Author Topic: Speaker coil swell  (Read 185 times)

Offline JWG

  • Trade Count: (+2)
  • AVForums Member
  • *
  • Posts: 35
Speaker coil swell
« on: January 17, 2017, 02:22:42 PM »
So I have a recurring issue with some 6" drivers, whose coils have repeatedly swollen. I repaired them previously but find myself in the same situation 18 months later.

I know it can be difficult to surmise what could be causing the issue, but I'm trying to understand if this is a result of extended use or a signal spike (like that of a tube pre amp cutting power whilst the power amp is still active)

On a related note, any speaker coil repair recomendations, I used Merle perviously but I'm not sure if she is still operating.

Thanks to all for any input

Offline grumpybear

  • Commercial Member
  • Trade Count: (0)
  • ***
  • Posts: 179
Re: Speaker coil swell
« Reply #1 on: January 17, 2017, 02:55:10 PM »
Without further info such as speaker model, amp, type of usage etc. my best guess is that the speaker is being overdriven  This would cause the coil to heat up and expand and when it cools it may be out of round and will catch /scrape in the voice coil gap.  It may also create bubbles in the coil or on the former which will have the same effect.

Offline JWG

  • Trade Count: (+2)
  • AVForums Member
  • *
  • Posts: 35
Re: Speaker coil swell
« Reply #2 on: January 17, 2017, 09:45:30 PM »
Certainly, I'm driving a pair of Dali Ikon 6's with a Conrad Johnson PV5 through an Audio Research D130

It certainly seems like the D130 has plenty of oomph for the Dali's and perhaps as you suggest this is inevitably going to overheat the coil on the driver.

It would seem the safest bet in the long term is to go bigger on the speaker

Online fdlsys

  • Vinylist
  • Trader
  • Trade Count: (+59)
  • *****
  • Posts: 6,570
  • Do you like life, sweetheart?
Re: Speaker coil swell
« Reply #3 on: January 17, 2017, 10:02:50 PM »
It would seem the safest bet in the long term is to go bigger on the speaker
Mmh, no - the safest is to take your power amp to a tech for a checkup before anything else.
Repeated problem as you described without explicitly stating that you have indeed driven them to smoke, indicates a possibility of permanent DC offset on the amp output.

DC offset you cannot hear, but you can see it.
Power up the power amp without any signal on the input (say, preamp disconnected).
If the speaker cones push out (or suck-in) and stay in the in/out position or very slowly move in/out, that is the evidence of DC offset.

If the amp gets a clean bill of health, well then, you are over-driving the speakers.

Reasonable pre-amp "pop" is not going to cook the speakers. Of course if the pop blows your hair back, that would be a bit of a concern.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when you’ve lived a little. Miles Davis

Offline Stanp

  • Trade Count: (0)
  • AVForums Member
  • **
  • Posts: 81
Re: Speaker coil swell
« Reply #4 on: January 17, 2017, 10:16:49 PM »
Grumpybear has given you the correct answer. If your amp has a much higher wattage output than your speakers rated wattage, and you drive the speakers at high volume levels too much current goes through the coils creating excessive heat, this damages the coils insulation. You just need to not play at very high volume levels. If your amp is rated at a much lower wattage rating than your speakers and you play at high volume levels, your amp will create distortion and damage your tweeters.

Fdlsys advice makes sense too
« Last Edit: January 17, 2017, 10:30:44 PM by Stanp »

Offline Ampdog

  • Trade Count: (+1)
  • AVForums Veteran
  • *****
  • Posts: 6,489
Re: Speaker coil swell
« Reply #5 on: January 17, 2017, 10:41:28 PM »
As said above.

If repeated swelling occurs you might also be using the wrong fixative/glue. Only some types of resin over the voice coil will be able to stand the high temperatures reached. 15 cm drivers ..... easily the casualties of high energy. Some loudspeaker ratings are quite conditional; apply anything near the spec. in the form of a continuous sine wave and the voice coil will fry in a matter of minutes.
Creativity requires the courage to let go of certainties.  (Erich Fromm)

Offline HBAutomation

  • Trade Count: (+2)
  • AVForums Member
  • ***
  • Posts: 169
Re: Speaker coil swell
« Reply #6 on: January 17, 2017, 10:42:08 PM »
The safest is Mike's suggestion. Only if making sense makes sense! :nfi:

Offline Ampdog

  • Trade Count: (+1)
  • AVForums Veteran
  • *****
  • Posts: 6,489
Re: Speaker coil swell
« Reply #7 on: January 17, 2017, 10:47:09 PM »
Yah - forgot to repeat that. Have the amp checked just in case.
Creativity requires the courage to let go of certainties.  (Erich Fromm)