Shure Unidyne III probhlem

Findlay

Member
I'm having problems with my 60's Unidyne III again. I get a big drop in bass response. The only way to cure this is to pull the black plastic top end around the capsule away from the body slightly. It then sounds great but after a few minutes slips back. I wonder if there is a loose connection? I've peeled off the silver label around plastic surrounding the capsule, expecting to see some screws but there are just brass pins.
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Hi Findlay,
Sounds like the diaphragm is getting obstructed intermittently,

Those brass pins are the ends of a circlip, holding the cap in place.
Push them in with something and the cap should come free.

From there, hopefully you'll see some loose debris that you can clean up.

If there's nothing obvious obstructing it from the outside then something's obstructing the coil and that's a lot harder to fix...if you'd even bother.
The fact that moving the black cap around solves the problem, even temporarily, suggests that either there's an obstruction in front of the diaphragm, or the diaphragm glue has given up and the whole thing is moving!

Anyway, get the cap off and see what's what.

You can safely test it with the cap removed. Just avoid badass plosives or use a pop filter.
 
Hey, I've got2 or 3 of those and I love them. Except for all the crappy foam that got stuck all over them from those old cases.
 
Thanks Steenamaroo. I've tried to push those brass pins in and can't seem to budge them. I've used a small screwdriver with as much force as I dare. Is there some sort of trick I'm missing? I dare not use a hammer to tap them out surely.....
 
It shouldn't take that much, no.
I have a unidyne III right here and it certainly has the circlip with brass pins, just like a 57.
I'm hesitant to suggest forcing them, though, incase there are variants I don't know about.

Try rotating the plastic cap and trying again. I'm not 100% but I think maybe there's a gap in that mostly-hidden silver mesh, or a weak point, that might help you out.
In your photo you can see the gap, just to the right of the hole? Try lining the hole up with that, maybe?
 
I have a 60s 545, which I think is basically the same mic except for copper vs aluminum, and i wanted to replace the foam. i wrote the guy who sold it to me, and he said the cap doesn't come off on those...

I looked around online to see if that's true but couldn't find much. Mine works fine but the foam looks a bit rotten in there. Great mic. I wish I could figure out how to open it. Steen, if you're youtube savvy and know how to open them, here's an opportunity to make a helpful/education video that would help many. The modern ones are easy to open and there are many videos for those, but not much on the 60s ones.
 
Just took another look at my III.
There are two holes, on opposite sides.
One has the two ends of the clip and the other just exposes a little notch (in the same clip) which is for lining everything up on reassembly.
The picture you've shown above looks to show the notch...Is there a hole on the other side?

If yours is the same as mine then pushing in the clip ends should let you take the plastic cap off at an angle - I didn't mention that earlier.
Also, it was a little tricky...I just removed mine to double check.. It took a bit of jiggling and poking.
I can also say that behind that circlip is solid metal so don't reach for the hammer or anything, but you should be safe enough putting reasonable pressure on there.

Also there are little recesses in the side of the capsule, at certain points, so the rotate/try again thing is a good idea.
There are points at which the clip ends just won't depress.


Hey Nola...Yeah, I could do a video if it helps. :)
 
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Hey Nola...Yeah, I could do a video if it helps. :)

That would be awesome. There is a video on youtube how to disassemble a 57, but it's a new 57.
https://www.youtube.com/watch?v=SpQR4cvUr_4

I couldn't find anything about the vintage ones. I will double check my mic again today, but I am 99% sure I tried to follow those exact instructions and the 545 doesn't have that ability. I don't know if something changed since the 1960s design or if the 545 is different than the 57 in terms of taking it apart. The guy I purchased it from said the cap doesn't come off when I asked about replacing the foam...so either he couldn't get it off either, or it's some design issue. I'd love to see you disassemble a vintage one if it's different from the video above. If not, I can take photos of mine and show what I mean.
 
I'm not sure what's up there, Nola. Maybe the 545 is just different from the rest?

My unidyne III is disassembled exactly as shown in that video.
 
Thanks Steenamaroo. Yes there is another hole on the other side and the clip looks just as you describe. Going to try again when I get home later tonight!
 
Hi Steenamaroo. I have just managed to get the top off using g your instructions. Thanks! Just a very small piece of fine cotton thread fell out. It seems to work fine with the head off. Anything I should check before putting it back? The diaphragm looks intact.
 
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That's great news.
No, not really. Just make sure there's no loose debris and check that the disc inside the cap has no loose material on it.

To save yourself a bit of trouble you can put the cap back on without the circlip and check how things sound.
I recommend holding the cap upside down (grill to the floor) and offering it up to the microphone, rather that trying to set the grill on the mic, grill facing ceiling,
because that little disc tends to fall out and could hit the diaphragm quite easily.
 
After testing again I've put the cap back on with the springclip and it is sounding great! Going to do some recording today to check it out for a longer time. Thanks so much for all your help Steenamaroo. This mic means a lot to me - it's been used for a number of albums and live gigs.
 
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