cleaned polydome

the 303 protectant is a great product, and works as claimed. it is pricey if buying in quantity, but is available in a "towelette" version that is both economical, and convenient.

http://www.amazon.com/303-Product-030910-Protectant-Towelettes/dp/B002YI72TS

i think the disintegration rate of plastics is different in different parts of the country (world). here in socal it seems particularly accelerated, so i shy away from any poly drivers. though not my cup of tea, i do understand the kappas have their niche. seeing what people are asking even for trashed polydomes tells me there are plenty to take up the kappa mantle. for infinitys of that vintage, personally, i lean towards the next step in infinity tech, the IMG drivers. they seem immune to the effects of UV, and sound superb. of course, all my 70s infinitys drivers have also weathered well, with their various dopings and treatments. one of the great things about infinity was they were willing to experiment with different materials.



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After doing a bit of research and coming up with a few potential alternative treatments, I posed a question regarding PP surface restoration to a chemistry forum and a few people chimed in to let me know that whatever option I went with, commercial or organic, would not really help much (most likely not at all)...since the material itself naturally breaks-down and decays regardless of what might be done to try and prevent it from happening.

So when the time comes, and it probably won't be any time soon, I'm planning on cleaning my domes with a bit of soapy water and then using some variety of non-drying oil (maybe an industrial-variety coconut) to condition them. PP is very resistive to almost every substance out there so I don't think I can make them any worse than they already are...the real question will be whether I prolong their functional lifespans or whether I just end up making them smell yummy.

If and when I undertake this unorthodox activity I will certainly follow-up and share my experience and any notable results.
 
this doesn't seem to happen to the clear mids in the RS series..

anyone know why...?

don't mean to hijack...
 
After doing a bit of research and coming up with a few potential alternative treatments, I posed a question regarding PP surface restoration to a chemistry forum and a few people chimed in to let me know that whatever option I went with, commercial or organic, would not really help much (most likely not at all)...since the material itself naturally breaks-down and decays regardless of what might be done to try and prevent it from happening.

My experience shows a great variation of decay in Kappa Polydomes that were all manufactured within a few years in the late 80s to perhaps the early 90s. A casual observation of Kappa Polydomes on eBay over the last decade shows great variation. There are Kappa owners in this AK group with similar testimonies.

I expect it's possible there were variations in formulation or in production of domes in batches that may have had something to do with longevity. If ozone is a problem, how can Kappa owners reduce ozone in their environment? Do people who keep their windows closed and the AC running have less ozone in their environment? Is it as simple as the domes in excellent shape today were kept in lower exposure environments? Do the protectants we've discussed protect from ozone? How safe is the back side of the dome in a sealed speaker? :scratch2:

I have a set of spare Kappa Polydomes taken from parted speakers from before the Kappa point era (the later Kappa production period with the reinforcing mesh behind the domes). They are lightly clouded and very soft. I have another set that are slightly more opaque in one of my sets of 6 Kappa. The other 3 sets of Polydomes in working speakers are somewhere closer to the middle. On the other end I had a set of yellowed, untreated spares boxed in a closet that I later discovered crumbled like dry, rotting leaves. These domes were all made within the few years they were being installed in the Kappa series speakers around 25 years ago.

The trick is to acquire the domes in as close to new condition as possible. I would stay away from domes that have transitioned from white into yellow unless they were less expensive and I was hard up for replacements. I can't discount the benefits of using the discussed protectants on domes that are set into decay. There's been a great deal of evidence indicating these protectants can at least greatly reduce drying (or hardening and becoming brittle) which is the usual ultimate cause of death. It's smart to have spares in preparation but there's no good reason to simply sit back and wait for decaying Kappa Polydomes to die. No reason to shy away from acquiring a set of Kappa with Polydomes in good working condition.

I'll add this again for potential owners who don't know: There is a trick using a hair drier to apply heat to Kappa Polydomes that causes the material to clear. I've not tried it and I'd be weary of what applying heat may do to decayed material, but I admit I don't know exactly what applying heat does to the material to make it clear. I'm not certain it doesn't somehow reset the material. It hasn't been common in eBay but it's something to keep in mind if you find a set of used Polydomes in unrealistically excellent condition. I have no idea how well the treatment works to clear Polydomes in advanced states of decay but it seems it works better on material with less decay. Anyone with better knowledge and experience, please say something.
 
this doesn't seem to happen to the clear mids in the RS series..

anyone know why...?

don't mean to hijack...

If you refer to the pre-Kappa Polydomes, they are smaller diameter (less mass) and made form a harder, more solid material. I expect less porous than Kappa Polydomes. Porous and softer being a couple of the apparent reasons the Kappas are much more susceptible to exposure, although no idea in the difference of materials.

Don't the older Polydomes have a tendency to yellow with age like some of the clear poly woofers?
 
Good experience with 303 Aerospace protectant

Hi folks, I guess I'm one of the fortunate Kappa owners: About a year ago I bought a set of Kappa 8.2 from the original owner. They had been sitting idle in a unheated room for almost 15 years, and in very good shape overall. Original woofer surrounds and the Polydomes were still supple to touch, although opague and milky - but no yellowing or cracking.

To preserve them, I first tried treating them inside and out with Armour All Vinyl protectant. This gave a very good visual result, and certainly did no harm to them. But after a few months they started to become a bit more opague again, so having read this thread, I tried 303 Aerospace protectant this time - see pics..

They are all "after" pics, as I can't find the "before" pic I took last year. Sorry about that, but it really is a dramatic improvement :banana: Even though they were in better shape than most, the steel mesh wasn't visible. Now the mesh is clearly seen from the couch, and it looks really really nice! Even the little tinsel wires are clearly seen from the outside. I treated them inside and out with a soft cloth, using a q-tip for the groove around the voicecoil.

They are very supple to touch, not hard or stiff at all. I have no evidence as such, but my impression is that they are softer now than before, and the 303 (and Armour all before that) is preserving and partially restoring the poly material.

I can't tell if sound has been affected either way (I doubt it), but I believe this treatment will add years to their lifespan.
Should you try it? That is up to you, but I am very happy I did it, and will probably give them a 303 touch'up every year now :thmbsp:
 

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Hi folks, I guess I'm one of the fortunate Kappa owners: About a year ago I bought a set of Kappa 8.2 from the original owner. They had been sitting idle in a unheated room for almost 15 years, and in very good shape overall. Original woofer surrounds and the Polydomes were still supple to touch, although opague and milky - but no yellowing or cracking.

To preserve them, I first tried treating them inside and out with Armour All Vinyl protectant. This gave a very good visual result, and certainly did no harm to them. But after a few months they started to become a bit more opague again, so having read this thread, I tried 303 Aerospace protectant this time - see pics..

They are all "after" pics, as I can't find the "before" pic I took last year. Sorry about that, but it really is a dramatic improvement :banana: Even though they were in better shape than most, the steel mesh wasn't visible. Now the mesh is clearly seen from the couch, and it looks really really nice! Even the little tinsel wires are clearly seen from the outside. I treated them inside and out with a soft cloth, using a q-tip for the groove around the voicecoil.

They are very supple to touch, not hard or stiff at all. I have no evidence as such, but my impression is that they are softer now than before, and the 303 (and Armour all before that) is preserving and partially restoring the poly material.

I can't tell if sound has been affected either way (I doubt it), but I believe this treatment will add years to their lifespan.
Should you try it? That is up to you, but I am very happy I did it, and will probably give them a 303 touch'up every year now :thmbsp:

Those look awesome! FWIW, I bought a pair of Kappa6's a couple of years ago. They had been stored for at decades at high altitude in SW Colorado (Durango) and the Polydomes looked and felt like NOS. My point is, under some conditions they just don't go bad. Very low humidity or virtually zero air pollution might have something to do with it.
 
Here are a few before and after pics of my kappa 9's polydomes, I treated them with 100% silicon oil and here is why, I have two extra pairs of polydomes that I treated about 4 years ago and stored them away in a small box, I treated one pair with armor-all and the other pair with 100% silicon oil, the ones treated with armor-all are shot, they got like hard plastic and crumbled with the slightest touch of your finger, the ones treated with 100% silicon oil look milky like the ones in my pics but were still soft to the touch, Well.. after seeing what happened to the two different treated polydomes after only 4 years... I went with the 100% silicon oil, hope they last, wish somebody would just make quality replacements, I have a new pair of infinity RSDS black polydomes that I bought off Ebay years ago, I actually think the RSDS polydomes sound better than the original polydomes being that they have a stiffer dome material and a surround material that allows the dome to move much more freely, I don't want to install them just yet as I like to keep my speakers looking original.
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Hi, I also have a pair of K8s that I recently acquired, and I did this treatment to one dome that was totally yellow and opaque. I used a product by Simoniz and was successful. Now I find this thread, one week late.

I believe that the important ingredient in the product to use is: PLASTICISERS
This is what allows plastics to be soft and pliable.
And this is the ingredient that has been probably long gone from the dome material.
I would love if a plastics engineer could come here and comment on this, and tell us exactly what is the best product to use. Or where to find plasticisers in small qty.
A quick search on google gave me nothing.

Anyway, I'm covinced that this treatment will extend the life of the cones by many years.

Cheers
Yes, you are absolutely right about plasticiser! I used ATP AT-205 re-seal on my Infinity Kappa 6.1i polydomes in January 2020 (brushed equal amount over the hole plastic surface outside (quite important to supply evenly, it is like "food" for the plastic), and waited). It really softened the polypropylene domes and I got back the original sound quality (as far as I can hear ...). But the domes are now no longer clear. Prepare yourself for a little swelling of the dome, this is like it should be. Manufacturer promise no overswelling and it doesn't! For clearing them I assume you can use 303 Aerospace Protectant afterwards (not tested myself). I have used ATP AT-205 on my leaky power steering in the past with very good results. So this is the product to use! Best regards from Norway!
 
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Yes, you are absolutely right about plasticiser! I used ATP AT-205 re-seal on my Infinity Kappa 6.1i polydomes in January 2020 (brused one even coat over the hole plastic surface outside (quite important to supply evenly, it is like "food" for the plastic), and waited). It really softened the polypropylene domes and I got back the original sound quality (as far as I can hear ...). But the domes are now no longer clear. For clearing them I assume you can use 303 Aerospace Protectant afterwards (not tested myself). I have used ATP AT-205 on my leaky power steering in the past with very good results. So this is the product to use! Best regards from Norway!

I have a working set of significantly stiffened opaque Kappa Polydomes that are perfect for an experiment using this stuff. It's appears to be readily available at Advance Auto Parts and those are common around here. If I get around to it I'll take pictures and hope there's some visual benefit to display. Which if they melt like I put alien blood-acid on them then there will be some interesting pics to show. The domes on this set are obviously stiffened to touch and completely opaque but only very lightly yellowed, so they're clearly into a slow decay but nowhere near ready to dive into a horrendous quick disintegration like some I've mistakenly bought. I should be able to get to it in the coming weeks. If there's anybody here thinks this could be a bad idea, please say something.

Thanks for the tip Helge_A! :thumbsup: Unless my Polydomes melt, then you'll be lucky you're on another planet. JK!
 
I have a working set of significantly stiffened opaque Kappa Polydomes that are perfect for an experiment using this stuff. It's appears to be readily available at Advance Auto Parts and those are common around here. If I get around to it I'll take pictures and hope there's some visual benefit to display. Which if they melt like I put alien blood-acid on them then there will be some interesting pics to show. The domes on this set are obviously stiffened to touch and completely opaque but only very lightly yellowed, so they're clearly into a slow decay but nowhere near ready to dive into a horrendous quick disintegration like some I've mistakenly bought. I should be able to get to it in the coming weeks. If there's anybody here thinks this could be a bad idea, please say something.

Thanks for the tip Helge_A! :thumbsup: Unless my Polydomes melt, then you'll be lucky you're on another planet. JK!
Just to remind you ... At first I just brushed a little part of one dome, several applications. After some time, a few hours, this "spot" had swelled because of the supplied plasticiser. Don't do the same mistake. Apply to the hole polydome in one application so it can swell equally and at the same time. But even if I did this mistake, the product is so "safe" that when I treated the rest of the dome, and after some hours, the dome ended up "equally large" all over. HA.
 
Just to remind you ... At first I just brushed a little part of one dome, several applications. After some time, a few hours, this "spot" had swelled because of the supplied plasticiser. Don't do the same mistake. Apply to the hole polydome in one application so it can swell equally and at the same time. But even if I did this mistake, the product is so "safe" that when I treated the rest of the dome, and after some hours, the dome ended up "equally large" all over. HA.

Could you please post a couple of close up pictures of your treated domes? I've been reading testimonies of people who had unfortunate results with over expansion of transmission components which makes me wonder if this stuff could make the domes swell beyond their original shape. I'm also a little apprehensive about applying it full strength when all the testimonies are based on a dilution of an 8 ounce bottle mixed into a much larger amount of lubricating fluid. I've been imagining a need to remove all possible excess plasticiser after the dome absorbs whatever it can. Or will it evaporate on its own? I'll probably put a little in a bowl and observe how long it takes to evaporate before I use it on a dome. Does it smell like it's mixed with a solvent that will evaporate? Thanks.
 
Could you please post a couple of close up pictures of your treated domes? I've been reading testimonies of people who had unfortunate results with over expansion of transmission components which makes me wonder if this stuff could make the domes swell beyond their original shape. I'm also a little apprehensive about applying it full strength when all the testimonies are based on a dilution of an 8 ounce bottle mixed into a much larger amount of lubricating fluid. I've been imagining a need to remove all possible excess plasticiser after the dome absorbs whatever it can. Or will it evaporate on its own? I'll probably put a little in a bowl and observe how long it takes to evaporate before I use it on a dome. Does it smell like it's mixed with a solvent that will evaporate? Thanks.
Here they are. From the left polydome which were treated all over at one time. When I should take the fotos I got surpriced! This one had started to show the mesh behind (clear up) by itself, as can be seen. The product dries on the surface and the "left over" product which is not soaked into the dome material maybe just get pushed off as dust when the speaker is in use. I understand your worries, and you should be, if you try to be smart and use another similar product from a competitor to ATP you might have a bad experience. It is only ATP AT-205 you should use!!! Read on Amazon ... But one tought come to my mind. You, or others, have (older) polydomes without mesh behind. Maybe the best solution is to put the ATP AT-205 on a small spray bottle, like small lens clear bottles, so you avoid direct contact. And when they start to soften up they can withstand a lot more, of course ... And everyone (besides me for now) have stiff polydomes, and they don't sound right. They simply can't. So if yours get broken, badly, then millersound.net repair might be next stop. What do you have to loose, I have already taken the risk for you?
 

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Here they are.

Thanks for the pictures. Your domes look to be in very good condition and there is no apparent residue on the material which is reassuring. I intend to pick up a bottle of the ATP the next time I go out. The application will happen in coming weeks.

Are you confident it penetrated all the way through the domes? I've been presuming it did but one of your domes look as if maybe not. (The one that looks as if it's becoming more transparent in a ring around the center.) That seems to suggest it didn't soak through any of the other dome. I expect it probably penetrated but I'm trying to build confidence before subjecting the treatment to a set of working Polydomes.

I've brushed Meguiar's protectant on Polydomes without issues in the past except it stays wet for a while that dulls the sensitivity of the dome requiring adjustment on the intensity pot. Probably changes the response characteristics too but I didn't obsess about it at the time, expecting it to dry over time. I anticipate no problems using a small brush but I'll be thinking about it a lot more before I do it.

Another issue I have is what the ATP is going to do to the adhesive attaching the coil. If it will weaken or dissolve it. I expect there's no way it can't do something and anything it does probably isn't going to be good. There's a lot of guessing going on here that doesn't inspire a lot of confidence, but it does inspire hope for domes destined to disintegrate even if it happens very slowly. The ATP may even go a long way to heal domes with a lot more deterioration. That would be very cool for people with very yellow or brownish domes. Those that would normally be considered advanced and virtually hopeless.

It would be cool if we could get Bobbyd38 to comment on this. He knows all about dome composition and adhesives. He would be able to say if this is a good idea. I'll probably go ahead and PM him and ask him to look at the thread.
 
What I have found works for me to recondition these is first Gently, and slowly use a hair dryer or Heat Gun (careful with a heat Gun, on Low from a good distance) on the dome. I can't emphasize enough to go slow and move the gun in a circular motion until you see the dome start to clear. Too close or too much heat will do more damage than good, but it does work! This will usually get rid of the yellowing, and soften the dome up some. Then I use 303 Protectant on Both sides, gently wiping on with a small sponge applicator, or new acid brush. BTW, to access the back side of the dome is 4 screws and they come apart, there are self aligning pins, so they go back together with the coil centered. I would caution that this method only worked for me on "Intact" domes, if they had ANY cracks, or are too dry to begin with, more damage than good will be done.

FYI, my most recent test of samples yielded pretty good results. The frequency response is damn close in comparison to Two Originals (see Plot), although the sensitivity compared to originals seems to be down -4 to -7db. I did assemble the coil to the dome by hand with no alignment jig, so I'm not sure if this is the material or perhaps a slightly skewed voice coil alignment. A slight bump in the Polydome Midrange Gain pot on the Crossover would correct this, but I would like to do further testing, and nail down the
cause before proceeding.

Kappa Polydome Test.pngIMG_5742.jpg
 
the sensitivity compared to originals seems to be down -4 to -7db.

Looks great!

Could the cone material get stiffer, and thus reduce sensitivity due to heating it? That is, perhaps the material got more rubbery and thus provides more resistance than the brittle yellowed cone?

It would be interesting to compare the treated one to a genuinely NOS part w/o any coloring...
 
Looks great!

Could the cone material get stiffer, and thus reduce sensitivity due to heating it? That is, perhaps the material got more rubbery and thus provides more resistance than the brittle yellowed cone?

It would be interesting to compare the treated one to a genuinely NOS part w/o any coloring...

The unit on the Left (AVA Sample) is a Sample of my Reproduction Project. It is new, not heated or treated. Sorry, I know the thread was about treating old ones, just thought I would add the progress on my project to create Replacements.
 
What I have found works for me to recondition these is first Gently, and slowly use a hair dryer or Heat Gun (careful with a heat Gun, on Low from a good distance) on the dome. I can't emphasize enough to go slow and move the gun in a circular motion until you see the dome start to clear. Too close or too much heat will do more damage than good, but it does work! This will usually get rid of the yellowing, and soften the dome up some. Then I use 303 Protectant on Both sides, gently wiping on with a small sponge applicator, or new acid brush. BTW, to access the back side of the dome is 4 screws and they come apart, there are self aligning pins, so they go back together with the coil centered. I would caution that this method only worked for me on "Intact" domes, if they had ANY cracks, or are too dry to begin with, more damage than good will be done.

FYI, my most recent test of samples yielded pretty good results. The frequency response is damn close in comparison to Two Originals (see Plot), although the sensitivity compared to originals seems to be down -4 to -7db. I did assemble the coil to the dome by hand with no alignment jig, so I'm not sure if this is the material or perhaps a slightly skewed voice coil alignment. A slight bump in the Polydome Midrange Gain pot on the Crossover would correct this, but I would like to do further testing, and nail down the
cause before proceeding.

View attachment 1762409View attachment 1762414
When I was playing around a few years ago building new domes out of different dust cap materials using a foam surround I remember that if the coil height was higher or lower into the magnet structure it made a significant impact on how loud the domes output was, it's been years so I don't remember which height of the coil higher or lower gave the dome more output, could the voice coil just have to be raised or lowered a little?
 
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I got a pair of 7 Kappa in a trade without original mids. I bought one Polydome that is a bit yellow but in good shape, no craks. I have not sourced a second but after spending hours reseraching all this on Polydomes and wondering if it is worth my trouble to try and get original Polydomes and maintain them or just purchase a pair of the ones offered by:
SimplySpeaker -
Infinity 4 ohm Copy Dome Midrange for 902-3075 Kappa 6 7 8 9 Speaker M-330v2
MidWest - MW Audio MM-2150 v2: 3" Dome Infinity Copy Midrange - 4 ohms
 
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