How to tell if tweeter ribbon is damaged in a 3.7i

Thom2

New Member
May 3, 2020
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#1
I accidently removed a tube from my preamp while the system was powered up and sent a surge through my Magnepan 3.7i speakers, a fairly loud pop. I'm worried that I might have damaged the tweeter ribbons, I know they have a reputation for being fragile. Is it possible that they can be damaged and still operate or would they shut down completely? Can part of a ribbon be damaged but not all of it? Can they distort? I'm not familair with ribbon technology so I need some advice. My paranoia thinks that there is a slight difference in the high end characteristics but I could just be imagining it. Any advice would be appreciated, thanks.
 

cjfrbw

Well-Known Member
Apr 20, 2010
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Pleasanton, CA
#2
Get somebody with a voltmeter to measure the impedance over the tweeter leads compared to the other side and check compared to the Maggie standard value. If the impedance is unaltered, the ribbon is probably OK.
 

audio.bill

Well-Known Member
May 27, 2013
478
30
110
Chicago suburbs
#3
Get somebody with a voltmeter to measure the impedance over the tweeter leads compared to the other side and check compared to the Maggie standard value. If the impedance is unaltered, the ribbon is probably OK.
Impedance cannot be measured by a standard voltmeter, they can measure simple DC resistance. Maybe you meant to just measure and compare the ribbon's resistance.
 

cjfrbw

Well-Known Member
Apr 20, 2010
2,716
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#4
Yes, thank you, you are correct. Impedance and resistance are not interchangeable, but they commonly are used that way.
 

Thom2

New Member
May 3, 2020
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#5
Thanks for the suggestion. I think they're fine, I gave them a good listen today and they sound as good as ever. I was just very freaked out by putting that through them and assumed the worst.
 

Big Dog RJ

Well-Known Member
Feb 3, 2012
708
41
113
Melbourne
#6
Ah! The Maggies ribbon tweeter...just came across this.

Not necessary to check with any meters, although it does help. There's a simpler method for trouble shooting ribbon tweeter damage;

1. If and when the ribbon tweeter goes off, all you need to do is hold a flash light at the back, along the ribbon from top to bottom, and you will see the damaged part. This is where the ribbon has broken in two pieces, with both pieces hanging freely, hence not joined together. Very similar to the filament in a light globe when it goes out, that filament is clearly visible as its broken off its point of contact.

2. The other method is by just listening, you won't hear any highs at all. No frequency extension at the top end whatsoever. Also, the tweeter fuse at the back panel will blow, so this needs to be replaced first with the correct fuse type.

That's about it!

The other issue and pain in the butt, with a capital B, is when the midrange panel goes off. Sometimes whiles playing you can't really tell since the highs and bass plays fine... until you check the midrange fuse as well. This is usually a fuse replacement and all should be OK... The bass panels are pretty sturdy and nothing should deter this section unless the panels were abused.

The other issue I was referring to is once the tweeter goes out, replacing it is mighty fun... not really! You have to be completely sober, purchase the ribbon tweeter kit from Magnepan, have a large cleared area for this operation and very very steady hands... oops there goes a ribbon!

The ribbon is so light and fragile, it's a marvellous thing when you just hold one in your hand. Fingers and palms get sweaty, no good for changing ribbons. The tweeter kit provides a few extras just for trial in case you break them... and very quickly they do break! After a few attempts you get the hang of it and after nearly 3hrs all is well including a stiff neck after all the glues and pasting in a Zig-Zag manner down the whole length of the ribbon.
And the owner's manual says 30mins tops with a Phillips screwdriver... yeah right!

I've replaced 16 tweeters in my audio journey with Maggies, towards the end I gave up and just shipped across the damaged tweeter element to mags in a tube. The wait was long but job done!
No more stiff necks and can enjoy a few beers or a nice single malt whiskey whiles the tweeter is being attended to...cheers!

BTW the mg3.7i is actually one of my favourite maggies, even more so than the 30.7's!
They're just far more coherent and way easier to set up plus don't require a football field to sound right.

Have a good one, big woof!
RJ
 

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