JBL L20t3 woofer surround

[Cozmo]

I just picked up a pair of L20t3's and after sitting down with them for an hour of critical listening, I'm happily impressed. However, I noticed that the surrounds on the 6.5 inch 115H-1 woofers are quite sticky and have a gloss to them. As if someone had applied some sort of treatment perhaps. Not being familiar with these, should I be concerned or is the normal state of the surrounds?

[hoschibill]

Hello :)
I have a pair of 4406. The 115H-1 is also installed there. The surround is matte and not sticky. I am pretty sure that this is original.

[Cozmo]

After taking the time to search some images of this woofer, I can see that it's not a normal condition (as I figured), and someone has tried to "condition" the surrounds at some point. Very discouraging. These weren't thrift store finds, I paid what is probably fair market value. The surrounds haven't started to dissolve or anything like that so far as I can tell. Is there anything I can do about this? Any suggestions as far as how to remove gunk like this from these surrounds?

[Cozmo]

87675

[BMWCCA]

Try Goo-Gone?
It seems to work on sticky stuff without being too drastic. It's citrus-based.

[Mr. Widget]

Why risk damaging them? I’d be inclined to leaving them as is.


Widget

[Cozmo]

Why risk damaging them? I’d be inclined to leaving them as is.


Widget

I would agree normally. It depends on what the "treatment" is. If it's Armor All then that isn't a good thing so I've heard. And if someone thinks putting some sort of treatment on their surrounds to somehow preserve then, I wouldn't count Armor All out. I have no idea how long this stuff has been on here and it seems to have not dissolved the surround material, or to have harmed it in any way at this point.
The guy I purchased them from was flipping them so I doubt he knows what took place. I'll reach out and ask though.

[Cozmo]

Does anyone know if Goo Gone would be too aggressive for this type of speaker surround? Citrus based means acidic.
I'd like to bring these back to "as new" condition and keep them. The cabinets need a bit of work as well.
Otherwise, these are impressive little speakers.:bouncy:

edit; after a quick search, it seems that Goo Gone will dissolve rubber. So to say that use on surrounds is not recommended would be an understatement.

[speakerdave]

No reason for alarm. The lesser brother L20T's (not 3) are being mined for their tweeters, so there are clean 115-1's lurking in many places, including eBay and my garage. I have mine because I actually bought some spares for an L20T-based low dollar mini HT that never got beyond the proof-of-concept stage. It's all available except the little HT Marantz receiver that went away almost immediately.

[Earl K]

Does anyone know if Goo Gone would be too aggressive for this type of speaker surround? Citrus based means acidic.
I'd like to bring these back to "as new" condition and keep them. The cabinets need a bit of work as well.
Otherwise, these are impressive little speakers.:bouncy:

edit; after a quick search, it seems that Goo Gone will dissolve rubber. So to say that use on surrounds is not recommended would be an understatement.


Why not just download REW ( Room EQ Wizard (https://www.roomeqwizard.com/)) for whichever computer type that you run.

Setup ( the recommended ) test-jig needed to measure TS parameters and then have at it.

By far , getting the Fs of your ( currently modded ) speakers is the most important parameter ( for this discussion ).

I suspect that Fs will be ballpark and that you're worrying about this needlessly.

Also, ( I'm sure somewhere in the depths of this forum ) there's an explanation of the surround type used by these 115H-1 drivers.

I seem to recall it was especially thin and non-replaceable ( from an OEM perspective ) .

:)

[SEAWOLF97]

Does anyone know if Goo Gone would be too aggressive for this type of speaker surround? Citrus based means acidic.
I'd like to bring these back to "as new" condition and keep them. The cabinets need a bit of work as well.
Otherwise, these are impressive little speakers.:bouncy:

edit; after a quick search, it seems that Goo Gone will dissolve rubber. So to say that use on surrounds is not recommended would be an understatement.

personally, I'd just try some rubbing alcohol.

[BMWCCA]

edit; after a quick search, it seems that Goo Gone will dissolve rubber. So to say that use on surrounds is not recommended would be an understatement.Well that's no good! Thanks for the info. I've used it safely on plenty of surfaces. Can't recall using it on rubber, exactly. Wish I had some sacrificial surrounds to try.

[bedrock602]

I use denatured alcohol to clean rubber turntable belts and rubber pinch rollers on my cassette and reel to reel tape decks.

[Kay Pirinha]

personally, I'd just try some rubbing alcohol.

Personally, I'd just try to drink some alcohol, put the grilles back (hopefully there are some…) and relax :p. But keep observing the surrounds and refoam the drivers if needed somewhen.

Best regards!

[Cozmo]

After more searching on the Google box, it seems that alcohol will degrade rubber. Drive belts may be OK on occasion but a thin membrane like these surrounds would likely be damaged. I might just try some soap and water (Dawn). If that has no effect, I'll just leave them and hope for the best. They seem to be performing well at this point. As mentioned, there are replacements available if they eventually go south. Too bad some ill informed owner in the past put something on them in the first place.:banghead:

[SEAWOLF97]

At Intel , we had a saying .... "If it ain't broke, fix it ..till it is"

I like K's suggestion :)

[Cozmo]

At Intel , we had a saying .... "If it ain't broke, fix it ..till it is"

I like K's suggestion :)

Earl K or Kay Pirinha? If Kay Pirinha, then yeah, that's the route I will go here.:p

[Cozmo]

I went at the surrounds with Dawn dish liquid in warm water. Seems to have gotten rid of most of the crap. They are still a bit tacky but then so am I.87735
Since I have these opened up, would it be to my advantage to replace the 31 year old capacitors or am I opening up a can of worms here with that suggestion?

[grumpy]

To your advantage? :skeptical:

Possibly lower resale value (not original and “had some work done”).
The bipolar electrolytic (blue) doesn’t appear to be bulging or oozing from the ends.
Do you hear something wrong, perhaps in one speaker only, to suggest a problem?
Do you have a way to measure cap values? Let alone at the crossover frequency range?
Is there room and budget to replace the blue cap with something “better”?
You -could- spend more time and money on crossover mods (e.g., charge-couple) than your purchase price.
(I hope not :D).

Thought/opinion: I’d save money for less gooey woofers.

[Mr. Widget]

Mylar caps are pretty stable. (The yellow 4uF cap.) The coils and resistors are likely in as new condition, so only the NP electrolytic would even possibly need changing. As Grumpy said, making a change could lower your resale value. I probably wouldn't bother. Then again, swapping in a pair of Dayton film caps won't cost much and could only be better... audibly? Hard to say.

https://www.parts-express.com/dayton-audio-dmpc-12-12uf-250v-polypropylene-capacitor--027-430?gclid=EAIaIQobChMIgYXetti37QIVJj2tBh1kUAeXEAQY ASABEgKwoPD_BwE


Widget

[Cozmo]

The photo shows a before and after comparison. The woofer on the right hasn't been cleaned and the one on the left has. So the "gooey" is as taken care of as it's going to get. Kinda hard to see it in the photo, but there is a substantial difference and I'm satisfied with the result.
I did measure the caps and they are 16.1 at each lead. Because they are still in the crossover circuit, they are in parallel (along with a 10 ohm resistor and 0.4mH coil, plus a 4 Ohm resistor and 1.6mH coil in series). The cap values are 4 and 12 microfarads (plus two .01 bypass caps), so 16.1 makes sense.
The speakers sound great, so I'm not looking to correct a fault. However I have them open and would have no problem spending some money on them as they are good speakers and I'm a hobbyist.
I know electrolytics degrade over time and these are over 30 years old. The blue cap is the 12 microfarad bypass cap for the woofer so not as critical as the yellow mylar in series with the 035TiA tweeter.
Or I could just leave well enough alone and open a beer.

[Kay Pirinha]

Hi,

the blue 12 µF 'lytic most probably is the bypass capacitor in the woofer's low pass filter. Lift one leg, measure it's capacity and it's ESR and leave it alone if both are in specs. Anyway, the polypropylene cap suggested by Mr. Widget isn't that pricey and hence won't hurt ;).

Best regards!

[Cozmo]

Hi,

the blue 12 µF 'lytic most probably is the bypass capacitor in the woofer's low pass filter. Lift one leg, measure it's capacity and it's ESR and leave it alone if both are in specs. Anyway, the polypropylene cap suggested by Mr. Widget isn't that pricey and hence won't hurt ;).

Best regards!
All I have in the way of measurement equipment is a Fluke 89 IV multi meter. So I can't measure ESR. And yes, the blue cap is the woofer bypass cap. Being in Canada, the closest I can get to what Mr. Widget suggested is a 400 volt Solen PB for 6 bucks Canadian. Or about $4.75 USD. So pretty cheap.

[grumpy]

All I have in the way of measurement equipment is a Fluke 89 IV multi meter. So I can't measure ESR. And yes, the blue cap is the woofer bypass cap. Being in Canada, the closest I can get to what Mr. Widget suggested is a 400 volt Solen PB for 6 bucks Canadian. Or about $4.75 USD. So pretty cheap.

If you just have the jones, do the mylar with a pair of 2x value Solens in series and put a dc bias between them ... 1M and 9v battery is easy... can look up recent JBL schematics to see how with a diode instead of the battery.

[Cozmo]

If you just have the jones, do the mylar with a pair of 2x value Solens in series and put a dc bias between them ... 1M and 9v battery is easy... can look up recent JBL schematics to see how with a diode instead of the battery.
Sorry Grumpy but that went right over my head. You'll have to dumb that down a tad.

[grumpy]

Four 8uF (if the mylar/yellow cap is now 4uF). Each mylar would get replaced by two caps (Solen is a manufacturer) of double the value. Wire them in series. So far, this sounds like an unreasonably expensive way to make a 4uF cap, but stay with me... The joint where the two meet and aren't connected to the board goes to a 1Mohm resistor (new) then the resistor's other end goes to the positive terminal of a 9v battery. The negative battery terminal goes to the black speaker terminal. This results in the same value capacitance where the mylar cap was (series cap values work like parallel resistance values) so no change in crossover frequency, but inserts a DC bias between the two caps. Supposed to sound better :) ... Just looked up some old references... perhaps use a 2.2 or 3 Mohm resistor instead... the battery might last longer.

Some light reading:
https://theartofsound.net/forum/showthread.php?9700-Charge-Coupled-Crossovers

[Cozmo]

If I were to replace the 4uF mylar in the tweeter circuit, I would most likely go with something more simple and long lasting it think. Just a decent quality film cap.
The best I can do locally; replace both caps in both crossovers with 2 Solen 12uF 630V PPE for woofer bypass and 4 Clarity Caps (a 1.8uF Clarity Cap SA 630V in parallel with a 2.2uF of the same, times two) in series with the tweeter. $30.40 USD.

[grumpy]

If I were to replace the 4uF mylar in the tweeter circuit, I would most likely go with something more simple and long lasting it think. Just a decent quality film cap.
The best I can do locally; replace both caps in both crossovers with 2 Solen 12uF 630V PPE for woofer bypass and 4 Clarity Caps (a 1.8uF Clarity Cap SA 630V in parallel with a 2.2uF of the same, times two) in series with the tweeter. $30.40 USD.

Hmm, I think I’d just leave it alone, for that price and effort, but will be interesting to get your take on how it goes. Good to experiment and have fun! :)

[Cozmo]

I realize that the whole "upgrading crossover capacitors" thing can be viewed as a bit of a B.S. / snake oil type topic, and to the JBL purists on this site, might be seen as sort of sacrilegious to mess with a factory design. And, that the mylar cap is likely just fine, as would be the two 0.01uF bypass caps in parallel with both the mylar and electrolytic. But the electrolytic is now over 30 years old and it may be out of whack or eventually will be, or so I've read many times. So...since I'm in there messing around anyways, "why not upgrade the caps" is my attitude. These small bookshelves are quite remarkable and deserve to sound their best. I'm a hobbyist who doesn't mind spending a bit of time and money on something in order to see an improvement. It keeps me out of the poolhalls and off the street corners.;)

[Mr. Widget]

I don’t think that quality components are snake oil, though there is plenty of that going around, and I certainly don’t think terribly highly of most vintage JBL crossovers, but unless you get pleasure messing around with this stuff, I’d call it a day and enjoy them as they are.

That said, you seem to enjoy messing about with them, so go for it.


Widget

[Cozmo]

Real estate is at a premium both on the crossover board and inside the cabinet. But it all fit.
I also cleaned up any corrosion on the connectors, added dielectric grease to prevent future corrosion and added some open cell foam around the speaker frames just for fun.
880218802288023

[DanMan]

Hi Cozmo, et al. -->

Just snooping about the dog den on this one a bit...

Also curious on your L20T(3) "sticky icky" surround issue; I've also had a few similar-condition surrounds on just regular L20T's. Did you ever find out 'why/what' was the cause of this phenomenon, and perhaps removal solution? It does seem particular to this model/driver/surround and is not the usual oddity you'd expect, nor find natively or otherwise, applied on a surround.

It seems to somewhat melt/deteriorate the surround material into a foreboding goo that deteriorates the surround-to-basket adhesive compound into a perpetually disgusting tar-like slime. Really strange! Luckily I've only found it existing on speakers I purchased with intent to part-out for backup components in other speakers; but still, would be really nice to know more about it as well for salvaging out the woofers if needed too, am super curious to its composition & background history.

[DanMan]

Here are pics of all my 115H-1 that succumbed to the same "sticky" phenomenon you encountered. I can't see any evidence that something was 'applied' to the surround, i.e. looks like just deterioration/melt (they all arrived this way). Maybe the Texas heat?? Never seen anything like this on any other surround but the 115H-1.

89188

89189

89190 (I really like the 034 in this application)

89191

89192 (everything (dust, dirt, cat hair) sticks to it and is hard to remove from fingers.

[Earl K]

Looks like some Armor-All was applied at one time.

Are they all from the same supplier ?

:)

[DanMan]

I have 6 L20T's, and 5 extra 115H-1 woofers; they are all from different suppliers.

About 1/2 of the woofers have this sticky/glossy surround issue and 1/2 are fine. The 'gross' factor can't be understated ... once you touch it, the material is transferred to the finger. I tried washing my hands with first regular liquid soap (no effect), then Dial (no effect), then Fast Orange with pumice (no effect) and finally the Goof-Off removes about 98% from my fingers.

I have a pair of L20T built into the bathroom cabinet next to the bathtub (for 15 years now) ... figured the 'plastic' type woofer cone (or what's the name of this cone material?) would hold up best there, and indeed those surrounds (and overall condition of both speakers) are just fine.

I gave my dad 3 near-perfect L20T's maybe 20 years ago, they were kept in his HVAC'ed theater room with grilles on. He just returned them to me; 1 is perfect, 2 have sticky surrounds (but the sticky-shiny part looks like when you spray paint glossy on something too fast - it's in a random sparkly pattern) almost like it's seeping outta the surround on its own accord. So weird.

One of the 115H-1 is seized, and overall suitable for destructive testing - (don't hate) - so I just now applied some Armor All to the surround. Instead of smooth, that part of the surround now has grip like a rubber bicycle tire, but it's neither sticky shiny or slimy, yet. Will see what it's like 10 years from now .... :)

[DanMan]

Maybe good news, and currently having an alternate theory about this . . .

Well, now that the 'Armor-All' has settled into the surround, the woofer is no longer seized! Hahahaha, I WISH!! :D

But I went further w/testing for you Cozmo:
1. I tried the 'Goof-Off' on part of a surround: with slight pressure it does remove the gook, but within ~1 second the Q-tip turns pitch black from absorbing the surround material.
2. I tried some 'Purell' on a Q-tip, and it seems to remove only the gook, and much more easily than the Goof-Off. No adverse impact seen from me doing this; although I'd worry about the long-term implications of any liquid contacting a woofer.
3. My less-impacted surrounds, while still glossy, are just barely sticky, such that the gook does NOT AT ALL transfer to my fingers.
4. No matter how sticky mine are, it has never seemed to impact the sound, nor the flexibility/function of the surround. (Unless you're getting glare lol or aesthetically bothered by it, maybe just keep the grills on (this will also prevent dust sticking to them).

My theory is based on my worst-condition woofer. I've also owned it ~15 years. With slight upwards pressure on the cone, the surround starts to separate from the basket. Hard to see it here (because the gasket comes up too obstructing the view) but when the surround comes off the basket, the adhesive is still 'gluey' and stretches like a spider web.

89193

Theory: Since the surround is lacking the texture/absorptivity of a typical foam surround, maybe the surround adhesive doesn't dry correctly/fully between the rubber surround & metal basket, and hence stays a little 'wet'? Maybe standard woofer frequency/vibration causes some glue molecules to separate (or aerosols itself) and reattaches in a fine mist spray back to the front of the surround? Hmm, probably 'aerosolizing glue' is too far a stretch, maybe it just vibrates/migrates back onto front of surround through improper drying. Or maybe there was a bad batch of glue at the factory for a stretch, and/or did they change the type of glue?

I'm sooo curious about this issue. Hope I wasn't being too tacky about this sticky situation!

<Update: the Purell removes the stickiness from my fingers instantaneously, while the Goof-Off requires much harder/longer pressure>