Crackling Ribbon Mic

I have a cheap Chinese ribbon mic which emits a faint but distinct crackling noise. The noise changes in response to the slightest movement of the mic, so I suspect something inside is microphonic, but it also occurs when the mic is stationary. I have done a shake test on the cable and that doesn't seem to be the problem. Visual inspection of the ribbon reveals no looseness or sagging, and there is clearance between the edges of the ribbon and the magnets. The clamps which hold the ribbon in place show no signs of looseness. The pickup wires appear to be firmly attached. No phantom power is being applied to the mic. It picks up audio just fine.

Thoughts?

Is the body grounding ok?

Otherwise, check for shorts to ground near the motor.

The body is grounded OK. Since my first post I've had a chance to try it on another mixer. The first was an ATI with no transformer coupling on the mic inputs. The second was a Shure M267 with transformer coupling on the mic inputs. On the ATI I hear crackling. On the Shure I don't hear crackling, but the VU meter goes crazy, which makes me wonder whether there is a subsonic component involved. When I engage the low-cut filter on the Shure, the VU meter deflection is reduced. Anyway, I'm starting to wonder whether the ribbon is a little slack and is causing this mic to be microphonic/sensitive to movement.

The mic is a Nady RSM-2 and I doubt very much QC was done to it on the assembly line. If I were to recommend a ribbon mic, I would recommend one where the ribbon has been properly tensioned, and with all of the extraneous silk and mesh already removed.

I'd inspect the insides very carefully. Make sure the ribbon does not rub the magnets ever.

[quote author="chris319"]If I were to recommend a ribbon mic, I would recommend one where the ribbon has been properly tensioned, and with all of the extraneous silk and mesh already removed.[/quote]

True, although be careful about removing "extraneous" silk and mesh - people on messageboards who don't really know what they are doing instantly assume that something "in the way" of the transducer is bad. Mesh and silk are required close to the motor in many ribbon mic designs to damp LF response.

Checked the ribbon for clearance and magnet rubbing, no problem found. Maybe it's the way the ribbon clamps are holding the ribbon?

Mesh and silk are required close to the motor in many ribbon mic designs to damp LF response.

Click to expand...

True. Tests with and without the rigid silk-covered metal plates show improved HF response with the plates left in. It appears to be the outer layers which muddy up the sound.

hmm maybe you should post an audio clip of the crackling.
From what your decribing, without hearing it, i'd have to also suspect the ribbon clamp connections.
if the ribbon is hitting the magnet , it won't be a subtle crackling.
crackling would more likely indicate a poor connection or oxidized connection.
Since you can pretty much assume the soldered connections are good the only "weak point" in the connections is the ribbon clamps.
you can try this:
take a wood or plastic tool ** cuz anything metal will just SUCK right to the magnet and possibly take the ribbon with it ..
Lay the mic down supported very well and use the tool to PRESS on the ribbon clamps. If you can hear the noise doing this, your clamps are the problem.
Unfortunatly that mean re-ribboning the mic because you can't un-install and re-install the same ribbon .. well maybe clarence kane or david royer can haha ..
Pressing on it just once may fix it .. but that may also be a temporary fix. I used to do this with my rca 74.
anyways .. good luck with that .. hope this info helps.
TS

I will try that, thanks.

With ribbon mics it appears that quality control justifies added expense.