Tweeter Questions (035TIA/027TI)

[milo63]

I've got a dead 027 with a good cone and a living 035 with a pushed-in cone. They *look* similar from the outside but I haven't dared pull apart the good tweeter. Any chance they're the interchangeable?

If I do pull apart the *035TIA I'm sure I'm going to find disintegrated foam. Is the $30 auction site the only option or have you guys figured a DIY solution?

*I've got eight 035TIAs in various speakers so a cheaper solution would be welcomed.

 

[Stan man]

Good question about the foam.
It appears to be ordinary open cell foam. That is an absurd price he's asking for though.
I just finished rebuilding a set of L7s , which are pretty good. The tweeter is the glaring weakness of the 7 though.
Maybe you could experiment on the tweeter rebuild and post your findings here for us. Or may be able to get more info on other JBL site.

 

[milo63]

Stumbled across this:
http://www.audioheritage.org/vbulletin/showthread.php?37005-035Ti-Tweeter-Repair/page2

 

[grey]

I used a 7/8 hole punch to make some foam plugs. I already had a foam sheet that looked close to the original material, but I'm not sure where it came from.

 

[Stan man]

Thanks grey,
did you notice a difference after the re-damp?

 

[grey]

Yes, there is absolutely a difference if the foam is to the point of falling apart. It will sound anywhere from too hot to just plain irritating. The new oem plugs provide more pressure on the dome than I would have suspected.
These plastic phrams have alignment tabs and are easily serviced. The coil can be destroyed if enough of the debris works it's way through assembly. Better to clean it out if nothing else.

 

[milo63]

Could you *estimate* the thickness of the foam? I'm guessing a bit over 1/2" but I'm new here...

 

[grey]

I put the measurements in this thread. I've seen the small 3mm plug above and below the larger foam plug.

 

[Stan man]

Nice,
thanks grey for the informative info which I'll eventually use.
Meanwhile, I discovered much of my tweeters harshness was do to the mid ranges being under damped with damping material, acousta stuff in my case. There was too upper much midrange glare overlapping with the tweeters lower end.

Also on a side note, (an important one), on my first investigating the treble harshness of my L7s, was to tighten the four Allen screws that bolt the diaphragm to the magnet,3/32 .
They were very loose causing a lot of "chadder".
I just re-tightened them again, which I'm surprised they needed in less than two months, at same time noticing an improvement in overall smoothness in the tweeters output.
So this should be checked regularly.

 

[grey]

Nice,
thanks grey for the informative info which I'll eventually use.
Meanwhile, I discovered much of my tweeters harshness was do to the mid ranges being under damped with damping material, acousta stuff in my case. There was too upper much midrange glare overlapping with the tweeters lower end.

Also on a side note, (an important one), on my first investigating the treble harshness of my L7s, was to tighten the four Allen screws that bolt the diaphragm to the magnet,3/32 .
They were very loose causing a lot of "chadder".
I just re-tightened them again, which I'm surprised they needed in less than two months, at same time noticing an improvement in overall smoothness in the tweeters output.
So this should be checked regularly.

Hmm, I've not checked any of the tweeters that I've done. Maybe a tiny dab of blue thread locker would be good thing and be done with it.