EMIT & EMIM Tweeter Diaphragm Repair How To

Kencat

Super Member
I successfully brought 2 EMIT diaphragms to life tonight. Surprised the heck out of myself actually. I did it just to see what would happen figuring I couldn't make a bad one worse.

The diaphragms I worked on were for the Quantum 2. I think this would work on other models as well. A brief history to get started. I had one Emit that was not working in one speaker. I picked up some spare diaphragms and proceded to change out the bad one. I found that the resistance of the bad one was 20 - 40 Ohms. I knew at that point that at least the foil was not broken, and looking at the solder joint suspected that was the problem. The good diaphragm measures 5.6 - 5.8 Ohms.

I ordered some more diaphragms lately, and one of the two measured 30 - 40 Ohms. This prompted me tonight to see if the solder joint could be repaired with with a remelt of the solder that connects the back-side metal frame to the leads of the foil strips on the Mylar-side. The winding foil strips I call the "racetrack".

I fired up the little Soldering Gun, using the pointed tip, and bravely touched each button on the frame-side, just long enough to melt the solder, and quickly removed the tip.

Word of caution: I had the mylar-side on top of newspaper, which was a good thing because the solder tended to fall downward and without coming to rest on the paper, it may have fallen right out. You can see in one the pics how the solder is raised on the mylar-side. I may have had the tip on the button too long for the first one, and made sure I was quicker on the second one.

BOTTOM LINE - It worked. Measured 5.7 to 5.8 Ohms rock solid

Below are the two Q2 EMIT Diaphragms and the tools of the trade.

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Below is the Frame-side of the Emit diaphragm showing the solder buttons. This is the side to "remelt". Ignore the big solder blobs. That was where the speaker wires were soldered on. It's the small buttons that connect to the foil.

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Below is the Mylar-side of the Emit diaphragm showing how the solder will tend to flow with gravity.

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SO, Don't chuck out those non-working Emits without checking the resistance. If it's high, it's not broken. This solder joint remelt might be all it needs.
 

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Great thread, Kencat. This problem is very common, having encountered it recently myself. Hopefully others will realize that they can repair their bad EMITs rather than resort immediately to replacement.

- JP
 
Great!

Thanks for the info KenCat.. I may need to check one of mine, it sounds very weak. I've been lucky with the emits but my problem is the Mids....

All this speaker talk made me pull the trigger last nite on a set of Kenwoods but I think the price was right, I'm putting a Kenwood system together for my daughters boyfriend. Like I need more speakers. The wife thinks I bought them for myself. Lets see,... where can I put these....

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=9706209028

I know it's a little off topic.... Sorry... :twak:
 
Kencat,
Thanks for sharing this tip- seems there's a million badEMITs out there that might not be bad after all.

sicman,
Good luck with the Kenwoods. I was eyeing the seller's Advent Legacys myself...

But I've got a few offers here from some AKers that I'd rather take care of first. I think.
 
Excellent thread Ken!

I was wondering when someone would post a thread like this. It is a source of frustration for many Infinity speaker owners.

I don't have any emit or emim's to experiment with that need repair. But I did pick my friend Jims brain on repair technics.

From what I gather most short out in the area shown in your third photo when overdriven with out enough power.

Jim takes an eraser and scuffs up the ends at the short, then uses scotch tape and masks off each section of mylar, so as not to creat another short. Folding the ends of the tape for easy removal. Then uses a silver based conductive contact pen from Parts Express. Once it dries two light coats of clear fingernail polish. He repaired my emim's about a year ago and they are still playing great :thmbsp:
 
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Just measured mine at the office... 3 and 29... I have a BRAND NEW soldering iron at home that will come to work with me on Monday for a little bit of DIY:)... Now the speakers sound GOOD now so after a lttle doctoring.... Hmmmmmmm Will see on Monday:)
 
OMI said:
Just measured mine at the office... 3 and 29... I have a BRAND NEW soldering iron at home that will come to work with me on Monday for a little bit of DIY:)... Now the speakers sound GOOD now so after a lttle doctoring.... Hmmmmmmm Will see on Monday:)

Cool, a good reason to go to work. Don't hear that too often. Kencat, great documentation and pics. Useful information for the future.
 
Great thread!

What does everyone think of a subforum called: "Repair and Parts"? If there's enough interest, Scott or I can ask the admins to clutter up the server just a little bit more...
 
EMIT Magnet Warning

A minor addition is that the older diaphragms don't have the etched '+' at the bottom, but have merely a red marker blotch near the positive terminal. An additional, but unimportant detail is that with the older the builder/assembler/QC wrote the impedance of the diaphragm (typically 5.6Ω ) at the top in red ink. Of course, the diaphragm alone measures as a dead short (the interaction within the magnetic field creates the impedance), so this bit of information was likely used for matching before assembly.

Something very important to remember when attempting Kencat's described repair on assembled EMITs is that the rare Earth element Samarium-Cobalt magnets are very strong and very fragile. Where this information becomes important is with the recognition that the glue holding the magnets to their respective halves of the housing has broken down in the intervening 30 years. So, a jig utilizing a board and non-flexible rods through the outer screw holes must be employed to prevent damage during disassembly and reassembly.

This is hard learned knowledge from today. When attempting to determine the cause of a severe mismatch in tweeter levels and roll-off between my two Quantum 2s, I discovered that the rear EMIT (4x4 slot arrangement vs. 2x8 of the front EMITs) was measuring nearly 50Ω. I had repaired one 2x8 EMIT a few weeks back using Kencat's idea when he first mentioned it without difficulty aside from a pinched finger tip. However, the rear EMIT's square shape prevents any torsional control compared the other's rectangular shape. The bad glue made this a destructive effect rather than just an inconvenience. The magnets repelled/attracted each other with a couple dozen lbs of force (in a very small area) causing 3 of the 5 magnet strips on the front plate sans glue to slide and roll when the plates snapped together with great force. The result is that two snapped into at least three pieces and the diaphragm was torn in a couple of places. Thanks to the nature of magnets what was once one magnet is now several making for realignment and regluing quite difficult, but hopefully the performance should still be relatively close to normal. I'll deal with this issue later, but I needed to share this warning.

- JP
 
Negotiableterms said:
Great thread!

What does everyone think of a subforum called: "Repair and Parts"? If there's enough interest, Scott or I can ask the admins to clutter up the server just a little bit more...

Do you mean a subforum under the Infinity Speakers Forum? (maybe a silly question but just making sure :D )

Would a sticky do the same thing?
 
For now I think we'll just sticky this thread.

At some point in the future we probably will look at a sub-forum for repairs and parts or some such.

Also we don't want to have too many stickies either, because it looks cluttered.

But this is a common problem for older Infinity speakers and I think very valuable information.

One thing I forgot to mention about repairing the emits that Jim told me he did to keep from breaking the magnet was he would use a longer set of screws to hold them in place. Does that make sense JP? I have yet to experiment with any.
 
Charivari said:
Of course, the diaphragm alone measures as a dead short (the interaction within the magnetic field creates the impedance), JP

JP, please explain "dead short". :confused: I measure 5.6 Ohms DC on the diaphragms with the meter. In fact, are these tweets actually not a pure resistive load to the amp (or at least primarily one) vs a reactive load?


Charivari said:
Something very important to remember when attempting Kencat's described repair on assembled EMITs is that the rare Earth element Samarium-Cobalt magnets are very strong and very fragile. Where this information becomes important is with the recognition that the glue holding the magnets to their respective halves of the housing has broken down in the intervening 30 years. So, a jig utilizing a board and non-flexible rods through the outer screw holes must be employed to prevent damage during disassembly and reassembly.

This is hard learned knowledge from today. When attempting to determine the cause of a severe mismatch in tweeter levels and roll-off between my two Quantum 2s, I discovered that the rear EMIT (4x4 slot arrangement vs. 2x8 of the front EMITs) was measuring nearly 50Ω. I had repaired one 2x8 EMIT a few weeks back using Kencat's idea when he first mentioned it without difficulty aside from a pinched finger tip. However, the rear EMIT's square shape prevents any torsional control compared the other's rectangular shape. The bad glue made this a destructive effect rather than just an inconvenience. The magnets repelled/attracted each other with a couple dozen lbs of force (in a very small area) causing 3 of the 5 magnet strips on the front plate sans glue to slide and roll when the plates snapped together with great force. The result is that two snapped into at least three pieces and the diaphragm was torn in a couple of places. Thanks to the nature of magnets what was once one magnet is now several making for realignment and regluing quite difficult, but hopefully the performance should still be relatively close to normal. I'll deal with this issue later, but I needed to share this warning.

- JP

This is a very good topic to mention JP. When I took mine apart I was dumb lucky in that I had a good grip on things and after the last screw came out I let the two halves come apart quickly and in-line with the magnets.

It is important for anyone attempting to disassemble these Emits to understand that the magnets in each half are opposite each other and the forces repel. As you are loosening the screws, the two halves try to open up. The magnets must be kept lined up to maintain the repulsion as they separate.

I also found out the hard way when assembling mine with the new diaphragm. As I brought the two pieces together, they twisted and shifted such that the repulsive force became attractive, and they snapped together like a 10 lb. clam on steroids. I wish I had a picture of what the look on my face was....I'm sure it was pretty funny. I think I sat there staring at this for 5 minutes wondering what the hell happened and pulling on it wondering how the hell I was going to get it apart. That attractive force is VERY powerful as JP alluded to.

They did finally come apart with some real hard tugging and the diaphragm survived (could easily have been destroyed though). To re-assemble the second time, I built everything up from the front face with the screws in place to act as alignment pegs, and brought the back half into place onto the screws.

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As JP has said, planning this before-hand is wise. If I were to do it again I think I'ld make up a jig to keep the two halves lined up. An arrangement of dowels in a board would probably do, with the dowels fitted closely to the sides of each half.

EDIT - Didn't see your post Army, while I was putting mine together. The longer screw idea is good, but you have to get the originals apart 1st, which is probably less risky than trying to put them together.

At least understanding the problem will allow others to come up with creative solutions :thmbsp:
 

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Here's a bunch more pictures of the Emit in pieces, that might be helpful for anyone going into a repair. This is the Quantum 2 Front Emit tweeter.
 

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Kencat said:
JP, please explain "dead short". :confused: I measure 5.6 Ohms DC on the diaphragms with the meter. In fact, are these tweets actually not a pure resistive load to the amp (or at least primarily one) vs a reactive load?
I was tired and frustrated when I wrote my warning, having just again unsuccessfully attempted repairing that particular EMIT. Like a dingus, I had inadvertently shorted the terminals where I had placed the diaphragm. Yes, on its own, the trace does measure 5.6Ω on the ol' Simpson (and something really weird on my trippy Triplett).

Army, thanks for the suggestion, it should make for nearly as easy repair as a jig would. Should've thought of it before attempting another repair, but such is the nature of experience. To clarify, there are six screws that hold the EMIT halves together. By pulling the four corner screws, leaving the middle two in place, and replace with longer screws, alignment should be maintained while adding a guide. The only issue I can see here is that the threads will likely catch on the front half and thus make it difficult to press the halves together smoothly and evenly. Also, the EMIT will not be attached to a firm base as it would with a jig and so make it a bit more difficult screwing in the center two screws one-handed.

- JP
 
I have had the tweets on my QAs apart a few times now. One time they did slide over and WHAM together:( What seems to work for me now is that I place everything back in order and have the 4 screws placed in the front piece. I find that I can hold the back magnet in place over the front magnet and lower the back end, the end opposite the connectors, down on the 2 screws and then pick up the tweet and get the 2 screws started so that they "take hold" of the back magnet. Once that is done, they are "locked" in place and it is a snap to start the other 2 screws. Then tighten them up...

I take 'em apart in the opposite order... Loosen the screws so that they are ALMOST out and then take out the 2 screw at the top. The magnets push apart and HINGE at the back 2 screws. Hold the tweet tight and take the last 2 screws out and no WHAMMING...
 
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Nice. Just getting back into town from a business trip I was hoping that there would be a great thread started for me to read during a coffee and HERE IT IS.
Many thanks,
Vito
 
OK...

Hit the tweet first thing when I got to work... Was reading 29.......

NOW READING 3.2 :banana: :banana: :banana: :banana:

I did not get the iron so hot as to melt the solder with one touch... The iron was hot enough to take the dark oxidization from the solder contact and soften it up... That seemed to do the trick.... For me at least....

Your mileage may vary...

:banana: :banana: :banana: :banana: :banana: :banana:

Listening to Kaki King now...... :banana: :banana: :banana:
 
OMI said:
OK...

Hit the tweet first thing when I got to work... Was reading 29.......

NOW READING 3.2 :banana: :banana: :banana: :banana:

I did not get the iron so hot as to melt the solder with one touch... The iron was hot enough to take the dark oxidization from the solder contact and soften it up... That seemed to do the trick.... For me at least....

Your mileage may vary...

:banana: :banana: :banana: :banana: :banana: :banana:

Listening to Kaki King now...... :banana: :banana: :banana:

Omi,

Do you notice a difference in the sound?
 
There seemed to be an improvement. I had a new soldering station, and one bud at work said I needed to tin the end to get it to do a better job of transferring heat and melting the old solder. As it was, it would burn wood (turn it brown where I touched a small piece of wood), but it did not get the 2 solder points flowing. I guess that was a good thing, as it appeared to get the solder soft, but it did not get the solder to “flow”. I did not want to push my luck and burn the Mylar base material...

I used a small piece of veneer (1/2 by 3/4 inch) as a base on the back side of the mylar (let the back side of the 2 solder points rest on the veneer), as I heated up the "front" side of the 2 points.

Will give it a week or so and will re-measure....
 
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may i have your advice

i do have problem in my Qe speaker emit tweeter ,
imposible to replace other type of tweeter like horm type? or other type ? i not known much in this,if can replace what is the watt ? i have see the repair guide ,thanks and useful but mine is beyond the repair . i need buy new diaphragm so expensive .but i like to keep this my old buddy too long with me , please help me to save .

thanks all of u.....
 
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