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Which give the noisier recordings: ribbons or moving-coil mics?

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Which give the noisier recordings: ribbons or moving-coil mics?

Postby Mike Senior » Wed Feb 26, 2014 6:40 am

I realise that neither of these types of mics have self-noise as such, but I'm intrigued about people's impressions about whether either of these designs end up producing noisier recordings than the other practice. I've always had the impression that moving-coil mics gave noisier recordings on the whole, assuming the same preamp (and gain settings that produce the same recorded signal level), but it might just be my misconception as I've not really done any wide-ranging practical comparisons. I wondered, for instance, whether the moving-coil design itself might be more susceptible to electromagnetic interference than the ribbon design, but I'm just speculating...
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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby James Perrett » Wed Feb 26, 2014 10:22 am

I'm sure that Hugh will be along shortly with all the technical detail but I just theought I'd mention that they actually will have a small amount of noise due to both the thermal effects of air molecules bumping into the diaphragm and also the random movement of electrons in the wire but this noise will be swamped by the noise of the preamp. If you are worried about this thermal noise it helps to have a lower electrical resistance so the ribbon mic would probably win out here - but I doubt that you would be using standard mics in this situation.

Moving coil mics can be susceptible to electromagnetic interference but some designs use hum-bucking coils to cancel out this interference.
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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby The Red Bladder » Wed Feb 26, 2014 10:36 am

They both have the same output levels. If you scream into an SM58, you will get about 25mV of AC. If you scream into a ribbon, you will get about 25mV of AC (after the transformer of course!)

The real difference is in the way people use the two types of mic.
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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby Hugh Robjohns » Wed Feb 26, 2014 2:22 pm

Mike Senior wrote:I realise that neither of these types of mics have self-noise as such...


Everything has some level of 'self noise'. In this case its just the random Johnson or thermal noise of the electrons in the coil and transformer windings. However, moving coil mics will have a higher winding resistance than a ribbon's output transformer, and thus a higher Johnson noise contribution. In reality, though the Johnson noise contribution from either will still be extremely small, and typically negligible in comparison with the noise contribution of the active preamp.

Historically, ribbons typically gave a much lower output than moving coil mics, and thus more gain would be required for the ribbon. That would tend to make them appear noisier overall...

But modern ribbons typically produce as much output as most dynamic mics these days (probably because high-gain preamps are rather rare), and so would require similar preamp gains. That being the case, maybe the fractionally higher self-noise of a moving coil mic might just be perceived as the noisier source compared to a ribbon on the same situation.

But the difference will be very, very small.

I wondered, for instance, whether the moving-coil design itself might be more susceptible to electromagnetic interference than the ribbon design, but I'm just speculating...


Yes -- there will be hundreds of turns in the dynamic mic's voice coil, whereas the ribbon is a single turn. More turns means more EM pickup and more potential interference -- and that's why some moving coil mics have an extra humbucker coil as James mentioned.

This assumes that the output transformer in a ribbon mic (and sometimes in moving coil mics, too) is well shielded, of course.

However, that interference would normally manifest as hums and buzzes, not broadband noise.

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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby Mike Senior » Sat Mar 01, 2014 12:26 am

Fantastic -- thanks for the input everyone! Learn new things every day...
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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby ef37a » Sun Mar 02, 2014 9:41 am

SoS did a survey of microphones a year or so ago and I was surprised to find that most of the ribbons listed had about the same sensitivity as dynamics (taking the SM57/58 as a reference).

I queried this with Hugh as I had been "brought up" to think of ribbons as feeble things for output?

He explained that many ribbons now do have a decent sensitivity but are usually used at a much greater distance from the source and therefore needing more gain.

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Re: Which give the noisier recordings: ribbons or moving-coil mics?

Postby Hugh Robjohns » Sun Mar 02, 2014 12:25 pm

ef37a wrote:SoS did a survey of microphones a year or so ago and I was surprised to find that most of the ribbons listed had about the same sensitivity as dynamics (taking the SM57/58 as a reference).


Yep. Tiz true. Partly because of the availability of far better and stronger permanent magnets, partly because of the greater use of internal active buffers, and partly the practical need to match need to match the relatively limited maximum gain on offer from the majority of budget preamps. 60dB is about all you get these days, rather than the 75 or 80dB that was commonplace fifty years ago.

I queried this with Hugh as I had been "brought up" to think of ribbons as feeble things for output?


Well they were... the classic STC4038 is only 0.5mV/Pa!

He explained that many ribbons now do have a decent sensitivity but are usually used at a much greater distance from the source and therefore needing more gain.


In general that's true. Most ribbons have to be used at a sensible distance to keep the proximity effect in check. But increasingly, some modern ribbons are being balanced for close-up use, particularly for applications with guitar cabinets etc.

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