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View Full Version : 4301B Crossover Rebuild



Zilch
03-04-2008, 11:15 PM
Schematic here:

http://www.jblproservice.com/pdf/Network%20Schematics/3103%20Network.pdf

Original L-Pads were fine, but the capacitors measured 10% high.

Heat gun melts the globbed-on components loose and allows scraping off the old glue.

Four solder terminals are mounted with countersunk flat-head screws from the underside. Nylon-insert locknuts make them secure.

4.3 uF + 2.7 uF = 7 uF

15 uF + 1.5 uF = 16.5 uF

AudioCap Theta 0.01 uF bypass caps are nestled between them.

Inductors relocated and secured with hotmelt adhesive.

Component leadwires redressed, cut to appropriate lengths and resoldered.

Cable ties organize the input and speaker leads, and provide a measure of strain relief.

Before and after:

ratitifb
03-04-2008, 11:47 PM
Hi could you post schematic with part list. Is 4301 sounding affected ?

Zilch
03-05-2008, 12:32 AM
Hi could you post schematic with part list?I edited to provide a link to the schematic, above. I have reused the original inductors. The capacitors are Dayton metallized polypropylene and AudioCap film and foil from Parts Express.

The parts are not expensive, but it takes several hours to do each one.


Is 4301 sounding affected?These are not mine; I am rebuildiing them for a forum friend. He will likely be reporting on the performance here once they are reinstalled. :thmbsup:

oznob
03-12-2008, 09:06 PM
I got the re-built crossovers from Zilch yesterday but didn't get a chance to install them until late this afternoon. I have been listening to them for about four hours now and the sound is simply amazing! I always felt the tweeter was a bit harsh with the stock crossovers. Harsh no more with extention cleanly into the higher registers, again, amazing! I have always been a metal tweeter guy but I may re-think that opinion? One of my all time favorite recordings is from an old Blue Horizon album of the original Fleetwood Mac with the great Otis Spann. It's disc two of the "Blues Jam in Chicago." The track is a loose studio recording of "Someday Soon Baby" without effects, one track, with Spann on piano and vocals, Peter Green on lead guitar, John McVie on bass and Mick Fleetewood on drums. To me it's one of those magical moments of music that not many have ever heard. I have listened to that track more times than I can count but NEVER better than through the "Zilchified" 4301B's! I could go on but I think I made my point. I am one happy guy! Now if I could just get the S3100's to sound this good!:hmm:

Thanks Zilch, you're the best!!!:applaud:

I would be remiss if I didn't send a special thanks to Edgewound who did a great job re-foaming the 116H's. Top notch job Edge, thanks!

ratitifb
03-13-2008, 12:18 AM
Lucky man who is so close to such reliable JBL people :)

tweeter
03-13-2008, 07:30 AM
4301B = Simpliest is the Best :applaud:

majick47
03-13-2008, 10:24 AM
I'm still useing a pair of 4301B in my second system and still think they are terrific. I was wondering if the crossover rebuild would be a project an "amature" could do with a RS soldering iron and no background working on electronics. If it's beyond my limited skills I could purchase the parts and ask my local JBL pro shop to build the crossovers.

oznob
03-17-2008, 05:29 PM
I'm still useing a pair of 4301B in my second system and still think they are terrific. I was wondering if the crossover rebuild would be a project an "amature" could do with a RS soldering iron and no background working on electronics. If it's beyond my limited skills I could purchase the parts and ask my local JBL pro shop to build the crossovers.

Why not send them to Zilch and let him work his magic on them! I am thoroughly enjoying mine more and more each day!:yes:

majick47
03-19-2008, 10:39 PM
OZNOB I'm sure Zilch did a fantastic job rebuilding your 4301B crossovers. Also I'm sure he is very busy and I wouldn't want to impose on him. In the past I'v acted in haste, sometimes for better and sometimes for worse. If anything Zilch has given us it's a lot of information to think about when it comes to makeing choices re JBL speakers. I want to explore all my options before I consider the 4301b crossover upgrade which I'm sure would be a marked improvement. What I'm considering is a pair of L46 that I already have to replace the 4301B in my second system. Another option is a JBL three way speaker, something like a 4412 I believe Zilch has mentioned in the past as having a lot of merit. I really don't want to make a quick decision on this one till the jury is in on what direction to go and I'd really listen to any advice offered. As of now the 4301b are bolted to heavy duty JBL pro wall/ceiling mounts about a foot or so from the ceiling angled down to my listening position in a 10x12 foot room with 7+ foot ceiling. If the 4301b stay or are replaced with another JBL speaker they will also be on the wall mounts.

majick47
06-09-2010, 06:09 PM
I want to update that Zilch rebuilt my 4301B crossovers. On first listen the difference was not noticable but after about two weeks the new components had time to burn in and the sound is now much smoother, detailed with extended bass/high end compared to the old/original/stock crossovers. The 4301B easly compete if not better a pair of 4406 I recently purchased. THe 4301b are very good to start with and now the performance has been taken up to a much higher level. If you have a pair of 4301B it would be well worth your while to have the crossovers upgraded. As to be expected Zilch did a beautiful job and the sound is terrific.

80n
06-07-2011, 06:42 AM
Hey. Very nice rebuild ! Do you think this crossover network would be a worthy upgrade to my Decade L16 (with 116h woofers) ? If so, is there a way to find the adequate inductances ?

peterz
11-01-2011, 05:02 PM
I own a pair of the 4301b's and am interested in doing a crossover recap. The pictures Zilch left us are a huge help and I think I could take this project on if only a few more pics were provided, and the associated parts list was a little more clear to my VERY inexperienced eyes.

That, or is there someone on these boards who would build these for me for a reasonable fee?

It goes without saying that without Zilch, I never would have owned these speakers to begin with. When I bought them, it was with a lot of insight from him both here and over at Audiokarma. His loss is felt by many including myself who barely ever exchanged a PM with the guy. RIP Zilch.

thanks for any help in advance,
peter

JeffW
11-01-2011, 06:41 PM
All he did, aside from tidying up the board, was to replace the two capacitors (round objects in the lower left corner) with new equivalents.

Evidently, the original caps were 16.5uf and 7uf. He simply placed a 15uf and a 1.5uf in parallel to make the 16.5uf, and a 4.3uf and 2.7uf in parallel to make a 7uf. Then put an AudioCap Theta 0.01 uF in parallel with each new "bundle". That's just a bypass capacitor to help the sonic qualities, it doesn't change the value of the bundle enough to matter.

You could just make up these two bundles of caps, clip the leads going to the two existing capacitors, and insert the bundles into the clipped leads. Zilch just went the extra mile to clean things up, and reducing all that extra wire can't hurt the circuit.

peterz
11-02-2011, 05:54 AM
JeffW
Thanks! A couple follow up questions.... and it appears I may have to do some wikipedia reading!

1. "In parallel" would mean that one lead from the original cap would be soldered to BOTH the 15 AND 1.5uf caps. And then the other lead from the old cap would again be soldered to BOTH the 15 and 1.5. Similarly with 4.3 and 2.7?

2. Does signal direction matter with those Dayton capacitors? Meaning does it matter which way the signal goes through those caps?

3. What would those extra bypass capacitors be doing? Cleaning up the signal 'noise' or something?

4. I'm assuming partsexpress will handle these four caps no problem correct?

Thanks for your help, sorry if I'm asking obvious questions, I'm just very new to all of this.
take care
peter


All he did, aside from tidying up the board, was to replace the two capacitors (round objects in the lower left corner) with new equivalents.

Evidently, the original caps were 16.5uf and 7uf. He simply placed a 15uf and a 1.5uf in parallel to make the 16.5uf, and a 4.3uf and 2.7uf in parallel to make a 7uf. Then put an AudioCap Theta 0.01 uF in parallel with each new "bundle". That's just a bypass capacitor to help the sonic qualities, it doesn't change the value of the bundle enough to matter.

You could just make up these two bundles of caps, clip the leads going to the two existing capacitors, and insert the bundles into the clipped leads. Zilch just went the extra mile to clean things up, and reducing all that extra wire can't hurt the circuit.

JeffW
11-02-2011, 07:10 AM
JeffW
Thanks! A couple follow up questions.... and it appears I may have to do some wikipedia reading!

1. "In parallel" would mean that one lead from the original cap would be soldered to BOTH the 15 AND 1.5uf caps. And then the other lead from the old cap would again be soldered to BOTH the 15 and 1.5. Similarly with 4.3 and 2.7?

Right. Just lay the caps along side each other, parallel as it were, and gather all the leads coming out each end together. You can see it in the pic Zilch provided.


2. Does signal direction matter with those Dayton capacitors? Meaning does it matter which way the signal goes through those caps?

Nope, they are the same in either direction.


3. What would those extra bypass capacitors be doing? Cleaning up the signal 'noise' or something?

Something along those lines, yes. There's more to it, of course, but adding them adds little cost or complexity.


4. I'm assuming partsexpress will handle these four caps no problem correct?

Looks like.

http://www.parts-express.com/dayton-metallized-capacitors.cfm

http://www.parts-express.com/audiocap-capacitors.cfm


Thanks for your help, sorry if I'm asking obvious questions, I'm just very new to all of this.
take care
peter

No problem. Good luck on your project!

peterz
11-02-2011, 08:25 AM
JeffW,
All 6 caps have been ordered. Thanks for the clarification and help. More on this after the work gets done.

what a simply amazing site this is!

thank you
peter



Right. Just lay the caps along side each other, parallel as it were, and gather all the leads coming out each end together. You can see it in the pic Zilch provided.



Nope, they are the same in either direction.



Something along those lines, yes. There's more to it, of course, but adding them adds little cost or complexity.



Looks like.

http://www.parts-express.com/dayton-metallized-capacitors.cfm

http://www.parts-express.com/audiocap-capacitors.cfm



No problem. Good luck on your project!

JuniorJBL
11-02-2011, 09:22 AM
Good luck with your project!!:applaud:

JeffW
11-02-2011, 10:21 AM
JeffW,
All 6 caps have been ordered.

Remember, it's 6 caps per speaker.

peterz
11-02-2011, 11:38 AM
ahhhhhh hahahahahaha!!!!!

see? even the most BASIC of repairs or improvements is a mild exercise in futility for the uninitiated! stay tuned, I'll be calling cust svc at parts express here shortly attempting to amend my order for 12 caps!

that is just too funny. Can you imagine the look on my face if I had gotten all the way to planning a night of repair, getting all the tools out, cleaning off the workbench, etc. only to find I needed a second set?!?! you saved me!

thanks again.
peter



Remember, it's 6 caps per speaker.

peterz
11-02-2011, 11:48 AM
thanks to the fast responses and my general intrigue into 'how I did', I was able to void the PE shipment and create a fresh new order with 12(!) caps, 6 for each speaker!

anyone need to find me, I'll be putting the dunce hat away ...
peter

pos
11-02-2011, 12:12 PM
HOLD ON!
Did you order new L-pads? ;)

peterz
11-02-2011, 03:23 PM
haha. errrr..... what are L pads?

in other words - nope. I have to assume L pads are related to another upgrade that can be done on these or other JBL's and if I had ordered them I would have saved on shipping by including them in this order.

Otherwise, if they are pertinent to upgrading the two in parallel capacitors in the 4301b's it appears I'll be 1,000,000 L pads short.:)

but thanks for sharing!
peter


HOLD ON!
Did you order new L-pads? ;)

JBL_620
11-02-2011, 08:21 PM
haha. errrr..... what are L pads?

in other words - nope. I have to assume L pads are related to another upgrade that can be done on these or other JBL's and if I had ordered them I would have saved on shipping by including them in this order.

Otherwise, if they are pertinent to upgrading the two in parallel capacitors in the 4301b's it appears I'll be 1,000,000 L pads short.:)

but thanks for sharing!
peter

So you're planning on reusing the original L-pads then? This should work if you don't want to order new ones.

peterz
11-04-2011, 02:29 PM
JBL620,
Glad to hear it will work. But I never saw any mention of the L pad upgrade in this thread... so what I was doing was what Zilch had laid out for 'sonic improvements' related to the crossover.

Is the L Pad the dial that changes the frequency in the speakers' response - the High and Low dials? I read it keeps the impedence presented to the amplifier the same. Is that a 'must have' upgrade relative to upgrading these crossovers? I mean, without doing the L pads ...

Anyway, I've kind of bitten off as much as I can chew and don't want to go any farther until after break in of my new crossovers. Much easier for me to take on one thing at a time. I'll complete this thread with a few pics/questions, and then any post upgrade thoughts I can come up with. And then if I feel the bug, maybe do the L pads and start a different thread...

thanks for everyone's help. Parts Express shipped yesterday, I should have the parts next week sometime.

take care, have a nice weekend
peter



So you're planning on reusing the original L-pads then? This should work if you don't want to order new ones.

pos
11-04-2011, 04:07 PM
Zilch said that in his particular case "Original L-Pads were fine" so he didn't had to change them.
If you do not hear noises or silent spots when turning your lpads you should be -relatively- safe keeping them. They are cheap to replace though, and those things do tend to oxide over time, and contacts get instable...

JBL_620
11-05-2011, 12:04 AM
If it was me, I would build the upgrades from scratch and keep the stocks in case you want to go back for whatever the reason.

peterz
11-05-2011, 03:44 PM
parts express sent exactly what I asked them to, so tomorrow (time permitting) I'll be upgrading the crossovers with the 12 (!) new caps.

pretty excited to get my hands dirty in this project.
now if someone would just start stocking the JBL blue grill cloth fabric again...

stay tuned.
peter

JuniorJBL
11-05-2011, 04:46 PM
Sweet!!
;)

peterz
11-06-2011, 11:32 AM
well I should probably look for some threads on good clean soldering stations and techniques, because my 'new' crossovers aren't exactly as pretty as the ones Zilch did in this thread.

All the same, the upgrades went MUCh easier than I expected and would easily suggest the information in this thread is enough for just about anyone to take on.

And I'm probably going to be splitting hairs and certainly don't want to step into the morass of 'upgraded crossovers vs originals' debate, but I am really liking the immediate 'improvements' I'm hearing. Immediacy. Pace. The veil that felt like an extra grill cloth or something, are all improved immediately upon completing. They are now 'burning in' (again, please let's not go there on burn in or not) or at least getting put through their paces all afternoon.

Thanks again for everyone here. Looks like the bug has hit, I'll probably be looking for a thread on upgrading L Pads next! ha.

take care and thanks again everyone, a VERY happy 4301b upgraded crossover user.
peter

mech986
11-27-2011, 10:46 AM
Now that you've lived with it for a few weeks, how's the 4301B sounding now?

Anyone ever decided to go with a charge coupled crossover? That might be interesting too!

mech986
11-27-2011, 10:49 AM
BTW, anyone ever compared the L19/19A and 4301/4301B directly and what about changing over the L19 to the 4301B crossover? Even though they have a slightly different crossover and cabinet dimensions, I recall JBL stated the L19 was an acoustic equivalent to the 4301.

Can anyone confirm these thoughts?

grumpy
11-27-2011, 03:10 PM
I have L19 and 4301B examples... main diff is cabinet depth (greater on 4301B) and height (shorter on 4301B).
I mostly like the way the 4301 sized cab -looks- especially on a stand (chunkier, lower center of mass looking)...
L19 might fit better on a shallow shelf or closer to a wall. 4301 looks nice all around (IMO). Quite likely typical placement
and usage were taken into consideration for each design. I've not done a direct comparison... I'm thinking this would
not be particularly helpful unless the intended environment were included. :dont-know: I can fire them both up if you'd
like to give them a listen some time...

pete1729
06-27-2014, 02:29 PM
So here I am doing some research on my L16's and wanting to know the difference between them and the L19's and 4301's that I enjoyed so much when I borrowed them. Who's going to run it all down for me? Zilch that's who.

My god I miss that guy.

fabrice11
06-28-2014, 10:52 AM
here is the update of my crossover with replacement L-PAD chemical polypropylene capacitors with SCR and Mundorf LE26 biased and also ceramic resistors by MOX