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Bose interaudio 3000 (1992) re-foam gone awry ...

Danzilla

Danzilla

Active Member
First off, I'm a hobbyist and I've re-foamed maybe 10 or so speaker pairs over the years. From the start, I noticed the cones on these Bose Interaudio 3000 8" woofers (1992) were hard to move without rubbing the coil, at least compared to other speakers I've dealt with (BA, Infinity, CerwinVega,...). I tried again and again and it was almost impossible to get the cone to move smoothly.

I usually just re-foam by hand, sometimes with a AAA battery assist for centering. This time I went all out, cut open the dust covers and shimmed them both. They both seemed as good as I could get them, but when done there was still a slight VC rubbing on one when I pushed on it. (The 2nd seemed fine, but was still easier to force it to rub than I'd like.) I figured the one slightly rubbing was just because I wasn't pushing perfectly straight. So installed the woofers and tried them out and the one speaker is just terrible, loudly rubbing on the VC. So while sitting flat there was barely any rubbing, once upright, the weight of the VC/cone was enough for it to rub quite a bit.

So now I'm really wondering if there was something I should have done differently with these speakers. Or maybe there was something wrong with them from the beginning? Or maybe these Bose woofers just have extremely tight tolerances?? Anyone experience with these speakers, or something similar have an idea what's going on?
 
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I can't really answer your question but I can offer a solution. Go back to the battery method. Sounds like you had good luck that way.
 
Some drivers are more tricky... depending on voice coil gap and spider stiffness, it can be easy to misalign it. I had to redo a Toby woofer once and a Norman woofer once. Just play s low volume test tone through it as it dries and you should be fine.
 
On the one that's rubbing, did you install it in the same position from where it was removed? I read somewhere about 'sagging' over time and it was suggested that after refoaming to rotate the driver 180 degrees from where it was when you took it out. Worth a try at this point I guess.

Like you, I've done BA, Infinity, and others without a problem, but I have read that some have tighter gaps.
 
JamVal said:
On the one that's rubbing, did you install it in the same position from where it was removed? I read somewhere about 'sagging' over time and it was suggested that after refoaming to rotate the driver 180 degrees from where it was when you took it out. Worth a try at this point I guess.

Like you, I've done BA, Infinity, and others without a problem, but I have read that some have tighter gaps.
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Ha... didn't even consider that. makes sense if gravity is dragging it the wrong way, just flip it over! Will try it out next time I'm out there fiddling around. :D
 
JamVal said:
On the one that's rubbing, did you install it in the same position from where it was removed? I read somewhere about 'sagging' over time and it was suggested that after refoaming to rotate the driver 180 degrees from where it was when you took it out....
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Hi again. Just wanted to update this... I did try rotating the speaker, 90,180, 270 degrees, all to no avail. I gave up and tried to pull the foam up whole to reuse, but that was no good either. Still, I tried again to find a sweet spot where the VC doesn't rub, and it's virtually non-existent. Just one spot and angle and if I breath wrong, it rubs. As of now I'm just about considering these woofers aren't worth wasting another speaker foam on and are beyond saving unless someone else has a suggestion. I guess I could pull up the spider and try and see what's going on in there... might be some actual damage to the VC... but I'm just not sure these speakers are worth the effort.
 
Maybe the voice coil former was deformed? If an aluminum former, check to see that it's not crunched, collapsed or worn in any way.
 
Did you test for this prior to the refoam just to be sure it was ok?

If the voice coil bobbin(s) have been drive so hard that they overheated, the bobbins will have deformed so they're rubbing no matter what you do. You should be able to see that sort of damage with the dust cap removed and then push up on the cone to get the bobbin out of the gap.

Cheers,

David
 
dshoaf said:
Did you test for this prior to the refoam just to be sure it was ok?

If the voice coil bobbin(s) have been drive so hard that they overheated, the bobbins will have deformed so they're rubbing no matter what you do. You should be able to see that sort of damage with the dust cap removed and then push up on the cone to get the bobbin out of the gap.

Cheers,

David
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When I had the dust caps off I did look at what I could see of the coil, while trying not to pull so hard as to damage it, and didn't see anything of note. At the moment, I'm leaning towards scrapping them and maybe trying to use the tweeters with an inexpensive pair of Infinity with dead Polycell tweeters.
 
I had the same problem on a jbl le15a even after shimming the voice coil. The impedance check out fine and it played but it still had a vc rub. I finally ended up pulling the cone and found out the vc had gotten hot and deformed :/ so it was now trash.
 
So, an update... I still haven't done anything with the woofers, but ended up pulling the tweeters to use in a pair of Infinities with blown Polycells. I thought they would end up with a weak highend, as the Bose tweeters were significantly lighter, but the new combination actually sounds a little too bright, but definitely usable. Now that I think about it, would lighter speakers mean they need less power to drive them?

Anyway, what I really wanted to add was a question. When re-examining the Bose to decide their fate, I took a moment to look at the crossovers and was surprised. They seem to consist solely of one capacitor, an odd blub (fuse? resistor?) thingy I haven't seen before, and another piece I not only haven't seen before, but have a hard time describing. What is resembles most to me is a braided metal tube, shrunk down to about 2mm wide. I'll include a pic below. can anyone tell me what the heck these parts are??

So there's no filter on the woofer, just the tweeter. Red and black to the tweeter, yellow and green to the woofer, and there's one other wire. A gray that connects to the same terminal as the black on the tweeter and goes to a 3rd connection on the woofer. It only appears to be connected to the basket. So not sure what's going on there.
IMG_0310.JPGIMG_0312.JPG
And finally, is wirewrap something you see in other speakers? (it looks crude because I reattached them. Was neatly wrapped at first.) I was a little surprised as I haven't seen that in a speaker before. Just one of a few things in these Bose that I hadn't seen previously.
 
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Good afternoon,

Most time the related Bose speaker like Studiocraft, Interaudio, Capella, etc., have often some cheaper parts. I think the voice coil is deformed or burned. However, the lamp is a kind of resistance that gets higher resistance when there is more power used.

The Bose has them to in their first models of the Bose 802. More to change the filter at higher power than really protection. (At the Bose 802 there is a fuse to save the speakers, though it doesn’t work proper all the time.).

It’s often possible to get the new placed surround in one peace off the frame gently with a about 3mm. wide screwdriver, piece by piece. If you can’t get the spider lose, it is in kind of need possible to cut te spider just near the frame. Unsolder the wires at the terminal and get the whole cone including voice coil out of the frame. Don’t forget to place a mark were the spider exactly was.

Maybe the voice coil has been deformed by bottoming in the back pole plate. If you can repair the voice coil you can reassemble again. Note that you glue the spider is has been cut not with a hard drying glue like 3-second glue, but a glue that is strong and a bit flexible.

Good luck! All at own risk!

Best regards, Fred
 
I had a woofer that had the magnet out of alignment, I don't know if heat or time caused the glue to loosen or soften, but it wasn't flush and parallel to the basket anymore.

When played low it worked perfect, as you turned it up it would stick in and a couple times it got stuck.
 
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