Speaker repair

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The surround just keeps shifting. The spider centers the coil. The other thing, spider can droop in or out. I would make adjustments when doing a repair. I usually wet it down and holding it in place. Kinda starchy material.
Greg
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On 05/26/2014 06:52 PM, J Burns wrote:

The surround is for acoustic loading. The spider keeps the motor aligned.
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"Robert Green" wrote in message
I've got a lot of big, small and medium speakers that have blown out over the years. Typically I take them to the attic where they usually make pretty good bookshelf supports.
In the spirit of domestic harmony, I am cleaning out said attic (anyone *really* refer to their old college texts or books they have read in the past anymore?). So with all the books being "de-accessioned" (librarian-speak for "thrown out") I am left with a lot of bowed knotty pine planks and burned out speakers.
If they can be salvaged, I can use them, but if they're likely to just blow out again, I will send them to the curb monster that comes by late at night before trash day.
So my question is this. Is it worth repairing 10 or 20 year old speakers? Can replacements be readily had?
Is there a good site for diagnosing speaker problems? I almost always assume it's a fine wire winding in the voice coil that shorted when a speaker no longer even responds to a battery "click" test but I that's an assumption.
Is it possible to match the characteristics of the old speakers closely enough without manufacturer info like a parts list?
Do crossover networks ever go bad? Can they be tested with a multimeter?
And yes, I googled it,
http://www.google.com/search?q=diagnosing+speaker+problems&btnG=Search
but I didn't like very many of the sites it revealed. I'll keep searching but Google ain't what she used to be.
Hmm, should have added "blown" to the search term - much better. Still not great, though.
Thanks in advance for your input.
--
Bobby G.

BG 65 years ago when doing radio and amplifiers repairs I replaced many
  Click to see the full signature.
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<stuff snipped>
<Glad to offer an opinion Bobby. My attic can reach well over 100 degrees F in the summer and below 0 in the winter, so the comments I offered were not merely theoretical! I have lost some equipment which was stored in working condition, only to find it inoperative years later. Now I am much more careful about what gets stored up there.>
Sometimes attics are like purgatory. You put things up there that you don't have the heart to throw away at the time. The books died a slow death up there, making it easy to decide to recycle them as waste. No library would want them. It was very easy to see which publishers used cheap paper and which didn't. Some pages just crumbled when turned.
The speakers that served as spacing blocks for the shelves will probably soon follow the books. I connected one up that had a scratchy midrange and watched the woofer speaker cone just shred at tje edges after just a few seconds of operation. Ironically, that same fate befell a speaker stored under much better conditions. Time seems to be a serious enemy of the speaker as much as sub-optimal storage conditions.
I have to admit that on occasion, the attic has "healed" things that were previously non-functional. Certainly not as often as it hastened their doom, but often enough to encourage a temporary retirement to the attic before heading out to feed the curb monster.
--
Bobby G.



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Some allegedly high quality speakers have some sort of flexible foam rubber as the suspension round the outside of the cone - it usually perishes sooner rather than later.
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"Ian Field" wrote in message

Foam has largely been abandoned because it eventually self-destructs. It isn't rubber, it's a synthetic polymer.
I have a pair of original Advents (final green-tweeter iteration), with foam surrounds in perfect condition. Why, I don't know.
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On 5/26/2014 11:56 AM, William Sommerwerck wrote:

Nothing allegedly about it. I have a pair of Infinity speakers (~ 30 yrs old now) and had to replace the surrounds on several of the speakers a year or so back. Foam becomes brittle (age? atmosphere? dog farts? sun/ambient light?) and just starts to disintegrate.
Fortunately, found an outfit on line that sells kits for DIY repair. Figured that I had nothing to lose I popped for the kits and repair was a piece of cake. All's well and I'm good for another 30 years (well, not me, but the speakers<g>)
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On 05/26/2014 10:05 AM, Unquestionably Confused wrote:

It is ozone that dissolves foam surrounds. They are real easy to repair. No biggie.
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"dave" wrote in message

Foam -- such as the foam in carrying cases -- softens and falls apart even when not exposed to environmental contaminants. It just isn't stable.
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Most of the bad surrounds I've seen soften up and fall apart. It's a fungus I think. The other case is too dry and breaking. On a good surround you can finger the thing and it will remain intact. If you get the right temps and humidity, it's likely to last a long time. I've resurected many with coatings, without replacement. Putting stuff on cones, surrounds, painting, etc, been there done that.
I would not prefer foam for surround, but I think it's still sold a lot.
Greg
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wrote:

If the "spider" is good, the surround doesn't do any locating. I rebuilt 8, 4 of them 12 inchers, With the surrounds totally removed there was no scratching I didn't need to shim the voice coil, and the surrounds went on quickly and easily, and the speakers sound EXCELLENT.They were pretty high end speakers - can't remember the brand and they are up in the mezzanine so I can't check.
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You talk about the voice coils becoming shorted, I think you probably meant to say burnt open. A voice coil with a shorted turn will still respond to the battery click test, it just will not respond well to higher frequency inputs.
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It's going to mess Qes and efficiency. I think I've seen rubbed turns. Smaller tweeters are more likely to fuse open near the connections. Woofers will burn over a large area.
Greg
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adding

VC

paper/plastic

I

I

soft.

aligned.
Not quite the case. The surround seals the airflow between the cone and the spider. It also provides axial tilt support for the voice coil. Both properties are important to overall function.
?-)
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On 05/28/2014 09:27 PM, josephkk wrote:

Speakers work without surrounds; "seals the airflow" is another way to say "acoustic loading", ain't it? I use shims so the surround is glued when the piston is at rest, thus favoring neither compression nor rarefaction.
Try torquing a spider supported voice coil with a piece of soft cardboard, not gonna happen.
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aligned.

and

Both

Your view of acoustic loading seem rather different from mine. Segregating the forward and rearward acoustic domains is a prerequisite for acoustic loading to occur. Acoustic loading is mainly determined by the physics of the speaker enclosure, be it stuffed with absorptive batting, folded horn, bass reflex, or some other design.
?-)
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On 06/08/2014 04:08 PM, josephkk wrote:

The surround separates the air behind the speaker from the air in the room, don't it? A sure sign your surrounds are gone is the bass falls off. If you have subwoofers you can go a long time before you even notice your mains have bad surrounds. I have some AR4x that appear to have the original surrounds from ca 1968. All foam not created equal. Refoaming is not difficult. You can do a a couple speakers in an hour, once they have been removed from the cabinets. Be "clean room" as possible when the dust caps are off. Get old glue off the frames before removing dust caps and shimming. I use little shims made from theatrical lighting gels, that's about the right thickness for 10" Advent/AR style low compliance woofers. The choices for replacement foam rings are size and the angle of the interface with the cone. Actually whether there is an angle. Either angled or not. That's it. YouTube has a million proud tutorials I'm sure.
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