Yamaha NS woofer shifted magnet video
- Thread starter saltwater
- Start date
Mr. Yamaha
Not so much Yamaha lately...
This is awesome 
Thx!
Thx!
SuperLead100
"These go to 11"
That was cool! If only it were in English it would help fill in the blanks. I wish he had shown the actual alignment of the magnet using the jig...neat video nonetheless.
saltwater
Super Member
darflinger
New Member
Thanks!!
saharajim
Active Member
I know this thread is old but I am looking for some opinions. After watching this video and reading other posts I decided to tackle my shifted magnet on a newly acquired pair of NS-690's. I've never worked on drivers before but figured what the hell it's broken as it is. After a bit of nervously getting it apart and building a jig and then putting it back together I was successful in getting it working and I'm impressed. They've replaced my stacked A25's and even my wife commented on the sound. My question is that since this process is so involved, for me, would you recommend I expoxy the sister speaker magnets in place as it is or wait for it to shift before messing with it? Thanks
saharajim
Active Member
A couple of tips I can offer to anyone tackling this job.
1) Make the diameter of the hole in the jig as close as possible to the diameter of the magnet. Mine was a bit sloppy and made it a bit awkward for pushing the pole piece around to center it.
2) I found that the diameter of the hole in the pole piece was adequate to tap as is with a 1/4-20 tap. Very slowly with removing it often to get filings out. Once it done it gave me a means to fasten the pole to a large piece of plywood and that gave me control when mating it to the magnet and basket.
1) Make the diameter of the hole in the jig as close as possible to the diameter of the magnet. Mine was a bit sloppy and made it a bit awkward for pushing the pole piece around to center it.
2) I found that the diameter of the hole in the pole piece was adequate to tap as is with a 1/4-20 tap. Very slowly with removing it often to get filings out. Once it done it gave me a means to fasten the pole to a large piece of plywood and that gave me control when mating it to the magnet and basket.
bobdod
Super Member
yes, it’s easy to do and cheap insurance. I’ve done it with a bunch of Polk drivers that are also known to shift their magnets. Jb weld work very well. Use masking tape to make it look neat.
saharajim
Active Member
Perfect JB weld is exactly what I used to fix the shifted one and I have left over so I'll mix it up. Thanks
saharajim
Active Member
If I can offer any assistance just ask. You've helped me in the past and I'd like to return the favor.I have a shifted 690 woofer just like the one in the video..Maybe I'll give it a go..
saharajim
Active Member
I wrote some notes in case I need to do this again. Hope it helps someone:Don't think I'll be standing on the woofer in bare feet to remove the magnet though.
- Measure the resistance of the voice coil. Mine was about 4.6 ohms which I believe is typical from what I've read.
- I first put painters tape over the holes in the back of the basket to stop anything from falling through onto the back of the speaker cone.
- Tap the existing hole in the top of the pole piece to 1/4 -20. It's tight, tap slowly, removing the tap often to let filings drop out. I got appox 1/2" depth.
- Screw the driver basket (4 mounting holes) to a 18" +- square piece of plywood with the tapped hole in the pole facing up. I used 3/4" plywood.
- Mark a vertical line on the basket, magnet, and pole so It can be reassembled in the same position. I read somewhere that it's important?
- Firmly tap thin putty knives between the pole piece and magnet until a small gap can be seen all around. Don't pry or it will chip the magnet. I did it. Then use larger and larger screwdrivers, shims, etc to get a 3/8" gap.
- Fasten a handle to the pole using a 1/4-20 bolt in the hole you tapped. I used a 18" piece of aluminum bar with a hole drilled in the middle to give good pulling power.
- Stand on the plywood and pull the pole piece from the magnet and basket.
- Remove the handle from the pole.
- Tap thin putty knives between the magnet and the basket until a small gap can be seen.
- Pull the magnet off the basket. It's not too strong a magnetic pull so I just grabbed it and pulled it off.
- Protect the voice coil by sliding thin plastic shims between it and the basket. I used a small plastic Pepsi bottle cut into pieces. Don't want to damage the coils while cleaning.
- Clean the mating surfaces of the basket, both sides of the magnet and the pole face.
- Remove the screws holding the basket to the plywood.
- Cut the dust cap off. I found this scary but once I finished it really wasn't too bad. Cut above the glue line on an angle and don't go deep. I tried cutting on the glue line and it didn't work. The cap is pretty tough paper so a sharp knife is needed.
- Center and epoxy the magnet back on the basket using the vertical alignment lines you put on at the beginning. I don't believe this has to be a perfect centering like when the pole is going to be installed later. I also used slow setting epoxy (gave me lots of time) and left it overnight. I put a thin layer about 1/4" wide around the outer edge only.
- To install the pole without damaging the voice coil is next.
- Drill a hole in the middle of the plywood (I made a recess for a bolt head) and bolt the pole to the plywood using a 1/4-20 bolt. I used washers between the pole and plywood to take up space.
- Clamp the plywood to a bench to hold it and the pole from moving.
- Remove the plastic shims protecting the voice coil if it's still installed.
- I did not apply epoxy to the mating surface of the pole and magnet. Slowly lower the basket with magnet attached onto the pole. Look down through the middle where the dust cap was and line it up carefully so that the pole goes into the middle of the voice coil tube. I was able to hold the basket until the pole was just starting into coil tube when the magnetic force pulled it quickly to the pole.
- Remove the bolt from the plywood.
- Place the jig over the magnet with the adjusting bolts resting on the top of the magnet and the bolts snug against the edge of the pole piece.
- Flip it over and adjust the bolts (pushing the pole around only) until the speaker cone moves freely in and out and there is no rubbing between the voice coil and the pole. Might need to remove some masking tape to let air in the back.
- Flip it back over and expoxy the edge of the pole to the magnet. Flip it back over and make sure nothing has moved. Again I used slow setting epoxy to give time for adjustment.
- Next day I removed the jig and epoxied where my jig was pushed on the pole to complete 100% of the circumference.
- I also added additional epoxy to the seam between the magnet and basket to reinforce this joint too.
- Glue the dust cap back on. I haven't actually done this yet. I need to purchase the proper glue to see if its thick enough. I don't want to have it run down the inside of the voice coil tube. I might need to purchase a new vented dust cap.
I also took some pictures if anyone is interested.
Hey thanks for that. My NS-1KM woofer magnets haven't shifted yet and I'm hoping to get them epoxy'ed before they do. That said, I'll keep a copy of your notes just in case.
Yes ndeed!
Last edited:
saharajim
Active Member
Here's where I started with the putty knifeHey thanks for that. My NS-1KM woofer magnets haven't shifted yet and I'm hoping to get them epoxy'ed before they do. That said, I'll keep a copy of your notes just in case.
Yes ndeed!
Then to screwdrivers
The jig I made.
Pole and basket clean with protection on coil
Cut the dust cap off.
saharajim
Active Member
Epoxy'ed the magnet to the basket
Setting up to adjust the pole. I actually added plastic pieces between the ends of the bolts and the pole to make it slip better than wood.
Once I had it centered I tested it before putting epoxy to the pole and magnet joint.
Installed in cabinet and waiting on a dust cap. I'm keeping the grill covers on until I get the proper glue.
Setting up to adjust the pole. I actually added plastic pieces between the ends of the bolts and the pole to make it slip better than wood.
Once I had it centered I tested it before putting epoxy to the pole and magnet joint.
Installed in cabinet and waiting on a dust cap. I'm keeping the grill covers on until I get the proper glue.
saharajim
Active Member
One more thing I found was that in the video he makes a tool from a piece of plastic to go over the pole which has holes for handles. I made this too. I think it's for making a test fit of the pole onto the magnet and with this plastic piece you get two handles to pull the pole off again after test fitting. I didn't use this method even after cutting up a washer fluid bottle to make the tool. I just bolted the magnet back to my plywood and clamped it on my bench and pulled the basket upwards to separate them again. Worked great!
saharajim
Active Member
I used JB Weld. It's still working perfectly and these speakers play daily.
saharajim
Active Member
I did end up gluing the original dust cap back on it's not perfect but ok. I suggest when cutting the dust cap off don't try to cut the old glue, it's hard, but cut just along the top edge of the old glue line. I think it will make a neater cut line and easier to glue the cap back later.
