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MG 20 buzz

208.189.200.2
Posted on August 14, 2012 at 13:56:37
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 Magnepan 20 R's - early serial # - ("earlier than 600")

1)
1 speaker buzzes on 1 song ("Way Down Deep" by Jennifer Warnes) - sort of a rattle - top of bass panel. Reproducible on this song. No other test speakers avaialable.

But no buzz on other songs with bass, no buzz with Stereophile test CD between 25-200Hz.

But I am neurotically convinced that I have the delamination issue.

Anything else I can do to confirm or diagnose?

2)
Magnepan does not encourage repairs of these speakers as they are sealed/riveted together. Repairs would be 2500+ shipping. Any commments on a DIY'er being able to repair

Thanks in advance

 

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RE: MG 20 buzz, posted on August 14, 2012 at 17:12:38
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 You could try sweeping some tones, the buzz will usually occur at a specific frequency. But it can be frustrating to find. I have a planar driver that buzzes only on certain piano recordings. You could listen to it for weeks, and think it was just fine, and then wham!

I don't know of anyone who's repaired the MG-20 drivers but someone here did repair a 1-D tweeter, which is also push-pull. As I recall, he said that the trick was in knowing which side to remove first! I think Magnepan puts in new drivers, you could verify that with them and if true attempt a repair, knowing that it won't cost you anything if the driver is destroyed.

On the positive side, the new adhesive they use doesn't delaminate and if you do indeed have delam and you get them rebuilt now, you should be able to enjoy them for the rest of your life.

 

RE: MG 20 buzz, posted on August 14, 2012 at 18:39:29
nooshinjohn


 
I did this repair, and though not an easy task, it CAN be done. I began by drilling out one rivet only, and getting bolts that matched the hole PERFECTLY. I then went down the panel and replaced the rivets with nuts and bolts. Once this was done, I loosened the nuts and worked down the panel until I had separated them, replacing the nuts and bolts on the mylar side of the driver as I went down. This allows you to use the panel as a jig for reassembly. Once separated, the repair was no different than the regular Maggie repair. After the repairs were complete, I reversed the above and rivetted things back together. This is not a repair for the faint of heart or the novice, but can be done if you simply take the proper care. The folks an Magnepan will put together a repair kit for you pretty cheap.

 

"sort of a rattle - top of bass panel" ..., posted on August 14, 2012 at 19:44:57
andyr
Manufacturer

Posts: 12550
Location: Melbourne
Joined: September 2, 2000
 I think this could be caused by 2 (different) things:

1. some wire has become delaminated on the mylar (which is sandwiched between the 2 metal pole pieces and thus hard to get to - unless you follow nooshinjohn's advice! :-)) ). Hence it rattles at a particular frequency.

2. one of the metal reinforcing strips on the metal plates has become loose, at one end. (I'm assuming here that the pole pieces on 20s have the same reinforcing strips as the pole pieces on other models?) I experienced this and heard a rattle at a particular bass frequency.

You can easily see if it's #2 (which will save you shipping the back to the factory) ... although I'm assuming:
a) it's a CD that you can put on "repeat", and
b) it doesn't just happen once, for a split second, during the track.

Anyway, play "Way Down Deep" and when your hear the rattle:
* use one hand to steady the panel
* use the thumb on the other hand to press (quite hard) the end of a reinforcing strip against the pole piece
* if none of the reinforcing strips look obviously loose, you will need to try this with the end of each strip ... on each side. (In my case, once heard the rattle, I could quite easily identify which were the loose reinforcing strips.)

Good luck,

Andy

PS: if it is a loose reinforcing bar, reply and I'll tell you what I did with my bars.

 

RE: "sort of a rattle - top of bass panel" ..., posted on August 14, 2012 at 19:53:46
nooshinjohn


 
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.

 

RE: "sort of a rattle - top of bass panel" ..., posted on August 15, 2012 at 15:04:54
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 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

 

Buzz Kill, posted on August 27, 2012 at 09:11:49
Mando
Audiophile

Posts: 248
Joined: September 18, 2007
 That song is notorious (at least on my system) for highlighting problems you may or may not have! The bass will resonate everything in your room and speakers and surrounding neighborhood.
I have Mye stands loaded with reptisand for some mass loading on my 3.6's, but I found that if the speakers are out of level (i.e., one footer is higher than another imparting some torque to the speaker) that can cause the very problem of which we speak, the dreaded BUZZ.

Even though my speakers are tilted back a bit, I threw a level transversely across the front and then the back, and made sure they were perfectly level side to side, with no "torque" on the panel.
The buzz sound went away.
It is worth a try and only takes 5 minutes.

Hope this helps!
Mando

 

RE: Buzz Kill, posted on August 27, 2012 at 13:46:57
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Interesting, I never would have thought of that.

 

RE: Buzz Kill, posted on August 28, 2012 at 10:27:54
Mando
Audiophile

Posts: 248
Joined: September 18, 2007
 Josh,
I had noticed that by applying pressure to one side of the panel that the buzz went away. That made me realize it was a torque issue, and the logic followed from there. It's not as much of an issue with the stock stands since they don't attach to the mid-back of the panel, and it's harder to apply torque just from the bottom stand.
Interesting, huh? Maybe I just think too much...

Mando

 

RE: Buzz Kill, posted on August 28, 2012 at 15:57:05
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Wonder why it happened? That is, what was buzzing?

 

RE: Buzz Kill, posted on August 29, 2012 at 05:36:32
berni
Audiophile

Posts: 184
Joined: May 30, 2011
 Aplying pressure on the front side helps?
Maybe the screws from behind(from top to bottom on each side) holding the front part of the frame(with visual wodden parts) are loose.

 

Magnepan 20 r buzz and anatomy lesson, posted on June 30, 2013 at 07:39:13
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 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, posted on May 9, 2015 at 10:14:06
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 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, posted on May 9, 2015 at 14:14:37
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 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: MG 20 buzz, posted on May 9, 2015 at 15:12:30
r3332698049
Audiophile

Posts: 27
Location: Roma
Joined: November 18, 2014
 On my Tympani ID had the same problem on TW .
I replaced the fuses and ... opla ' everything OK .
Sometimes the most simplest is the best-

Great Music
Rudy
TIMPANI ID & QUAD ESL63

 

RE: MG 20 buzz, posted on May 10, 2015 at 10:24:20
macmagman
Audiophile

Posts: 501
Location: NW Indiana
Joined: October 17, 2010






The mid-range went out in one of my 20.1's and after taking them apart I found that the problem was with the panel itself, probably a broken wire somewhere. Since the panels were riveted together I decided not to go any further. I had in the past completely reconditioned my 3.3's but I did not want to attempt this. I ended up removing the panel from the frame and I made a shipping crate to send to Magnepan, this saved me a lot foe shipping. removing the panel assembly wasn't that bad and I figured I would do as much of the work as I could.

 

RE: Magnepan 20 r buzz and anatomy lesson, posted on May 16, 2015 at 10:24:35
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 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, posted on May 16, 2015 at 11:15:45
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 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, posted on May 16, 2015 at 11:56:27
iamimdoc
Audiophile

Posts: 24
Joined: February 27, 2010
 "Search the MUG for pics"

Would love to see some but can't find any

 

RE: Magnepan 20 r buzz find an expert, posted on May 16, 2015 at 14:02:36
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 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

 

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