MoonBassAlpha Posted December 4, 2011 Share Posted December 4, 2011 Ok, I've got a speaker that has had a bad jolt which has fractured the glue holding the magnet on. This has meant the magnet assembly has clamped itself off centre and trapped the voice coil. Everything else is in working order, just doesn't work as a speaker, very quiet and no bass I'm going to try to glue it back on-centre. I think the received wisdom is to remove the cone entirely and centre the magnet "plug" in the assembly by shimming it symmetrically in the hole and glueing (presumably with a slow setting glue to allow movement while aligning) I've a couple of ideas as to how to do it without removing the cone entirely, just the dust cover. The speaker is a small Celestion (K5C-30, 4ohm) which isn't strictly a bass speaker, but I'm hoping anything I learn will be applicable to larger speakers that have suffered the same fate. Plan 1: remove the dust cover, try to shim the Plug with the voice coil in situ while the glue sets. Plan 2: make a centring tool out of sheet metal with 3 adjusting screws at 120 degrees. This would fit over the back of the magnet, locating over a convenient hole in the centre of the magnet. If I get the geometry right I should be able to centre it visually with the dust cover removed. Could also centre it with a signal to the speaker to check it isn't rubbing. Sorry for the long post, feel free to chip in/shoot it down before I start! Hopefully this will be at least interesting to one or two folks! Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted December 5, 2011 Share Posted December 5, 2011 I've managed to fix a few Peavey Black Widows over the years but these have been mainly 15" and 18" units.. Good luck with the fix, your plans to shim it as you're going sound like to key to an effective repair as the gap between magnet and voice coil are very slim! Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted December 7, 2011 Author Share Posted December 7, 2011 ok, plan A didn't quite work, nearly though. Even though I got as much shim in as I could, the voice coil was still not moving freely after the magnet was glued up. Now to work out how to implement plan B Quote Link to comment Share on other sites More sharing options...
Musky Posted December 8, 2011 Share Posted December 8, 2011 Ooh, just seen this thread. Years ago I had a very similar problem in that I had a speaker where the magnet had become completely detached, so I took it along to Wembley Loudspeakers (they specialise in speaker reconditioning). "We can fix just about anything that's wrong with a speaker", they proudly told me, "Except replace the magnet. They're centred to within hundredths of an inch and we've no way of aligning them accurately". Like I said, this was years ago and maybe technology and the capabilities of Wembley Loudspeakers has moved on, but I wouldn't fancy the chances of a home fix. Still nothing ventured, nothing gained. Best of luck! Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted December 11, 2011 Author Share Posted December 11, 2011 I've used Wembley Loudspeakers before, to re-centre the cone on an old Audax driver for my mum's Audiomaster speakers, and they did a fine job. I feel certain i SHOULD be able to make an adjustable jig to do this, I've just got little time at work to do it, though we do have the facilities. I will bolt the speaker to a plate, mount 3 sturdy pillars at 120degrees with tapped holes and long bolts to act on the magnet, or the plate holding the magnet. Ideally one of the bolts would be a spring-loaded plunger, but I don't think our scrap bin runs to anything suitably forceful. If the mounting plate has a hole in it I should be able to check the movement of the cone as I adjust the magnet, or could apply a signal and tune for best sound. I know it sounds like a lot of trouble, but it has become a challenge now, and I'm not quite ready to concede defeat yet. Also, Celestion don't seem to offer an equivalent in 4 ohm these days, probably a special made for Trace. What can go wrong?... Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted January 30, 2012 Author Share Posted January 30, 2012 So, Plan B failed too, so I bit the bullet and bought a Celestion 5" speaker, in 8 Ohms, the Truvox TF0510. Shame the mounting centres are larger (why would they do that? -moral- never assume!) out with the file. It does sound nice now though. I did try bass through it, and it sounded terrible. There were a couple of screws missing and the box isn't exactly airtight, so it chuffs like a goodn. I filled the screw holes and it made a huge difference, now perfectly usable for bass in the house, and a bit of sealant/gasket for the rest of the box should eliminate all the rest of the unwanted noises. A proper result in the end! I'll try it out at the monthly jazz jam next sunday and see if it keeps up! By the way, the amp is a Trace Elliot Acoustic Cube, a 7" metal cube. It's very nice with acoustic guitar, and violin too apparently. Quote Link to comment Share on other sites More sharing options...
Musky Posted January 31, 2012 Share Posted January 31, 2012 Good to see that you've got it up and running, even if you couldn't fix the old speaker yourself. Good to know that Wembley Loudspeakers can realign magnets nowadays as well! Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted February 2, 2012 Author Share Posted February 2, 2012 Thanks Musky. I wish I had re checked wembley speakers website before I bought the new one. The 4ohm original would have potentially been louder, though I guess Wembley would have charged double the cost of the new one (£23 odd incl.) Quote Link to comment Share on other sites More sharing options...
laurence bird Posted January 10, 2022 Share Posted January 10, 2022 I have just seen this info from MoonBassAlpha I too have an acoustic cube with a faulty speaker 4 ohms Nobody seems able to repair it Did the Truvox work well and still going? All help appreciated Laurence Bird Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted April 16, 2022 Author Share Posted April 16, 2022 @laurence birdhi there, I've only just seen this thread (tip, use @xxxxx next time!), but to answer, yes, the Truvox did work, with all the caveats outlined above. Acoustic instruments sound really nice, and the reverb is lush. As long as your expectations are realistic for bass use ( pretty quiet) and seal the box properly, you're good. I played around with customised settings on a tc spectracomp to help keep the cone under control which also helps get a bit more out of it too. Hope this helps! MBA 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.