The title should say 4612B not 4162B! Sorry.
I picked up an old beat up pair of JBL 4612B recently. Seller told me they need some work. Came home and figured out some of the issues.
Here's my situation:
I removed both tweeters. They both play when connected directly to my amp. Great news.
When the tweeters are connected in the cabinets,
The two 8" woofers in the first cabinet play properly, the tweeter does not.
EDIT: I got the tweeter to play along with the woofers. The volume knob for the tweeter was acting up. Must have been dirty. So now, one whole speaker works!
In the second cabinet, nothing plays at all.
I removed the woofers from the second cabinet. One moves when I press it and plays well when connected directly to my amp.
The second woofer is frozen in place, doesn't respond to any gentle finger-pressing, and it seems to have been serviced at one point, because the glue is a different colour than the others. The magnet is cracked horizontally in half, but still sitting on the base of the woofer. When connected to my amp, it plays, but there is no bass at all.
Any insight on what I can do to restore these? Are crossovers available or repairable? (I'm assuming that might be the reason I'm having issues.)
Any insight on that cracked woofer? Can it be repaired you think?
Finally, any idea about how much a restored pair of these go for?
Anyone interested in the parts I've mentioned, reach out. Local pickup in Brampton, ON, Canada.
Thank you all for your time.
Congrats and welcome to AudioKarma! We can help you troubleshoot these 4612B's.
Regarding the working cabinet, the tweeter control is an L-pad which get dirty and oxidize over time. If you can obtain some DeOxit D5 spray cleaner with a thin tube, you can spray that into the vent holes on the back of the control and twist and turn the control about 20 times. Repeat this procedure twice more and it should clean and flush out most if not all the oxidation. Follow with DeOxit G5 to protect the exposed metal windings inside the L-Pad.
You can purchase them both at Parts Connexion which happens to be in Burlington, about 30 mins from you, local pickup is available. This stuff is not inexpensive but is some of the best to clean controls in both speakers and electronics plus contact points like jacks and plugs. If you do any electronics or audio troubleshooting, especially with vintage gear or other electronics, it will be invaluable in addressing connectors, controls, pots, and L-pads, with a few caveats. A can of each is in some cases a lifetime supply! If in a pinch with budget, buy just the D5 spray to start with. Much cheaper at Parts Connexion than at Amazon.
https://www.partsconnexion.com/CAIG-67259.html#
https://www.partsconnexion.com/CAIG-67260.html
Be very cautious when connecting just a tweeter out of circuit without a crossover directly to your amp - tweeters are not built to handle midrange or low (bass) frequencies and can be damaged quickly if you feed it a full frequency spectrum signal. If you're just testing for function, use tone controls and turn down (filter out) the bass and mid (if you have that control) completely and only feed 3khz or higher to a tweeter to check for function, and then not at very high volume. If they both function, that's great, then you've got two functioning 2404H-1 tweeters.
Try each tweeter in the working cabinet. If they both function properly, then the crossover, L-Pad and woofers plus wiring and connectors are working. Use some DeOxit D5 on the wire & connectors on each tweeter and woofer connection, plus apply to a 1/4 speaker plug and the jack and work them a few times to clean the jacks' contact surface. This ensures all electrical contact surfaces have been cleaned. Remember not to overtighten down the tweeter mounting screws as the tweeter horn is made of plastic and can crack. If the wood where the screw threads into seems a little weak, place 1/4 of a toothpick into the hole before screwing the screw in, it will add material for the threads to bite.
As for the second cabinet, you can switch the working 2118J woofer to the good cabinet to check its function. You can replace either woofer with it. The woofers act in a 1.5 setup, that is, one woofer is for low bass-midrange, and the other functions in midrange only. Likely you have 3 good working mid-woofers. As for the damaged one, it's magnet could have been damaged by a drop in or out of the cabinet, I would look for signs of cabinet damage on corners or the back. In any case, if the magnet is cracked horizontally or vertically in at least two places, it has probably failed and cannot hold the center pole piece in correct position, leading to the central pole piece (cylinder) shifting and, being inside the inner circumference of the voice coil, trapping the voice coil against the top plate's magnetic gap.
The correct solution is to replace with another known working 2118J driver, or optionally, find a 2118J or H frame with intact magnet and gap, and recone, possibly with the original cone if you could get it out intact with surround, spider and voice coil without damage. I have such a frame, but unless you know what you're doing, you're unlikely to get the parts out in usable condition, and the voice coil is suspect for damage, plus the need to properly install the removed cone assembly like a recone. The JBL 2118J isn't a particularly uncommon driver as it was used a lot and has been parted out a lot from speakers like these.
***Be very mindful of the speaker wire connectors and where they hook up relative to the woofers and tweeters. Proper polarity is maintained by the use of male/female faston connectors on wire and woofer connections. When in doubt, take a few pictures of each original connection before disconnecting. You can refer to the schematic enclosed for wire colors.
Please provide photos of both speakers and their cosmetics, the good tweeter and woofer drivers, and the bad driver showing the damaged magnets. Also, take good high res pictures of the crossovers, including any potentially suspect areas. The crossovers are pretty robust, but can be damaged by badly behaving amps. Crossovers are many times available as parted out pieces too.
They are not particularly highly regarded for home usage. Meant more for stage use or in some kind of auditorium. That doesn't mean they can't be used in the home of course. The cracked magnet on the woofer is concerning. If the woofer is frozen in-place, the cracked magnet has probably compromised the voice coil gap, which would restrict movement of the voice coil (and thus the cone). While it's possible to re-cone a speaker (which would include a new voice coil), I don't think you have many options when it comes to a cracked magnet. You're probably looking for a replacement woofer at that point.
Thanks for the insight. I appreciate it. You’re right. So it looks like I need a new woofer and probably a crossover too.
Considering I have one working cabinet, is this model something people use in mono, for monitoring and that sort of thing? Or is it kind of useless with only one?
IMO, the 4612B were very nice portable PA/sound reinforcement speakers for keyboards and general midrange - upper frequency work like guitars and horns. They work very well in a home environment if you have a good subwoofer running from 120hz and below. They are pretty decent in terms of sound volume, reasonable accuracy and fair on imaging, properly set up. They are by no means flat frequency response though so aren't really thought of as a monitor, but rather a sound producer. They can fill a good size room given enough clean power like any good speaker. Check the bottom of the speakers to see if they have any kind of stand mounting screwed into the bottoms, there were plates for either inner pole or stand mounting with a mounting plate. I combined two pair of these with a pair of double 15" JBL woofer cabinets plus 6 amps to run them for my son's wedding reception and many complimented me on how good they sounded without being overboosted and harsh like so many DJ setups for dancing and music.
