Shure Unidyne III problem

F

Findlay

Member
I have a '60's Shure Unidyne III I inherited from my brother. He did some pretty decent recordings with it and I had it working ok but recently it is sounding very shrill with hardly any bass response. I wonder if anyone has had a similar problem and knows how to fix it? I've tried it in both balanced and unbalanced mode and get the same effect. The output level is still decent, just no bass. Grateful for any help....
 
Hey,
I can't say for certain but usually with moving coil mics, heavy bass reduction means the coil is physically obstructed somehow.

If the glue has given around the diaphragm and allowed it to move sightly, that'd allow the coil to rub. Alternatively there could just be corrosion or some foreign/loose object in there.

If you give it a firm tap on the top side while it's on and hear any change in the output volume or tone, that would suggest movement in the diaphragm and coil.

That's just one angle, though. It could be something else.
 
The diaphragm could be jammed in, I have had this after a singer screamed into an sm58, put you mouth over the end of the mic and suck it gently (this is not a joke and no rude comments please, LOL) the diaphragm sometimes frees up.

Alan.
 
Thanks guys. I put my mouth over the end and sucked gently and it now sounds great! Plenty of bass - back to how it was. Thanks so much - this mic means quite a lot to me.
 
It's spit bound. Actually it's normally dust, and moisture, and then a big puff of wind makes it stick. Not that common, but you can do similar on a 57, although I wonder if there is some extra protection on them because my very old 57 has never done it, but I've seen newer ones put on the faulty shelf for this reason.
 
I have this picture in my mind's eye of everyone deep throating mics trying to eak out more tone.
 
Just wanted to thank you guys again for your help - the mic is still working beautifully.

Using it has made me wonder a few things. I'm plugging it into my old Tascam 244 and it sounds wonderful. Even with the gain trim at max there is hardly any hiss. Yest when I use it with my latest Tascam digital recorders - DP008, DP004 and DP01 it sounds terrible - the tone is ok (same as with the 244) but there is so much hiss it is unusable. The same when I plug in to my Soundcraft compact 30 and Tapco Blend 6 mixers. I get the same when using my old Marantz electret mic - whisper quiet with the 244 but dreadful hiss with the later gear. Is there any reason for this? Maybe an impedance thing or is the 244 pre-amp design just superior to the modern stuff? I;d be grateful for any thoughts. I'd love to use these mics with the other recorders!
 
Just wanted to add that I'm using the mics with balanced cable into the other recorders - the 244 is unbalanced.
 
Findlay said:
Just wanted to add that I'm using the mics with balanced cable into the other recorders - the 244 is unbalanced.
Click to expand...

A lot of the early shure Mics were low Z mics even though they were balanced, it could be that they are low Z and you have to turn the gain too high. The old portastudio is prober by designed around high Z

Alan
 
witzendoz said:
A lot of the early shure Mics were low Z mics even though they were balanced, it could be that they are low Z and you have to turn the gain too high. The old portastudio is prober by designed around high Z

Alan
Click to expand...

Almost all the early unidyne are dual/switchable from hi to lo z.

My guess is it's wired for hi-z. I'm not sure which mic you have, OP, but you can google the manual and find how to change the impedance. It doesn't require soldering.

I have an old 565sd and 545sd and like them both more than sm58 and sm57s. Good job keeping that mic and using it.
 
Well! The suck it and see repair technique is a new one on me!

Yes, the mic is surely wired for high Z. The source Z (calculated from the speccs) is around 47k so no wonder you lose signal going into a typical 1k5 balanced input!

Simplest solution. Wire it for low Z then buy an in line XLR to jack plug transformer.

Dave.
 
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