VTypeV4 Posted July 3, 2013 Share Posted July 3, 2013 (edited) Hey guys, i'm in the process of building a monster PA. I've picked these huge horns up very cheaply from a friend with a view to getting another pair built. They haven't been used for many years hence them being so cheap and whilst one works without fault, one had a bit of a rattle so I thought I'd investigate hoping it might be a loose driver or banging panel. [url="http://s778.photobucket.com/user/VTypeV4/media/BigJBL2_zps7618db0c.jpg.html"][/url] Quick test of both. One on the left works fine so will be re-finished and tidied up before it gets put into service. [url="http://s778.photobucket.com/user/VTypeV4/media/BigJBL1_zps6ae419ba.jpg.html"][/url] This is the faulty one recieving further attention. Please forgive my 'hi-tech' test rig! [url="http://s778.photobucket.com/user/VTypeV4/media/BigJBL3_zps7d638167.jpg.html"][/url] Further inspection found no loose or banging panels but I did find the big, heavy cast frame JBL secured by only three pins and a self tapping screw! The shame of it. On removing the driver I'm really sad to say it has the beginings of a coil rub. My question is [b][i]do you think I'll get away with old trick of dust cap off, little bit of forward voltage applied to the coil, some card shims and light smear of acetone on the spider to re-align it[/i][/b]? On some older Celestions and EVs I've simply removed the magnet and re-aligned them to cure the rub. I can't remove the magnet from the frame on the JBL so thats not an option. I like the JBL and it'd be great if I could get it back into service. An after-market re-cone isn't too bad at £65 but the genuine part is nearly as much as a new Celestion FTR that i've used in this application before. What d'ya think chaps and chapesses? Edited July 18, 2013 by VTypeV4 Quote Link to comment Share on other sites More sharing options...
bertbass Posted July 3, 2013 Share Posted July 3, 2013 I used to know a bloke who jammed rolled up, old socks between the spider and the frame to stop this very thing. I'd go for and after-market re-cone. Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 4, 2013 Author Share Posted July 4, 2013 Rolled up socks? i hadn't considered that.. Ha! I couldn't believe how expensive the genuine re-cone kit is.. Cheapest I could find was just shy of £200 but thankfully Bluearan do the aftermarket one.. I could believe even less the cost of a new 2241, cheapest I've found was £373, most expensive was £741!!!!! I could buy three Celestions for that! Quote Link to comment Share on other sites More sharing options...
stevie Posted July 4, 2013 Share Posted July 4, 2013 It might be worth persevering to fix the rubbing. My experience of generic JBL recones is that they don't sound anything like the originals. Quote Link to comment Share on other sites More sharing options...
Dad3353 Posted July 4, 2013 Share Posted July 4, 2013 You're not going to lose much in attempting a re-alignment, except a bit of time and patience, so I would suggest that as a first option..? Any recone of this type and generation of speaker would probably not sound the same at first, but should 'warm up' somewhat over time. When new, these JBLs didn't sound as they do now. Some folks go to the trouble of running them in with various tones for a few days or so; I'm not sure how efficient this practice really is. They look like nice units, but blimey..! What a difference in volume and weight compared to most modern stuff..! A big truck needed for hauling rigs of that nature around, and lotion for back pain..! Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 4, 2013 Author Share Posted July 4, 2013 Cheers chaps.. To be fair, I'm not massively concerned with keeping the 'JBL sound', I just want it to be reasonably loud and low without any unpleasant 'extras' so to speak.. As stated, I don't really have anything to lose as I guess it's a case of fix or make it worse but as it currently stands it's not really serviceable anyways. The Celestion I put in the one at work has now gone through it's run in / break in period. A week of normal use saw it out performing it's partner sub loaded with PD.918. The Celestion is probably the best driver out of all three mentioned here, it's certainly the most modern and it specs very well, outstripping both others. If the JBL does need a re-cone then so be it but as stated they are a lovely looking thing and if it could go back into service, that would be great. Back-breaking indeed but we have the transport and I'm still young(ish) for the time being! Ha! And just for the record, it's not a crazy bass guitar rig, it's the foundations of a big PA.. Sorry to disappoint! Quote Link to comment Share on other sites More sharing options...
bertbass Posted July 4, 2013 Share Posted July 4, 2013 Ah, but what a [color=#282828][font=helvetica, arial, sans-serif]crazy bass guitar rig it would be![/font][/color] Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 5, 2013 Author Share Posted July 5, 2013 [quote name='bertbass' timestamp='1372979853' post='2132551'] Ah, but what a [color=#282828][font=helvetica, arial, sans-serif]crazy bass guitar rig it would be![/font][/color] [/quote] A true monster! Ha! It may have to be tried just for giggles.. Quote Link to comment Share on other sites More sharing options...
bertbass Posted July 5, 2013 Share Posted July 5, 2013 (edited) Need a few more to match this though. 1.26 for the best view. Wouldn't want to stack them on my own though. [media]http://www.youtube.com/watch?v=pfzv3bf9-OY[/media] Edited July 5, 2013 by bertbass Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 5, 2013 Author Share Posted July 5, 2013 Wow! Looks like I need another 20! Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 7, 2013 Author Share Posted July 7, 2013 So I took the plunge.. We'll have to see! [URL=http://s778.photobucket.com/user/VTypeV4/media/2241ReConeMaybe_zpsef970267.jpg.html][IMG]http://i778.photobucket.com/albums/yy70/VTypeV4/2241ReConeMaybe_zpsef970267.jpg[/IMG][/URL] Failing that, it'll have to be a risk on an after market or in FTR Celestion.. Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 18, 2013 Author Share Posted July 18, 2013 Well it seems that I might have just done it and broought it back from the brink. I'll post some pix tomorrow but after a week or so making adjustments with business cards as shims and some cheap n nasty nail polish remover on the spider that I've manged to 'pull it all over'. The problem was the former rubbing the inner pole peice as can be seen in the shim pic above. JBL state an Xmax of 7.8mm for this unit so whilst running in free air, I made a visual measurement of how far I can let the cone move before it complains. It rolled past what looked to be 15mm (ie + and - 7.5mm) without drama but approaching 20mm saw the beginnings of complaint and much beyond that, it sounded like the back plate being hammered by the voice coil former. I'm not sure what the Xmech of this driver to be but I'll assume it to be to be at least 50% greater than Xmax which would roughly tie in with the start of the unpleasnt noises. To be fair I've given the driver a 'worse than typical operations' scenario and probably won't run it as low or hard when it's loaded back into it's horn. 30Hz at around -3 dB on my Crest VS in bridge mode was where the driver began to complain. I could nearly drive it into clip above 40Hz before it got upset. So fingers crossed, I'll get some more work out it before it does anything daft again! Quote Link to comment Share on other sites More sharing options...
bertbass Posted July 18, 2013 Share Posted July 18, 2013 I'm impressed, congratulations. A man after my own heart. Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 18, 2013 Author Share Posted July 18, 2013 [URL=http://s778.photobucket.com/user/VTypeV4/media/2241Fix2_zpsf0c57419.jpg.html][IMG]http://i778.photobucket.com/albums/yy70/VTypeV4/2241Fix2_zpsf0c57419.jpg[/IMG][/URL] Just before the final test this morning. I got a bit messy with the epoxy but the new dome is held fast and no-one can see the cone anyways. Sounded great with a bit of heavy kick-drum dance through it! [URL=http://s778.photobucket.com/user/VTypeV4/media/2241Fix1_zps82f1a8f1.jpg.html][IMG]http://i778.photobucket.com/albums/yy70/VTypeV4/2241Fix1_zps82f1a8f1.jpg[/IMG][/URL] And this it reloaded into it's home now I've also finished the repairs to the cab which caused the driver damge in the first place. A lick of paint and a new grille and hopefully they'll upsetting people far and wide very soon! Thanks for the kind words Bert. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.