sparklow

Pete B. - I used the 5/8" paper dust caps from SpeakerWorks.com. If there is a loss of quality in the pair of NLA tweeters with the glued on center domes that I repaired it is not evident to me. I have my other pair of NLA's that have nice original tweeters and they do not sound "better" than my repaired set. Both of these sets of NLA's have their capacitors replaced with Dayton polypropylene caps of identical value to the original caps. As to the ferrofluid change, I would not hesitate to attempt it if I ever have a pair of these tweeters apart in the future.

When I did the center cone repair on two NLA tweeters in the past I think that I could have changed the ferrofluid at that time. I was too busy trying to do the actual repair to add a ferrofluid change to the process, but it could have been done successfully I believe. Typically what are the sonic symptoms of a tweeter that require fresh ferrofluid?

I own two pairs of NLAs, both from 1978, which with the help of the experts on this forum I refurbished and they sound great. I have two good extra tweeters which I will keep until (and if) I need them. My question is can the ferrofluid in the second generation NLA fried egg tweeter be changed? I don't think that I need to do this currently but I am curious as to the answer.

Your speakers are indeed the original Advent speaker, now referred to as OLAs. The naked tweeters, no cage, along with the low serial numbers show that these are early production. The foam woofer surrounds look intact and most likely they have been replaced as the originals would almost certainly have disintegrated by now. It raises the question as to whether the crossovers may have been recapped at the same time the woofer surrounds were replaced. You will need to remove a woofer from the cabinet to access the crossover. If the original electrolytic capacitors are still in place replacing them would be a very good idea. These are a great find, enjoy.

I had two second generation fried egg tweeters, both with cone punctures from pushed in wire cages. These were both pretty bad and of course the best action is to replace them. I decided to attempt a repair of the pair because why not? So I ordered two "speaker dust cap paper 3/4 inch" from SpeakerWorks.com. These, when they arrived, were heavy paper dust caps which I took to be a good sign as the Advent tweeters are a slurry formed very heavy paper. The wire cages I cut back carefully with small snips exposing most of the tweeter cone. Dry fit the new dust caps of course to get a feel for how much material you can remove from the damaged tweeter domes. I thought I'd use a razor knife to cut out the damaged domed cones of the tweeters but when I got down to it I found that it was easier to get the shape I needed (round and a bit smaller than the dust caps I bought) using a pair of cuticle scissors that I had. So the black dust caps were carefully glued to the orange tweeter cones. It is a bit tough to center and glue the small dust cap but it is doable. I used the same glue I use for woofer foam surround repair. I let this first coat of glue set for twenty four hours and then applied a second coat of glue. They looked OK but I knew I'd have to hear them to make any judgement. When I had finished the rest of the refurb of this set of NLA's, cabinets, crossover recapping, new woofer surrounds, it was time. In short they sound better than I thought they would. I have a previously refurbed pair of NLA's (with good tweeters) that I use in my main system to compare them to so I do have a frame of reference. The repaired tweeters are smooth, no breakup or buzz that I can hear is present. I am making no claim as to the actual quality of the sound compared to a fully functional undamaged Advent tweeter but as I do not have instruments to measure these results I'm going to go but unscientific ears only testing! I don't know what the life of repair might be but I have a spare pair of good tweeters to swap in if the need arises. This was fun and very inexpensive, and I think a success.