Help for JBL k2

[Paul001]

Good morning, I ask you for help to restore to the best of JBL K2, unfortunately they have decentralized 435BE drivers and in my opinion they are useless, even the diaphragms are badly put only one diaphragm is recoverable, the other is gone. I am thinking of replacing Driver and Diaphragm with a new pair but being the 435Be not found I have to settle for mounting either 435Al-1 or alternatively 2435HPL. I ask if replacement is possible, do they mount on the horn?

[Mr. Widget]

Welcome to the forum, I saw your other thread and it sounds like you have a nice JBL collection.

Unfortunately the JBL of today is pretty poor at supporting their products. You used to be able to buy repair parts to support 50 year old JBLs, today it can be difficult to even get them repaired under warranty. I am not sure if there are any current JBLs that use the 435Be. I don’t think they are still producing that driver and I don’t think they ever supplied replacement diaphragms for them.

Obviously swapping out both 435Be drivers would be your best course of action, but if that is not possible and you can get the 435AL drivers they will bolt right in and will sound close to the same. A network modification will be required.

Anecdotally, there have been 2435s with widely varying performance. This is likely due to someone dumping factory rejects or partially blown drivers from PA systems. Personally I would avoid those drivers unless you had proof that they were new “A” stock drivers.


Widget

[Paul001]

Thanks for the reply, I would buy the new drivers I had thought of both the 435AL-1 (acquaplas), and the 2435hpl which have the beryllium diaphragm, also I could use my rear cover of the 435Be to transform the 2435hpl to something very close to the 435Be.
What do you think about it?

[Mr. Widget]

I think that back cap will fit the 2435, but I personally would not open these drivers. As I recall, the back cap holds the diaphragm in place. If the diaphragm moves slightly the performance will be affected. Also as I stated, based on numerous posts by members on this forum, quite a few 2435 drivers that were sourced through various means were not satisfactory.

I do not think the beautifully made 435AL/435Be back caps provide a performance upgrade over the smaller back cap of the Pro series of 3" drivers. I think it is an aesthetic change... though there has been some debate on that.

Do you have factory built K2-S9800s? If yes, have you tried to have these repaired through contacting Harman in Europe?


Widget

[Paul001]

I bought the k2s knowing of a defect in the 435be drivers and paying for them relatively little. I thought it was the diaphragm instead inside the driver was decentralized, it should be unglued and centered well however the beryllium / aquaplas membranes are nowhere to be found as spare parts.
I think I can easily live with a new 435AL - 1 driver at this point if you think it will snap into my h9800 horn.

[Mr. Widget]

Physically the two drivers are identical so yes, you can easily bolt them in, but you must replace both so that they match.

Have you tried to contact Harman to see if they would sell you the correct drivers? It might be expensive but it will make your speakers worth an order of magnitude more than without them. Furthermore if they are available today it’s very likely they will not be available soon.


Widget

[Earl K]

RobH3606 fixed one of his eBay bought 2431H drivers where the internal pole piece had broken loose from the magnet after he dropped it.

This sounds like what might have happened to the OP's 435Be.

The diaphragm's voice-coil is plastic protected and wrapped ( in teflon tape ?? ) ( meaning, even though the OP's diaphragm might appear to be bad <> it might just be "captured tight within the gap" & needing an extra careful release ( to be saved ) .

See Rob's How to Ruin Your Day (http://www.audioheritage.org/vbulletin/showthread.php?11490-How-to-ruin-your-day) thread to review his Best Save of the Decade.

A preview :

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=16909&stc=1&d=1153262280
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=16910&stc=1&d=1153262315
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=16911&stc=1&d=1153262338


:)

[Paul001]

He was good, very good.
I think for now I will take two 435Al-1 I am quite convinced that it will sound very good too, at the limit through the resistive network already present in the crossover I will change the attenuation .... I expect that the aluminum is less lively than the beryllium .... for the rest I think the engine is the same.
I have already asked Harman for no spare parts unfortunately.
For the rest the speakers are very nice, in my opinion it is a more than acceptable solution

[Paul001]

He was good, very good.
I think for now I will take two 435Al-1 I am quite convinced that it will sound very good too, at the limit through the resistive network already present in the crossover I will change the attenuation .... I expect that the aluminum is less lively than the beryllium .... for the rest I think the engine is the same.
I have already asked Harman for non spare parts unfortunately.
For the rest the speakers are very nice, in my opinion it is a more than acceptable solution

[Paul001]

unfortunately the 435AL-1 is not available as a spare .....
At this point I have to take either a pair of 2430s or a pair of 2431s.
Which one do you recommend to insert in place of the 435AL-1 and that it attaches to my horn 9800?

[pos]

Swapping drivers will require a modification of the crossover, or going active.
If you are prepared for such an endeavor (measurements + simulations, etc.) then going for a 4" driver might be the best solution.
Something like a 476Mg would be ideal, if you manage to get a pair.

[Mr. Widget]

Swapping drivers will require a modification of the crossover, or going active.True if you want to achieve the best possible performance, but I believe Paul001 is willing to do a direct driver swap and live with the performance hit.


If you are prepared for such an endeavor (measurements + simulations, etc.) then going for a 4" driver might be the best solution.
Something like a 476Mg would be ideal, if you manage to get a pair.Agreed, and properly implemented the 476Mg would be a definite upgrade, however I don't think even JBL can get them anymore. They have resorted to using rebadged Radian drivers.


Widget

[Paul001]

I don't think the diaphragm change between 435AL 1 and 435 Be has a heavy influence on listening, obviously the filter is better regulated on the beryllium... let's see what happens the k2 also have a medium adjustment to intervene on. In the meantime I am also intervening on the 435Be drivers that I have disassembled, cleaned and built a dima to re-enter them, currently I am in the process of bonding with specific two-component epoxy glue.

[Paul001]

Some photos of the work done, once the upper crown has been detached by screwing the screws must be carried out a thorough cleaning of everything, at this point a robust dima must be built to reinsert the upper crown precisely, everything must be reglued with two epoxy components suitable for magnetic metals, I used a specific pattex, the 435 BE drivers now work perfectly, I tried with frequency generator and even at 700hz- 800hz they are good in working without emitting any particular noise, also I am buying a pair of 435AL to store.




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[Paul001]

Il driver che soffriva di creep surround aveva questo aspetto al momento dello smontaggio,
decentralization prevents the coil from flowing freely inside magnetic cavities, and in working it makes friction in the neodymium.

890488904989049

[Earl K]

Fixed!

Fantastic Good News!

Job Well Done!


:)

[Paul001]

I thank the whole forum and especially Mr. Widget for the contribution i was given by telling me where to take the cue for this repair.

[Mr. Widget]

I thank the whole forum and especially Mr. Widget for the contribution i was given by telling me where to take the cue for this repair.Can’t accept the credit. Earl pointed you to Rob’s thread... But I must say, I am impressed.

Well done!


Widget

[Paul001]

The girls play for us...




89058890598906089061

[Robh3606]

That's great news! You fixed them the same way I fixed mine!! Well Done!!

Rob:)

[Paul001]

Questa è un'ottima notizia! Li hai riparati nello stesso modo in cui ho riparato i miei!! Ben fatto!!

Rob :)



Thanks to you Robh...;)

[Titanium Dome]

Nice job, Paul! Eventually, we all come to this: finding ways to save what we have because we cannot get it any more.

Nice rug, by the way. I like its patterns.

[Paul001]

Bel lavoro, Paul! Alla fine, arriviamo tutti a questo: trovare modi per salvare ciò che abbiamo perché non possiamo più ottenerlo.

Bel tappeto, tra l'altro. Mi piacciono i suoi modelli.



This plant is my uncle's, we have a lot of JBL in my family, I have a slightly different plant..... after having tried so many JBL I always remain tied to 4333, with a slight update of the filters and an adequate environmental treatment I prefer them all.... but it's just my taste.... moreover, the 4333 are satisfied with a good high current class A amplifier while for others you have to have a heavy hand often losing in refinement....

[Paul001]

Questo è il mio preferito...


89070

[Paul001]

Replacement of the old Chinese elytone electrolytics with the new solen electrolytics.


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[Paul001]

after replacing the capacities the sound is much improved in my opinion.

[Odd]

There is a possibility that this may sound better in your ears.
There are many who think they can replace capacitors and hear improvements.

But, if one tries to be realistic and think the following, the top models of JBL have never been produced in very large numbers. If it is the case that a few capacitors of possibly better quality will give significantly better sound what would it cost JBL?
JBL, which is a very large customer, does not pay the same prices for components as one that buys 10 or 100 pieces.
What would a small extra cost for capacitors mean for the price of the product to the consumer?

Probably nothing.
:crying:

[Mr. Widget]

after replacing the capacities the sound is much improved in my opinion.I am very happy for you and impressed that you have been able to repair these speakers and make them work once again. That said, while I tend to agree with Odd, if you are enjoying them even more after the cap swap, good for you…. Keep it up!


Widget

[speakerdave]

There is a possibility that this may sound better in your ears.
There are many who think they can replace capacitors and hear improvements.

But, if one tries to be realistic and think the following, the top models of JBL have never been produced in very large numbers. If it is the case that a few capacitors of possibly better quality will give significantly better sound what would it cost JBL?
JBL, which is a very large customer, does not pay the same prices for components as one that buys 10 or 100 pieces.
What would a small extra cost for capacitors mean for the price of the product to the consumer?

Probably nothing.
:crying:

A counter example: JBL made 100 pairs of its top of the line 4345, but according to G.T. the sound quality was compromised by the cost engineer's choice of a cheesy biamp switch.

[Mr. Widget]

A counter example: JBL made 100 pairs of its top of the line 4345, but according to G.T. the sound quality was compromised by the cost engineer's choice of a cheesy biamp switch.Yep, and I think there are likely many other examples where the bean counters made choices we would disagree with.

In this particular case however, when these speakers were designed and built the K2-S9800 was JBL's flagship speaker and GT was actually being listened to at that time. I doubt that a significant improvement would have been left on the table by such a simple and inexpensive change.


Widget

[Paul001]

There is a possibility that this may sound better in your ears.
There are many who think they can replace capacitors and hear improvements.

But, if one tries to be realistic and think the following, the top models of JBL have never been produced in very large numbers. If it is the case that a few capacitors of possibly better quality will give significantly better sound what would it cost JBL?
JBL, which is a very large customer, does not pay the same prices for components as one that buys 10 or 100 pieces.
What would a small extra cost for capacitors mean for the price of the product to the consumer?

Probably nothing.
:crying:


I agree, however in my experience the electrolytic capacitors can decline in performance after 20 years and it is not always measurable by a capacimeter.
Chinese elytones are also very cheap in terms of electrolytics.

I just think that in JBL they used that type of capacitors because they had full stock ....

Probabilmente in un futuro non troppo distante si procederà per la modifica in SE sostituendo i condensatori elettrolitici con i solen MKP.

[Odd]

Your last line was a little hard to read.
Probabilmente in un futuro non troppo distante si procederà per la modifica in SE sostituendo i condensatori elettrolitici con i solen MKP.

But Google says
Probably in the not too distant future we will proceed for the modification in SE by replacing the electrolytic capacitors with the MKP solen.

[Paul001]

the Special Editions have the same filter but use solen mkp instead of the electrolytic of the normal version.
It is a very easy modification, if you want to be picky you can also easily adjust the coil of the 435BE L4 by 0.1 mH


http://www.audioheritage.org/vbulletin/showthread.php?42919-K2-9800-upgrade-to-K2-9800-Special-Edition

[Earl K]

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=89324&d=1627640960

Yes, >> I know if I owned those networks I'd swap out all the yellow caps for 250Volt MKP Solens ( as used by JBL ) .

I regularly listen to 400Volt MKP Solens ( dc-biased ) > BUT I do so at a drastically lower bias voltage ( compared to the STANDARD 9Volt DC Bias >> it's typically less than 1 Volt DC ).


Considering that you've stated that like what you hear ( due to swapping out the Elytones ) you would do yourself a ( educational ) favor by measuring your existing DC voltage ( from the center of any pair of caps to ground > using a multimeter ) to see what your voltage is at today.
- Remember that GT evolved the DC biased networks to being biased through a diodic "tap" taken from the LF drivers input voltage ( for when/if biamping is being used ).
- That form of variable biasing can result in a much lower dc voltage if ones normal listening habits are well controlled.

- It may turn out that you too prefer the sound of a lower bias voltage.

It takes a while for the caps to charge up to a full 9 volts after they've been discharged ( the charging slowness is due to the 2.2 meg resistor ).
- If your networks discharged when you were working on them // they might ( currently ) be only partially charged >> hence a lower bias voltage possibly being a contributing factor to a "different//preferred sound".

It's worth checking just to get a snap-shot ( reality-check ) to create a marker that's connected to your current satisfaction level.

:)

[Paul001]

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=89324&d=1627640960

Yes, >> I know if I owned those networks I'd swap out all the yellow caps for 250Volt MKP Solens ( as used by JBL ) .

I regularly listen to 400Volt MKP Solens ( dc-biased ) > BUT I do so at a drastically lower bias voltage ( compared to the STANDARD 9Volt DC Bias >> it's typically less than 1 Volt DC ).


Considering that you've stated that like what you hear ( due to swapping out the Elytones ) you would do yourself a ( educational ) favor by measuring your existing DC voltage ( from the center of any pair of caps to ground > using a multimeter ) to see what your voltage is at today.
- Remember that GT evolved the DC biased networks to being biased through a diodic "tap" taken from the LF drivers input voltage ( for when/if biamping is being used ).
- That form of variable biasing can result in a much lower dc voltage if ones normal listening habits are well controlled.

- It may turn out that you too prefer the sound of a lower bias voltage.

It takes a while for the caps to charge up to a full 9 volts after they've been discharged ( the charging slowness is due to the 2.2 meg resistor ).
- If your networks discharged when you were working on them // they might ( currently ) be only partially charged >> hence a lower bias voltage possibly being a contributing factor to a "different//preferred sound".

It's worth checking just to get a snap-shot ( reality-check ) to create a marker that's connected to your current satisfaction level.

:)


Interesting, and I could also adjust the bias voltage to my liking.

[Earl K]

Interesting, and I could also adjust the bias voltage to my liking.

Assuming you can hear the differences.

So much of this all comes down to personal circumstances.

For instance, ( even though the room where my speakers currently reside is very cluttered ) I have a fairly effective LEDE room treatment setup (https://www.google.com/search?q=LEDE+room+treatment+&rlz=1C1CHBD_enCA823CA823&sxsrf=ALeKk03f_Saohyviy9kYxnQ_oatQmbLKTg%3A1627852 770215&ei=4g8HYZG-DJSztQahkrm4Dw&oq=LEDE+room+treatment+&gs_lcp=Cgdnd3Mtd2l6EAMyBAgjECc6BwgAEEcQsANKBAhBGAB Qj0NYj0Ng0UhoAXACeACAAXyIAdQBkgEDMS4xmAEAoAEByAEIw AEB&sclient=gws-wiz&ved=0ahUKEwiRt_WQ4JDyAhWUWc0KHSFJDvcQ4dUDCA4&uact=5).

8932689327

Figures like seen above, really helps one maintain focus on what's coming out of the speakers.

( Plus, I've made my living through my ears since about the mid 1970's . )

:)

[Paul001]

Penso spesso di rendere il crossover semplificato come da progetto JBL, fare delle bobine di qualità non sarebbe un problema, con questa realizzazione tutto sarebbe molto semplice e si potrebbero usare condensatori di qualità, I would remove battery and complications





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[Paul001]

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=89324&d=1627640960

Yes, >> I know if I owned those networks I'd swap out all the yellow caps for 250Volt MKP Solens ( as used by JBL ) .

I regularly listen to 400Volt MKP Solens ( dc-biased ) > BUT I do so at a drastically lower bias voltage ( compared to the STANDARD 9Volt DC Bias >> it's typically less than 1 Volt DC ).


Considering that you've stated that like what you hear ( due to swapping out the Elytones ) you would do yourself a ( educational ) favor by measuring your existing DC voltage ( from the center of any pair of caps to ground > using a multimeter ) to see what your voltage is at today.
- Remember that GT evolved the DC biased networks to being biased through a diodic "tap" taken from the LF drivers input voltage ( for when/if biamping is being used ).
- That form of variable biasing can result in a much lower dc voltage if ones normal listening habits are well controlled.

- It may turn out that you too prefer the sound of a lower bias voltage.

It takes a while for the caps to charge up to a full 9 volts after they've been discharged ( the charging slowness is due to the 2.2 meg resistor ).
- If your networks discharged when you were working on them // they might ( currently ) be only partially charged >> hence a lower bias voltage possibly being a contributing factor to a "different//preferred sound".

It's worth checking just to get a snap-shot ( reality-check ) to create a marker that's connected to your current satisfaction level.

:)

you're right the sound has closed and is back as before, so I could try to remove the battery to do the double check ..... in theory the sound should return more polished?

[Earl K]

Do you not have a multimeter to measure the DC voltages of the charged capacitor pairs?

If not, buy one ( otherwise you're flying blind ).

You can partially ( even fully ) discharge any DC charged system by ( unhooking the battery ) and then measuring the dc voltage with the meter ( set to measure DC voltage @ 20 V range ) .
- One lead goes to the common point of the 2 capacitors ( + resistor ) while the other lead attaches either in front ( or behind the 2 capacitors ) .
- You'll need to do this to each pair of capacitors.

The meter ( itself ) will slowly discharge the capacitors charge ( once the leads are attached and meter is turned on ) .


I would take all capacitor pairs down to a 1/4 volt ( 0.25V ) and then start listening for a few days ( or a week ) >> then re-install the 9 volt battery and let it recharge ( listen for more days ).

Repeat ( ad naseum ) until you have formed a fully informed opinion ( for your preferred voltage ).

:)

PS; Yes I would encourage you to build a second set on networks ( that live externally to the 9800 ) where you can play with installing boutique capacitors .

Build them for easy capacitor swapping ( even leaving room for DC biasing certain parts of the Horn circuit ).

[Paul001]

yes of course I have a multimeter, I also play a little with the electronics ..... you gave me great advice, I will try the voltage that I like best ..... even if I am very determined to build a ex novo external filter with simplified circuit according to JBL specifications and without battery. Thank you

[Paul001]

I built this simple system to power the armatures of the capacitors to 1.5V or 3V or 4.5v 0 6v instead of the 9v provided by origin. In the next period I will start to rehearse.







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[Riley Casey]

JBL used that switch in a number of products and I suspect the choice had more to do with providing an 'elegant' customer facing solution more than saving a few cents on the switches. A high current, sealed switch solution would likely have required two or three large toggle switches that all needed to be switched simultaneously to avoid shorting amp outputs to each other and that would have looked like a bit of a kludge on the back panel.



A counter example: JBL made 100 pairs of its top of the line 4345, but according to G.T. the sound quality was compromised by the cost engineer's choice of a cheesy biamp switch.