jbl4301 and 4301e repair and restore

Discussion in 'Speakers' started by muscmp, Feb 27, 2017.

  1. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    i've begun work on these two speakers. i'm enclosing pictures of each speaker.

    i've replaced the le25-2 tweeter(thanks (L200b) in the 01 and have just received the surrounds for both woofers. i'm posting some of my PM with mech986 so everyone can see what has recommended but i would like to get other people's opinions. note that the 01e no longer has the amplifier. both speakers have the very dark blue grill cloth and black baffles. someone has put some sort of goop to replace the rotten surrounds so i'll have to get the goop off and put on the new surrounds. a couple of the corners of the cabs are dinged and there are scratches in the veneer. i'll also replace the caps with axon as mech986 suggests. i've found 4.3 and 2.7 uf, 250volt for the 7uf, and, 13 and 3.6uf, 250 volt for the 16.5. he also recommends adding a small bypass cap which i will do.
    thanks,
    mikeB


    from mech986:


    Aside from the amplifier, the speakers are otherwise the same in acoustic equivalent drivers and the crossover is the same in both. If for some reason the amp isn't there or is bypassed (sometimes the amp fails and owners convert it to a passive speaker), then the speakers are essentially the same.

    Regarding the crossover, I would not recommend to vary more than 5% from the stated values of 7uf and 16.5uf non-polarized film caps (original are mylar polyester, recommend going to a good metallized or regular film polypropylene) plus a small value 0.01-0.1uf polypropylene bypass cap. Really, since there are only 4 caps total for the pair of speakers, it is quite inexpensive to get the correct size caps (or parallel a couple to get the correct value, ie 4+3 =7, 12+4.5uf=16.5, etc.). I've used Aeon (Axon I guess) caps from Parts Connexion in Canada (now with a really favorable exchange rate offset by shipping and time considerations), and a lot of people like Clarity Caps. I'm not much of a fan of original Solen or Parts Express caps as many say they tend to be bright sounding.

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

    http://www.audioheritage.org/vbulletin/showthread.php?15529-JBL-4301-Rebuilding-Network


    As for the woofers, I would pull each one and see how much "goop" there is on the cones - I've used goop to fasten caps to the crossover boards, and in my experience, sometimes it actually pulls off without much damage to the cones. In any case, you can't really use the woofers correctly as they are because the "surrounds" have nowhere near the correct compliance and give as normal foam surrounds, so you'd have to try pulling the stuff off anyway. If you're lucky, you can get most or all of it off both front and back.

    Here's what I would suggest doing depending a bit on how rubbery or hard this material is. I would inspect the woofer cone edge carefully and determine where the actual paper edge is - if lucky, the edge is actually exposed and the glue/goop is all on the back of the cone. I'd then carefully and cautiously, with a plastic or metal flat bladed scraper or wood chisel, lift up and save the outside 4 piece neoprene gasket - this is to be reused to get the oem JBL appearance. Then carefully cut around the cone edge into the goop so that you can separate the cone from the rest of the goop surround, leave at least 1/8" attached to the cone for safety purposes. Once the cone is free, then you can cut and scrape away the goop from the frame, trying to get a reasonably clean and flat surface on the frame landing area.

    After that is done, the more delicate part - essentially lifting or scraping away, bit by bit, the goop that is adherent to the cone edge. Again, if you're lucky, you can get it to lift off in bits, maybe away from the old glue line that was there before instead of lifting off any paper layers which would weaken the cone edge. Work slowly, with sharp chisel or scraper, probably no wider than 1/2" and use a medium size lazy susan to rotate the driver, face down, plus lots of light so you can see the front and back of the cone edge as you work. In some cases working under the frame ribs, you can't see everything but you can still get in there. Again, if you're careful, you will be able to get all the goop stuff off and end up with a clean cone and frame, ready for a refoam. Maybe some judicious heat from a hair dryer might help soften and help the glue off, maybe, although I suppose there's a possible concern it may activate the glue again and make it worse. I even thought putting the driver in the fridge for an hour might harden the glue so it would lose adhesion and crack off - nope, Goop maker says it stays flexible down to -40 deg.

    If you are doing the refoam, its very straightforward using a tone to center the voice coil rather than cutting off the large concave dustcap of this particular driver. If you need instructions let me know. the surrounds are available from many many vendors, but Rick Cobb in Florida is well known for correct fitting surrounds, easy to contact him, search on AK for his contact info.

    Otherwise, if you want to send it somewhere, I recommend SpeakerRepairPros, the successor to Orange County Speaker Repair, in Garden Grove, California. They have a website.

    thanks for the reply and pics. The 2nd speaker with the black baffle you have is the original 4301 as noted on the foilcal label, not 4301B. It should have the alnico magnet woofer. The Simply Speakers surrounds should work fine. Search for the "tone method" of refoaming for tips, and correlate that with JBL woofers need to glue the surrounds on the back of the cone edge.

    JBL veneer responds very well to TLC. You may consider starting a new thread in Speakers and update all of us with pics of the cabinets and the work to get both speakers up to snuff again. There's tons of threads about restoring and refinishing JBL walnut veneer. The usual stuff is to lightly steam out the scratches and gouges if veneer is not missing - use a moist towel heated by a hot (cotton setting) clothes iron to steam swell the gouged fibers back to the surface. If veneer is missing, there are ways to patch it with wood or bondo and color it / figure it to look like original so again, search AK for veneer repairs. Most will then figure on whether they will sand and refinish, or put a few coats of Howard Restor-A-Finish + Feed-N-Wax, or go to sanding with 220, then 400, and 600 sandpaper or artificial sanding material (3M), then apply finish of choice, oil, tung oil, poly, satin, semi-gloss, or gloss.

    Did the speakers come with grilles and what is their condition?

    As I mentioned, not uncommon to find the 4301E models with the amps disabled or removed. Personally, I would not have used acrylic or plexiglass / Lexan as its very reflective soundwise and tends to be thin so leaks sound (like a diaphragm) plus doesn't stay very stiff unless thick - vibrates, and I suspect the panel is 1/4" thick or less.. Also in the pic, you can see the connection panel looks riveted which can induce cracking. As you can see, the panel is attached by only 3 screws, which means one screw is missing and that corner is loose, plus there's no fiberglass insulation covering that panel so there isn't absorption right behind the woofer where it needs to be - likely the product of someone emulating the unfortunate trend of plexiglas "look at me" car audio woofer / subwoofer enclosures, and not thinking about how a proper speaker needs to work. The original JBL amplifier was built on metal plate and bolted in place with flat head phillips machine screws, typically 8/32. IMO, you should consider making a new panel out of either 1/2" MDF cut to cover the hole and mounting holes, or use 1/2" Birch plywood similarly cut, and install T-Nuts or a threaded insert to accept the machine screws. I personally like plywood as it accepts T-nuts better. Drill two holes at 3/4" apart in the center of the panel to accept some nice gold plated binding posts of your choice and install them on both speakers so they are the same and can use either banana plugs, paired plugs, bare wire or spades for connections to your speaker cable. You can paint the rear panel and the replacement panel plus the cutout with satin black paint to get the all uniform. Zonker92 has a few recommendations for the paint (he likes automotive paint while others like Rustoleum or similar) so check his very nice and informative restoration threads. Be sure to remember to find and install additional 1-2" thick compressed fiberglass mats into the back of the speaker like the originals to cover up the new panel.

    You may also want to update the wiring from the input connectors to the crossover and consider updating the wiring from the crossover to the drivers - but one caveat - important to keep the same color code if possible, and use new and appropriate Fast-On connectors (spade and female) to keep JBL's original wiring and polarity intact - they used appropriate colors and connectors to ensure that with the specific driver terminals they used.

    I suspect your speakers are going to come out very nice once they are done.

    01 116a.jpg 01 front woofer.jpg 4301.jpg connection.jpg surround.jpg 01ewoofer.jpg 01ewoofer1.jpg 01ecorner.jpg
    01e.jpg 01eplexiglas.jpg
     
    Last edited: Feb 28, 2017
  2. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

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    19,875
    Location:
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    Well, nice to see the thread and more pics of the woofers. Here's my take:

    The woofers are the original 116A alnico versions, and the goop was applied over the failing foam surrounds. Interesting how the front surface looks a little like JBL's accordion or double roll surrounds but that's more just an optical, as the pics from behind clearly still show the original foam surrounds glued to the backs. The good news is, except for a little goop on the front cone edges, I think all of it is just on the old surround and my method above to clear out the old surround, the goop, and the old surround from the back edge of the cone should work fine - you should even be able to salvage and re-use the neoprene front gasket without much trouble. then you should be able to refoam using the tone method.

    As mentioned, I would suggest making a wood plate to cover the large hole/opening left for the energizer - you can make it from 1/4-3/8" thick plywood or masonite, I would apply a layer of something like Dynamat (or a generic equivalent) to damp that panel, then cover it with the same 2" thick flat layered fiberglass that JBL uses in all its speakers of that era. You can then mount new and matching gold plated 5 way binding posts for the input connectors, same with the other speaker.

    Otherwise the cabinet fronts look very good, as do the tweeters. The veneers will benefit from some touch up, minor repairs, and veneer raising and cleanup, but I fully expect the JBL veneers to respond to some TLC well.
     
  3. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    mech986: thanks for all of your recommendations. i had to look up dynamat--sound deadening. i do have some extra fiberglass but it may not be quite enough. where can i purchase a small amount to cover that area?

    i should get the caps from partsconnection in the next couple of days and i'll order the binding posts from antique electronics as they are having a 20% sale.
    thanks again,
    mikeB
     
    bichitus likes this.
  4. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

    Messages:
    19,875
    Location:
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    You might consider hitting up / calling a local car stereo installer and see if they have any scrap pieces of adhesive mass loaded sound deaden-er sheets, I would assume you don't need much more than one or two layers about a foot or two square, leaving a rectangular space for the input connectors. JBL used captive nut / threaded fasteners (kinda like T-nuts but in a metal grommet format) to attach plates and such - you'll see that on the crossover board) and you could consider using either a bit of foam gasket like window draft sealers or a bead of silicone to seal the plate to the cabinet when screwed in. Some nice black colored flat headed philips screws would look good on the back panel (you could also use a sharpie on regular bright screws).

    BTW, some people have used those dynamat and similar sheets to dampen woofer frames, might be fun to experiment. The open cell draft window seals (use about 1/4" wide,maybe 1/8-3/16" tall, usually available from local Home Depot or similar) can also be used for the woofer and tweeter openings as a seal too. Might be hard to compress fully though if thick.

    All the woofer front frame edges look nice with the raw filed or machined look. If not, you can easily brighten them up using a flat metal file of medium coarseness but be sure to round off the outer edges so you don't catch or cut yourself.
     
  5. JustinCase

    JustinCase AK Subscriber Subscriber

    Messages:
    68
    Location:
    Ontario Canada
    Right on. I've got a pair myself that I'll be giving the same treatment eventually. It'll be great to hear more feedback. As is mine sound really good for their size- can't wait to hear what an upgrade like this will do.
     
  6. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    for the fiberglass, i struck out with the car stereo people so i'll have to try an upholstery shop.

    i should be getting the caps in today so i pulled the two boards. note the difference in the two. the 01e board has only the two caps while 01 has three. the 01 has the two smaller 4.3 and 2.7uf, while the 01e small one is most likely a single 7uf but it has no markings. earlier today i purchased four 2" machine screws and 4 tnuts to emplace the wood in the area vacated by the plexiglas for the 01e. once i get the new caps, and .01 bypass caps stuffed in, i'll start to clean off the goop from the woofers. still need to order the binding posts for each.

    mech986: i believe this is the link to the surround replacement as well as using a 30hz test tone thru the woofer to ensure it is properly centered with no rub. one thing i can't find is a picture of the recap with bypass caps that someone placed on this site or the lansing. i can't find it on either site. i want to see how they stuffed the new caps.

    http://www.audioheritage.org/vbulletin/showthread.php?469-Resurround-Step-by-step






    4301board.jpg 4301e board.jpg
     
    Last edited: Mar 9, 2017
  7. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

    Messages:
    19,875
    Location:
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    Heh, I agree, both speakers should have the same functional crossover, so the 4.7 and 2.3 in parallel will give the required 7uf cap. In the case of recapping, it is not required nor necessary to restuff the original cardboard tubed caps for original appearance, unless you're really going to get OCD about it. Normally, the old cap containers are removed, the old hardened glue taken off (try not to disturb the glue holding down the inductors though), and then new caps are wired in where the old caps went - this can present a spatial challenge as most caps today are either radial or axial leaded, and tend to be a bit larger or longer. JBL's original mylars have the extra length of flexible leads to help with wiring them to the terminal strip, convenient. After the new caps are soldered in, a small amount of GOOP adhesive will hold them in after it dries. You can also wire solder in bypass caps the same way. If needed, insulate any extra length of bare leads with some heat shrink or teflon tubing.

    I'm surprised you could not find additional dynamat like materials in surplus at car stereo installation places, they have that stuff or generic versions of it in droves, or at least you should be able to buy some there. You can order some on Ebay or amazon though. The fiberglass is best found at a construction site, or in larger amounts at Home Depot/Lowes - look for flat compressed fiberglass, 2" as opposed to the large >4" fiberglass batts that are used in attics and walls - fiberglass wraps for pipes and the like are similar compressed bits.

    The tutorial by bouputnam on LH is very good and the first one I found. The only difference is the 2122 driver he was working on has a very small frame gluing edge/surface as opposed to most true woofers which have a larger frame flat area to work with.
     
  8. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    the two boards with new caps and with the .01 bypass cap. today i'll put the boards back in and hopefully start cleaning the woofers.

    mech986: with the car stereo people, one place had no idea what sound dampening was so he just did installs without using any. the other guy sold it for $45/sq. ft. way too much $$. so, eventually i'll hit the upholstery people. still need to order binding posts. also, i'm looking for screw-in binding posts for my scott299a as it presently only has the small screws that make it difficult to connect the thicker wiring i'm using.

    01capped.jpg 01e capped.jpg
     
  9. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

    Messages:
    19,875
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    Here's a couple with Dynamat that are cheaper, a 10x10" should be plenty and you get 2 pieces. There are also some generic versions available on Ebay too. Free shipping on the below also.

    http://www.ebay.com/itm/PLAIN-PAK-D...179222?hash=item3ad7a77596:g:UjAAAOSw~OdVbgWt

    http://www.ebay.com/itm/DYNAMAT-XTR...713664?hash=item3f24863080:g:yQIAAMXQNbxReTxM

    Check Parts Express for a nice selection of gold binding posts for the speakers. As for the Scott 299 screw in replacements or adapters, try something like this, I'm choosing from US based vendors (not the OEM Hong Kong) for ease of shipping: I suspect they also sell in groups of 4 as well, the below are 8 piece sets.

    http://www.ebay.com/itm/8x-Hi-Fi-Go...id=100005&rk=5&rkt=6&mehot=ag&sd=271804581952

    [​IMG]


    http://www.ebay.com/itm/8-Adapter-F...581952?hash=item3f48d0c840:g:dpwAAOSw34FVAo9C
    [​IMG]

    Or determine the machine screw size and threading of the Scott terminal, and then search for a binding post with a threaded post of that threading. Problem may be that the spacing may not allow the binding post heads any room to turn, or even touch, a problem with metal heads.
     
  10. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    i was able to get the goop off the woofers and replace the surrounds. tedious isn't the word, excruciating is. if i ever do another set of surrounds, i'd first want to see if someone else had already made the effort, properly or not. now i will say that my first gluing of the surround was not perfect, but the second one worked out quite well. the iron and wet towel sure did the trick for bringing up some of the scratches but there are some gouges that only came up a little bit. i also created two new corners on the 4301e and, thought i'd done a good job until i applied the howards and realized that it wouldn't properly cover natural wood filler. overall they look much better but still with the corners and the gouges it isn't even close to pretty. the wood i used to replace the plexiglas on the 4301e that someone had placed over the hole formerly housing the amp was too thick and i had to drill enough down to accept the binding posts. eventually, it worked well. the first picture is of the felt strips i used to decouple the wood from the cab. when i emplaced the wood, i used the tnuts which worked out well also.

    however, the sound is fantastic and that is the real purpose of these speakers! i'm enclosing pics of the finished product. i'm sure more work can be done on the cabs and that may be done at a later date.
    thanks to mech986 and others who provide(d) recommendations.

    felt.jpg however, the sound is fantastic and that is the real purpose of these speakers! i'm enclosing pics of the finished product. i'm sure more work can be done on the cabs and that may be done at a later date.
    thanks to mech986 and others who provide(d) recommendations.
    4301 woofer.jpg 4301e back.jpg 4301e corner.jpg 4301e side.jpg 4301grill.jpg 4301top.jpg
     
    mech986 likes this.
  11. GD70

    GD70 AK Subscriber Subscriber

    Messages:
    9,903
    Location:
    Northern Westchester Co, NY
    Good to see you have them singing! Fabulous speakers for their size.
    Did you use a test tone when doing the surrounds? I recently refoamed a pair of these woofers for another AKer, and it went quickly, and used the supplied CD test tone. My 4301bs had just been refoamed prior to my purchase so I missed out on the fun with those.
     
  12. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    GD70: i bought the surrounds thru simply speakers. they recommend a centering with the finger pressure north, south, east and west as it dries. i used that method, plus i used a 31hz looped test tone for about 1/2hr. each.
     
    GD70 likes this.
  13. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

    Messages:
    19,875
    Location:
    La Habra, California, USA
    Excellent work! The veneer shows "patina" and some will suggest leaving it as is, others might go more aggressively with the moist rag/iron, others would consider a complete reveneer, its a matter of choices, time and money. There are no bad choices. The only thing you need now is some JBL badges or the original long name badges which may be hard to come by.
     
  14. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    mech986: thanks to people like you providing information, it made my job much easier. it was a learning experience and as usual, there are a couple of screwups but there are always workarounds. some just take longer than others. ha!

    i wouldn't mind finding the badges so i will do a search. i don't know which badge is proper since the only brochure i've been able to find online is in black and white. googling jbl 4301 and images seems to show more of the small black and silver badge than the longer strip.

    otherwise, they just sound great!!
    thanks again.
     
    Last edited: Mar 20, 2017 at 11:58 AM
  15. GD70

    GD70 AK Subscriber Subscriber

    Messages:
    9,903
    Location:
    Northern Westchester Co, NY
    If you get ambitious and decide to repair & refinish the cabs, I can help you with any questions.
     
  16. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    they are pretty deep gouges. what would it take to repair rather than reveneer?
    thanks,
    mikeB
     
  17. GD70

    GD70 AK Subscriber Subscriber

    Messages:
    9,903
    Location:
    Northern Westchester Co, NY
    Hey Mike,
    The cabs need to be sanded to the veneer surface. Often sanding removes 75% or more of the scratches. Then where the deep ones remain use a steam iron and a wet q-tip to put water on the scratches. Let it sit a bit and then steam with a t-shirt between the iron and veneer surface. Repeat a few times. Sometimes it will raise the scratches, sometimes not.
    Corners can be repaired by making a clean an LED cut and with extra veneer spliced in to patch the area. Once sanded and the cabs are oiled, they will be hard to see. I've done this numerous times. If you look at some of my restoration threads, there's plenty of photos showing the process.
    Those 4301's are well worth it!
    Glenn
     
  18. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

    Messages:
    19,875
    Location:
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    In my experience, unless the veneer gouges penetrated to the underlying wood substrate, you don't have much to lose by being a bit more aggressive with the steam raising. The main issue is to try concentrating the heat / steam at a cotton setting on the iron, and leave the steaming for about 10-15 seconds to avoid scorching the veneer. Keeping the rag or T-shirt moist is key. Multiple passes with short time is preferable to overheating. In that way, you may be able to raise / swell the deeply gouged areas higher in their depressions so that overall sanding may be less. While JBL veneer is robust, it isn't super thick. If you're lucky enough to raise the gouges and scratches to close to the surface, take an overnight break, let it dry out, then approach it again the next day. You may find some pretty good improvement before sanding is needed.

    Are most of the gouges on the bottom or tops or both? You might consider cleaning the surface afterward steaming and drying with mineral spirits to remove some of the Howard RAF stain from the gouges where they may have picked up more than their share before sanding.
     
  19. westend

    westend Audiopile

    Messages:
    10,120
    Location:
    Shorewood MN
    I'd suggest to do some research on wood refinishing. There are too many techniques and processes to lay them all out in this thread. Bottom line is to remove the Howards RAF and remaining finish and start anew. With proper prep, grain filling, sanding repairs, and touch up, you should be able to get the JBL's back to a handsome finish.

    Here is my restoration thread of a JBL 4313b (with Walnut veneer): http://www.audiokarma.org/forums/index.php?threads/jbl-4313-restoration.192204/
     
  20. muscmp

    muscmp Member

    Messages:
    80
    Location:
    socal
    great info. mech986,gd70 and westend. the gouges are all over-tops, sides and bottoms. i don't know how someone could get them everywhere. but, that's what i have now.
    i'll report back on my progress.
    thanks to all.
    mikeB
     

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