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ngccglp
02-14-2004, 04:22 PM
Hi,

I saw a pair of 4333As, the drivers are all in good condition. Only problem is the sound of one of the speakers come on and off, sounds like intermittent connection. But when the sound do comes on, I was blown away by the classic JBL sound. The grill cloth was also torn.

I would like to request for some advice before I commit to the purchase:

1. Are the parts of 4333A still available, so that in case if the crossover or the control switches are really damaged, I can replace them.

2. How do I clean the switches and cable binding posts?

3. Where can I get replacement grill cloth?

All advice are welcome. Thanks in advance.

David

Tom Loizeaux
02-14-2004, 05:29 PM
There were many parts used in making these 4333s. Some are still available from JBL. Others can be found, used, and many from members of this Lansing Heritage Forum.
I've restored a pair of 4333s myself and came to know these very intimately (see photo at left). If you get these, I would start by cleaning and tightening the connectors (inside and out) and spray pot cleaner into the L pads.
As you progress with these steps, keep us posted on this forum and you will find a wealth of knowledge and support.

Tom

boputnam
02-14-2004, 06:37 PM
Originally posted by ngccglp
1. Are the parts of 4333A still available, so that in case if the crossover or the control switches are really damaged, I can replace them. Hey, David - welcome. :wave:

Here's a brochure on the 4333A's (4333A - Link (http://www.jblpro.com/pub/obsolete/4331a_4333a.pdf)), if that's of any help.

If you do decide to get these (you should follow Tom's advice! :yes: ), then start working on them with the Forum's help, and many here can help diagnose with you.

Grill cloth is near impossible to find (or replicate :( ), but let us know if you find any over there! ;)

ngccglp
02-14-2004, 08:38 PM
Dear Tom and Bo,

Thanks for the advice. I will go down to the shop today and have another round of inspection of the speakers to make sure I can pin-point the defects.

BTW, what is L pads? Is it the two knobs found at the front used to adjust the frequency?

Also, how does 4320 compare with 4333A? Honestly, I cannot bear to see these beauties fall in the wrong hands.

Thanks.

David

lpd
02-14-2004, 09:50 PM
As a proud owner of 4333's I will beging to say, I tried to clean the l-pads with ill effects and decided to replace them. What a difference, real clean sharp highs and the intermittent music has ended. The l-pads are the knobs in the front upper left corner for lowering, raising mid horn and tweeter levels. I would check the condition of the foam on the bass drivers and you may have to replace it. Not impossible to repair, but I wasn't comfortable with 15 inch drivers and had a professional repair mine. Check all leads and if you really want to be anal, check the driver and tweeter to see if the wax seals are still intact (mine were).

Great sounding speaker, but will need some TLC to get up and running, as most vintage gear is.

Peter

boputnam
02-15-2004, 12:10 AM
Originally posted by ngccglp
BTW, what is L pads? Is it the two knobs found at the front used to adjust the frequency?

Also, how does 4320 compare with 4333A? Honestly, I cannot bear to see these beauties fall in the wrong hands.
Firstly, :yes: , but not frequency, per se, but relative gain (i.e., "pad").
And second, well, it's easy to guess that JBL increased the numeric designation with increased engineering. IMO, you won't go wrong with any 43xx-series - but higher number seems to equate with higher "understanding" on JBL's part... ;)

ngccglp
02-17-2004, 03:31 PM
Dear all,

1. How do I remove the L Pads for cleaning? Is it from the front or rear? I notice a warning behind stating that there is a seal in the rear panel and removing them will affect the performance of the speakers. Can I replace the seal?

2. There are two panels at the rear which I can open. Which one should I open to gain access to the interior of the speakers? The outer one or the inner one?

3. One of the speakers the JBL label is peeling off and is held by masking tape. What do I used to stick it back?

4. What do I used to fill up the small opening at the cabinet joints?

I'm getting quite excited about this speaker. I have not bought it yet becuase there are still too many 'what if'.

Thanks

David.

Tom Loizeaux
02-17-2004, 05:52 PM
Originally posted by ngccglp
Dear all,

1. How do I remove the L Pads for cleaning? Is it from the front or rear? I notice a warning behind stating that there is a seal in the rear panel and removing them will affect the performance of the speakers. Can I replace the seal?

2. There are two panels at the rear which I can open. Which one should I open to gain access to the interior of the speakers? The outer one or the inner one?

3. One of the speakers the JBL label is peeling off and is held by masking tape. What do I used to stick it back?

4. What do I used to fill up the small opening at the cabinet joints?

I'm getting quite excited about this speaker. I have not bought it yet becuase there are still too many 'what if'.

Thanks

David.

You don't need to to remove the L Pads to clean them.
When you get these you might want to carefully remove the woofers. You can reach the L Pads through the woofer cut-outs. The upper panel on the back holds the compression driver. If you carefully remove this panel, you will be able to see the back of the L Pads...sort-of. Spray a little burst of cleaner (made for potentiometers) into the little openings in the sides of the L Pad housings, and then rotate them all the way, back and forth.
A contact cement will re-glue JBL lables.
There shouldn't be any openings at the cabinet joints!
If the driver all work (not blown), the crossover works, and the cabinets are "restorable", then I think you have a managable project without committing to any major expense. Of course, anything can be restored, repaired or even replaced, but the cost just goes up!
Keep us posted.

Tom

Speakertown
02-17-2004, 07:59 PM
Be sure to point out all the defects to the seller, so you
can get them for very cheap!. ;)

ngccglp
02-18-2004, 06:52 PM
Last but not least, based on my description of the speakers, how much do you think I should pay for them?

David

Mr. Widget
02-19-2004, 09:46 AM
The market for them in Singapore will help determine that, but here in the US they would probably go for $500-$1500 depending on condition. While they are acoustically identical (more or less) to the L-300 the consumer models tend to go for much higher prices.

Good Luck!:)

ngccglp
02-22-2004, 07:04 AM
Currently in the process of price negotiation with the dealer...I am really quite excited about the whole project.

BTW, are the speakers supposed to be placed against the wall?

David

ngccglp
02-28-2004, 03:50 PM
Hi everybody,

Seems like the deal may come through. I went back to scrutinize the speakers again and these are the new faults:

1. The L Pads only works at one or two specific positions. Will cleaning solve the problem or where can I get replacements?

2. For me to clean the L pads as Tom suggested, I need to remove the bass drivers. But I noticed the bass drivers are attached to the baffle with a thin layer of 'something'. When I take out the screws, how do I lift the bass driver up?

3. When I play vocals really loud, the right mid range 2420 gives off the siblance sound that might suggest that it has already worn out and need repairs. Where can I get it repaired or replaced?

I am really impressed by the JBLs. Driven by just an old Audiolab 8000A and a cheap source, many speakers costing more just could not reproduced that kind of deep bass and air around the vocals. It is like you are there at the recording studio!

Thanks.

David

Tom Loizeaux
03-01-2004, 08:26 AM
[QUOTE]
1. The L Pads only works at one or two specific positions. Will cleaning solve the problem or where can I get replacements?

2. For me to clean the L pads as Tom suggested, I need to remove the bass drivers. But I noticed the bass drivers are attached to the baffle with a thin layer of 'something'. When I take out the screws, how do I lift the bass driver up?

3. When I play vocals really loud, the right mid range 2420 gives off the siblance sound that might suggest that it has already worn out and need repairs. Where can I get it repaired or replaced?

The L pads can often be cleaned to work fine. Sometimes they need to be replaced. These are still available.
The woofers are supposeed to be resting on a flat cork gasket. If these are still stock, then, once you remove the clamps, the drivers should pull free.
You need to inspect and clean these up before you know you've got a problem that might require replacement. Diaphragms are still available for the 2420. I think they are called D162421 from JBL (they're not cheap!). We can help you with all this if you determine that you need to replace your diaphragms.

Tom

Alex Lancaster
03-01-2004, 01:45 PM
ng:

You are in the process of getting a great pr of speakers; In addition to the other advice:

the D16R2421s are better, and as mentioned, very expensive, I would try the replacement for 2425s from P.Audio, Im sure there is a dealer near You, I have used about 30 of them.

In pre owned speakers You might find the woofers glued on, take a real sharp razor blade, and slowly cut around it.

Congratulations!.

Alex.

ngccglp
03-03-2004, 01:49 AM
Gentlemen,

The deal is closed at about USD$1500. The speakers are on its way. Very excited.

My planned operations:

1. Remove Woofer, assess L Pads, spray cleaner on L Pads, cross fingers, hope that it will work and clear up the right mid sibilance.

2. If still encounter sibilance, remove back panel, assess 2420, replace diaphragm or replace 2420. Is there a way to clean the 2420?

3. Check L Pads, replace if necessary.

4. Touch up wood work and wax cabinet.

Any other suggestions guys?
Tom, you mentioned earlier that you would start cleaning the connectors inside out, could you kindly elaborate how this is done. Thanks.

BTW, what cleaner should I use to clean the L Pads?

Thanks

David.

ngccglp
03-03-2004, 06:01 AM
Gentlemen,

The 4333As are here and man, are they heavy! Just noticed some of the structures of the grill frames are missing or broken. Most likely I will not repair them as I prefer the 'naked' blue baffle look with the horn lens.

Will probably start work this weekend. Will try to borrow a digital camera so that I can post some pix here.

Cheers everybody.:D
David

4313B
03-03-2004, 06:21 AM
Cool! :)

Can't wait to see some pictures :yes:

JuniorJBL
03-03-2004, 06:45 AM
Have alot of fun!! Can't wait to see pics!:D

ngccglp
03-03-2004, 08:15 AM
Couldn't wait, I just hooked the speakers up using one of those home theatre DVD player with build-in amp and satellite speakers type thingy, TEAC to be exact.

The sibilence is still there on the right 2420, but the sound...

....man... all the details, air etc. around the instruments, voice has real presence. Drums with snap, snare scratching, high hat vibrating , awesome. All I can say is its full of potential.

I am convince and glad that in the early days, the concept seems to be 'to make quality products that will last a lifetime', unlike now the concept seems to be 'use and throw' e.g. swatch nation.

Hope I really can restore it to its full potential.

PS - took a peak inside using the rear panel, and saw the L pads - where should I spray the cleaner? seems like there is no opening at all. Also, the sound oscillate between loud and soft, could it be the L Pads or crossover, or the speakers just need a little bit of warm-up?

David
:confused:

ngccglp
03-04-2004, 06:06 AM
Hi,

Anybody know where I can buy L Pads for the mid and hi driver for the 4333A? Cleaning does not seem to work. :(

David

4313B
03-04-2004, 06:16 AM
"Cleaning does not seem to work."

Yeah, my time is worth a bit more than to sit around cleaning L-Pads. File them in the circular and spend the $5 each to replace them.

"Anybody know where I can buy L Pads for the mid and hi driver for the 4333A?"

JBL Pro

51594 is the 16 ohm pad that goes on the MF
10285 is the 8 ohm pad that goes on the HF, it's junk - try to use the 58450 high power 8 ohm pad instead.

Parts Express is another option - lower price, same part.

Let me look in my catalog tonight to see if there are any solutions near Singapore.

boputnam
03-04-2004, 07:39 AM
I'm glad Giskard dropped in - I have never had luck cleaning an L-pad, and have spent hours trying. If they are badly corroded, they just don't clean well. And, replacements are readily available and not so costly.

The biggest problem you will face is removing them. That foilcal on the baffle needs to be removed to get to the screws holding the L-pads. It was installed without any easy way to remove it. Recently, a Thread here suggested taking a hot clothes iron and putting it on the foilcal with a damp cloth between - the idea being to warm the glue on the foilcal without damaging the baffle. I've not tried this, but maybe something along these lines would work (or even try using a hair dryer to soften the glue). The foilcal is pretty thin and will evidence of your efforts to remove it. :(

One off, the L-pads come right out, and are a cinch to replace.

ngccglp
03-04-2004, 07:53 AM
Thanks guys.

Just went to my brother's place to borrow his Thorens integrated that has been gathering dust on the shelve. The 4333A is singing now.

Still, the L Pads only work in one position, and the right mid still sound distortion with vocals when I play loud.

Seems like it really needs a lot of TLC.

David.

ngccglp
03-05-2004, 06:02 AM
I cannot find any of the HF L-PAds from JBL Pro nor part express. Help:confused:

Currently re-running in the speakers at moderately loud volume. The bass, my god...Steely Dan is in the house my man...

David

4313B
03-05-2004, 06:08 AM
All the L-Pads are listed on the JBL Pro misc price list. I notice JBL slipped a few extra letters/numbers in -

N36-10285 - L PAD 8 OHM W/HDWR 4401 $4.93 USD EA
N36-58450 - L-PAD,ATTEN $11.74 USD EA
51594 - L-PAD 16 OHM 100 W $23.52 USD EA

I've posted the PE numbers elsewhere on this forum.

ngccglp
03-05-2004, 06:34 AM
Dear Giskard,

Thanks, you're a great help. Unfortunately, JBL Pro do not support international sales. I will forward the numbers to my local JBL dealer.

One more thing, the bass on the left speaker seems much stronger than the right. I switched the cables and its still the same. Since the woofer is not connected to the L Pads, I really do not know what could be the cause.

Overall, given the age of these speakers, I must say they are still KILLERS!!!

I want to thank everybody for your encouragement and support, without which I would never have gather the courage to undertake this project.

David.:D

boputnam
03-05-2004, 07:30 AM
Originally posted by ngccglp
Unfortunately, JBL Pro do not support international sales.

One more thing, the bass on the left speaker seems much stronger than the right. I switched the cables and its still the same. Since the woofer is not connected to the L Pads, I really do not know what could be the cause.
Hey, David...

I'd be happy ro intermediate shipping those L-pads to you, if need be. Lemme know - I've helped our European brethren in the past, and they all "got the goods"!

On the left 2231 - what are the condition of the surrounds? Have these been redone? Can you post some pictures? You might have some failure compromising cone suspension and cabinet air-tightness. :hmm:

Chas
03-05-2004, 07:57 AM
MCM electronics have L Pads. I don't know if they will ship international orders. Give them a try.

http://mcmelectronics.com/
Charles.

JuniorJBL
03-05-2004, 09:13 AM
Have you checked the phase of the woofers?
Someone could have taken the drivers out and put back in wrong?
Just a thought.
Shane:hmm:

Mr. Widget
03-05-2004, 09:14 AM
Originally posted by ngccglp


One more thing, the bass on the left speaker seems much stronger than the right. I switched the cables and its still the same. Since the woofer is not connected to the L Pads, I really do not know what could be the cause.




Just a thought, is the left speaker in a corner and the right not?

Assuming the speakers are symmetrically in the room, you should switch woofers left to right and see if the problem moves. If they are symmetrically in the room and the problem does not move, there is something very wrong with the wiring (as in loose wire or partially shorting) or a failure of some type in the crossover. (certainly unrelated to the L-Pads)

As to the L-Pads. I have purchased from JBL and as Giskard has pointed out their L-Pads are the same ceramic cased 100 watt L-Pads (made in Taiwan or China) sold by PE and others. Paying $25 for the 16 ohm one is kind of dumb, when everyone else charges $5 to $10 for the same thing. I would guess you can find them locally or at least nearer to you than ordering them from the States.

Widget

Tom Loizeaux
03-05-2004, 01:48 PM
L pads of that size usually have little openings, vents, around the sides. Try spraying a little burst of cleaner in and then promptly turn the pot fully one way and then the other. I may take a number of applications. I also think that you will wind up setting them inear the mid position (most of us do) so if they seem to work in that position, I think you'll be OK. Replacing the pots is going to be a little tricky because of the foilcal. Only do it if you really need to!

Whenever I get a new (old) speaker, I always clean the terminals, tighten them, inspect and tighten all wiring, clean all pots, double check wiring polarity, etc., etc.
Are you bi-amping these? If not, the woofer imbalance could be a problem with the crossover/wiring.

To find any problem you can use the substitution meathod. In the case of the distortion on your compression driver - you can remove the driver and horn and exchange it with the other one. If the distortion remains in the cabinet, it's probably the crossover or wiring. If it moves with the driver, then you've narrowed down the possibilities. You can remove the cover of the 2420 and carefully inspect the diaphragm for loose wires, debris, etc.

If you have concerns about getting into any part of these kinds of things, post it here and we will try to guide you.

Tom

Tom Loizeaux
03-05-2004, 01:52 PM
Originally posted by Tom Loizeaux
L pads of that size usually have little openings, vents, around the sides. Try spraying a little burst of cleaner in and then promptly turn the pot fully one way and then the other, a number of times. It may take a number of applications to clean the coil and contacts inside. I also think that you will wind up setting them near the mid position (most of us do) so if they seem to work in that position, I think you'll be OK. Replacing the pots is going to be a little tricky because of the foilcal. Only do it if you really need to!

Whenever I get a new (old) speaker, I always clean the terminals, tighten them, inspect and tighten all wiring, clean all pots, double check wiring polarity, etc., etc.
Are you bi-amping these? If not, the woofer imbalance could be a problem with the crossover/wiring.

To find any problem you can use the substitution meathod. In the case of the distortion on your compression driver - you can remove the driver and horn and exchange it with the other one. If the distortion remains in the cabinet, it's probably the crossover or wiring. If it moves with the driver, then you've narrowed down the possibilities. You can remove the cover of the 2420 and carefully inspect the diaphragm for loose wires, debris, etc.

If you have concerns about getting into any part of these kinds of things, post it here and we will try to guide you.

Tom ,

ngccglp
03-05-2004, 06:10 PM
Bo, thanks for the offer, I will keep that in mind.

Tom, maybe I will give the L-Pads one more try. But I did spray a fair amount of cleaner into the small openings and turned the volume knob to and fro a couple of times. And the sad thing is, the contact point is quite near max, not in the middle.


BTW, if I bypass the L-Pads, will it be same as the 'middle/neutral' position or is that 'max' position. I am thinking of bypassing the L-Pads altogether because I do not forsee myself adjusting them. This way I save the trouble and I suppose better sound because one less obstacle in the signal path.

Thanks.
David

PS - currently rocking to Beatles Naked.

ngccglp
03-06-2004, 10:02 PM
I've gathered enough courage to open the 2420.

The foam has completely disintegrated and the inside is a mess. I carefully dusted every part and spray contact cleaner to every electrical connection. I don't think anything is damaged, except there are two slight dents on the diaphragm. I supposed the distortion is caused by these dents hitting against the semi-circle exit point.

I have the following idea but not sure if it will affect the overall sound/performance of the 2420. I was thinking of puting three thin washers at the mounting screws to raise the diaphragm such that it will not hit against the semi circle exit point.

Is my diagnosis of the problem correct? Any comments are welcome. Thanks.

David.

Mr. Widget
03-06-2004, 10:25 PM
While it is possible that the "dents" are the problem, you are probably not correct. I have seen brand new diaphragms from the factory with very small dents. In any case moving the diaphragm away from the phase plug (the semi circle) will most definitely adversely affect the response of the driver. The distance between the diaphragm dome and the phase plug is very critical. It is most likely you have a fatigued diaphragm and it must be replaced. You will need to replace the diaphragms in both speakers to keep them the same. If you buy new ones from JBL they will be about $500 for the pair:eek: but they will drastically improve the sound of your speakers.

As to your L-pad question if you bypass them, they will be set at max.

Widget

ngccglp
03-06-2004, 10:47 PM
Dear Widget,

Thanks for your reply. May I asked is fatigued diaphragm refering to the the diaphragm surround losing it resilience? Therefore the diaphragm keep hitting the phase plug when played loud. Oh yes, I forgot to mention the distortion increases with volume.

David.

Mr. Widget
03-06-2004, 11:27 PM
What happens to aluminum diaphragms (all metal diaphragms actually, but unfortunately it happens earlier with aluminum) is that the metal work hardens and yes it looses it's resiliency. I doubt that the diaphragm is actually hitting the phase plug, it is most likely breaking up (not behaving pistonically) and distorting significantly more than normal. Unfortunately that while a new aluminum diaphragm has lower distortion than a titanium one, after extended or hard use, the aluminum degrades more than titanium. Under normal domestic use an aluminum diaphragm may never need to be replaced, but in pro audio where drivers are frequently over driven they must be regularly replaced. This is why all of JBLs current PA drivers use titanium for their diaphragms.

The bad news is that the replacements for your divers are quite expensive. The good news is that JBL still supports that driver and in fact the current 2421B diaphragm is an improved version over the original 2420 model.

It is possible that you do not need to replace your diaphragms and that there is some other problem, but I would definitely suspect the diaphragm(s).


Widget

Mr. Widget
03-06-2004, 11:33 PM
Since we are talking about the 4333, we are dealing with a 2420 being used down to 800Hz. That means that it is working significantly harder than a system with say a 1200Hz crossover. This would be another reason that the mid drivers could have been over driven. Again since I haven't seen or heard these, I am only guessing and you will need to do some additional sleuthing.

ngccglp
03-07-2004, 12:00 AM
I tried putting thin washers to elevate the diaphragm, and lo and hehold, the sound became very soft. :(

Guess I have no choice but to get a new diaphragm. My local dealer do not have D16R2421. May I asked whether the D16R2425 can be used. Will it caused a big imbalance if I only change one side. The other side is sounding fine and it is costly.

The bright side to all this work is that I am getting to know the 4333A inside out.

Thanks.
David

Mr. Widget
03-07-2004, 12:18 AM
I would suggest if the money is a problem you get an inexpensive JBL copy from Australia that are regularly sold on eBay for the interim and save up to buy a proper pair of diaphragms from JBL.

I assume you intend to listen to stereo.:)
Both speakers should sound the same. I certainly wouldn't pay JBL prices to degrade the performance of your speakers with a titanium 2425 diaphragm.

When Bo replaced the 2421 diaphragms in his working pair he was amazed at the improvement the new diaphragms made.

You might buy or ask to borrow one or both of Bo's old diaphragms. Send him a PM and ask. Can't hurt to inquire.

Good luck,

Widget

ngccglp
03-07-2004, 01:02 AM
Dear Widget,

Thanks for the tip. I already ordered from Australia a pair of the the diaphragms. About US$90. Cool price.

David

ngccglp
03-08-2004, 09:53 PM
Because I aim to complete refurbishing the speakers by March:)

As promised, pictures!

ngccglp
03-08-2004, 09:56 PM
one more...work in progress...

boputnam
03-09-2004, 07:03 AM
Thanks, David! Those look to be in great shape!

Tom Loizeaux
03-09-2004, 08:59 AM
David,
Your 4333s look great! I think when you get the diaphragm problem and L-pad problems solved, you're going to really enjoy these speakers.
Be careful with the L-pad foilcals. You know, you can bypass the L-pads with resistors set at specific values, once you determine the levels you want from your 2420s and 2405s. You may even gain a little in sonic performance with the L-pads out of the circuit.
Congratulations!

Tom

ngccglp
03-13-2004, 02:03 AM
The diaphragms arrived today and now both my speakers are up. I ordered two diaphragms, unfortunately, one is not usable because it does not fit the phase plug gap, its too tight. I'll ask for a replacement. So in the meantime, left is aluminium and right is titanium.

I also got my L Pads working. When I opened the mid L Pads, I noticed the wipers are off. So I just depressed it a little to make sure it has some residual pressure on the slide. Now both my L Pads are working fine. Great.

The shxx thing is my amp right channel stop functioning, probably due to the heavy rain for the last few days. Hope it come around because it was working fine last week.:banghead:

Bo - Pls see my private message.

David.

ngccglp
03-13-2004, 02:41 AM
What a blunder, because I am using a sony DVD/CD player, I accidentally connected the right channel of the amp to the video output, he he he

Steely Dan is in the house again!!!

David

PS - If the 4333A sounds this good, I can imagine how good the 4 ways will sound, 4343, 4344, 4345, 4350, 4355...

Alex Lancaster
03-13-2004, 07:13 AM
Hi:

I am glad they are up and running (sounding), please let us know what differences You hear betwen the diaphragms.

Alex.

ngccglp
03-13-2004, 07:21 AM
Alex,

I am not sure if its because its not run in yet, but the titanium diaphragms sounds slightly softer. I turned the L Pads on the titanium a bit louder to balance the sound. Other than that, no glaring difference. So for those who are worried about non-OEM parts, I think its safe.

The only thing is the quality checks may be a bit lacking for non-OEM parts, which probably accounts for its lower costs. I ordered two, but one is too tight when fitted into the phase plug gap.

David

ngccglp
03-15-2004, 01:16 AM
I have a connection query:

The shop I bought the 4333 used a short jumper cable to connect the low terminal to the high/mid terminals. The speaker cables are then connected to the low terminals. I have been using the speakers this way since I got them from the shop.

However, I just discovered that the jumper cable is redundant i.e. the high/mid and low is connected internally. Did I cause any permanent damage to the drivers by playing with the jumper cable in place?

Thanks.

Tom Loizeaux
03-15-2004, 06:27 AM
When the selector switch is in the INTERNAL position the upper terminals are switched out of the circuit.
You should remove these jumpers as they are unnecessary and will cause damage to your amps shoul;d they be left there when you connect two amps in the bi-amp mode.

Tom

ngccglp
03-20-2004, 04:59 AM
Its only been a week and the after-market diaphragm seems to be showing signs of fatigue. I noticed there is distortion when I played loud. Or could it be the 2420? But I didn't noticed that when I first installed the diaphragm last week, everything seems fine. But after 1 week of regular playing (sometimes quite loud), I hear distortion setting in again, but it is not as bad as the old diaphragm I just replaced.

What's going on:confused:

David

Alex Lancaster
03-20-2004, 08:09 AM
What brand is the replacement diaph?.

Mr. Widget
03-20-2004, 12:05 PM
Originally posted by ngccglp
But after 1 week of regular playing (sometimes quite loud), I hear distortion setting in again, but it is not as bad as the old diaphragm I just replaced.

What's going on:confused:

David

The 4333A has a fairly low crossover point for a 1" driver. It is quite possible that the "(sometimes quite loud)" has blown the diaphragm. It is also possible that the after market diaphragm is poorly made, it is also possible that the old caps in the crossover might have lowered the crossover frequency or changed the slope a bit allowing more LF into the 2420.

A 2420 with a new JBL diaphragm will play extremely loudly without damage, but they certainly can be damaged. It is unlikely there is a problem with your driver.

Another thought, when you installed the new diaphragm, did you use a sweep tone to make sure the coil was properly centered?

Widget

ngccglp
03-20-2004, 02:22 PM
Alex,
There is no brand, but it comes in a box with the dealer's sticker.

Widget,

Another thought, when you installed the new diaphragm, did you use a sweep tone to make sure the coil was properly centered?

There are these centering studs on the 2420 and when I installed the diaphragm, there is not much play. Could this really be the problem?


It is quite possible that the "(sometimes quite loud)" has blown the diaphragm

But it don't seemed to have affected the old alumunium diaphragm. Maybe this is what they called 'quality'.


it is also possible that the old caps in the crossover might have lowered the crossover frequency or changed the slope a bit allowing more LF into the 2420.

If this is the problem, I'm doomed. Because I have no confident in performing any electronics repairs.

David

Tim Rinkerman
04-01-2004, 10:45 AM
I saw that the low terminals were jumped to the mid/hi terminals at one point...uhhhh.....isn't that effectively bypassing the crossover? Those terminals are there to give you a direct path to the mid/hi and low driver when you bi-amp the cabinet. I'm not sure if you did any damage to the crossover by running full range program into what was only supposed to see 800hz. and up, but I know you didn't do any good to the driver that was only supposed to see 800hz. and up...just my two cents...

boputnam
04-01-2004, 05:32 PM
Originally posted by ngccglp
The shop I bought the 4333 used a short jumper cable to connect the low terminal to the high/mid terminals. The speaker cables are then connected to the low terminals. I have been using the speakers this way since I got them from the shop.

However, I just discovered that the jumper cable is redundant i.e. the high/mid and low is connected internally. Did I cause any permanent damage to the drivers by playing with the jumper cable in place?
I'm late to this party, but agree with Tim. This post of ngccglp's is most concerning.

The external jumper would bypass the internal, passive crossover. Thus, all transducers were seeing full-range. This could be why/how you keep damaging your diaphragm(s).

The high/mid and low are connected internally, but THROUGH THE PASSIVE CROSSOVER.

ngccglp you need to better describe how you are running these. :confused:

First, DISCONNECT THE EXTERNAL JUMPER, and throw it away.
Second, are you running regular stereo, or stereo bi-amped (different amps for the woofer and different amp for the compression driver, etc.? If you are running regular stereo, connect ONLY to the lower set of connections and switch to "Internal".

ngccglp
04-02-2004, 01:46 PM
The jumpers were long gone. It was used by the dealer, obviously he didn't know much about JBL speakers.

However, Tom had earlier replied that when you switched to internal crossover, the high terminals are effectively bypassed. So if this is correct, then no damage has been caused by the jumper.

The distortion is audible only at certain frequencies, especially during intense piano segment when the keys are hit hard. I suspect it may be due to ageing caps.

I mentioned I ordered two after market diaphragms earlier. One was too tight and I sent it back for a replacement. I have received the replacement and will try to swop the diaphragms to see if it helps

Thanks.
David

ngccglp
04-20-2004, 10:08 PM
Hi,

Just to keep everybody an update. I bought one original JBL D16R2425 to try to see if the problem is indeed the crossover or the after-market diaphragms.

The distortion is gone! So I guess its the quality/specs of the after market diaphragms afterall.

Cheers
David

4313B
04-21-2004, 05:33 AM
JBL goes to great lengths to maintain excellent product. I know it's really, really, really hard to believe but they really, really do.