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?
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.
Greets Oliver
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?
Try Goo-Gone?
It seems to work on sticky stuff without being too drastic. It's citrus-based.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
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.Originally Posted by Mr. Widget
The guy I purchased them from was flipping them so I doubt he knows what took place. I'll reach out and ask though.
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.
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!!
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.
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>
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.
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.
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.
"Audio is filled with dangerous amateurs." --- Tim de Paravicini
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.
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 ) 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 ) .
personally, I'd just try some rubbing alcohol.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.
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.
Some kind of happiness is measured out in miles
Personally, I'd just try to drink some alcohol, put the grilles back (hopefully there are some…) and relax. But keep observing the surrounds and refoam the drivers if needed somewhen.
Best regards!
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.
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