Need HELP! Speaker cone stuck stiff? - diyAudio
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Old 3rd April 2009, 06:22 PM   #1
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Default Need HELP! Speaker cone stuck stiff?

Im trying to find help for a friend, he bought a pair of the cult classic yamaha NS1000M for alot of money (lovely monitors) but there is one major problem with them.

Click the image to open in full size.

He put them on and noticed there is no bass he told me and thought maybe his 85w amp did not have enough power so i bought round my big 120w power amp and fired it all up....

No bass at all?

We took out the bass drivers to find the cone is stiff no movement at all...

We found the magnet had come off one and could be placed back on or we could even glue it back but we found with the magnet off the cone moves fines if pushed but when placed back on the cone is stiff again?

I have no idea why? the driver works we fed it a full range signal, there is no bass it sounds like a midrange obvoiusly because the cone can not move it can not produce bass.

Here are some pics.

The Back of the driver with the magnet off. The Cone moves with this off but as soon as I place the magnet back on the cone no longer moves.
Click the image to open in full size.

The hole into which the magnet drops into.
Click the image to open in full size.

Click the image to open in full size.


Any idea what caused this or how to fix it?

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Old 3rd April 2009, 07:11 PM   #2
DaveG is offline DaveG  United States
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stuck voice coil usually means it overheated. Yours probably expanded but did not actually burn completely open.
Don't know why the magnet is off. Maybe someone popped them off to explore.

Probably is not much you can do about it except to replace the drivers. Possibly someone who can recone could glue the magnet back on, then replace the entire cone/voice coil assembly.

Dave
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Old 3rd April 2009, 07:25 PM   #3
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Default it sounds like a total rebuild maybe necessary

Corrosion or the loose magnet assembly in the voice coil and the magnet core assembly being lose caused it to become distorted. Since the voice coil shape is distorted causing it to rub very hard the maybe signs of arching and electrical arcing to happen in the barrel causing small mounds of metal to be welded to the barrel (explaining no movement when magnet core in place). Check for continuity and resistance if resistance is less than 1 ohms you have a (shorted voice)bad voice coil. Check around for speaker repair places or ask if some one has a good recommendation of a newer version replacement
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Old 3rd April 2009, 08:56 PM   #4
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Reconing speakers in not a super big deal. There are lots of places that will do it.

I would just make one suggestion, if you plan to replace one woofer cone, it is far better to replace both woofer cones to keep the sound of the speakers balanced.

It will probably cost a little extra to have the magnet glued back on because they have to make sure the alignment is perfect, but it shouldn't be that much extra.

Which brings up another point, you can't just slap the magnet back on and expect it to be magically aligned with the voice coil. I suspect the placement has to be very precise. The clearance around the voice coil is about like a thick piece of paper on all sides.

What area of the country are you in, we may be able to help find a speaker re-coner in your area, though, you can probably find one in the yellow pages.

You could also contact Yamaha and see if they still have a direct replacement for the woofer, or maybe, that they can re-cone it with an exact replacement cone.

Steve/bluewizard
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Old 3rd April 2009, 09:03 PM   #5
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Thanks for the help guys. It is not just one driver that is stuck stiff but both, my friend got them off ebay for 600 and the guy he got them off is blaming the shipping company.... I find this hard to believe being that both are like it.

Could storing it in a shed for a period of time do this, they came from scotland very cold weather.

Two replacments is 179 x2 for the same yamaha driver.

The issue is unresolved with the seller who asked my friend to pay via paypal but to send a gift payment to aviod fees? was the seller being dishonest and blaming the shipping company for what he knew was faulty goods, can this be caused by shipping? or is he trying to out my friend?

This is such a bummer as my friend borrowed the money to get these as he has allways wanted a pair for years, must say the midrange is the cleanest I have ever heard, I played a track I know and have listened to for years and heard things I have never heard withen seconds like feet tapping and clicking fingers was amazing, I see why there so sort after and exspensive.
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Old 3rd April 2009, 09:10 PM   #6
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Default definitely storing in a high humidity

will cause considerable damage
moisture will cause corrision, oxidation, and deposits plus maybe even weaken the cones
why do you think they are wrapped in plastic when new
I hope that the person did not state sold as is
for he can fight it other wise if the person stated that they were stored
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Old 3rd April 2009, 09:13 PM   #7
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Thanks, I edited the above with more infomation on the seller.

IMHO he was being dishonest and decided to blame the shipping company, I just dont see how both bass drivers seize in shipping?
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Old 3rd April 2009, 09:14 PM   #8
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Default you may want to look for an alternative replace

there is probably a set of cone that could be used to replace the bad ones so you may want to put a post for alternative replacement suggestion sometimes they are way better for improvement made through the years.
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Old 3rd April 2009, 09:18 PM   #9
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Magnets falling off or shifting is invariably due to shock damage, such as being dropped. Were they shipped together? I suspect the seller is right about the courier company being at fault, but they could say they weren't packed correctly. Either way, it is down to the seller to sort out, (unless your friend paid for shipping).

Oh, and if that fails, try Wembley Loudspeakers for a repair quote, if they can't fix them, no-one can.
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Old 3rd April 2009, 09:19 PM   #10
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Cheers I did think of that but Im not sure what my friend will do because there is still comunication going on with the seller, my friend wants to be paid for replacement driver or have a full refund.

The chasis would have to match but yer a alternative driver would be better as there is nothing special about the yamaha bass driver unlike the exspensive Beryllium domes, they seem exspensive replacments.
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