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[Seth Huling]

I have been trying to work on making the stock JF80s at my shop consistent.  Unfortunately, EAW seems to change the design of their speakers frequently.  I have multiple "acceptable" LF drivers and multiple crossovers.  I am having a problem with one specific speaker that has a 10db dip around 3k.  I cannot see any damage to the crossover or damage to the drivers, both HF and LF. The only thing I can think of is that there is an old crossover and a new tweeter or vice versa.  Does anyone here have experience repairing JF80s and/or other JF series EAW speakers? Any advice is greatly appreciated.

[Langston Holland]

Hello and welcome:

The first thing to do is go into your account and change your alias to your real name per the posting rules.

---

Your post is quite well written, BTW. Make sure the (2) woofers are in polarity with each other. You can go by wire colors, but I'd suggest placing a 9 volt battery on the input and make sure both drivers move in the same direction.

If they were not in polarity, remeasure and see if that fixed it. If they were in polarity, try reversing polarity of the tweeter leads and see if that fixes it.

Oh yeah, unfortunately I do have experience fixing JF80's...

[Seth Huling]

Hello and welcome:

The first thing to do is go into your account and change your alias to your real name per the posting rules.

---

Your post is quite well written, BTW. Make sure the (2) woofers are in polarity with each other. You can go by wire colors, but I'd suggest placing a 9 volt battery on the input and make sure both drivers move in the same direction.

If they were not in polarity, remeasure and see if that fixed it. If they were in polarity, try reversing polarity of the tweeter leads and see if that fixes it.

Oh yeah, unfortunately I do have experience fixing JF80's...

Name all set---

thanks for the input.

I'm fairly certain that the problem i'm experiencing has nothing to do with the polarity of the 2 LF drivers because the crossover point is something like 1.8k and when I put a 3k tone in the LF drivers are completely still.  I changed the HF driver as well as switching it's polarity (with bad results) and still had no success.  As of now the speaker is on a pile of "parts".  UNCLE

[Langston Holland]

UNCLE

Seth! Never let something inorganic beat you! :)

Sounds like it's time to steal a tweeter from one of your functioning JF80's and see if that fixes it.

[Seth Huling]

Sounds like it's time to steal a tweeter from one of your functioning JF80's and see if that fixes it.

I tried that and unfortunately it didn't help :-/

[Geri O'Neil]

Seth! Never let something inorganic beat you!

Sounds like it's time to steal a crossover from one of your functioning JF80's and see if that fixes it. (Okay, if you haven't already).

Sorry, Lang, you made it sooo easy...

Geri O

[Ricky Lighthall]

I have repaired literally scores and scores of these.  They were and still are very popular Broadway boxes when I worked up there.

There are two major possibilities.  Either the electrolytic caps in the xover are dried up and/or  one or more cement resistors has broken loose (if any wiggle- replace them and reglue), or it's time for a new diaphragm.
If you swapped a driver from a good box of the same version it's probably the xover.
You might as well replace all electrolytics and check all resistors while you're in there.
Also, the inductors like to break loose and may need new glue.   
They use some odd values so it's much easier to order parts from EAW or Performance Audio.
I can PM you current part numbers if needed.

[Greg Ruddell]

Seth! Never let something inorganic beat you!

Sounds like it's time to steal a crossover from one of your functioning JF80's and see if that fixes it. (Okay, if you haven't already).

Sorry, Lang, you made it sooo easy...

Geri O

This is good advice. I recently bought 6 JF80's from a sound company that was downsizing. I bought all 6 for $600.00..So, they all had the original RCF drivers, and the original horn drivers. After evaluating each box I discovered huge inconsistencies. I couldn't even find any two that were similar sounding. However, upon removing all of the crossovers I soon discovered the issue. The 4.7Ohm  resistor on the LF Xover board next to the two elecrolytic caps gets very hot when it's getting a lot of signal. This will partially fail and also cause the caps above it (21MFD, and 15 MFD) to leak or fail. That's pretty much the issue.  But don't ever expect these things to sound exactly the same from box to box over generations. Any change in a vital component can yield a different result somewhat...but not dramatically. The sound of these things regardless of variations is just stunning. 120 db all day long and extremely hi fi. There isn't a box on the planet that can touch that. They are amazing.

[Mac Kerr]

This is good advice. .

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules clearly displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

Mac

[paul bell]

Is there a reasonable replacement woofer for these boxes without using the RCF version?

[Greg Ruddell]

Hello and welcome:

The first thing to do is go into your account and change your alias to your real name per the posting rules.

---

Your post is quite well written, BTW. Make sure the (2) woofers are in polarity with each other. You can go by wire colors, but I'd suggest placing a 9 volt battery on the input and make sure both drivers move in the same direction.

If they were not in polarity, remeasure and see if that fixed it. If they were in polarity, try reversing polarity of the tweeter leads and see if that fixes it.

Oh yeah, unfortunately I do have experience fixing JF80's...

Just wanted to report what I know now that I have finished repairing my 6 JF80's. These were grouped into pairs of close serial numbers, but all of them had the smae rcf drivers which were all in great shape as well as the original horn drivers which were also in great shape.

Two of the LF crossover boards looked fine with no visible damage to components, but the still sounded different from each other and all others sounded different from all others. I think it's a case of varying degrees of capacitor damage or decay.

I replaced the 15 Uf cap with a 15 Uf cap on the upper board.
I replaced the 21Uf cap on the upper board with a 22 Uf cap (can't get a 21 anymore).
I replaced the 15 Uf cap on the lower board with a 15 uf cap
I replaced the 4.7Ohm 25 watt resistor on the top board with a 4.7 Ohm 25 watt resistor
I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

I was surprised at how they all sound almost identical now. They sound brand new. Really punchy bottom end and crisp pristine highs like they are supposed to have. Of course they need eq. or processing, but not much.

[Bob Leonard]

It's a well known fact that once an electrolytic reaches a certain "age" it needs to be changed. That can vary depending on manufacturer, use and environment, but regardless that age tends to be somewhere around 10-15 years. How old are your cabinets, and correct, you can't buy 21MFD electrolytics anymore??

[Greg Ruddell]

It's a well known fact that once an electrolytic reaches a certain "age" it needs to be changed. That can vary depending on manufacturer, use and environment, but regardless that age tends to be somewhere around 10-15 years. How old are your cabinets, and correct, you can't buy 21MFD electrolytics anymore??

Bob, I think the oldest pair is probably at least 15 years old. The serial numbers are very early. The other two sets are probably at least ten years old. All of theses boxes would have been used at the edge of their envelope in terms of duty cycle and probably beyond on occasion. The sound company was well established and had some large KF rigs that they provided for large events. On the whole the jf80'S were very well looked after cosmetically, even had the original road cases for them which they generously gave us. I ordered some new grills for them through my distributor and luckily EAW still has them.

[David Morison]

I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

Typo?
Am not familiar with the exact circuit but I'd think that an order of magnitude change might be problematic if that wasn't a finger-slip.
Cheers,
David.

[Chris Davis]

Just wanted to report what I know now that I have finished repairing my 6 JF80's. These were grouped into pairs of close serial numbers, but all of them had the smae rcf drivers which were all in great shape as well as the original horn drivers which were also in great shape.

Two of the LF crossover boards looked fine with no visible damage to components, but the still sounded different from each other and all others sounded different from all others. I think it's a case of varying degrees of capacitor damage or decay.

I replaced the 15 Uf cap with a 15 Uf cap on the upper board.
I replaced the 21Uf cap on the upper board with a 22 Uf cap (can't get a 21 anymore).
I replaced the 15 Uf cap on the lower board with a 15 uf cap
I replaced the 4.7Ohm 25 watt resistor on the top board with a 4.7 Ohm 25 watt resistor
I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

I was surprised at how they all sound almost identical now. They sound brand new. Really punchy bottom end and crisp pristine highs like they are supposed to have. Of course they need eq. or processing, but not much.

Thanks for filling us in with your outcome.  I wish more people did that.  It never fails to amaze me how much of a difference fresh caps can make when restoring speakers.

[Greg Ruddell]

Typo?
Am not familiar with the exact circuit but I'd think that an order of magnitude change might be problematic if that wasn't a finger-slip.
Cheers,
David.

Ah yes. It's a typo David. Thanks for catching that. It should have been 0.33 Ohm. 

[Greg Ruddell]

Thanks for filling us in with your outcome.  I wish more people did that.  It never fails to amaze me how much of a difference fresh caps can make when restoring speakers.

My pleasure Chris. It was a valuable learning experience for me. I really didn't expect that kind of dramatic result.

[ProSoundWeb Community]