Planar Speaker Asylum

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Planar Speaker Asylum

RE: "sort of a rattle - top of bass panel" ...

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In Reply to: RE: "sort of a rattle - top of bass panel" ... posted by andyr on August 14, 2012 at 19:44:57

If you live in a humid climate, you have delamination, and I would bet on that as the cause. My speakers came from Missouri, and were delaminated in places along the entire panel from top to bottom. I have actually never seen a worse case of it... ever. Your speakers being very early in the run(as mine are) would likely mean that he older style adheisive was used as well, thus making it a near certainty that delam is the cause. The nice thing about Magnepan is they are there and willing to help in any way to make them sing again.

Follow Ups:

RE: "sort of a rattle - top of bass panel" ... - iamimdoc 15:04:54 08/15/12 (7)
I have read what you all have suggested but can't quite fathom EXACTLY what to do.

Would anyone put up with a phone/skype call to facilitate before I do something unwise?

Thanks
- Magnepan 20 r buzz and anatomy lesson - iamimdoc 07:39:13 06/30/13 (6)
  Approximately one year ago and noticed a buzin the top of one of my Magnepan 20r speakers.
  
  This began about one year ago and has not worsened. Sound occurs only with certain deep, loud transients. These sound appears to emanate approximately 4-6 inches just inside the tweeter, near the top of the speaker. The sound does not seem to be coming from the part of the panel away from the tweeter, ie the far side horizontally speaking. I would presume the mid-rage panel is next to the tweeter but did not know this for sure.
  
  Using a flashlight, on the backside of the speaker, I can see multiple holes where presumably sound emanates from the speakers. In addition, I see several other holes, that appear to have flanges on the backside of the speaker. These "flanges/washers" are approximately 1/2 inch across. These holes transmit light. These are in columns approximately 8-10 inches apart in the vertical dimension. There are at least several columns of them.
  
  In this forum, I found a discussion of rivets holding the panels together that may come loose. I would presume that this might cause a rattle.
  
  Questions
  
  Does anyone have a picture of my speaker "nude"? I need an anatomy lesson to know what I am looking for.
  
  For the holes with flanges, are these the rivets?
  
  Is it likely that this could be the cause of a problem (single location, not getting worse after one year)?, ie rivet fatigue/failure
  
  Is there a way that a human being (me) could further diagnose this problem without causing harm? The grill cloth could stand to be replaced (stains).
  
  I have called thre manufacturer and they seem to want to replace the panels for approximately $3000. I am willing to do this if necessary but prefer not to if not necessary. Sound is irritating when it occurs, however.
  
  Any help appreciated.
  - RE: Magnepan 20 r buzz and anatomy lesson - iamimdoc 10:14:06 05/09/15 (5)
    I posted this a Cooke of years ago . Buzz is no worse but irritating only on very low loud bass transients. Because it has not worsened, I feel this may be a loose rivet or support structure between the panels. I still have not been able to locate a picture of a panel without grill covering
    
    If it is a rivet, perhaps a bit of superglue or aquarium seal could be used to knock out the rattle
    
    Or perhaps I should just ignore the rattle or get rid of the few albums that buzz
    
    Has anyone a picture of the rivets or nude panels?
    Does the collective wisdom of the group have any more suggestions?
    
    Thanks
    - RE: Magnepan 20 r buzz and anatomy lesson - Satie 14:14:37 05/09/15 (4)
      The MG20 (as opposed to 20.1 and 20.7) has a single ended midrange driver so if you have a problem with a loose rivet or of delam on the midrange driver it is one sided and reatively easy to repair.
      
      You were saying that the buzz was coming from a particular spot on the top of the speaker by the tweeter but not from the tweeter itself. That would indicate the top of the midrange driver contains the culprit.
      
      The midrange driver is mounted between the bass and the tweeter as close to the tweeter as they could manage. It runs most of the length of the speaker as the other drivers do.
      
      The mid driver is composed of a perforated magnet board where the magnets are arranged in rows between the holes on the inside of the board. The board is mounted onto a spacer frame and strengthened at intervals with cross pieces going horizontally and either glued or riveted to the frame and (or) magnet board. The mylar is stretched over the spacer frame and the edges are covered with a steel frame. The wires or foil are glued on the mylar and aligned with the magnets to make the most of their magnetic fields.
      
      If the noise is indeed coming from the midrange and you feel ok with removing the decorative cloth yourself, you may be able to dismount the midrange and either fix the rivet yourself or send the driver to magnepan for repair - or if it is beyond just the rivet.
      - RE: Magnepan 20 r buzz and anatomy lesson - iamimdoc 10:24:35 05/16/15 (3)
        
        In Reply to: RE: Magnepan 20 r buzz and anatomy lesson posted by 13473 on May 09, 2015 at 14:14:37
        
        Further questions. Any help appreciated
        
        Before I "break into the speaker"
        
        My rattle occurs only with very low frequency bass transients ~ 30 Hz
        
        From the rear panel thru the grill cover I see vertical dark stripes. Nearest the tweeter these stripes are thinner than farther away from the tweeter. These are the vertical strips of magnets I presume?
        
        From the front thru the grill cloth next to the tweeter, I see what I think is tape applied vertically and running up and down in a continuous strip. This is the midrange conductor applied to the Mylar? [I thought the conductor was thin wire and not flat tape - clarification requested]
        
        If above correct, none appears to be unglued. Would this make it unlikely that the tape on the bass panel is unglued or delaminated?
        
        The bass panel has perforated metal on both sides and hence I can't see into it. It is riveted front to back and these could come loose and rattle?
        
        The midrange has some horizontal supports every 6 inches or so from top to bottom. Are these attached to the perforated metal? Can they come loose and rattle? Can this be fixed by me if the case?
        
        It would appear that removing the front grill would make it easy to at least get at the midrange panel and perhaps the rivets on the bass panel. Is this correct? Is this just a matter of removing the screws on the back of the speaker?
        
        Any gotchas to consider otherwise?
        
        Thanks in advance
        
        RE: Magnepan 20 r buzz find an expert - Satie 11:15:45 05/16/15 (2)
        
        In Reply to: RE: Magnepan 20 r buzz and anatomy lesson posted by iamimdoc on May 16, 2015 at 10:24:35
        
        I have not been involved with taking apart an MG20 so have limited insight. I think you should find someone who has direct experience. Search the MUG for pics and experienced hands.
        
        Since the rattle (rather than buzz) indicates something other than a wire delam issue then you should look at the cross braces once you have the sock off. It is also possible that the midrange has a couple of mounting staples missing.
        
        The tape you see may be a damping tape applied to the back of the midrange's magnet board. The magnets are on the inside of the driver in between the perforations and arranged in vertical strips, they should not be visible from the back at all.
        
        If you can repeat the track where the rattle occurs and try to use your finger to find a spot where you can damp it just by pressing your finger against it, that will go a long way towards finding the cause.
        
        There have been a few reports of the rivets coming loose as well as cross braces coming unglued - those would produce a rattle rather than a buzz. Neither are common occurrences. Both the rivets and loose crosspieces can be repaired DIY. You can glue back the crosspieces and replace a single rivet or two with aprropriate tools.
        
        RE: Magnepan 20 r buzz find an expert - iamimdoc 11:56:27 05/16/15 (1)
        
        In Reply to: RE: Magnepan 20 r buzz find an expert posted by Satie on May 16, 2015 at 11:15:45
        
        "Search the MUG for pics"
        
        Would love to see some but can't find any
        
        RE: Magnepan 20 r buzz find an expert - Satie 14:02:36 05/16/15 (0)
        
        In Reply to: RE: Magnepan 20 r buzz find an expert posted by iamimdoc on May 16, 2015 at 11:56:27
        
        I know I saw some
        
        here is a search that had some results
        
        http://db.audioasylum.com/cgi/search.mpl?searchtext=mg+20+picture&b=AND&topic=&topics_only=Y&author=&date1=&date2=&slowmessage=&sort=score&sortOrder=DESC&forum=mug
        
        note the foil conductors on the mid section
        Roger's pic of a naked mg 20 bass and mid driver (Open in New Window)

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