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Tips, tricks and fun for the recording musician

The Audio Blog is a set of thoughts, techniques, knowledge bits and the occasional rant about the wonderful world of audio and music recording. Follow me on the path to great sounding music, never a boring moment!

What's so special with the SM7B?

Just the other day, chatting with a friend on a video meet (pandemic-style), he came up saying that the Shure SM 7B is a great mic for recording vocals in not-acustically treated (aka "bad") rooms.


Immediately some of the other good fellas nodded in agreement... but one came up saying "bull***t, I've tried it and was a nightmare".

That conversation made me realize that the myth of the SM7B as "the vocal microphone to use in bad rooms" is quite widespread... I've actually heard it many times over the years,


And I also heard of quite a few people who got disappointed with it. Why?


Well, the reason is, as it often happens, a misunderstanding on what's going on. Fact first: it's true that the Shure is a good microphone for vocals in "bad rooms". But only if you use it right. So let's have a look on why it's good, and what it means using it right.


Let's say you have a bad room.


No acoustic treatment, not even a carpet on the wall or the equally hopeless cartoon eggs; it's noisy, square, very reflective walls, the works.. and for some reason you can't hang broadband absorbers or bass traps in the right places.


Now: the definition of a bad room is a room where a signal and its reflections hit the microphone capsule within a very short time, causing comb filtering at least for certain frequencies. This kills the sound and makes it sound ugly and much worse than it should. EQ doesn't help because the information has been destroyed on recording, so there's nothing to equalize.


How do you go about recording something at least half-decent in a room like that?


Well, there's four things that can help you:


1) sing as near to the capsule as possible

2) use a microphone with an internal pop filter and low "popping"

3) use a microphone with as large a frequency response as possible, to capture all that there's to capture of the performance (just like you can do in a nice-sounding studio space).

4) use a microphone with as much rejection as possible (i.e. a narrow cardioid pattern) at high frequencies


Why? Let's have a look at each.


For 1): if a singer uses a normal side-address microphone (say an U87 or a AT2020) there will be some space between his/her mouth and the capsule. Probably there will be a pop filter in between. That means that a certain amount of direct signal will hit the capsule, and a certain amount of reflections (aka "noise") will hit it as well.


The more direct signal, the less the noise will matter or be audible. In other words, in a bad room the S/N ratio (Signal/Noise) should be as high as possible.


Given that the room is what is its, how can you increase the signal with respect to then noise?


Easy!


By singing as near as possible to the capsule!


And, which microphones are made so that you can (or must) sing with your lips touching or almost touching the grille, while retaining an optimal bass response?


Well, stage dynamic vocals mics of course!... for example a SM58.


Or a SM7B.


For 2): stage mics such as the 58 are also good at avoiding popping, thanks to their built-in pop filters and ad-hoc grilles and whatnot. They have to be, since a pop filter doesn't look great on stage. You can breathe directly on a SM 58 and it will be nonplussed.


Which other microphone has a similar behavior?


The SM7B.


For 3): most microphones which benefit from 1) and 2), like the 58, have a limited frequency response, rolling off highs fast and hard much earlier than the 20 KHz of a typical studio condenser mic. Ideally we'd want to have a dynamic microphone which does 1) and 2) but also has a full 20 Hz-20 KHz response.


Which microphone has such a response? No prize for guessing...


The SM7B.


For 4): many dynamic mics for live use are supercardiod - i.e. they are meant to reject more of the loud people who are playing on stage just behind the singer (who keeps the mic in his/her hands so firmly in position with respect to the mouth).


Supercardioid microphones, however, have a "back lobe" - meaning they pick up some sound also from the back. On a live scene, that's not a big deal: the back of the microphone usually points to the audience - which can be noisy, but it's far and not remotely as noisy as the band on stage. But in a bad room, at the back of the microphone there's noise (reflections or a spinning washing machine, or both).


So you really want a cardioid pickup pattern - one which stays cardioid at pretty much all frequencies, and gets even narrower at higher frequencies (capturing even less reflections or washing machine sounds).


Guess which microphone has that type of pattern?


The SM7B.

So here you have it: the SM7B is one of the few microphones that can be worked very close without much popping, has the full frequency response of a studio mic and a stable cardioid pattern progressively narrowing with the frequency.

And it's not crazy expensive either.


Sure, its sensitivity is very low so you will need a Cloudlifter or a similar clean-gain device to get to use it with regular preamps, but it can be well worth it...


...even if it would be even more worth to use the money to treat your room and use whatever mic you have. Gotta say it!

Coming to back to the myth: if you go for a SM7B to record vocals in a bad room, remember that you will have to work it very close!


If you don't, and sing into a SM7B and a few inches or centimeters from it, you will see no benefit at all (and you'll still have to use a Cloudlifter).

Since we are at it, a few more things worth noticing:

  • It should be obvious by now that you won't see much gain from using a SM7B in a bad room with any source with which you can't use it close. For example, it works well attached to the grille of an electric guitar amp, but it won't do you much good than a regular condenser mic if use to record an acoustic guitar, because you can't mic an acoustic guitar sufficiently close. It's still a very good sounding mic in its own right, so well worth using for its sound alone, but in these conditions it won't particularly help you with reflections or noise.

  • It's still true that the bigger and/or least reflective the room, the better it is. If you can choose, don't pick your tiled bathroom: even a 7B will struggle there! But worked close, the 7B can make a normal living room sound half decent. Just half - but the rest is, as always, the performance.

  • The SM7B has a full frequency response, but it still may be perceived as a little darker than your average condenser - depending on your ears and likings. The trick here is that you can (moderately) brighten things up a little with a high shelf boost, without being too much afraid of bringing up the noise. That's because - since you have worked the mic very close when recording - you had a very high S/N ratio... so that the boost should bring up almost exclusively the direct signal - i.e. your vocals - and not the noise.


So now you know why, when and especially how to use a SM7B.


Enjoy your recordings!

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