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Old 16th Feb 2010, 4:59 pm   #1
Boom
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Default Removing loudspeaker cone?

I have a couple of DAC90A loudpseakers in the scrap pile. They have the usual problem of rubbing coils which I've not been able to cure by glueing the dust cover back in place there seems to be possibly rust in the way. For want of something to do I'd like to try and remove the cones and clean them up, after all I have nothing to lose.

Any advice on how to seperate the cones edge from the frame?

Dave
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Old 16th Feb 2010, 5:06 pm   #2
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Default Re: Removing loudspeaker cone?

At this stage I would carefully cut the dustcap away from the centre of the cone to expose the magnet polepiece. Tear the corner off a piece of standard A4 and it should be possible to slip it down between the magnet and the coil. Try this a few times and with luck you should be able to clear any bits of rust out. You can then glue the dustcap back or fabricate a new one.


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Old 16th Feb 2010, 5:29 pm   #3
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Default Re: Removing loudspeaker cone?

One further point to add to Richard's post, I suggest you centralise the voice coil in the pole piece with strips of suitably heavy paper before gluing the speaker 'bellows' back to the frame. I don't know if you did this before, but I thought it worth mentioning.

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Old 16th Feb 2010, 5:56 pm   #4
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Default Re: Removing loudspeaker cone?

Thanks for replies. Ron this one has the closed dust cover so I can't do that.

Dave
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Old 16th Feb 2010, 6:00 pm   #5
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Default Re: Removing loudspeaker cone?

I've done all of the above, plus, before gluing the suspension to the pole piece, use a vacuum cleaner to give it a good suck. The cone may get sucked to the cleaner nozzle, so much the better as you can then withdraw the cone hald an inch or so, and effectively remove any rust/debris from the gap. To release bthe cone, switch off the cleaner - don't try to prise it away.
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Old 16th Feb 2010, 7:20 pm   #6
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Default Re: Removing loudspeaker cone?

Came up with what might be an idea. There is a line on the cone which (I thunk) acts to keep the cone rigid.

After unsoldering the coil leads I very carefully cut away along the line with a craft knife. (I made a couple of marks with a felt tip pen to ensure it all goes back in the same place).

I've now cleaned the rust out and Araldited the dust cap in place and it is now setting with the solder reels holding it all central.

When the Araldite is set tomorrow I can carefully glue the cones edges together with PVA glue.

It looks promising and there is probably a 50/50 chance of it being ok.

Dave
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Old 16th Feb 2010, 7:40 pm   #7
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Default Re: Removing loudspeaker cone?

... and the golden liquid is a new form of ferromagnetic lubricant for the coil I assume...
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Old 16th Feb 2010, 7:51 pm   #8
AlanBeckett
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Default Re: Removing loudspeaker cone?

That will be the Arthur Bell version from the Scottish glue factory of the same name
Seriously, the ridge in the cone is there for a purpose, but it's not really to stiffen it. It's there to generate a 'break' in the cone resonances. At low(ish) frequencies the whole cone should act as a piston. With increasing frequency that won't work any longer and the cone will start to vibrate with odd (peculiar) modes, known a break up. The ridge should persuade the inner part of the cone to act as a smaller piston and also control the break up. When you glue it back together there will still be a discontinuity there so it should be OK. Anyway, I doubt if the set will generate enough high frequencies to make much difference.
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Old 17th Feb 2010, 10:59 am   #9
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Post Re: Removing loudspeaker cone?

Quote:
Originally Posted by Pamphonica View Post
... and the golden liquid is a new form of ferromagnetic lubricant for the coil I assume...
Not this but a small amount of WD40 or switch cleaner on the coil does no harm, and some rust neutraliser could be applied to the rusty surfaces.

This is drastic surgery but if the speaker was to be scrapped otherwise it will be worth doing.

Geof
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Old 17th Feb 2010, 1:09 pm   #10
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Default Re: Removing loudspeaker cone?

I have a PYE75 thta is currently being restored. I have noticed that the cone is 'crunchy'. When gentle pressure is applied it moves, but makes crunching sounds.

Is this the same problem as above?



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Old 17th Feb 2010, 2:38 pm   #11
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Default Re: Removing loudspeaker cone?

Maybe I should not advise on speakers after my Phillips disaster But I have in the past prised off the hard card ring round the outer edge of the cone then carefully prised /cut the cone away from the metalwork .After cleaning it can all be glued back .Thorough cleaning is necessary obviously as the magnet holds onto any small metal swarfy bits inside the coil area .I have even used damp cloth to try and trap these bits .
Im keeping away from speakers for a bit!
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Old 17th Feb 2010, 3:18 pm   #12
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Default Re: Removing loudspeaker cone?

Wowee. It works fine with no distortion or rubbing at all!

Yes Sean it is exactly that problem. Before you go down this route though consider that it is the first time I have done this so don't go jumping in too fast.

Chip That was the problem that sent me down this route. I couldn't get the cardboard ring off.

Ps the Scotch was to steady my hand and it worked. The ridge on the cone is very narrow and great care was needed to cut along the middle of fit.

Dave
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Old 17th Feb 2010, 3:30 pm   #13
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Post Re: Removing loudspeaker cone?

Quote:
Originally Posted by chipp1968 View Post
Maybe I should not advise on speakers after my Phillips disaster
This is the way Philips speakers are made, see my post on the subject, they can be repaired successfully if certain points are watched.

Quote:
Originally Posted by David Tilley View Post
Wowee. It works fine with no distortion or rubbing at all!

Dave
Well done Dave, a neat job and worth all the effort, just make sure the damp doesn't get to it any more. You could run some PVA around the cone edge to strengthen it and fill in the cracks here.

Geof
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Old 29th Mar 2010, 7:25 pm   #14
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Default Re: Removing loudspeaker cone?

I'm currently following The David Tilley, methodology for reparing a DAC90a speaker, albeit minus the golden liquid

Same as you David nothing to lose, I have a set without a speaker and this old cruchy speaker knocking about. I've followed the cut out procedure, cleaned-up and Its now sitting with solder real on top letting the araldite dry. Fingers crossed i have your success
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Old 29th Mar 2010, 7:33 pm   #15
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Default Re: Removing loudspeaker cone?

I did two. The first one was fine and still works the other never worked so you're on a 50/50 chance. It is essential to get all of the muck out of the gap.

Dave
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Old 30th Mar 2010, 5:30 pm   #16
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Default Re: Removing loudspeaker cone?

David,

100% success, thanks for the excellent procedure , another DAC90a is fixed.

Chris
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Old 30th Mar 2010, 5:32 pm   #17
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Default Re: Removing loudspeaker cone?

That's good news. Between us a success rate of 66% then.

Dave
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Old 31st Mar 2010, 8:11 am   #18
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Default Re: Removing loudspeaker cone?

You guys never cease to amaze...
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