Fostex Tweeter Voice Coil Replacement (t500aMkII)

[Zeotrope]

For reasons that I will post later, I have a burned out tweeter voice coil. I have a spare coil.
After removing the phase plug, the voice coil is now exposed (the coil is underneath this image). Anyone know how to remove it? Is it just held in magnetically?
Thanks

 

[Zeotrope]

It was quite straightforward, actually.

Lesson learned: when experimenting with different XLR interconnects between pre and power amps, use cheap speakers first!

 

[Don Reid]

My DIY horn speakers use Fostex t900a bullet tweeters. I suppose the process to change voice coils would likely be the same as for your t500a tweets so I would really appreciate it if you would write a sentence or to to describe the straightforward easy method you used.

 

[Zeotrope]

Yes, absolutely. Fostex provides zero instructions on how to do it, and Madison Sound (which sold me the replacements) had no instructions either.
Anyway, it's fairly straightforward. The phase plug just unscrews.
After that, you lift up the voice coil. Be very careful not to bring anything magnetic near the top of the voice coil, or the strong magnet will pull the tool into the voice coil and dent it! So if you are using a tool to pry up the voice coil, make sure it's plastic.
Soldering the leads is not easy. I used a pair of magnification glasses and even so, the wire is extremely delicate. I wrapped it around the posts then soldered it to the posts. It's not as clean as at the factory, but it works.

 

[Zeotrope]

My DIY horn speakers use Fostex t900a bullet tweeters. I suppose the process to change voice coils would likely be the same as for your t500a tweets so I would really appreciate it if you would write a sentence or to to describe the straightforward easy method you used.

I just checked a DIY Forum page which showed the t900a opened, and they are completely the same as the t500 in this regard. Grab a set of spare voice coils while you can! You never know when a mishap will occur and they are not that expensive. Fostex seems to have a habit of discontinuing models as well.