Goodmans 212C speaker saga

[retailer]

Back when I did a stint in the building industry I preped a house for sale and under the owners orders I removed 2 large speaker boxes left behind by the previous owner - they were bolted high up on the wall and sported a pair of Goodmans 212C's, I gave them to my son he - had a pair of new enclosures made to Goodmans specs - they were used daily for around 8 yrs until the tweeters failed on each in short succession, I was able to remove one and found the aluminium voice coil wire had corroded close to the terminal where it had been soldered, I'm guessing it was the flux that started the corrosion - I used a "liquid wire" compound to complete the circuit which worked very well until the adhesive holding one of the bass driver voice coils let go and the voice coil wire simply fell off. I removed the cone and rewound the voice coil, it was dual layer, so I did the first layer waited for the epoxy set and then wound the second layer, this worked fine but a short while later the tweeter operation became intermittent, this time the corrosion had worked it's way right back to the actual diaphragm. Not to be deterred I found and ordered some tweeter diaphragms that were the right size and impedance on Aliexpress, the Goodmans tweeter has the diaphragm glued to a plastic diffuser so I had to turn up a centering jig to ensure the new diaphragm was centered on the diffuser. Once returned to my son he complained of harshness from the tweeter so it looked as if we had come to the end of the line.
He then suggested a replacement may work and a search found a pair of Dayton Audio ribbon tweeters the right size to fit into the voice coil space. Once on the bench I found I couldn't budge the nut holding the old tweeter in place, after a bit of a struggle with a home made spanner I thought I had it but it turned out that the nut at the back of the main magnet had come loose, the magnet was covered by a large nice looking metal look embossed Goodmans logo, it was no easy feat but I managed to remove the logo with out damaging it, after cutting away a small section thick cardboard I could access the nut and finally could remove the old tweeter. Looking down into the voice coil gap I could see bits of metal - in my struggle tiny bits of metal had come away from my home made spanner and dropped down into the gap between the magnet and voice coil - compressed air wouldn't budge them they just got deeper each time I depressed the cone. I cut a tool from some old 35mm negatives and the idea was that I may be able to hook the bits of metal and drag them up close enough to the top so I could pick them off with fine tweezers - needless to say this didn't work and to top it off the end of the 35mm negative hooked itself onto the bottom of the voice and couldn't be shaken loose so it was out with the solvent to remove the cone. After taking some measurements I drew a holder for the Dayton tweeter that would screw onto the existing Goodmans 5/16 threaded rod the held the original tweeter, I just needed to shorten the rod a bit. A few hours with the 3D printer and I had the holder and an hour or so later I had the brass inserts and nut for the holder, next job tomorrow is to fit the new tweeter, I'm just wondering what else can go wrong.
I had a good look at the tweeter I repaired and I hadn't noticed before but it looks as if there is minimal clearance between the new diaphragm and the plastic diffuser, maybe they had been touching causing the harshness - possibly if I had used the lathe to skin some material from the inside of the diffuser it may have been ok.

[Radio Wrangler]

Dedication above and beyond the call of duty, I reckon.

With special mention for the use of a home-made spanner!

David

[retailer]

Yes - if they had been for me I would have passed them onto someone else by now but I feel bit responsible, my son Matt spent some $ on the cabinets which are quite large and made from veneer faced plywood, while he is not a total perfectionist he went to some trouble to blacken visible screw heads etc so the cabinets would have the right look. Apart from that these are probably not the first 212C's to suffer tweeter failure, the Trebax tweeters are available secondhand if you have enough money and possibly other owners that are not willing to fork out $$$ for original tweeters may read this as a possible fix. Matt is going to compare the one I am working on to the one that is still operational - I'll report back on the results.

[retailer]

I thought I'd post an update on the Goodmans 212C saga, the new tweeter is a Dayton Audio mini ribbon tweeter.

No. 1 son picked up the speaker and later that evening messaged me saying he believed it sounded nice and better than the original tweeter - so far only the one has been done so he can do a comparison, all I have to do now is the other speaker.