Jubal woofer fubar?

[DanMan]

Thanks for the replies everyone. This has made me realize how fubar'd this situation really is. Details and guts to follow.

If anyone finds that that JBL takeout menu, I'll have one of everything! "better get a bucket"

Oh, and I must say in my defense, from the head-on pictures on ebay, i couldn't tell the gasket was on the wrong side, there were no angled pics to ascertain that (go figure) but the speakers really appeared in awesome condition and it was the best packing job ever. I should have stayed on the re-seller (an ebay store) but I lost contact so the fix $ must come from my wallet.

Ok, I pulled the woofers from the cabinets, judging from the pull force alone, they hadn't been off before (but shipment in the texas heat could have done that).

The driver is indeed a 126A from a Jubal L65 (pic #1). The spider does seem 'at rest' or completely horizontal (you can see it in pic #2). Ok, the 7.7 ohms really perplexed me. I tested that resistance numerous times b4 reporting it here and it really was 7.7 ohms. After testing it again and again I found that the resistance was changing based on the amount of pressure I used to hold the volt meter wires against the push-pin type wire connectors on the basket. Next thing I did was check the battery in the volt meter and it checks out fine. I didnt have any known resistors to test if the ohm meter was working correctly (it checks out on the ac/dc side of electricity) so I pulled woofers from L100T, L56, and L1's, and checked the resistance of those woofers - and they all check out to within specifications - regardless of how much force I use to hold the volt meter wires to the driver. So I tested the resistance again of the 126A's in 2 places (see pics) (A: at the push type connectors) and (B: at the Lshaped piece of metal that connects the wire to the cone). I get 7.7 ohms at point A and 5.5 ohms at point B. I dont see where I could be gaining that much resistance - the connectors are clean, look original,etc etc. If I mash the volt meter into the connector pins as hard as I can (without breaking them) the resistance drops from 7.7 to 5.5. Strange...

Knowing that the spider is at rest, but the surround seems placed incorrectly, I wanted to be able to determine the displacement of the cone vs the force required to displace, in both directions. As edgewound says "there cant possibly be equal travel in both directions", thats gotta have an odd impact on the sound characteristics. I dont have any real equipment here that checks cone displacement as a function of voltage or sheer force, so out of curiousity I had to devise my own method to check this.

Basically this involves using a laser attached to the cone to determine the change in distance as a function of voltage, in both directions. Pictures of this experiments below. Now, since the last terror alert was raised to crimson, I'm out of duct tape, but luckily I have scotch tape which is much lighter. Also my laser pointer is made from aircraft-grade aluminum so its lightweight, and the placeholder is balsa wood so the combination is very light weight, the tape is really used to hold the laser pointer button depressed during the experiment.

I used 2 C batteries together (around 3 volts) supplied to points A, and to points B, in the pics (the push type connector, versus the actual metal connected to the cone wire) in the positive and negative, whilst the laser pointed at the ruler in order to measure the cone's displacement.

Granted, this may be akin to holding a ruler to your monitor to measure distances, but if you're using a flat monitor, a good ruler, AND you have the image scaled on the screen correctly, its possible to get a measurement that may be semi-accurate relative to other similarly taken measurements..

Anyhow, it seemed to work well enough, and showed some interesting results:

At (A) the push type connectors (where I get 7.7 ohms):
+3 volts pushed the woofer out 3/30 of an inch
-3 volts pulled the woofer in 2/30 of an inch
Shouldn't they be the same distance?

At (B) the L-shaped cone wire connector (where I get 5.5 ohms):
+3 volts pushed the woofer out 4/30 of an inch
-3 volts pulled the woofer in 3/30 of an inch

The cone's different displacement (in vs. out) for the same applied voltage seems to me to indicate that the surround placement would indeed wreak havoc with the overall performance of the driver, (as well as the response of the entire speaker)?

Also, the push type connectors seem to have 2.2 ohms of internal resistance - that seems really odd - but the displacement experiment proves the resistance values. (granted i'm {also} bucking up for a more expensive volt meter soon.. )

Another issue I realized (and can be seen in the pics) is that the gasket is not manufactured to the same specs as the basket, so that the width of the gasket is not uniform along its length, meaning the surround, even sitting still, is deformed, and if its "out" bad enough, at volume, could deform the cone as well.

was 'fubar' the right word for this driver ?!?!

comments on the above are appreciated.. also beyond the technicals of all that, im still interested in salvaging the L65's and appreciate advice on what to do about getting the best woofer back into the cabinet - whatever that may be. thanks forum!

[Hoerninger]

Basically this involves using a laser attached to the cone to determine the change in distance as a function of voltage, in both directions.

Thank you for the tip! Great things are easy.
____________
Peter

[Zilch]

Buy the correct refoam kit from Rick Cobb and redo it yourself.

[grumpy]

cool displacement test rig ... can't help thinking that some of the assymetry you're
seeing might be due to gravity and non-linearity of the existing foam surround,
as-installed (seeing that the gravity-assisted direction wasn't larger).
If you had a way to temporarily attach it to the cone (blu-tac?), you might be able to
separate the effects (for fun... ). Heck... blu-tac a small/lighter reflector on the cone and
measure the reflection motion...

I'd get some contact cleaner or "deoxit" into those terminals and work them a bit...
dissassemble if it's obvious how to. They should not add that much resistance to the
circuit.

FWIW, last place that I saw advertising 126A recones (which Edgewound found are
now NLA) wanted over $300/ea... part of my "clench" comment. If recones are
eventually required, you might want to run box simulations on the suggested cone
alternatives/substitutes.

-grumpy

[mech986]

If the lead wires/tinsel is directly measured at 5.5 ohms, I'd say that is likely a true JBL voice coil. There is probably some corrosion at the wire/screw interface or there is a bad solder joint at the wire/solder ring spade connection. If it were me, I'd have a JBL authorized station replace the cnnectors with new gold plated binding posts and resolder a new ring spade to the lead wires or solder directly to the binding post. Once assembled, the binding post should be no more than 0.2 ohms above the lead wire measured directly.

Assuming the spider is mostly horizontal, I'd still opt for stripping the surround and frame trim off, check spider for condition and elasticitiy, and voice coil for centering. If all is well, I'd try refoaming correctly with the correct size foam/roll and properly placed on the cone backside. The slight cosmetic hit could be made up by salvaging a good cone. Heck, for the price of $25 worth of surrounds and some time, you're not into it for much and you can always recone if it doesn't work out.

BTW, nicely engineered optical displacement gauge you made. With the correct frequency, probably 70 hz or greater, you can easily measure the Xmax as a sort of Bar Graph Eye Tube like indicator display. I suspect though that the added mass is still making an impact though.

Regards,

Bart

[DanMan]

thanks for the tips and the accolades on the displacement test 'rig'.

i dont normally touch or attach items to my JBL woofers - but the experiment sounded too good to pass up.

btw - the laser point makes a great instrument for aiming speakers in the right direction - i use the laser pointer attached to a t-square in order to get my surround sound speakers pointing exactly where i want em to.

the blu-tac sounds like it would be great for reflecting the laser pointer to the right spot if you're trying to bounce sound off walls in the right direction, and the deoxit also makes a great addition to my toolkit - thanks for the tips on those. i would have probably used wd-40 (just kidding) but 2.2 ohms seems like a huge loss to me - who knows maybe a bugs inside the terminal or something - thats what usually happens to our software ;-)

well while these all may sound like easy fixes to you guys - i'm really just a hack (as you can probably tell from my lack of proper terminology), a jbl nut for sure, but i'm a civil engineer, and i view my speakers as instruments, and i dont fix my own instruments, i leave that to the pros. so it sounds like these speakers need more tlc than i can give them. im currently involved in other projects (trying to get my own business into the big time) and i just dont have time for these.

honestly these jubals were my indication that i have a speaker addiction. i simply dont have room for these in my house. ive got jbl speakers in every corner of the house, that all work, and are all hooked up. i bought the jubals to replace my L100T's and while that may seem 'nuts' i was looking for the sound quality of the jubal (especially the tweets). but i missed my L100T's and putting them back in place means i have no where to put the jubals. i mean really no where. if you guys saw where the jubals are sitting now, id probably win some darwin award for the worst speaker placement ever! the L100T's were scheduled to go to my brother until he got his system going, but he's an idiot, and they're not going to be placed into his care. so i'm back to nowhere to place the jubals. i could store them but it would be years till im ready to work on them, and by then the parts would be even more scarce. (the jubals would have to be stored in a spare room - facing the wall - for protection - and it would just feel like i was constantly punishing someone that way ;-)

so for me the jubals are the speakers i couldnt have and it would just serve as a reminder that this jblnut went one overboard. im willing to sell them, probably not part them out, but just sell em whole. you guys now know what shape they're in - and the price would accomodate that - even though the rest of the speakers are almost near flawless - I'd say whoever originally owned em didnt do anything to them until the refoam, saw what job he got, and sold em to an ebay store.

if anyone is interested in making a good home for these i guess pm me as they say, or any other advise y'all have.. i will not ship these... so much trouble involved in shipping speakers correctly.. and i doubt i'd ebay them knowing the condition they're in, and my 100% feedback rating, and that i dont want to ship them. im in austin texas and you can pick up from my house or i could deliver anywhere in austin. i make the austin-houston journey every couple months and could deliver anywhere along the way (though these might not fit into my car)...

any (more) advice on selling these appreciated. thanks.

[macaroonie]

Take your time and the advice and helping hand from the folks here. You will not regret it 65's are lovely.

[DanMan]

thanks. i love all my JBL speakers equally, i know that a space might one day open up for the jubals, and i'll probably regret selling them then. uh, change that, i'll probably regret selling them the day they're gone

my dad has built some JBL speakers and I've seen him recone a lot, but i'm a little bit (ok, a lot) obsessive compulsive when it comes to symmetry, and so i've always had my recones done professionally for that reason.

i've accepted rubber when it was supposed to be foam, and vice versa, just because the parts weren't available, and its never worked out well enough.

i couldnt refoam, because i'd not be willing to suffer the cosmetic hit, guess im more ocd than i thought . and a recone at 300 a pop is a notch more than i'd sell em for. even still, messing with the terminals would add to the price. i think fixin these is for someone other than me...

for me, the only acceptable solution would be the 128H-1 replacement. I know the 128H - I think that was a great driver. I see there's some 128H's now on ebay but again, i'm not putting a white cone in my jubals, i'm assuming the 128H-1 are the black coned versions of the 128H, am I right on this?

i see some other posts that suggest even with the 128H-1 replacement, i'd still need to modify the network, is this right? if not, i'll keep my eyes out for the 128H-1's and probably get two of them for the jubals as long as i dont have to mod the networks...

i havent seen a 128H-1 in a long time, anyone know what these go for?

[grumpy]

hmm... if you go back to post #11 in this thread, I believe you might have
a few more options with fewer electrical and visual issues... -grumpy

here too (scroll back to check out the whole thread):
http://audioheritage.csdco.com/vbull...3&postcount=16

guessing the suggested spacer gasket might be a bit shy of the thickness used on
yours, but ???

[macaroonie]

For $30 you can refoam yourself. There is a great step by step thread here with pictures. As it stands that driver is a mess but it is anything but dead.
With a little care and some patience YOU can do it.
Worst case you mess up somewhat and are $30 out but it would be hard to have the drivers in as poor a condition as a result. All that old glue is easily removed with just a little care.
Trust me i'm a doktor...

[coherent_guy]

Just came across this post and I couldn't resist. I'm glad you have pics of that butcher job, it should be in a hall of shame. I'm tempted to ask who the ePay'r is that sold those to you, but maybe they did not "fix" those woofers.

Please forgive me, but given that you have JBL's in every corner of the house and though characterize yourself as a hack (but came up with a nifty laser pointer excursion-o-meter) I find it kinda hard to believe you didn't take one look at those woofers and

It did take nerve to ask about it on the forum although 99.99% of the members are very forgiving, I salute you for that

And who among us can say we were never surprised by what arrived via good old ePay. . .

I wish I had seen your pics about a year ago, I could of saved myself a lot of work refoaming my friends L65's. . .

I'm sure your's will be good as new very soon Consider, did you ever see the painted 077's I think T'Dome found out there somewhere? It could have been much worse

[DanMan]

Well you guys are great. You've convinced me to give this a shot myself. Perhaps they still have a chance at finding a space in my home.

I dont want to give the ebay'er a bad name so I'm not saying who. I will say he's got around 2700 sales with 99.7% positive feedback, So hes 99.7% a good guy . He deals mostly in plates, im a bachelor, so i should say 'fine china' - and also vintage camera equip - all his stuff is near mint and even the plates (whatever..) go for +$300. Looks like fine vintage audio is maybe 5% of his sales or less. I seriously doubt he knew what was up - but who knows. I relooked at my old emails (im such a softee) that i never went after him.

I checked and I bought theses about 2 years ago - this was the 1st chance i've had at seriously looking at them for repairs - although i still dont currently have the time.

Yes, when the came i was flabergasted is putting it mildly. I knew i got what i deserved for putting the L100T's "facing against the wall" - it was their revenge against me!

You guys have been great consider the shape of these. Most of my time at this site is not in this forum - but reading it this week has been happily consuming. In the other forums I read daily, everyone is a genius, except everyone else who is an idiot. Statistically, I just dont see how its possible .

I found the resurround step-by-step links (you guys make it looks so easy) and cobb's ebay site. I know my dad will be 'over my shoulder' as i do this. Im opting for swapping out the binding posts to the gold ones. This will be my first JBL repair because even though these are minty (elsewise) theres some crackling in the control knobs. So hopefully forum is still as nice when i get back to reconditioning these puppies.

I need to learn how to effectively search these forums. And how do I get my picture under my username, it was showing up under my signature? (dont worry - i'll change the pic - it displeases me to see my L250's showing left on the right and right on the left)

[c402c1]

What a great site. I got turned on to it by any ebayer that had bought a Rick Cobb kit. Fortunatly this just after I bought a pair of mint (exception of the woofer foam) L65 Jubals off ebay. I this knew when I bought them and figured I would have to drop $150 for refoaming. After poking around the site I feel very confident to purchase the items and do the work. So if anybody has any tips tricks I would welcome the input. What a wealth of information. I also have a pair of L100 Century that I bougth new 75 that I just love. Can't wait to get those Jubals going.

[mech986]

Hi c402c1,

Welcome to Lansing Heritage! Hope you become a regular. Congrats on the Jubals, they'll be great after you get the woofers done. When you finish them, pop a few pics up and show us your handiwork. Remember to resize your pics to less than 1024 x 800 so they will upload.

Have fun, and if you need any help, just holler and someone will answer.

Regards,

Bart

[mech986]

hi DanMan,

Did you ever get your refoams done? Inquiring minds want to know (and see!).

Bart