Members Dogoth Posted April 13, 2015 Members Share Posted April 13, 2015 Lost a tweeter in one of our 712M's (not on my watch but I still get to repair it :-). I checked it with a meter and sure enough the VC is open. The JBL part number is D8R2431. It says comes with ferrofluid. I've never replaced a ferrofluid Dia. What is the trick (how do you clean out the gap and how do you get the new fluid back into that gap)? Hopefully my cheap management will order it soon. I DID point out that the factory part (don't want a Chinese knock off) costs more than one of my days pay :-). Thanks for any tips Link to comment Share on other sites More sharing options...
Members agedhorse Posted April 13, 2015 Members Share Posted April 13, 2015 Follow the instructions that come with the factory diaphragm. Some kits provide top off fluid (to compensate for what sticks to the bobbin upon removal, and some kits include a blotter shim, solvent and expect you to thoroughly clean all old fluid from the gap and put in the provided amount of new fluid. So, the answer is "it depends". That's a VERY expensive driver and diaphragm, also very hard to blow... unless it was set to biamp mode and somebody fed full range signal into 2+/2- and then they are quite easy to blow. Link to comment Share on other sites More sharing options...
Members dboomer Posted April 13, 2015 Members Share Posted April 13, 2015 As Andy says ... you use a blotter to remove the old ferrofluid. It's just a piece of a paper/felt like material that soaks it up out of the gap. Pretty easy to do if you go slow. Likewise the ferrofluid will probably come in a little tube that you snip off the top and squeeze in the gap. Ferrofluid is typically poisonous so use appropriate caution. Now if the old diaphragm shredded in the gap you may have problems. But if it's a clean burn it shouldn't be very hard to replace. Link to comment Share on other sites More sharing options...
Members Audiopile Posted April 13, 2015 Members Share Posted April 13, 2015 also very hard to blow... Yea, I can't imagine if it came undone via just too much SPL... and if so... holy guacamoly... probably best you weren't there. Link to comment Share on other sites More sharing options...
Members Dogoth Posted April 13, 2015 Author Members Share Posted April 13, 2015 The conditions were, a band originally four walled the room, then management saw the potential and decided to do some promo and make it a dinner show & split the take. When someone rents our room, the labor is billed separately and nobody wanted to hire the extra monitor guy. This venue isn't setup to do more than a couple of mixes from FOH (management is oblivious to this fact and when told of it they said "just give them side fills"). For a 5 piece band? The FOH guy asked me to give him a quick rundown on the console (He's not too digital savvy) and preset for him (I inserted the box EQ's from my library, labeled & wired everything (5 mixes)). It was to be a set static monitor gig. My guess is something took off and there was nobody at the monitor desk to stop it until it lost the driver (it must have been painful!). As I pointed out, the rebuild cost more than my pay. Possibly they will learn something from this (I won't hold my breath). Corporate weenies ........what can you say? Personally I would have given them side fills and then later explain why the show didn't go well and the band was unhappy. Since this just happened last weekend and we had a major act in this weekend, there was no time for troubleshooting & repair (so we already rented 1ea 712M from a local provider (along with extra wedges, wireless horn mics etc,,,,,)). Keep in mind that I work a county venue so have little time for anything else in the week (there is a substitute mixer/babysitter for when I'm frying bigger fish :-). Agreed It takes a lot to take out one of those drivers. You can get those speakers crazy loud with the minimal curve I've built for them. Had I been there (even at their cost), this wouldn't have happened. I'm real happy with the FOH guy. He blows up part of my rig and then leaves for vacation (we're good friends but I get to razz him about this when he returns :-). Thanks for the tips. It sounds straight forward. I'll just be careful and all should go well. Cheers Link to comment Share on other sites More sharing options...
Members wesg Posted April 13, 2015 Members Share Posted April 13, 2015 Make sure management knows that you are not competent to perform this repair, but are willing to try if they don't mind taking the risk. Link to comment Share on other sites More sharing options...
Members Dogoth Posted April 15, 2015 Author Members Share Posted April 15, 2015 Make sure management knows that you are not competent to perform this repair' date=' but are willing to try if they don't mind taking the risk.[/quote'] Ah but with the knowledge I've gleaned here, I do feel competent to perform this repair. I'm not worried about botching the job - I'll approach it with patience (I don't think it's rocket science). There is a very small chance the pole has shifted in which case the whole driver is no good. I haven't disassembled it to check the perfection of the gap. Or are you saying I should make it clear what the cost would be to have the factory or a third party do the job? I suppose that brings home the true cost of the damage. Maybe I'll get a quote just for comparison. Thanks! :-) I usually see minor repairs as a part of my job and a regular cost of doing business. I can't imagine a sound guy who wouldn't replace diaphragms, re-solder bad cables, rebuild mic stand clutches, clean out scratchy pots, blow the dust out of amps etc....... It's like maintenance and part of what I'm hired to do (as a full time employee). I CAN imagine a clueless corporation not buying the part. Now if I was doing an occasional for someone and had to rebuild THEIR tweeter (heaven forbid - if there was time :-), I'd expect extra pay for the service. It would also put me on guard for other issues with that system and make me re-assess if I wanted to work for them in the future :-). Link to comment Share on other sites More sharing options...
Members wesg Posted April 15, 2015 Members Share Posted April 15, 2015 Note that I wasn't using incompetent as an insult -- just a description that describes your level of training and typical job responsibilities. I'm not sure loudspeaker repairs are part of a typical sound guy's employment responsibilities (although having not worked in the field, I can't comment directly) -- beyond parts-swapping and cord fixing (etc) anyhow. But then I guess, the real question is, where does parts swapping stop? Are you good with replacing spiders, coils, replacing surrounds, and reconing? Especially at your pay rate (which is probably less than a repair technician earns). By all means, go ahead and give it shot -- I would in your shoes -- but I would also find out what the cost (and timeframe) for a repair tech to do it was, as well as the worst-case scenario if you botch the job. "Boss - we can get a specialist to fix it for $X, or I can try for $Y. Worst case scenario, we're out $(X+Y+Z). But I'm pretty sure I can do it right." It's important, IMO, to paint an accurate risk assessment for your manager, and also that you make him/her aware of the value of the skills you bring to the table. Wes Link to comment Share on other sites More sharing options...
Members Audiopile Posted April 15, 2015 Members Share Posted April 15, 2015 I'm not worried about botching the job - I'll approach it with patience (I don't think it's rocket science). Maybe you've been there, done that, and got the tee-shirt a long time ago... but in-case you haven't, one tid-bit of advice I'll pass on is this (which may or may-not apply as I've never been into a 2431): When installing the screws into the diaphragm's mounting ring, finger thread the screws in till they're well started, then tighten with a screwdriver while keeping both hands on the screwdriver... one hand on the screwdriver's handle, and the other hand on the screwdriver tip... being super attentive to the driver's magnet's desire to suck the tip of the screwdriver off the screw and towards the center of the magnet... through the diaphragm. Link to comment Share on other sites More sharing options...
Members agedhorse Posted April 16, 2015 Members Share Posted April 16, 2015 Yeah, I hate it when that happens Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted April 16, 2015 Members Share Posted April 16, 2015 OH yea...the old suck of the phillips head into the diaphragm. I remember seeing that and that tiny dent turning into a a shattered diaphragm within minutes of high output. Why not put the whole thing in a box and send it to Andy? Link to comment Share on other sites More sharing options...
Members agedhorse Posted April 16, 2015 Members Share Posted April 16, 2015 Or come down with the driver and for lunch? Link to comment Share on other sites More sharing options...
Members Dogoth Posted April 16, 2015 Author Members Share Posted April 16, 2015 I've rebuilt many compression drivers in the past. Just never run into one that was ferrofluid cooled. I have no problem with tackling this project (I'd give it a 99% chance of success). The drive over for lunch may happen anyway soon - I'm in need of a road trip :-). Now when it comes to re coning a woofer with all of the various adhesives & materials (cone, spider, dust cap, bobbin etc....) I'll pass that one on to someone who's done it before. It's the difference between a tune up and a motor rebuild :-). Link to comment Share on other sites More sharing options...
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