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RCF L18S800 cloth surround not doped after repair?
RCF L18S800 cloth surround not doped after repair?
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Old 29th January 2015, 08:44 AM   #11
athlon64 is offline athlon64  Croatia
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Could i take a can of spray and just do one layer? The suspension should soak the spray and go nicely black. I don't think it would do any damage?

When i say a speaker is clipping i mean the red clipping lamp on my amp is going on earliear for one speaker then for another. So i have a peecker sound TVA 1800 amp (2x900w @4ohm, 2x585 @8ohm) These are 8 ohm drivers so he clips after the 585w point. So the amp is getting a mono signal and both channels are running at the same power. One side is sligtly clipping, the other one starts clipping only when i push the amp 20% further.

Conanski: They do still sound decent at 40hz. You hear them lees but you hear them. If lowcutting at something like 45hz they loose some juice. I saw the coils when the guy took them out. 3 of them have been completly black but not deformed. The 4th one had been slightly fried and still not deformed. I have a picture of that 4th one that was in best condition. But we still replaced it:

http://i30.photobucket.com/albums/c3...ps6389faa1.jpg
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Old 29th January 2015, 09:47 AM   #12
googlyone is offline googlyone  Australia
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Join Date: Nov 2006
Location: Adelaide, South Australia
RCF L18S800 cloth surround not doped after repair?
Athlon,
I have bought recone kits from OEM's that include untreated cones, and you need to treat them once installed. So it does not surprise me that the repair guy got them untreated. Most recently this happened for a Beyma 10XC driver I did. This kit included a bottle of doping compound and instructions for its applicaton.

The photo you originally linked to from my blog showed a sub that I reconed using an aftermarket kit. I had to buy the doping material seperately. The supplier knew exactly what I was after when I called him.

Here is the bottom line:
- For a bass driver, you need to dope the surround.
- There is no choice, as the Q in the box is completely and utterly destroyed. What does this mean? That driver in a ported enclosure showed the SAME impedance as the driver in free air. The enclosure resonance did nothing at all.
- Without doping the surrounds the loading from the enclosure will just not be working, and your speakers will die a very early death.

So you are worried that doping the surrounds might stiffen them up a bit?
- OK, worst case it will. But...
- That is a lot better than doing nothing, as you will very rapidly destroy the drivers as they will be "unloaded" at low frequencies.


If I were in your shoes, I would have a very direct talk to the repair guy. If he does not understand the implication of not completing the job, then you need to talk to someone else. Alternatively just buy some and do it yourself. If you can colour in a picture then you can apply doping compound, you simply paint it on until the cloth is "wetted". I bought my last lot from "Queensland Speaker Repair" though I am sure you have plenty of people closer to you who can supply the required material.

Is the above coming across as being very direct? I hope so - as I was utterly stunned at how completely the lack of doping destroyed the performance of the driver. And how immediately applying doping put things right.
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Old 29th January 2015, 09:57 AM   #13
athlon64 is offline athlon64  Croatia
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Yes and believe me i'm still shocked by the fact that the guy who is doing this job for 20 years and is recommended by everyone in the country just looked at me and sayed. Oh i don't treat the surrounds, that just slows the driver down for nothing.

I sent an email to RCF italy. They repied quick and told me yes. The original cloth surround is yellow. So he did not lie to me about it being an original cloth surround. But they also told me it needs to be treated but RCF themselves don't sell the treatment. So now what i'm about to do is get a bottle of the damn glue and treat the cones.

I remember that on the old surrounds, if you scratched the treatment / surface od the surround, you could see the yellow material below. Witch means the treatment used for the surround is originally dyed black. Damn if i could just get that black treatment!

Look at this picture: http://i30.photobucket.com/albums/c3...psa0992ce1.jpg

That's one of my S800's pictured this summer. Not take a good look at the surround slightly left from the red terminal. See the small yellow dots? Those are places at witch the treatment didn't go trought well so they remained yellow. So the conclusion is, they sell original yellow surrounds. But they are supossed to be treated!

I have a party i need to do this saturday with the subs. I don't have time to treat them right now. What should i do to prevent damage. Lowcut them a bit higher?
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Old 29th January 2015, 10:06 AM   #14
afa is offline afa  Australia
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You said he "ordered a new coil from RCF" ?? how did he do that??? I thought it was a complete recone or a mixture of OEM parts
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Old 29th January 2015, 10:10 AM   #15
athlon64 is offline athlon64  Croatia
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One out of 4 drivers got a full OEM recone kit. And that one is working fantastic now.

The other 3 drivers did not need a recone, just a repair. A repair included a new coil and a new cloth surround. He ordered both of those from RCF and installed them. But he claims the cloth surround does not need doping. Witch is just stupid.
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Old 29th January 2015, 10:11 AM   #16
googlyone is offline googlyone  Australia
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RCF L18S800 cloth surround not doped after repair?
I don't know what to advise you here.

My drivers were in a ported enclosure. The performance was rubbish with untreated surrounds as previously discussed. Yes, you get some bass, but as you noted not a lot.

In a horn loaded system, I expect that things will be at least as bad, if not worse.

Can you talk to your repairer to see if he has some suitable material? Else borrow some drivers / enclosures off him for the weekend?
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Old 29th January 2015, 10:15 AM   #17
googlyone is offline googlyone  Australia
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RCF L18S800 cloth surround not doped after repair?
Are you jumping at shadows? One thing to check is whether the cloth surround has clear doping on it.

Is the surround obviously "clean cloth" or is it covered in clear "stuff". Clear doping material dries kind of like PVA glue. (that white woodworking clue that dries clear)
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Old 29th January 2015, 10:16 AM   #18
athlon64 is offline athlon64  Croatia
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I don't think i can, i really need my boxes. I was testing them allready. They work quiet well withouth the doping, but not as good as they do with the doping. In the club i'm running them in i also have 4 yamaha CW218V. Dual 18's. Here is how it looks when we set it up:

https://fbcdn-sphotos-h-a.akamaihd.n...19140778_o.jpg

So what i can do and that might be a good idea is. Run my EV'S as kickers (70-135hz) and run yamahas as woofers (35-70hz) So i will avoid doing too much mechanical stress to my EV's.

Sounds like a good idea?

EDIT: No it has got no clear doping. I checked 15 times. It's naked and air can go trough it. You can feel with yours finger it's completly dry.
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Old 29th January 2015, 10:18 AM   #19
afa is offline afa  Australia
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RCF don't supply individual voice coils unless your supplier has an an inside supplier, some cloth surrounds come pretreated with a dampening edge treatment..
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Old 29th January 2015, 10:24 AM   #20
athlon64 is offline athlon64  Croatia
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Yes he does have an inside supplier. He has been in the job for a long time and he told me it's impossible buying a replacement suspension or a replacement coil if you are ordering yourself. But they do send it to their partners who do repairs.
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