View Full Version : Centering Voice Coil
I seem to remember that there was a thread on here where someone documented with pictures the re-coning of a drive unit, and centering the voice coil (there were lots of shims used - I think)
Anyone able to give a title thread? I will do a search but just in case I draw a blank.
cloth-ears
27-09-2013, 18:37
This may help
http://www.youtube.com/watch?v=lxGswEB3O_Q
Was it the Gale refurbishment thread...?
I've done a couple of re-foam on cones and my friend Dave has done loads - it's not that difficult in all honesty - neither of us used shims - if you are careful the rear suspension spider centres everything for you.
Oh sorry, that's re-foam, not re-cone :(.
This may help
http://www.youtube.com/watch?v=lxGswEB3O_Q
Thanks Bob. There was also a link to this on that page which is spot on.
http://www.youtube.com/watch?v=dBETBjROvIc
The Grand Wazoo
27-09-2013, 19:20
Rob, take a look at the Feedback thread, after your post. Shims are too much hassle.
Also this (http://theartofsound.net/forum/showthread.php?17353) may help - not just what I wrote there but there are links and references to other similar threads.
James' battery trick works really well, I've used it on 4 different drivers now.
Rob, take a look at the Feedback thread, after your post. Shims are too much hassle.
Also this (http://theartofsound.net/forum/showthread.php?17353) may help - not just what I wrote there but there are links and references to other similar threads.
James' battery trick works really well, I've used it on 4 different drivers now.
Nice. I didn't really want to cut the dust cap as the cone just needs re-centering (voice coil rubbing), so I can release the cone surround from the chassis with a scalpel (hopefully) do the battery trick and re-glue the surround. I assume that as the lead out wires will not be exposed, that I put the battery on the spade terminals (same thing I suppose?)
The Grand Wazoo
27-09-2013, 19:38
Yes, I just attached a short length of wire to each spade tag on the drivers and then held one wire onto the negative end of the battery. Very quickly touching the other wire onto the positive is enough to pulse the driver.
It's just occurred to me that if you don't remove the dust cap, will the cone seat in the right place? In the video I linked to the bloke drew a line around the inside of the voice coil (3.06m in to the video) for the natural seating position.
Try connecting the coil to a 1.5v battery momentarily. That'll automatically centre the voice coil for you. An old trick but it works. No shims required.
It's just occurred to me that if you don't remove the dust cap, will the cone seat in the right place? In the video I linked to the bloke drew a line around the inside of the voice coil (3.06m in to the video) for the natural seating position.
Any comments anyone?
The Grand Wazoo
28-09-2013, 10:45
I wouldn't be able to comment Rob - perhaps someone who's got a bit more experience will be along in a minute?
I've used both methods: cutting off the dome and using shims in the VC gap; and using a battery to pulse the VC centrally and glue the outside of the roll surround down. The latter is by far the easiest.
Been out all day and just seen your replies. Thanks Martin.
Which product would be the best to use to re-seal the rubber gasket (not foam gasket)
Was looking at this?
http://www.ebay.co.uk/itm/1-x-TECHNICAL-ADHESIVE-SUPER-GLUE-ELASTIC-JOINTS-O-RINGS-GASKETS-BELTS-SPEAKER-/300654693193?pt=UK_Crafts_Cardmaking_Scrapbooking_ Glue_Tape_EH&hash=item46006a8b49
Tricky, Rob, as I managed to re-use the gaskets on my drivers. That stuff looks like it might glue the drivers down permanently? Bad idea!
I would be tempted to buy thin rubber sheet and cut my own.
Martin, perhaps I should explain. What I am proposing to do is cut the rubber surround away from the basket, leaving the whole cone and surround attached to the voice coil. Then re-center it and glue it back to the chassis.
I assume I need a rubbery type glue so that when the "battery" does it's stuff that there is enough movement in the gasket to allow it to re-center and I can then press the surround down and leave it to dry.
I have seen some people use a proprietary white gasket glue (that some have suggested might simply be PVA?
This is the white stuff
http://www.ebay.co.uk/itm/Speaker-Adhesive-Cone-Repair-Surround-Adhesive-Glue-/310421795316?pt=LH_DefaultDomain_0&hash=item484694b1f4
Oh I see, you mean the surround not the gasket! In that case, Aleene's Tacky glue is the stuff to use (or a near equivalent tacky glue). You can get it on eBay. Apply to both the cone and surround, allow to go sticky for 10 mins, then apply. It allows for repositioning and will then form an air-tight bond.
The Grand Wazoo
29-09-2013, 09:04
Rob,
The white stuff is more like Copydex than PVA as it seems to have more of a rubber type component in it. When you buy foam surrounds from Audiofriends in Holland, that's what you get. However, when you buy rubber surrounds from them, they send something that is, to my eyes and to those of a cycle-geek I know, indistinguishable from puncture repair glue.
Thanks for your replies. I seem to have been confused by terminology. I thought that the gasket was the rubber/foam ring that attaches to the cone and basket/chassis. I now realise that this is the surround and the additional pieces that are then stuck over the top of that are the gasket.
Oh I see, you mean the surround not the gasket! In that case, Aleene's Tacky glue is the stuff to use (or a near equivalent tacky glue). You can get it on eBay. Apply to both the cone and surround, allow to go sticky for 10 mins, then apply. It allows for repositioning and will then form an air-tight bond.
The magic done by the battery is enough to position the surround whilst the glue is tacky?
The Grand Wazoo
29-09-2013, 09:30
You've got it Rob.
Phew. Have ordered Aleene's Original Tacky Glue. Now I get the scalpel out!
Thanks for all the help.
The Grand Wazoo
29-09-2013, 09:40
Good luck!
There's also a gasket between the driver and cabinet, that's the one I thought you were talking about.
walpurgis
29-09-2013, 10:16
I'm actually away on holiday and missed this.
I've refitted or recentralised a number of cones and although I know the battery trick, I've not had to use it or use shims.
My method is to install the cone/coil assembly loosely and then hold the cone surround in what looks to be a central position on the chassis rim with blutac or clothes pegs, then centralise the rear spider by feel, i.e. moving it from side to side until I've established a position where the cone moves back and forth freely. The rear spider then has to be held in place temporarlily with, again if they reach, clothes pegs or blutac or a very small dab of adhesive. Then I recheck the cone surround for positioning and glue it in place. Assuming the cone still moves freely, without binding anywhere, I then glue the rear spider. Job done. I've not had a failure yet.
Hi Geoff, yes I had thought of trying a push and feel method. However, you have now added more terminology! the rear spider.
Googling tells me that this is : the corrugated disk attached to the cone and voice coil at the base of the cone. As I am not renewing the cone, I assume that this does not affect me. I am leaving that part as it is. It is only the outer surround that I propose to detach and re-attach.
Canetoad
29-09-2013, 14:08
How long should the battery be connected for? :scratch:
How long should the battery be connected for? :scratch:
It should just be pulsed, which has a centering action on the voicecoil. Don't leave it connected for any length of time.
Canetoad
29-09-2013, 19:29
Thanks Martin. :)
I’ve always removed the dust cap and used the correct sized shim when I’ve repaired drive units.
The problem with not removing the dust cap and using a battery to locate the cone is at the extremes of the voice coil travel along the pole piece, particularly with long throw units, it is quite difficult to get the coil (a hollow cylinder) to travel its full range outside the pole piece while maintaining an even gap, especially if the spider has sagged or has been replaced. The coils motion should ideally stay perfectly parallel to the pole piece!
With shims I find I can feel the tight spots when the cone is physically moved to its extremes of travel be gently trying to slide the shim back and forth.
It is also worth getting the correct adhesive for fixing the roll to the basket and if you are replacing or repairing the spider the correct adhesive for that. They should be different adhesives; a contact adhesive for the spider (often a wood pulp to metal joint and a rubber to metal adhesive for the roll to basket edge join.
Morning stranger! Hope life is treating you well :)
Any sunburn on yer bum, yet? :eyebrows:
Marco.
Hello Marco :)
Well, for the first few winter weeks last year I did do a bit of that Sun worshipping. Getting sunburn in mid December brought quickly made me adopt the local practice of keeping covered up when working outside and preferably, when it does get hot, keeping out of the sun alltogether. ;)
Most years here apparently at least one of our guests gets sunstroke; usually from doing something really stupid like going out for a run in the middle of the day, or lying on the beach for too long.
Failed at the first hurdle!
The gasket and surround appear to be one piece. You may be able to see in the pics that the concertina surround starts where the gasket (removed portion) is, There is no part of the surround under the gasket. I had expected to see part of the surround under the gasket. Bugger.
Unfortunately you cannot remove the gasket without it leaving part of the cardboard construction stuck to the basket.
it looks like I have three options :-
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2233_zpsbfcb8099.jpg
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2232_zps4a33d3a3.jpg
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2230_zps5fd8b19b.jpg
1. Cut the surround as close to the basket as is possible and when re-locating, try to stretch the surround over the basket. The cone moves very little (sealed box - not ported)
2. Turn the speaker and hope that gravity cures the rubbing (it hasn't so far over the last week)
3. Try to find a surround of the same diameter and glue this to the existing surround and basket.
Any comments/help would be appreciated.
Or 4. Get 2 new surrounds and renew them completely.
I think you might need to bite the bullet and remove/replace the entire roll surround, since the voicecoil has clearly become misaligned. In any case, you now risk the air seal so it's not going to run very well.
First thing is to establish whether a roll surround kit exists for that driver. What is it?
The seal is still intact. If you push the cone with the securing screws removed, air is forced through the holes.
The speaker is a Klipsch T10. There does not appear to be anyone on ebay selling replacement surrounds for any Klipsch speakers. From what I have seen trawling through, the surround may be fabric with some kind of doping treatment to it?
Mmmm, tricky. I don't know how you can re-centre that cone without removing the outer surround/suspension.
It seems this is the woofer.
T30 Woofers K-6-K 8" - 8 Ohms
DCR = 6.8 Ohms U 1 $75. ea Good
http://i73.photobucket.com/albums/i239/saxonsex/Klipsch_Tangent_T30_Parts_Web_small_zps64827d2d.jp g
The Grand Wazoo
02-10-2013, 22:32
Rob,
Try emailing Fred at Audiofriends (http://www.audiofriends.nl/speakerfoam/en/img6.gif) in the Netherlands. With his advice and you doing a few measurements, I reckon he'll be able to find something that will do the job.
Rob,
Try emailing Fred at Audiofriends (http://www.audiofriends.nl/speakerfoam/en/img6.gif) in the Netherlands. With his advice and you doing a few measurements, I reckon he'll be able to find something that will do the job.
Thanks, will try that. I have emailed a place in the US, so will see what happens.
It looks like the cost of repair, other than DIY is massively more than the speakers cost.
The cone only resonates at certain frequencies and is not intrusive 90% of the time. Am I making the problem worse by continuing to use the faulty one?
What I am getting at is, what if I just did nothing?
I'm not sure that constant rubbing is going to do it much good. Is it not possible to get a repair surround that is close enough in dimensions to your driver? In view of the fact that it's unlistenable, I would take the plunge and use a nearest-size repair kit and do the work. You haven't much to lose.
Ninanina
03-10-2013, 20:07
Rob
I believe the T10 woofer is a K-7-K 8" (20.32cm) Fiber-composite cone, well that's what the Klipsch site says. I think they are similar to the woofer in your KG3's
I'm not sure that constant rubbing is going to do it much good. Is it not possible to get a repair surround that is close enough in dimensions to your driver? In view of the fact that it's unlistenable, I would take the plunge and use a nearest-size repair kit and do the work. You haven't much to lose.
The trouble is that it is quite listenable, strange but true.
This is what one outfit in the US say :
Thanks for the photos. In your model, we would need the speaker removed and sent into us for reconing service. There is not an easy way to peel the surround and gasket off the frame to re-center the coil. Usually, when these types of units develop coil rubs, there is another underlying issue inside the coil former which we address by replacing the entire moving assembly.
What I have thought of doing is cutting the surround as close to the basket as possible, centering the coil and cutting some duct tape strips to re-attach the surround. I used to have some Goodmans Goodwood speakers. The bass unit's surround seemed to be nothing more than electricians tape.
Rob
I believe the T10 woofer is a K-7-K 8" (20.32cm) Fiber-composite cone, well that's what the Klipsch site says. I think they are similar to the woofer in your KG3's
Bev the driver in the KG3 is very different. The surround in the Tangent 10's is doped fabric. The KG3 is rubber.
Today I decided was D-Day.
I felt that the best way to attack it was to cut the dust cover and after releasing the cone, use shims to re-center the voice coil. It was likely that there was going to be some difficulty in re-attaching the surround and the resulting movement would have made the "battery" trick useless.
This is what I found after I removed the dust cap! Another sort of cap covered in gunk.
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2235_zps91069cb7.jpg
I removed this to expose the voice coil and then cut the surround as close as I could to the gasket to release it. I then removed the rest of the gasket and used shims to (hopefully) re-center.
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2238_zps87693499.jpg
I then tried to re-attach the surround using duct tape. Although at first it appeared that it was stuck to the surround and basket, by the time I got half way round it had started to lift where I had begun. So I gently pulled it all off.
I had bought some Allene's Tacky Glue and thought I would have to give this a go. After applying this to the underside of the very small portion of surround that I hoped would be enough to attach to the basket, I found that I could very gently stretch what was there and press it down on to the basket. After repeatedly turning the speaker and methodically pressing it down all round it seemed to be holding. I thought that before the glue set I would re-attach the gasket with lots of glue so that this would in effect make a double bond and make sure that the few MM of surround that was holding would in fact stay held down. I could also re-jig the surround so that it was slightly more over the edge of the surround.
This is the finished article. It is currently upside down on the worktop with the very heavy speaker cabinet on top. The added weight should make a good bond.
http://i73.photobucket.com/albums/i239/saxonsex/DSCF2241_zpsf9088e8c.jpg
Of course until I release the shims I will not know if I have cured the problem. However the gap between the shims looks nice and uniform so I live in hope. I couldn't really think of any other way to do it so it could be a success or a lot of work for nothing. I will report back later.
Nice job, Rob. Let's hope for a good outcome.
Up-date. Not a complete success as there is still a small amount of rubbing. It seems the guys in the US know about these drive units. I am off the to the Audiojumble on Sunday, so will see if there are any 8" drive units knocking about. These seem to go quite a way up the HF spectrum, maybe they are run open. Will have to check the crossover.
Most likely, the voicecoil is heat damaged and the coils have loosened in the gap.
The thing is, Klipsch are usually horn loaded so the woofer will be a very light paper cone with limited travel - thus the corrugated surround. You can't swap in anything other than a similar type with frequency response that goes up into the midrange. Best buy a pair, too. Even then, it's pot luck whether they will integrate well with the other drivers.
Are original drivers not available?
Yes, they are 94dB so the xmax is not very much at all. Having built my own back loaded horns with 97dB Fostex I could see that these were of the same ilk.
However. As there is not anything to lose, I will see if there is anything that might be suitable......or even not:)
Are the drive units available? Not sure...but there are a pair of these on ebay.com for $70, but the shipping........probably not going to be commercially viable. My pair were
£25.
Ninanina
04-10-2013, 20:23
Rob
You sound like you've become a bit of a Klipsch nutter like myself..... :D:D
Rob
You sound like you've become a bit of a Klipsch nutter like myself..... :D:D
Nah i'm just a nutter.....full stop!
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