General voice coil question. - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 2 Old 11-09-2013, 04:08 AM - Thread Starter
AVS Special Member
 
stefuel's Avatar
 
Join Date: Apr 2001
Location: Marshfield, MA, USA
Posts: 5,880
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 13
I don't think this matters what brand it is but it's a Velodyne HGS-15. I'm trying to get to the bottom of a funky sounding sub.
The amp has already been replaced but the funky sound remains, At the request of Velodyne, I pulled the driver to check that the front and rear spiders were not coming un-glued. They were fine. Then I asked what ohm reading I should get from the coil assembly but that went unanswered. A few hours later, I went back to it, turned on the meter and got 5.5 ohms. I did not hear back from V yet, so I shut the meter off and went to bed. This morning while having my coffee, I turned the meter back on and read 7.4 ohms. The other weird thing I noticed this AM is that manually moving the cone in and out changes the ohm readings a lot. I don't think that should happen. I don't think the coil resistance should change at all, should it?

Current owner of the last/best AmPro on the planet. The mighty 4600HD, and it's still running...better than Barco's, especially southern ones.
stefuel is offline  
Sponsored Links
Advertisement
 
post #2 of 2 Old 11-09-2013, 04:29 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 13,906
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 457 Post(s)
Liked: 1067
Quote:
Originally Posted by stefuel View Post

I don't think this matters what brand it is but it's a Velodyne HGS-15. I'm trying to get to the bottom of a funky sounding sub.
The amp has already been replaced but the funky sound remains, At the request of Velodyne, I pulled the driver to check that the front and rear spiders were not coming un-glued. They were fine. Then I asked what ohm reading I should get from the coil assembly but that went unanswered. A few hours later, I went back to it, turned on the meter and got 5.5 ohms. I did not hear back from V yet, so I shut the meter off and went to bed. This morning while having my coffee, I turned the meter back on and read 7.4 ohms. The other weird thing I noticed this AM is that manually moving the cone in and out changes the ohm readings a lot. I don't think that should happen. I don't think the coil resistance should change at all, should it?

Your prognostications sound correct and likely to me.

Seems very much to me like you have a rubbing voice coil. What happens is the rubbing scrapes the insulation off the wire in the voice coil and rubbing against the metal pole pieces of the magnet assembly shorts out a varying amount of turns. That and the scraping is what causes the funky sound.

Rubbing is caused by things like shock in shipping, cone suspension sagging (seems like they had you check for that) or a form of overpowering that results in a slow cooking and eventual deformation of the voice coil.

It is very common.
arnyk is online now  
Reply Subwoofers, Bass, and Transducers

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off