Tim, the SM57 and the SM58 have been the two best selling microphones in the world for more than 40 years now.  What has made these two microphones so popular for so long?

I think it’s a combination of several things.  The first would have to be the sound quality for vocals and instrument applications.  The sound quality is excellent.  The industry has kind of revolved around the sound quality at this point. 

Well, let’s dive into that a little deeper.  When we talk about sound quality, there are a number of different aspects to microphone design that contribute to sound quality.  One of them is frequency response.  What is it about the frequency response of the 57 and 58 that are particularly significant? 

The 58 is a vocal microphone and it has a frequency range that is appropriate for the voice. It rolls off below 100 Hz or so, so you don’t get a lot of low-end rumble in the microphone. And it rolls off a little bit above 15 or 16 kHz so you don’t have to worry about high-frequency stuff outside the range of the voice.  

Within that range, the mic is relatively flat and has an accurate response except for a rising response between about 3kHz and 10kHz – a presence rise which goes a long way toward improving intelligibility of the human voice particularly in the presence of a lot of amplified instruments and other competing sound sources in a live music application. That’s what gives the mics that clarity and ‘punch’ that lets ‘em cut through the mix. Most sound engineers find that they don’t have to EQ them as much.  

OK, what about pickup pattern?  That’s another aspect of mic performance that contributes to sound quality, indirectly in some ways.   The SM57 and SM58 are both cardioid pattern microphones, which is one of the most popular directional types.   Tell us about the polar pattern for each of these and how it affects the sound of the microphone.

The directional characteristic of these microphones is the classic cardioid pattern.  And one of the things that sets these apart from other cardioid types is that these have a very uniform directional characteristic throughout their frequency response.  The directional characteristics of low frequencies and high frequencies are pretty similar.   Because they’re smooth across that range, they’ve very good at rejecting feedback from nearby monitors and speakers.  

The directional uniformity not only gives great control in terms of feedback, pickup and ambient noise but it allows the performer to work the microphone a little bit off-axis without changing the quality of his or her voice.   In other words, all cardioids are not the same.  Just because three microphones in the store all have a cardioid pattern doesn’t mean that they’re going to sound the same and behave the same way on-axis and off-axis. 

Another aspect of microphone design that a lot of people overlook until it’s really too late is the issue of the shock mount.  What’s the purpose of the shock mount? How does it contribute to the sound of the microphone? 

Directional microphones have mechanical sensitivity to impact noises and rubbing and so forth on the case of the microphone. If the microphone is going to be used handheld or on a stand on a stage where there’s a lot of vibration, you need to have some mechanical isolation built into the microphone to prevent the thumping and bumping noise from being picked up by the microphone.  

Although mics may be similar in their sound quality and even their polar pattern, if you’re going to use the thing in a live application, the performance of the shock mount in isolating the mechanical noise is very apparent as soon as you pick up the mic or hold it. Handling noise is one of the things that you really need to pay attention to when you’re evaluating a microphone. 

You can hear Tim and Chris perform a handling noise test by listening to the Shure Cast “SM57 & SM58: Inside the Legends”. 

If you’re going to spend $100 or more on a microphone, one of the big questions is “how long is it going to last?”  The durability of the 57 and 58 is legendary – so the question is – why do they hold up so well?

Durability – or in this case – survivability of these microphones in live applications is the result of great design and high quality parts and a consistent assembly technique that’s been refined over forty years. These microphones go through a lot of testing in the design phase and conditional testing throughout their manufacturing life to make sure that those standards are being kept.  It’s probably worth pointing out that Shure adopted mil-spec (military specification) testing procedures during WWII when it was a major supplier to the government of microphones for the military.  The company has maintained those standards since then and even applies it to our studio microphones today.  

Shure microphones have always had tremendous survivability under very difficult conditions.  

We have lots of examples of microphones in our archives that are damaged almost to the point where you can’t recognize them as microphones.   And they still work. They’ve been through floods, they’ve baked at high temperatures and frozen at low temperatures, been run over by trucks and forklifts  … all manner of things.  They can survive just about anything. 

Another aspect of performance is consistency and since these mics have been around for so many years now, people are really used to working with them.   How does consistency come into play with the manufacturing of a SM57 or an SM58?

Over the course of 40 years, we’ve made improvements in the materials or in the assembly process but since the basic design hasn’t changed, the inherent reliability from the first models carries through to the ones that are manufactured today.   We have microphones we keep as shelf aging units and some are more than 20 or 30 years old.  New production models are compared to them in terms of frequency response and polar pattern and there has been very little change – just a decibel or so – in all that time.  In the field, it translates into a high degree of predictability and familiarity on the part of engineers.  Anybody who has worked in a live sound environment, under the time constraints and pressures and the unknown factors of weather and venues and so forth appreciates a product that continues to be exactly the same night after night, city after city, year after year.  

That brings up another question that comes up all the time.  What’s the real difference between an SM57 and an SM58?  There are actually a fair number of myths and misconceptions about what the difference really is. 

The basic difference is the grille. The other parts -- the diaphragm and voice coil combination, the magnet, the transformer that’s in the handle, the handle itself, the closing ring that surrounds the cartridge – are identical.    

In the SM58, the ball grille with the foam lining provides an extra degree of pop protection and wind protection.  The SM57 has a much more compact grille arrangement that doesn’t provide nearly as much protection against blast or wind.   But the basic frequency response and polar patterns are almost identical – there is only a slight difference in high frequencies where the shape of the grille starts to affect the response.  But that probably doesn’t kick in until 13, 14 or 15 kHz – something like that. 

What’s the advantage of the SM57 in having a smaller head design? 

The SM57 is often used as a drum mic - on snare drums or tom toms for instance - or an instrument mic for guitar amps.  Particularly around drum kits, the smaller head of the 57 allows it to fit in among the drums and other hardware that make it difficult to get a larger mic in the right position.   The smaller size lends itself to getting it into the right place, where the SM58 might interfere.   

From a sound quality standpoint, you wouldn’t expect much of a difference, but you don’t need the blast filter capability of the 58 for instrument miking, since you don’t have blasts of air coming off the drum heads or the guitar amps.  It’s more of a size and compactness issue that gives it a nod in that application. 

Listen to Tim and Chris compare the SM57 and SM58 for blast filtering and wind noise here. 

The SM58 also provides a measure of pop protection and resists wind turbulence.  That makes it a better choice for close-up vocals. 

Check out the Shure Cast page for a growing list of downloadable podcasts covering a wide spectrum of microphone basics – directionality, frequency response, transducers, stereo miking techniques – along with artist interviews, White Spaces updates and other helpful pro audio discussions.