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Shure KSM313 ribbon mic

Issue #27

There are probably more myths and misconceptions about ribbon mics than just about any other piece of studio kit. They have come a bit of a full-circle over the past few decades, from being just another piece of kit in the studio with a job to do, to being dull, old-fashioned and unwanted, and on to being the latest magic bullet in the quest for fine, smooth recordings of “scratchy” instruments like strings, brass and guitars.

Let’s start with what a ribbon mic actually is. Microphones are transducers that convert sounds into signals. Some types of microphone have a charged capsule that changes its electrical capacitance when it is deformed by moving air (Condenser mics), some have a diaphragm with a conducting coil attached, which is moved in a magnetic field by moving air (Moving Coil/Dynamic mics), and some have a ribbon of a conductor suspended in a magnetic field, and, yes, that ribbon is moved by air pressing against it (Ribbon mics). Ribbons are actually a type of Dynamic but in common usage we tend to treat them as a separate group.

Those Myths

Ribbon Mics are very delicate - the ribbon is made of a very thin piece of conductive material. Physical shocks and even blasts of air can stretch or break it, and in some cases even storing a microphone on its side has reportedly stretched ribbons. This doesn’t mean that the mics can’t be used on loud sources; even loud sounds above the “thump” frequencies tend to have relatively little energy, and modern alloys can be used to make ribbons that are far more robust than those of “vintage” mics. You still wouldn’t want to blow into one though, or drop one off a mic stand - and I’d personally be a bit nervy about putting one in front of a kick drum or in front of a vocalist with a tendency towards explosive B and P sounds without a good pop-filter.

Ribbon mics are dark sounding - typical ribbon mics do have less top-end than capacitor mics, smoother top-ends than most moving-coil mics, and pronounced proximity effect, but this one could be a bit of a self-fulfilling myth. Because people think that ribbon mikes are supposed to sound dark they seek out dark sounding mics, so manufacturers entering the market make dark sounding mics, so the majority of ribbon mics are dark-sounding! Not all though.

Ribbon mics have a figure-8 pickup pattern – yup, I don’t think I’ve ever seen a “regular” ribbon that doesn’t, so it’s worthwhile to think about what the back of the mic is pointing at, and consider some sort of acoustic shield if you want to reduce its pick-up. The sides of a fig-8 mic are usually pretty insensitive so try to point these towards noise you DON’T want!

Ribbon mics sound great – they tend to have very simple electronics and physical mechanisms, and unavoidable mechanical resonances are usually out of the frequency range that we’re hearing. This means that they usually sound smooth in the top-end, and this is what tends to appeal to us. They also have good off-axis responses, so reflected sound hitting them tends to sound good too.

Ribbon mics explode if you apply Phantom Power to them - nope – though you CAN destroy one with a faulty power supply or lead - if you don’t want to risk permanently magnetising your mic or snapping the ribbon then avoid phantom power unless you’re confident that you know what you’re doing (the BBC must be amongst the heaviest users of ribbon mics and they allow hot-plugging - but then it’s not YOUR mic they’re doing it to). Of course, some modern ribbon mics require phantom power anyway..... .

Ribbon mics have very low output - many do, some have built-in gain stages and use phantom-power. Modern magnet and ribbon materials make a big difference to output levels. Check the specs.

So, how does the catchily named Shure KSM313 stand-up to the myths? Well, its ribbon is made of a material called Roswellite, and no - I have no idea what it is, but it’s supposed to be tough and strong and have great resistance to stretching and tearing. I still wouldn’t be tempted to use one as a hammer, but it has a quoted SPL limit of 146 dB, and the manual says that you can use it on kick drums and bass cabs! Relatively unusually, the front and back of the mic have different sounds, warmer/darker on the front and brighter with more presence to the back. Output is a bit hotter than an SM57!

The satin black, machined steel body is compact (around 5” long) with a “LOOK AT ME” bright red grill. There are no selector switches, so just choose which side of the mic you want to use (badge on the “front”), and where you want to put it. The mount holds the mic rigidly parallel to the stand (more or less - the demo version was a bit off-true when it reached me) so you’ll want to use a good, adjustable stand to get your positioning right; then plug it in, set your levels and go!

I used it on electric and acoustic guitar, spoken and sung vocal and as a room mic. I preferred electric guitars into the front (darker) side of the mic, which is closer to what I think of as being the ”classic ribbon” sound;  vocals, acoustic guitar and room worked well with the brighter (back) side. In all cases the sound was smooth and very classy.

The KSM313 is quite a long way from being a budget microphone. When you choose gear of this class you are making a fairly serious commitment, and it’s typically a very subjective choice. I can’t tell you that the 313 will be right for what YOU want to hear, but I can certainly tell you that it is a first class mic, and with the different front/rear sound character it’s almost a first-class pair of mics. Only you can decide of the sound is right for you, but in any case this is a lovely sounding and very well made and versatile microphone.

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