Vibrating nosie from woofer - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th January 2013, 12:10 PM   #1
diyAudio Member
 
Join Date: Dec 2010
Location: Malaysia, Selangor
Default Vibrating nosie from woofer

I got a very old woofer unit, JBL's PS-120 Click the image to open in full size.

This speaker only produce low frequency, range 200hz and below. But it has a fatal problem now ( didn't really notice when it started):

When the bass is very strong, the back panel (removeable steel portion, mark with red frame in picture) which has all the circuit attached except driver, it refuse to stay as a flat piece of metal, STARTED to flex back and forth with the speaker cone This make a loud noise that annoys me.

The noise can be reduce to very low level with my hand press strongly against the back panel, but then I wouldn't able to sit down and enjoy my music/video.

Beside, I couldn't supress it with the strength of hands only I need to use my body weight with my hand to reduce roughly 80-95% of the vibration noise.

So I'm seeking helps from forumers which have knowledge, experience and wisdom to solve this problem.

Quote:
Just as extra, I open the back panel before. Maybe due to its old age, it ceiling's soft material aren't stick to it (half fallen) would it be much effect on the sound ?
Or should I say repair/replace it will brings me any benefit of SQ ?
Attached Images
File Type: jpg photo 3.JPG (243.5 KB, 87 views)
File Type: jpg photo 4.JPG (212.3 KB, 86 views)
  Reply With Quote
Old 24th January 2013, 12:35 PM   #2
Puffin is offline Puffin  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: U.K
Sounds like this is a sealed and not ported sub. Sounds like the rear panel (with amp) is flexing as the air is shifted. I would have thought that if the seal around the amp plate is broken, that this would have made the pressure escape and not flex the panel. Is the panel made of cardboard?
  Reply With Quote
Old 24th January 2013, 12:41 PM   #3
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Not where whatever I am looking for is at.
I don't think the steel plate will be flexing, more likely the screws will be loose.
__________________
Everything is somewhere. Where the @!#$ is it.
  Reply With Quote
Old 24th January 2013, 02:04 PM   #4
epa is offline epa  Netherlands
diyAudio Member
 
Join Date: Apr 2010
Location: amsterdam
first stapel/nail the wool back,then put the backplate back wil a seal.
this could be a silecone/rubber or foam seal.
make sure the screws are thight .
__________________
one good thing about music ,when it hit you feel no pain.
so hit me with music
.
  Reply With Quote
Old 25th January 2013, 01:38 AM   #5
diyAudio Member
 
Join Date: Dec 2010
Location: Malaysia, Selangor
Quote:
Originally Posted by Puffin View Post
Sounds like this is a sealed and not ported sub. Sounds like the rear panel (with amp) is flexing as the air is shifted. I would have thought that if the seal around the amp plate is broken, that this would have made the pressure escape and not flex the panel. Is the panel made of cardboard?
Yeah, it is a sealed woofer, so the amp plate easily move with the cone.
Anyway, it doesn't have any seal around it, just screw directly and side mates with woof/MDF material directly. The panel is made of metal. (normally plated steel I think)

Quote:
Originally Posted by vacuphile View Post
I don't think the steel plate will be flexing, more likely the screws will be loose.
I had rescrew it, make sure it doesn't cause the problem, but still persist. But the thingy I'm sure is that it doesn't have any rubber seal/ring that make it vibration-proof. There is even no washer or that sort of thing. Just directly screw into wood.

Quote:
Originally Posted by epa View Post
first stapel/nail the wool back,then put the backplate back wil a seal.
this could be a silecone/rubber or foam seal.
make sure the screws are thight .
Hm.... If I put a seal around the panel/plate, then I couldn't reduce it simply ^^ would like to find better solution. Of course I will put back the wool back first ^^ But I think the main problem is not sealing.
  Reply With Quote
Old 25th January 2013, 01:56 AM   #6
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

You can reinforce the panel or seal it off from the back pressure.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 25th January 2013, 02:10 AM   #7
diyAudio Member
 
Join Date: Dec 2010
Location: Malaysia, Selangor
Quote:
Originally Posted by sreten View Post
Hi,

You can reinforce the panel or seal it off from the back pressure.

rgds, sreten.
Hi, sreten.
Seal it off from back pressure ? what does that mean ? do you mean to apply seal, thus possibly it is more affected (flexing) by the air pressure inside ? or make it leak ?

Reinforce is a better way, but is there any method that able reinforcement of the back panel without making degradation of SQ, permanent damage (to the enclosure) ?
In other words, can I make a reinforcement structure that is reversible/safe ? (at least won't harm the woofer)

Regards,
Leong.
  Reply With Quote
Old 25th January 2013, 02:53 AM   #8
diyAudio Member
 
Richard Ellis's Avatar
 
Join Date: Sep 2006
Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Yes, it needs to be resealed but the attachment mechanism isn't working for you (stripping out)..'long term'........
Depending on the stiffness of the electronics " plate" the silly woodscrews have to go. Use thru-bolts with washers & lockwashers. The overlap of the plate should be enough to use a 1/2 " flat washer (Check how much)...have the flat washer, lockwasher, nut on the outside (Duh!)....drill all the way thru...probably 5/8" MDF wood.
When this is all considered........you might consider doubling the amount of screws (Now thru-bolts). Of course it would require you to drill out new holes in the Plate assy.

__________________________________________________ _____Rick.......
Attached Images
File Type: jpg SCrews.JPG (23.4 KB, 56 views)
  Reply With Quote
Old 25th January 2013, 03:21 AM   #9
diyAudio Member
 
Join Date: Dec 2010
Location: Malaysia, Selangor
Quote:
Originally Posted by Richard Ellis View Post
Yes, it needs to be resealed but the attachment mechanism isn't working for you (stripping out)..'long term'........
Depending on the stiffness of the electronics " plate" the silly woodscrews have to go. Use thru-bolts with washers & lockwashers. The overlap of the plate should be enough to use a 1/2 " flat washer (Check how much)...have the flat washer, lockwasher, nut on the outside (Duh!)....drill all the way thru...probably 5/8" MDF wood.
When this is all considered........you might consider doubling the amount of screws (Now thru-bolts). Of course it would require you to drill out new holes in the Plate assy.

__________________________________________________ _____Rick.......
Well, your method most of the time only can reduce, but couldn't eliminate the problem. At least in my case, because the wood part that been screw is very thin, less than half a centimeter.

The problem now is with the metal flexing, I think the only way to stop it effectively is to make reinforcement in the middle.

I will take picture (of dismantled) when I get hold of better camera.
Attached Images
File Type: jpg 1.jpg (41.7 KB, 51 views)
  Reply With Quote
Old 25th January 2013, 04:15 AM   #10
diyAudio Member
 
Join Date: Dec 2010
Location: Malaysia, Selangor
Quote:
Originally Posted by Richard Ellis View Post
Yes, it needs to be resealed but the attachment mechanism isn't working for you (stripping out)..'long term'........
Depending on the stiffness of the electronics " plate" the silly woodscrews have to go. Use thru-bolts with washers & lockwashers. The overlap of the plate should be enough to use a 1/2 " flat washer (Check how much)...have the flat washer, lockwasher, nut on the outside (Duh!)....drill all the way thru...probably 5/8" MDF wood.
When this is all considered........you might consider doubling the amount of screws (Now thru-bolts). Of course it would require you to drill out new holes in the Plate assy.

__________________________________________________ _____Rick.......
Srry for the above post, my memory just blurring up. The MDF wood is just slightly over than 5/8" ^^ but the screw are originally pass through the MDF wood. (metal 2mm thick, screw longer than 1")
I attached some picture. 1st and 2nd picture is the woofer with back panel attached (mounting screw removed)

3rd picture is the internal near the driver. (taken without any intention though) don't know why there is black paint within the box.
4th is backpanel removed, and there is a thin paper-like material sandwiched between wood and metal.
Attached Images
File Type: jpg y1.jpg (945.4 KB, 20 views)
File Type: jpg y2.jpg (530.1 KB, 13 views)
File Type: jpg y3.jpg (774.0 KB, 21 views)
File Type: jpg y4.jpg (497.4 KB, 20 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
headphones for nosie cancellation project branm Parts 0 11th August 2011 05:05 PM
Vibrating capacitor blue lander Tubes / Valves 14 11th February 2011 03:50 AM
New NHT Classic 3 woofer vibrating. Help neeed spinnerbait15 Multi-Way 8 23rd June 2010 02:01 AM
Why is my amp vibrating? wwenze Chip Amps 4 13th May 2009 03:50 PM
Vibrating cutter...any available gmphadte Parts 10 7th December 2007 08:10 AM


New To Site? Need Help?

All times are GMT. The time now is 07:02 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2