Need Some Basic 101 Help Woofer 4b

[PIONEER1981]

I am close to done with restoring my 4 b speakers. One 8'' Woofer is not working correctly. I refoamed and had no issuses with other Woofers. I used a bowl that fit over Rubber & Cone prefectly while glue set up. At first speaker vibrated more than I did anything else. Faint sound. While I played music I slowly felt the cone vibrate with my finger and all of a sudden it stopped, it died. It was the bottom speaker the top played fine and bottom vibrated. Most times I try to google for help it defaults to foam repair. .Only questions I can find are the following..Centering of Cone ? Dust Cap ? Problems? Is this only a tech can repair ? What ever my finger did it killed speaker and my finger was in middle of cone light, light pressure. It had to be extremly sensitive to go dead due to my finger. I get a reading between 3.0 & 3.1 . I was hoping I can fix before spending $75.. I know enough to be dangerious. More of novice than anything else...Any help would be greatly appreciated. Thanks Rick

 

[Vince1966]

If i am not mistaken the woofer is 4.0 ohm, 3.0 would be considered good. the fact that your getting a reading means the coil is good. does the cone move freely? do you feel any rubbing when you press in the cone? from what you describing i would think the cone is off center. if the cone does not move freely up and down then its off center and causing the voice coil to bind in its channel, that can short out the coil. if it is off center the only way to proceed is to remove the surround from the frame and try re centering the cone. you may have to remove the dust cap and use shims for the voice coil. you can find examples on youtube on shimming a voice coil. hope this helps. good luck

 

[PIONEER1981]

If i am not mistaken the woofer is 4.0 ohm, 3.0 would be considered good. the fact that your getting a reading means the coil is good. does the cone move freely? do you feel any rubbing when you press in the cone? from what you describing i would think the cone is off center. if the cone does not move freely up and down then its off center and causing the voice coil to bind in its channel, that can short out the coil. if it is off center the only way to proceed is to remove the surround from the frame and try re centering the cone. you may have to remove the dust cap and use shims for the voice coil. you can find examples on youtube on shimming a voice coil. hope this helps. good luck

Vince, thank you. I will be trying these tomorrow. When I called local speaker repair first thing he asked if it was centered. Since when refoaming I did not think I moved or did anything but, must of done something. Cone it seemed at first to move freely but, when I did start feeling cone it completly stopped doing anything, it died. With you information I think your correct. Like I said just touching cone made it completly die.

A few more questions..Once I remove surround and center Is there a special way know when all is correct ? Can I hear sound or know when and I have everything in correct location in place ? Or can I use my tester ? Is the centering by eye or sound or measurment ? I saw videos on shims. So is my only option at this point to have surgery and shim center. Once this is done can I do a sound check ? Or test to confirm I have it centered.. Thank you very much Rick

 

[Vince1966]

Hi Rick,
If you have a good ohms reading from the speaker then this is what I would do.

first option is to remove the surround from the frame, if you can do that and keep it in one piece it is possible to recenter the cone and voice coil. I use a AA battery with with wires tapped to the + and -. When you reapply the glue to the frame attach the + from the battery to the - lead of the speaker and - battery to positive lead of speaker. This will cause the voice coil to center in its channel and draw down the cone, only do this long enough to press the surround back onto the frame. Disconnect battery when done.

second option.
I have used some 3x5 card stock to make shims, I cut them about 1/4 inch wide 3” long, make 8 of them. Remove the dust cap first, I have a fine blade exactly knife for that, carefully cut the cap as close to the glue line as possible, be aware the tensile wires under the cap where they go through the cone, cut very shallow near those. With the cap off, you will find a plastic cap over the center of the cone. Carefully remove it, it will be glued down, don’t twist the cone or move it side to side very much, the voice coil former is very fragile and will wrinkle causing the coil to jam.

start removing the surround from the frame, depending on the glue you used the surround may tear so have a replacement ready.

with the cone free from the frame start shimming between the voice coil and inner cylinder. Do it evenly, 12-6-3-9 o’clock and then in between those. The coil will be centered and you can reattach the surround to the frame.

hope this helps. Take your time and go slow, this is how I fixed mine, I also rebuilt 2 woofers with new voice coils, spiders. Worked like a champ.

 

[PIONEER1981]

Thank you so much for detailed information. In 1981 I spent my entire tax return at Pioneer store buying Six componets that I still have today. Most if not all issues over the years were fixed with Deoxit. That was my total experience " Fixing " my stereo equipment. Have B & O 4002 I bought at yard sale $20 in 1988 needed a little work a few weeks back, it is still apart at this point needs to go to local shop to fix as I am sure I made worse. I am not loyal to my speakers. I saw these Infinitys at $200 and bought for $150 thinking it is a speaker only a few parts I can do this. I will advise you on how this comes out but without your help I was stuck..Thanks again Rick