Lans-a-loy Repair Question

[Oldmics]

Gentlemen

We have some pretty creative minds on this forum so heres todays delema.

Looking for some sort of chemical to melt and then refuse Lans-a-loy surrounds.

Have a few units that have small separations but not split all the way thru.If I could liquify and move some of the existing Lans-a-loy material around and then have it dry in its new location as a patch,it would be a beautiful thing.

I"ve tried most of the usual household and reconing chemicals with no success.

M.E.K. doesnt work and neither do lacquer thinner,wd-40,alcohol and some chemical cleaners.I just thought about ammonia and will try that.


Any suggestions ??????


Oldmics

[aust-ted]

Hi Oldmics

We need to find out the chemical composition of Lansalloy. Once we find that out it should be easy to determine what will bond to it. I have a friend who is an industrial chemist who may be able to help out.

Regards
Ted

[Oldmics]

Since you can use brake fluid to reactivate stiffined Lans-a-loy,I would assume that its a petrochemical.


So what would dissolve a rubber band?

Oldmics

[aust-ted]

Since you can use brake fluid to reactivate stiffined Lans-a-loy,I would assume that its a petrochemical.


So what would dissolve a rubber band?

Oldmics

Yeah but we need to know which petrochemical. Anyone got an idea? Polyethlene? polyproplyene? etc

Regards
Ted

[Mr. Widget]

Is this for you or a paying job? If it is yours, ship it to me and I can most likely fix it.

Widget

[Earl K]

Hi There,


Looking for some sort of chemical to melt and then refuse Lans-a-loy surrounds.

- Have you tried applying heat ? ( a chemical catalyst isn't necessarily the only sort needed )

- I realize you're hoping to discover that this stuff can be treated as if it was PVC where you can add acetone/? ,,,,which chemically melts it ,,,, and then have it reconstitute itself once the acetone vapourizes .

- I think LansaLoy is a lot closer to rubber than plastic, so I'm pretty sceptical about this whole process . Rubber turns back into a shapeless glob that needs reforming ( vulcanization ? ) after it has been heated .

- I'll think some more about this .


:cheers:

[aust-ted]

Earl

If we knew for sure it was a butyl rubber then we could easily work out what bonds to it

Regards
Ted

[Earl K]

Hey Ted,

:birthday:


- I have a few le14a(s) with the LansaLoy surrounds. Some are eventually destined for refoams since I "pooched" a few rehabs .

- My first LansaLoy rehab was of a surround that had 2 concentic splits that circled around @ 80% of the surrounds' circumference ( this appears to be similar or worse than Oldmics situation ). I chose to DOT 3 Brake Fluid the material and then apply a thinned down, silicone-based skin over these splits in the LansaLoy. This worked well and I ended up with a Fs in the low 20s. This would still be my first choice ( apart from refoaming ) if confronted again with a similar situation .

- FWIW ; Zmax on these older surrounds is considerably lower than the newer foam types with a lower Q ( a broader impedance skirt ). This lower Zmax is somewhat electrically similar to throwing a conjugate resistor across the woofer . ie , it aids in dampening . That is the singlular most important reason that I try to maintain these old surrounds ( apart from just being lazy ).

- Some excess/surplus LansaLoy is needed so someone can experiment within a crucible ( to test this melting theory ).
- Bunsun Burner anyone ?

:)

[Zilch]

What we REALLY need is a suitable butyl surround like LE14H-3.

Ask a volume reconer/refoamer to save Lans-a-loy surround fragments for experimentation, maybe.

In about 30 days, we'll have plenty to work with. :D

[gerard]

hello

Sorry Gentlemen but what is a lansaloy ?
And what do you look for ? A special type of glue ?
if yes I may help you !

gerard

[Mr. Widget]

It is the foam material JBL used from the late 50's through the mid 70's as a surround material. Originally it was an off white. With age it darkens to a tan color and stiffens. An application of DOT-3 brake fluid will soften it and return it to a state that is similar to new as long as the surround hasn't been cracked by trying to operate the driver while the foam is stiff.

Widget

[boputnam]

Widget, Ms. Gadet - and you... - take beautiful pictures!! :yes:

Hey, Oldmics :wave:

In a vacuum of real compositional knowledge, I'd be tempted to treat with DOT3 to the extent you can, and then carefully mend the splits with Household Goop, or other rubber-type cement that stays pliable.

I worry that any attempt at using a Lans-a-loy solvents could end in a disaster of unstructured goo, where the original surround shape gets lost and cannot be recovered. :dont-know:

[Mr. Widget]

Widget, Ms. Gadet - and you... - take beautiful pictures!! :yes:


Thanks... I took them awhile back when I was eBaying off my LE15A collection.

Bo...you should keep to the Front of House!

DO NOT USE CONTACT ADHESIVE ON YOUR LANS-A-LOY!!!!

"I worry that any attempt at using a Lans-a-loy solvents could end in a disaster of unstructured goo, where the original surround shape gets lost and cannot be recovered. http://audioheritage.org/vbulletin/images/smilies/dont-know.gif:"

I'll second that.

Widget

[boputnam]

DO NOT USE CONTACT ADHESIVE ON YOUR LANS-A-LOY!!!!
:rotfl:

Yea, well it ain't really like contact adhesive - it's more of a robust rubber cement. Bonds not-too-fast. I've used it in situations where it lasts for years and remains very pliable, and is completely airtight.

Anyway, what the hell is the polarity?? :D

[4313B]

I'd be tempted to treat with DOT3 to the extent you canOh God! Not you too! :p

Oh what am I saying! I too would dump brake fluid on other people's JBL's. :rotfl:

[tomt]

might use turpentine for total melt

[4313B]

Latest from JBL -

"it definitely is not suitable for loudspeakers to today's standards. We do not have any documentation as to the chemical composition of the material"

Soooo, off to the chemist I guess...

[spkrman57]

We can send a man to the moon and back, but can't figure out how to make
"lans-a-loy" surrounds"!

I have a lead on a pair of L55 cabs(with tweeters), but no LE14A's as the surrounds went south. Since the LE-14's are hard to come by I was thinking of trying to fit a different driver in them.

Sad part is, I don't want to ruin a classic cabinet, but what would you all think? Hold onto the cabinet for someone who has a pair of LE-14's, or modify it for a 15" driver that would work in a (almost) 2 cubic ft cabinet with minor modifications.

A dilemma for me as I have various drivers, but no LE-14A's anymore. The cabinets can be had for a affordable amount according to a lead from one of my friends. I believe it might even have the "smoked" glass top!:banghead:

Ron

[4313B]

"We can send a man to the moon and back, but can't figure out how to make
"lans-a-loy" surrounds"!"

We don't want to know how to make lans-a-loy surrounds as evidenced above. :p

"Sad part is, I don't want to ruin a classic cabinet, but what would you all think?"

Seriously? Take the stock measurements, put them in AutoCAD and then do what you want with them. Or just wait for LE14A's... Be aware that that system is pure nostalgia so unless you're running a museum...

[spkrman57]

I know some folks out there might be in need of such a cabinet and that after modifications done to it would not be the same.

It seems that I should see what it would cost for me to get the pair and use it for a 15" midbass system.

Ron

[4313B]

"I know some folks out there might be in need of such a cabinet and that after modifications done to it would not be the same.
" True, true.

It's too bad you couldn't fit a 2204H/2206H in it and put a 2344A/2425H on top! :p Find some 1400Nd's or 2217H's and stuff them in. :p

[Zilch]

Since the LE-14's are hard to come by....HUH?

[spkrman57]

There are many out there, but with shot surrounds.

Ron

[Zilch]

A $50 or less per pair fix. I've never seen a Lans-a-loy surround worth preserving, at least performance-wise.

Reconing LE14H-1's a better result, too....

[Anthony L100]

Hello guys, this is my first post on this excellent forum, i've learn't so much thank you! I have many vintage JBLs and am in the process of restoring the hardware in my 4341s. The 2231s had been re-foamed on the fronts, which I wasn't happy with so i've now done them correctly with Rick Cobb goods. They look and play fine. The 2121s have what looks like these lans a loy surrounds which are very stiff but undamaged. They allow a cone excursion of about 1 mm total, so am I correct in assuming they need the DOT 3 treatment? How compliant should they be, surely not as soft as a bass driver surround. Any help would be much appreciated! I have other issues regarding these monsters (they are in the UK!) but would it be more appropriate to start a new thread? Thankyou, Tony.

[Mr. Widget]

Hi Tony,

Actually, yes they should be as compliant as bass drivers... at least the Lans-a-loy would have been when new. The DOT-3 treatment can be done without measuring equipment but for best results you should measure the free air resonance of the driver and make several light applications until the resonance is correct. The resonance for that driver has been posted on this forum, but it is deep in there.

Widget

[Anthony L100]

Thank you Mr Widget, unfortunately I do not have those facilities, but with your info I now realise these drivers need some surgery before use. I will let you know as I progress. If I need to re-surround, is there a suitable replacement surround for the 2121s?

[Mr. Widget]

Here you go.

http://www.audioheritage.org/vbulletin/showthread.php?t=3527

and for comparison...

http://www.audioheritage.org/vbulletin/showthread.php?t=2669

Good Luck!

Widget

[Anthony L100]

Thanks Mr Widget, i've now got all the info I need to decide which route to take. Rather than risk the possibility of contaminating the cone with brake fluid, I might just re-surround 'caus I just love doing that, it's like open heart surgery! (almost). 4341s do not seem that popular on the forum, is there a reason for that? With the same driver line up as 4343s in a smaller cab I would have thought every home would have some.:) I have to say it was the influence of you guys that persuaded me to get them, all that talk about large format JBLs got me moist! L166s actually work better in my modest size room, but hey, it's a pride of ownership thing!

[dmtp]

I just became the proud owner of a beautiful looking pair of LE-14C's (with LX2-1 XO). As expected the lansaloy suspension is a bit stiff and Fs is now 63 on one and 126 on the other. I've searched the forum and read what I could about the Dot 3 brakefluid treatment, but still have some questions:

Do you apply the brake fluid to both sides? (I already have)
How long do you wait between applications?
How many applications before it is worth testing again?In other words, just HOW do you do this?
Thanks

[Zilch]

Refoam and be done with it. Brake fluid is only a temporary fix, and you risk rendering the cone unrefoamable.

That'd be fine with an LE14A, but not an LE12C....

[Mr. Widget]

Do you apply the brake fluid to both sides? (I already have)
How long do you wait between applications?
How many applications before it is worth testing again?First off, Zilch is correct. (Well even a stopped... sorry that was a different thread.) Seriously, if you aren't very careful you may get the stuff on the cone and then the glue for refoaming won't stick... it will also stain the cone.

That aside, you do apply it to both the front and the back of the foam. You apply it very sparingly. Wait overnight and measure your Fs in free air... repeat as necessary until the Fs is correct. The treatment should last a year or more, then you may need to touch it up again.

Replacing the foam will give you about ten years and then you have to do that again.


Widget

BTW: I wasn't able to find the Fs for the LE14C... LE14A is 25Hz.... I would assume it should be close to that value.