muscmp
Active Member
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.
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.
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