Hi all,
I have a couple of wharfedale 12" drivers that needs refoam/rubbering. What should be a straightforward job is complicated by the presence of an aluminum ring glued (very securely) at the top of the voice coil former preventing the application of shims to center the voice coil once the surrounds are removed.
These aluminum rings are not coming out. I tried heating to 200 degrees with a SMD rework hot air gun, freezing to -50 with freezer spray and cellulose thinners and nothing loosens the adhesive enough to remove the rings without ripping the entire voice coil out of the cone.
Does anyone have any tips on how to deal with this situation?
Thanks
I have a couple of wharfedale 12" drivers that needs refoam/rubbering. What should be a straightforward job is complicated by the presence of an aluminum ring glued (very securely) at the top of the voice coil former preventing the application of shims to center the voice coil once the surrounds are removed.
These aluminum rings are not coming out. I tried heating to 200 degrees with a SMD rework hot air gun, freezing to -50 with freezer spray and cellulose thinners and nothing loosens the adhesive enough to remove the rings without ripping the entire voice coil out of the cone.
Does anyone have any tips on how to deal with this situation?
Thanks
I would use acetone as a solvent for the adhesive bonding the aluminium alloy weight to the voice coil. I would also suggest removing the cone assembly from the frame , if the speaker magnet is the square shaped ceramic type, as releasing the bolts can cause the pole plates to shift. Otherwise remove the magnet for access. The acetone needs to be applied sparingly to the bonded area only and not on the voice coil turns to prevent it from unwinding.
I had the same issue when replacing surrounds on a Focal 7K011DBL - the dust cap is part of the highs and and if it is damaged or replace the driver will not sound the same. Here's what I did:
Heat for the surround-to-cone, savagely tear off surround-to-frame, clean frame with lacquer thinner.
With a router, make a ring that will press on the replacement surround-to-frame. Course sandpaper is glued and trimmed to the bottom in order to grab the rubber.
Make a disk that will press on the surround-to-cone. Bevel the circumference close the angle and width of the cone stick surface. Apply non-stick masking tape so adhesive won't stick.
Bear with me if you've already attached the surround-to-cone, for the other guys this is a great way to avoid fluted, wavy surrounds, especially with foam. Let it cure overnight.
After pulling off the disk, the ring can be placed with grit side against surround-to-frame and move the cone X and Y. I made lines and a flat for each axis.
Out to the weather-beaten test table. Frequency generator app on smart phone, 1-centimeter range dial indicators (cheaper than 1 inch), power amp, brick or roll of sheet lead for weight. I placed the indicator points about mid-range on the ring flats and fed the driver 150 Hz, IIRC. Pushed left until distortion, wrote down the distance, pushed right until the same amount of distortion, wrote that down, then /2. Did the same thing up and down! THEN, I used the toothpick next to the adhesive, not the brush, to tack-adhere surround-to-frame at 4 points.
I used both toothpick and brush to slip glue under the rest of the surround-to-frame. It is precisely centered.
Heat for the surround-to-cone, savagely tear off surround-to-frame, clean frame with lacquer thinner.
With a router, make a ring that will press on the replacement surround-to-frame. Course sandpaper is glued and trimmed to the bottom in order to grab the rubber.
Make a disk that will press on the surround-to-cone. Bevel the circumference close the angle and width of the cone stick surface. Apply non-stick masking tape so adhesive won't stick.
Bear with me if you've already attached the surround-to-cone, for the other guys this is a great way to avoid fluted, wavy surrounds, especially with foam. Let it cure overnight.
After pulling off the disk, the ring can be placed with grit side against surround-to-frame and move the cone X and Y. I made lines and a flat for each axis.
I used both toothpick and brush to slip glue under the rest of the surround-to-frame. It is precisely centered.
@VaNarn hmm i haven't tried acetone. Will give it a go. Removing the entire cone, spider and voice coil seems a bit extreme but it may come to that. Being able to liberate this ring also affords the interesting (or possibly dumb) possibility of cutting a slit in the ring to prevent it acting like a big shorted turn as i suspect it is right now, and adding a copper cap to the pole piece to behave as a shorted ring... where it is suppose to be to reduce distortion.
It is the squair ceramic magnet version. Those bolts have 'nope' written all over them!
@paulfx aaaah a jig! I was pondering something like that. If i could find some way to securely hold the aluminum ring in place while i refoamed that would be satisfactory i think.. Suppose i could also do some trial and error wiggling back and forth method with a signal generator, there isn't much clearance for the voice coil though.
It is the squair ceramic magnet version. Those bolts have 'nope' written all over them!
@paulfx aaaah a jig! I was pondering something like that. If i could find some way to securely hold the aluminum ring in place while i refoamed that would be satisfactory i think.. Suppose i could also do some trial and error wiggling back and forth method with a signal generator, there isn't much clearance for the voice coil though.
I tried Acetone. it does indeed soften the adhesive more than cellulose thinners did, but this ring is still not budging. i think the paper of the voice coil form if somehow impervious to solvents so the glue between the ring and form is unaffected.
Anyway the simplest solution turned out to be best. I found some super flexible bits of plastic and with he aid of some non-magnetic stainless tweezers worked them through the hole in the ring and round the corner to shim the thing in the conventional manner. It worked out fine!
Photo of new vs old attached, looking pretty good apart from the messy desk! my one has 2 little lines where i had to splice together 2 surrounds to make one the right size. I also had to trim the outer and inner edge to make them fit properly. Hopefully the superglue on the splices holds and the T7000 keeps the new rubber sufficiently bonded to the cone. It’s shaking my desk at 30Hz quite happily right now though!
Anyway the simplest solution turned out to be best. I found some super flexible bits of plastic and with he aid of some non-magnetic stainless tweezers worked them through the hole in the ring and round the corner to shim the thing in the conventional manner. It worked out fine!
Photo of new vs old attached, looking pretty good apart from the messy desk! my one has 2 little lines where i had to splice together 2 surrounds to make one the right size. I also had to trim the outer and inner edge to make them fit properly. Hopefully the superglue on the splices holds and the T7000 keeps the new rubber sufficiently bonded to the cone. It’s shaking my desk at 30Hz quite happily right now though!
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Yes they are 3014s from a 'pair' Dovedale IIIA. Annoyingly they are slightly different, with one having large bolt ears and the wharfedale 'W' in the casting of one of the frame arms that the other doesn't have. Bolts that hold the magnet assembly together face in different directions between the two units too. Nothing that would affect performance, but it does bug me nonetheless, wonder if they were the made in different factories or at different times.
Im undecided whether I should attempt to accumulate more of them for future projects, they are nice sturdy drivers and can still be had for reasonably cheap with bad surrounds, even with cost of repair. Guess if this Dovedale restoration project works out well enough i might just have no future need though.
Im undecided whether I should attempt to accumulate more of them for future projects, they are nice sturdy drivers and can still be had for reasonably cheap with bad surrounds, even with cost of repair. Guess if this Dovedale restoration project works out well enough i might just have no future need though.
The alloy baskets of my two Wharfedale RS12DD full range 12" drivers are similarly different!
I bought them new from the same shop a few months apart, and put the difference down to their different dates of manufacture - 1967 and 1969.
P.S. I offered a tidy, undamaged pair of 3014s at online auction a few years back - they sold quickly!
P.P.S. There have been other threads mentioning the replacement of 3014 surrounds. Since the Wharfedale drivers do not have surrounds of modern dimensions, I am sure there are other owners out there who would like to know more about how you went about their replacement.
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The Wharfedale 3014 specs below mention a 'high stability rear suspension' which may hold the voice coil securely in alignment.
Heavy duty paper cone with rubber roll surround
High stability rear suspension
Outer chassis diameter 315mm
Inner cone + surround diameter 305mm
Mounting hole circle diameter 320mm
Nominal impedance 6Ω
Large ceramic magnet, flux density 135,000 maxwell
System power handling 50W DIN
Driver free air resonance 25Hz
Response only 3dB down at 45Hz in a 45 litre sealed cabinet
Upper crossover frequency 600 - 1,500Hz
I've added photos of one of the 3014s I sold - just because I can!
Heavy duty paper cone with rubber roll surround
High stability rear suspension
Outer chassis diameter 315mm
Inner cone + surround diameter 305mm
Mounting hole circle diameter 320mm
Nominal impedance 6Ω
Large ceramic magnet, flux density 135,000 maxwell
System power handling 50W DIN
Driver free air resonance 25Hz
Response only 3dB down at 45Hz in a 45 litre sealed cabinet
Upper crossover frequency 600 - 1,500Hz
I've added photos of one of the 3014s I sold - just because I can!
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ooh specifications, nice! I wonder if i can measure the free air resonance of my restored one. Would that correspond to an impedance spike that i could measure electronically or do I have to measure Xmax or SPL?
the suspension is fairly stiff, not much clearance for the coil though, the shims i used were 0.3mm and i could barely get 3 little strips in, wouldn't take much to throw it off i think
the suspension is fairly stiff, not much clearance for the coil though, the shims i used were 0.3mm and i could barely get 3 little strips in, wouldn't take much to throw it off i think