Instructables
Picture of re-foam your old speakers
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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.
 
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Step 1: Is it really to trash?

Picture of is it really to trash?
speaker03.jpg
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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. 
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winmichaels4 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)  winmichaels3 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...

Dr. Science6 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.

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. Science6 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!

sawatzky6 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!

blackepyon6 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)  blackepyon6 months ago

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

sekarganesh936 months ago

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

andrea biffi (author)  sekarganesh936 months ago

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

Dr. Science6 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.

Shims didn't always work for me, but that's how I started out as well. Allowing the i.5 volts to run through the circuit guarantees the voice coil will find its home. Way easier when dealing with higher quality drivers like JBL that have less space tolerance. Also, vintage drivers lose some value when they are visibly altered.

I used to repair high end audio back in the 80's this included re coning and repairing speakers for a living. In order to correctly surround a speaker you actually need a shim kit. You have to remove the dust cap for correct alignment. We used to use special gauged plastic, but paper is fine for the home repair.

andrea biffi (author)  Dr. Science6 months ago

that's cool, it deserves a try!

I like it!

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