkers
speaker38.jpg
speaker39.jpg
The process to glue back in place the cover caps of the midrange speakers is identical to what you did for the subwoofers. Also in this case I suggest to use paper tape, you will have less damage to your caps when you'll take it off.

Step 16: Refinishing

Picture of refinishing
speaker41.jpg
When the glue around the caps is dry you can check there are no splits, and you can add some more glue just to be sure. Spread it with your finger and let it dry. The white will disappear if the glue is transparent enough, if not you can paint it with a black marker. Try not to add too much glue to keep low the weight of the cone and consequent inertia.

Step 17: Final breaking in

Picture of final breaking in
speaker43.jpg
Assemble everything back and screw tighten each screw.
Your speakers are not ready to be placed around your hi-fi... you have to wire them but also to wait some more time before hearing them in all their new shape... anyway don't worry, all the exertion is done.
Indeed when you'll turn the hi-fi on, the sound will be horrific, that's because the new surrounds need to work for some time to loose their rigidity.
To do this process in the shorter time possible place speakers one face to the other, connect one speaker's wires reversed (positive wire on negative connection, and negative on positive), and let both speakers working with music at high volume... not too much high depending on your neighborhood ;-) By the way one speaker will cancel the sound of the other, and you will hear a low music.
After one hour, more or less, you can connect both speakers with right polarity and place them at your hi-fi sides.

Step 18: Ready to play!

Picture of ready to play!
Place also the two covers back in position, obviously after washing them. I had also to glue four new velcro pieces at their corners, because old velcro didn't work well anymore.
Now I can enjoy my new stereo system! Do you recognize another interesting project in the picture? ;-)
1-40 of 104Next »
primosanch7 days ago
Very cool! Thanks for sharing.
rlamprecht7 days ago

I agree - excellent Instructable. I only replace the foam rubber surround on my 8inch SEAS woofers. These are priceless (in South Africa anyway) and they sound good as new. i got the surrounds from SimplySpeakers.com in the US. Good job ..

andrea biffi (author)  rlamprecht7 days ago

that's cool! :-)

Dr. Science7 months ago

MIGHT I SUGGEST? This step is optional.... Paint the new surrounds with a black paint (brush or spray). By covering the surrounds with paint, they will last much longer. The reason they disintegrate is because of ultraviolet light. Paint protects them from this.

Surrounds disintegrate due to many things - theories abound, ultraviolet light, ozone and fungus and others. None of them stand up to much scrutiny. Ultraviolet light the least of them. I have speakers that never saw much if any light - still crumbled surrounds after 15 years. Time and material is the main factor. Painting a surround will change the frequency response - especially of a midrange or tweeter. The surround has two functions - cone centering and terminating the resonances of the cone. Changing the mass or flexibility of the surround by paining will change how this happens.

True story... but visible light (which contains ultraviolet light) is their worst enemy, much like PVC pipe.

Yeah, no. These materials degrade over time no matter what conditions you keep them in, though lots of factors can speed it up. UV, however, can hardly be a major factor when they are enclosed behind opaque cloth, as older speakers generally would be. To confirm that conclusion: old cloth-faced speakers that lost that cloth often degraded rather quickly. After that. Modern speakers and cabinets with grids or silicone surrounds are another story.

Ultraviolet means "beyond violet" In other words it isn't visible ;) LOL!

Daylight and fluorescent lamps contain both visible and ultraviolet light. LOL!

andrea biffi (author)  Dr. Science7 months ago

I don't suggest it, since they are made by rubber or foam to have a very soft flexibility, if you cover them with a paint you'll change their behavior. You can paint the cone, which is rigid, anyway it has to be as much light as possible to reduce inertia...

Honestly, Andrea, that is a valid concern if the waveform were shorter. Do NOT use a thick paint like latex house paint. Woofers have a much longer (lower) wave form. I'm not saying that there is not a difference, but it would take a signal noise generator and a fine mic hooked to an oscilloscope to notice the contrast. And please do not take offense, but those Phillips in the pix aren't exactly super accurate anyway. Speakers such as A/D/S/ use the solid rubber surrounds. I've even used vasoline and smeared the foam surrounds with that to prolong the life. Find an old pair and experiment... listen for a week. Use the fine paint like they use on models (its more like ink). PS: you can really improve those Phillips by ordering some soft domes tweeters from Parts Express in Ohio. Great company. http://www.parts-express.com/goldwood-gt-510-1-soft-dome-tweeter--270-176

Yeah, of course you have looked at them (not listened, or measured) and believe you can improve them with a cheap tweeter - good grief!

Paper cone tweeters cannot respond to super high frequencies as well as the soft domes, plus the dispersion characteristics are totally different from a cone vs. a dome. AR made a pretty decent one in the early 80's that had a lubricant applied to the voice coil, allowing higher levels of voltage to pass through (like the AR-18's). But, the dome type tweeter provides an even higher frequency response out beyond 22,500 cycles while the paper cone starts dropping off at around 13,500. A fine microphone and a real time analyzer with a pink noise generator hooked up to a scope will prove that. Some folks cannot hear beyond 10k and for them, its a moot point. Finding decent soft domes for that price is a good deal. Of course, all of this is subject to one's own opinion, but the real time analyzer does not lie.

I have a fine microphone and I have measurement equipment and I have measured several paper tweeters that go beyond 20k. I have also seen many cheap "dome" tweeters like you are suggesting (if you take it apart it is actually a cone, so LOL! ;) ) that are complete garbage. Dispersion between cones and domes of the same diameter is comparable, and a well engineered cone may actually have better dispersion because the voice coil is smaller. An RTA is useful for measuring noise, but it is not useful for designing or evaluating speakers. I have been designing speakers for 25 years and most of what you say in this thread is VERY misleading, or misinformed opinion.

A paper cone can produce beyond 20,000 hz but it won't be flat as most start to drop off at 15,000. There might be exceptions but none that I'm aware of. I've seen "cheap" dome tweeters as well that do not produce flat also, but I've also had "inexpensive" ones that do an outstanding job. A good example is the Radio Shack Minimus 7, no longer produced, but still sought after. That little 2-way was very accurate to within the range it could produce. A/D/S/ also produced extremely (almost perfect) response. Comparing speaker designs is like comparing the colors of paint for your living room, what sounds great to you might not sound good to the next person. A RTA and a good flat mike with a pink noise generator does not lie. I've done the same tests of which you speak. If you've been designing loudspeakers for 25 years, which ones have you designed? Which mike are you using? Are you using an anechoic chamber? How far away do you place your mike? I do know of what I speak as I currently own over 200 different pair of "classic" loudspeakers and many different amps. I've also been in the business of selling different major name brands since 1975. There is much I do know, and much I do not know, but I'm not green to this. I've literally sold $millions in audio equipment.

Read "tweeters" Wikipedia: "It was typical of 1960s/1970s-era cone tweeters, exhibiting flat response from 2,000 to 15,000 Hz, low distortion and fast transient response. The CTS "phenolic ring" tweeter was used in many makes and models of well-regarded vintage speakers, and was a mid-priced unit. (see photo there)

Cone tweeters have a narrower dispersion characteristic that is the same as a cone woofer's. Many designers therefore believed this made them a good match to cone midranges and woofers, allowing for superb stereo imaging. However, the "sweet spot" created by the narrow dispersion of cone tweeters is narrow. Speakers with cone tweeters offered the best stereo imaging when positioned in the room's corners, a common practice in the 1950s, 1960s and 1970s.

During the 1970s, the introduction of higher quality audiophile discs and the advent of the CD caused the cone tweeter to fall out of popularity because cone tweeters seldom extend past 15 kHz. Audiophiles felt that cone tweeters lacked the "airiness" of dome tweeters or other types. Nevertheless, many high-end cone tweeters remained in limited production by Audax and SEAS until the mid-1980s."

So if comparing speakers is like comparing paint colors, why are you telling the writer of this 'ible that they need to put cheap mylar tweeters in their speakers for high fidelity? Have you measured them? have you listened to the finished speakers? Selling or owning speakers hardly qualifies you to "re-engineer" them without even a listen.

Which has better dispersion, a perfect 1" dome tweeter or a perfect 1" cone tweeter, or a perfect flat 1" circular tweeter, or a perfect 1" ring radiator ;)

Your last three paragraphs are really entertaining in their completely broken assumptions.

One only needs to listen and compare. Using a signal noise generator and setting it at around 10khz, set at a moderate range of amplification, walking by a single speaker with a cone tweeter will prove my point. There are "sweet spots" as one does this. Its due to the laws of physics. A cone will radiate its energy in the shape of a cone. Low frequencies are more omnipresent move through objects, therefore cones work well for the longer waveforms. High frequencies bounce off of objects. A dome tweeter, if working properly, will radiate in the shape of that dome, and doing the same test with a speaker having a dome tweeter should reveal that the dome tweeter is superior in dispersion characteristics.

I only brought up the fact that I was the guy who sold the loudspeakers because, as some folks are color blind and certain shades of paint are lost to them, some folks have hearing deficiencies that might not allow them to hear what I am talking about. If you've ever tried to sell a pair of $1000 and up loudspeakers to the "common" man or woman, these are points that must be made. Wouldn't life be a bummer if all loudspeaker were the same? I sold plenty of pairs that, in my opinion, sucked. But if the customer was satisfied, that is all that mattered. So, if you are happy with paper cone tweeters, I say, enjoy!

Your explanation has nothing to do with science, "Dr. Science" Domes and cones do not radiate in the shape of either ;) Using an RTA to measure loudspeakers is like using a bathroom scale to measure postage. It doesn't have the necessary resolution. Take the last word buddy, 'cause I am done with you ;)

I do not "need" to take the last word. However, I'd love to hear you tell us what your favorite loudspeaker is, or what your favorite design of loudspeaker is. Everyone has their own opinions, and since this site is one of those places to share opinions, and since you have not only opinion but a vast experience and knowledge, I was hoping to get down to the bottom line as to what you have in your listening environment? Please, do share?

One of the better cone tweeters ever made: http://spicaspeakers.com/pdfs/peerless-801730.pdf

Better response AND dispersion than the majority of dome tweeters. This tweeter was mostly done in by mistaken assumptions such as yours.

There was a manufacture back in the 70's that used a silicon (the glue) like product. I dont remember who it was, but it worked I don't recall repairing many of those when I was in college. I personally would not mess with the surround, but I would dope the cones all the time.

Infinity use to goop a black substance on their drivers.

You are correct. It was the infinity speakers.. I remember we used to dope Seas 10's. ..

Foam edges are only one of several choices. Almost unaffected by time are pleated fabric, coated with a flexible clear glue, and black neoprene edges. Guitar speakers merely have flexible glue painted around the paper edge. Only long-travel acoustic suspension speakers need such flexible edges as foam and the neoprene.

true story... I have a pair of Pioneer HPM100's and JBL L-200's with that design..... still sound great!

winmichaels6 months ago

The reason these surrounds (the cracked looking part)fail is that they are foam, replace with linen or cloth and they'll last forever

andrea biffi (author)  winmichaels4 months ago

yes, but I prefer to keep the original material... for me it's enough if they last other twenty years ;-) anyway new foam and rubber edges should last more...

sawatzky7 months ago

Many years ago I threw out my blown Boston Acoustics A70's. I'm sorry I did that... I didn't know this process was so cheap. Oh well. The replacement CR9's are much better and still going strong!

blackepyon7 months ago

If you know the vendor and model number of your driver(s) you can search that way. (Found an easy match for mine that way)

andrea biffi (author)  blackepyon7 months ago

but it's easy enough measure diameters.. or were you answering to sekarganesh93?

sekarganesh937 months ago

awesome .,,,,, but my speakers makes kreepy unwanted sound how to change the inner coil of the speaker? ...... thank you

andrea biffi (author)  sekarganesh937 months ago

are the surrounds ok? are you sure it's coils' blame?

Dr. Science7 months ago

might I suggest? Don't take the dust cover dome off at all. Instead, find a decent "D" cell battery, solder a speaker wire onto each end. Attach one end to each speaker terminal (set it up so that the polarity "throws" the voice coil out, not in) and leave it attached while you glue the new surround on. This centers the cone perfectly, without having to use spacers, thus, not needing to even take the dome dust cover off. --JD

First, you want the voice coil centered, not all the way in or out. Easiest to see this when shimming. Second, if the voice coil has unequal forces pushing it, it will go the direction of greatest force. A speaker is usually used 'sideways' so right there, gravity pulls cone downward.

A simple tone thru the driver at low volume will keep the coil centered throughout the gluing process without the need for shimming. Note: this means using a steady audio signal, not a DC power source (oscillating, not pushing).

I've used an old Heathkit audio generator for this. I set it at around 275Hz for the woofer I was repairing. Enough to produce a faint hum at low volume.

You want to use a frequency that's around the mid-range of what the driver is made for. Keep the volume low, but still audible (too high and the glue might not set properly, especially on woofers).

There are a few advantages to this method. As mentioned above, you don't need to remove the dust cover and you avoid potential damage to the coil if you slip up. And due to the oscillations (if done right), the coil will be 'centered' on all 3 axis, making the repair more accurate.

I've heard that music will also work, but it needs to be quiet and constant. I haven't tried that.

Anyway, this method does in fact work if you have the option available, and if done properly.

My advice is to do it the way you'd like to do it. We all have our own techniques but its the end results and our own satisfactions that ultimately matter. I think its awesome that many did not even know about replacing surrounds, and now many great vintage loudspeakers will be saved from ending up in the landfill.

A clever idea, but I would caution against this. Constant DC current can actually damage voice coils.

I suppose that would depend on the voice coil, but most woofers are power hungry. In fact, they consume about 85% of the current supplied to the speaker from the amplifier. I've never had a problem with this technique. Car stereo installers use the trick when sorting cables for pre-existing 4 speaker car systems which have even weaker voice coils, to determine L-R and F-R.

True, but car installers touch the wires very briefly to check phase, and to determine which speaker is which. And true, that woofers consume the majority of the energy. A constant DC current will definitely heat the voice coil, and possibly deform it. The other issue is that the speaker should be at rest when replacing the foam. The foam would normally be stretched when the cone is at the extreme of its throw.

Shims are how they are made at the factory. While some speakers are best resurrounded without removing the dustcaps, you will almost always have a better result if you can shim.

1-40 of 104Next »