L65a - I had to wait 35 years to get them!

[roelwelters]

When I was a little boy, around 8, I must have been so intrigued by the looks of the wooden glass top speakers at my aunt and uncle's place that 35 years later I could identify them by doing an image search for glass top speakers on google. I hoped they were l65's but I wasn't sure. Anyway my aunt and uncle both passed away and i asked my cousins if they still had those speakers. And they did! And guess what ... I could come by and take them! Oh joy when I found out they were the L65's I had hoped for. Me so happy!
The state is fair, the cloth is stained with mold, the veneer is relatively ok, the midtone and tweeters are like new and the 122 woofer just needs a new foam. My cousin told me that something was wrong with one of the speakers but didn't now what.

I'm now in the state that I have the new foams for the woofers, the cabinets are cleaned and polished.
Before I put everything back together I would like to rebuild the crossover network, since the caps are 40 years old.
I bought some German MKT-A audio caps from visaton, nothing fancy but good quality.

I have some questions:

- I'd like to clean the potmeters, as this might be the cause of the earlier mentioned problem. There is a JBL sticker on top op the pots that I'd rather not remove. Can i clean these pots from the inside and how would i do that?
- Is it a good idea to replace the caps on the crossover?
- Some of the original values are not made anymore so this is what i got:
C1: 15uF (13,5 on the datasheet, 14 on the cap)
C2: 1,5uF (same as the original value)
C3: 4,7uF (original value is 4uF)
Is that ok? What will that do with the sound?

Kind regards from belgium.

[BMWCCA]

Personally, I'd leave the crossovers alone. If you've not even played them yet, wait. If the L-pads have a dropout issue once you have them hooked up, try some spray cleaner in the pots without removing the label (foilcal). If you find just rotating the L-pad knobs back and forth (sound off) doesn't clear up the issue, then use heat to carefully remove the foilcals without bending them. Good luck and welcome.

Google this site or just keep reading, there's lots of good information here. Hopefully you got your surrounds from Rick Cobb?

[roelwelters]

Thank you for your advice, and forgive my ignorance, but what are the L-pads?
I got the foams from goodhifi.com, a company that is specialised in speaker components, is there a potential problem with these foams? I haven't used them yet.

These are the ones I ordered (http://speakerrepairshop.nl//index.php?action=article&aid=4440&group_id=20000070&lang=en&srchval=Foamring%20for%20JBL%20128H%20woofer#.WI8x _UUrJE4)

Do i put the spray cleaner on the pods from the outside of the cabinet or from the inside with the woofer build out?

[Odd]

Well, L-pad is not potentiometer, but they look like.
Spray those from the inside.

I do not know the surrounds you buy, but looks ok.

[roelwelters]

Well, L-pad is not potentiometer, but they look like.
Spray those from the inside.

I do not know the surrounds you buy, but looks ok.

Any advice on the crossover network? Recap or not?

[Mannermusic]

Any advice on the crossover network? Recap or not?

Post #2, first sentence, +1. Type "recap" into the database search box. HUGE library of info.

[SEAWOLF97]

Personally, I'd leave the crossovers alone. If you've not even played them yet, wait.

+2
recapping seems to be a standard knee jerk reaction with new owners.
I'm not convinced that it is always needed and may even degrade if not
done properly.

L65's (at least mine were) sound bass heavy because of the "close to floor" LF driver.
Putting them on stands does help with that, but they have little built in pedestals
that make stand mounting difficult. I removed mine (and saved them) , next owner did remount the pedestals.
They also need to be tilted a bit, but I worried that the glass would slide off, since there
is nothing securing it.

[Flodstroem]

Thank you for your advice, and forgive my ignorance, but what are the L-pads?

L-pads is a sort if constant ohmage potentiometer that always has the 8 (or 16) ohms at the input no matter what position you turn it to. At the output the ohmage will of course differ with position you turn it to. L-pads are constructed for to receive linear and constant load to the crossover (and of course for to balance the SPLs in the listeners room) .

[Flodstroem]

Btw, are you going to re-foam the speaker by your self? If yes and if you are not skilled or if you have never done it before, then you have to read this thread carefully
http://www.audioheritage.org/vbulletin/showthread.php?469-Resurround-Step-by-step

[roelwelters]

Btw, are you going to re-foam the speaker by your self? If yes and if you are not skilled or if you have never done it before, then you have to read this thread carefully
http://www.audioheritage.org/vbulletin/showthread.php?469-Resurround-Step-by-step

Thanks for the link, I'v successfully done a pair of woofers form the JBL LX 155. I used a test tone to center the cone.

[roelwelters]

Well this is BAD, i started the refoam with gluing the new foams to the cone and today i wanted to finish the job by centering the cone and gluing it to the edge.
No sound from 1 speaker! No test tone and no music. When measuring the resistance : endless.
Is a recone the solution or are there alternatives?
I was so hoping to hear them sing :-(

Kind regards.

[Flodstroem]

Well this is BAD, i started the refoam with gluing the new foams to the cone and today i wanted to finish the job by centering the cone and gluing it to the edge.
No sound from 1 speaker! No test tone and no music. When measuring the resistance : endless.
Is a recone the solution or are there alternatives?
I was so hoping to hear them sing :-(

Kind regards.

depends on if you have ever hear any sound from that speaker or if you never has
If you have hear sound from the speaker before the re-foaming then check for loose speaker terminal screws, the screws are located on the inside of the basket and its a bitt tricky to reach them for to tighten them.

Also check for open circuit on the speaker cone leads: do the ohm-measure right behind the cone as near as possible to the cone and check for a "normal reading"
There is also a possibility for an open circuit in the soldered point where the speaker leads meet the voice coil leads on the cone. For example if you have cut of the dust dome then it could be the possibility of an open circuit. Thats the last chance/point for to save the cone I guess. My two cents.............. ;)

[roelwelters]

Hi,
I sent both my woofers to speakerfix.be, a guy that, guess what, fixes speakers :-)
He repaired the voicecoil with the unlimited resistance and checked my refoam job.
All ok! Good job repairing those woofers without a recone.


Now I've assembled them and have been listening to them for a while and while playing some rock music i noticed guitars being louder from one side.
After some testing I've come up with the following:


- one mid's volume is lower than the other.
- the L-pad change the volume, but just a bit and they cannot be matched.
- both units measure approximately the same resistance.
- problem stays when changing speaker cable positions from L to R.
- no visible problems on the filter caps


So, my guess is that i have to change some caps in the crossover network. I listed the values I got vs the values on the caps/datasheet, can I use these?


For the MF they are


C1: 15uF (13,5uF on the datasheet, 14uF on the cap)
C3: 4,7uF (original value is 4uF)


For the HF


C2: 1,5uF (same as the original value)


Should I change them all, or none, or …


So for now I've changed back to my LX155.

Thank you.

[JeffW]

You might try swapping just the mid driver and see if the problem follows the driver or stays with the cabinet/crossover.

[mech986]

Thank you for your advice, and forgive my ignorance, but what are the L-pads?
I got the foams from goodhifi.com, a company that is specialised in speaker components, is there a potential problem with these foams? I haven't used them yet.

These are the ones I ordered (http://speakerrepairshop.nl//index.php?action=article&aid=4440&group_id=20000070&lang=en&srchval=Foamring%20for%20JBL%20128H%20woofer#.WI8x _UUrJE4)

Do i put the spray cleaner on the pods from the outside of the cabinet or from the inside with the woofer build out?

Take the woofer out to spray the L-pad controls - As above, L-Pads are special high power potentiometers that give a constant impedance to both sides while changing levels. Potentiometers usually refers to lower signal level (<5V) controls which are primarily resistive in nature and wound either linearly, audio taper, or exponentially. If you have access to DeOxit from Caig Labs, or a similar contact or control cleaner, you can use it - have a spray can with a long tube on the spray tip and spray into the vent holes in the back of the control. If you cannot gain access very well, they you'll have to carefully remove the foilcal with heat from a hair dryer, and gently get under and s-l-o-w-l-y and carefully lift the aluminum foilcal when the adhesive softens and gives way. Then the screws which hold the L-pad control board to the baffle are exposed.



- Is it a good idea to replace the caps on the crossover?
- Some of the original values are not made anymore so this is what i got:
C1: 15uF (13,5 on the datasheet, 14 on the cap)
C2: 1,5uF (same as the original value)
C3: 4,7uF (original value is 4uF)
Is that ok? What will that do with the sound?

Kind regards from belgium.

The MKT-A caps from Visaton are similar metallized polyester to the original mylar (polyester) that JBL used. Its not a problem to replace them if you wish, but sonically, they would be pretty similar, and most film caps, even from that era of 40 years ago, are pretty stable. If you are looking for an upgrade, usually folks will use the metallized polypropylene which has better capacitor characteristics closer to ideal and are not terribly large or expensive comparatively.

Here's an ebay seller with a listing of the MKT-A types and representative values.
http://www.ebay.co.uk/itm/Visaton-MKT-A-Capacitators-1-0-F-up-to-100-F-/152289245473?var=&hash=item2375257921

I would not deviate from the original network values on the datasheet. You can easily parallel solder a pair of caps to achieve a much closer match to the original values. Here's what I would do:

C1: 15uF (13,5 on the datasheet, 14 on the cap) = 11.1% off - 10uf+3.3uf = 13.3uf, or 5.6uF+4.7uf+3.3uf=13.6uf, either being only 1.5%-0.7% off.
C2: 1,5uF (same as the original value) - no change
C3: 4,7uF (original value is 4uF) = 17.5% off - 3.3uf+1.0uf=4.3uf (7.5% off) or 2.2+1+1=4.2.

All of the above assumes the film caps are at their exact value, something that isn't likely as most film caps are rated at +/- 10% or 5% if you pay for it. If you're really compulsive about accuracy, you could buy a bunch of similar values and then match them up in pairs for the values you want with a capacitance meter, or pay the vendor to do so at a bit more cost.

[mech986]

The surrounds you're using were for the similar 128H so sounds like they were likely a good match, and looks like they passed inspection by your tech.

[roelwelters]

Well,
I just got a chance to switch the mid drivers and the problem stays with the crossover.
In a lucky guess i changed C3 with a visaton MKT-A 4,7uF that i had laying around.
Problem solved! So I will have to put some work in the crossover.
The L-pad controls also work fine now.

My question: Since the speakers haven't been operational for 30 years, and I've allready destroyed an original cap, just after playing a few songs, would it be best to change C1 and C2 as well, or do I just change both C3, and leave the rest untill they break?

I don't like taking out the woofer too much, as there's allways one screw that is not cooperative.

[Mr. Widget]

Congratulations on the speakers and getting this far.

I would try to locate a pair of 4uF caps. There are other manufacturers that do make 4uF caps, alternatively you can parallel a pair of 2uF caps. I would only replace the two 4uF caps and call it a day. I doubt the original cap failed due to your playing the speaker, I'd bet it simply failed due to age. Even so, like most of the other posters, I'd keep the originals in there and only replace the two 4uF caps.

Widget