Red Dog Music | Oct 9, 2018 | 0
Recording microphone buyer’s guide
Recording microphones come in a huge range of different shapes and sizes, and choosing the right one for a particular project can seem like a difficult process, with loads of jargon and weird, confusing diagrams. However, microphones are actually very simple beasts and, aside from trying them out, it is relatively easy to work out what type of mic will be best for you. In this article we cover the different types of microphone available, how to make sense of “polar patterns”, the meaning and usefulness of frequency response graphs, and finally the differences between large and small diaphragm mics, and what the “pad” and “bass roll-off” switches do.
By the end of the article, you should hopefully realise that what seems like a minefield is actually pretty easy to understand, and you’ll be in a good position to buy a recording microphone without being blinded by science. Bear in mind, though, that there is nothing quite like actually hearing the difference between different mics to get an idea of what will suit your particular application.
Firstly, we’ll look at the different types of microphone out there…
Recording microphone types
Dynamic mics work by means of physical moving parts: basically a very thin diaphragm moves back and forth as a result of the pressure of the sound waves, and this movement is turned into electrical signals that represent the sound. For this reason, they are less sensitive than most other mics, meaning they are not so good at capturing subtle sounds or complex rhythmic patterns. However, they can be great for use with loud sound sources such as guitar amps and snare drums, and generally take a lot more punishment than more sophisticated mics.
Condenser mics are designed to offer far more detail and fidelity to the source than dynamic mics. Think of it like having a computer screen with far higher resolution: the sonic edges are sharper and if you listen closely you can hear a lot more detail in the sound (e.g. the subtle harmonic overtones of a good quality acoustic guitar). Because of the way they are designed, condenser mics need some sort of power source to work. Occasionally they take batteries, but more often they will be powered through the cable from a mixing desk or audio interface by means of something called “phantom power”.
Strictly speaking, valve microphones are just a subset of condenser mics: they are broadly designed in the same way but have a built-in valve to boost the signal level. This adds a certain type of “warmth” which is considered pleasing to the ear and sounds more “vintage” than standard transistor-based condenser mics (mainly because old records were generally recorded with valve mics because that was all that was around in those days!).
Ribbon mics have a fundamentally different internal design to condenser or dynamic mics but, in terms of quality, are up there with the best condensers. Although arguably they do not offer as precise detail as condenser mics and they can sound duller, they have a distinctive “sound” that is pleasing to most ears. To return to a visual analogy, they add a kind of Instagram- photo-like sheen to a recording – not picture-perfect but brimming with warmth and musicality.
Bass mics are specifically designed for recording sound sources with predominantly low-end frequencies – for example, kick drums or bass amps. As such, they are pretty limited in their applications. You probably wouldn’t want to record a flute with one as most of the important frequencies would be lost (though, as ever, it’s worth a try, as you might get an interesting sound!).
A relatively new addition, a USB microphone is basically a traditional mic (as per above) but with added circuitry: a built-in pre-amp to amplify the signal, and an analogue to digital converter to turn that signal into the sort of information that your computer can understand. Generally a feature of lower end mics, the added USB functionality is more a convenience than anything else (as it means you can plug your mic directly into your computer without needing a separate audio interface).
Microphone polar patterns explained
Aside from the basic design of a microphone, one other important factor is the “polar pattern”. This basically describes which parts of its surroundings a mic records: just what’s directly in front of it, what’s all around it, what’s in front of and behind it, or any combination of the above.
The different polar patterns are traditionally broken down as follows:
Cardioid mics (or mics set to “cardioid”) are designed to pick up mainly what is directly in front of them, and reject any sounds coming from behind them or from the sides. The fact they only pick up a relatively small area makes cardioid mics particularly good in situations where several things are being recorded at once but separately (e.g. recording a drum kit). This also means that they don’t pick up a lot of “room” sound and ambient noise, which is desirable in most situations. Cardioid mics are by far the most prevalent for these reasons.
Supercardioid & Hypercardioid
Supercardioid mics are even more directional than cardioid mics, meaning they pick up less of the sounds coming from the side; hypercardioid mics are even more so. As a trade-off for their very focused nature, though, they can tend to pick up small amounts of cound from behind them (see diagram), making placement tricky.
Quite the opposite of hypercardioid, omnidirectional mics are designed to pick up sound equally from all directions. For this reason they are generally used for picking up room sounds and general ambiences, rather than individual instruments or sound sources.
Figure-of-8 (also known as “bi-directional”)
Figure-of-8 microphones pick up sounds equally from directly in front of them and directly behind them, but reject sounds from the sides. They are generally used for recording two vocalists simultaneously, or for recording e.g. an acoustic guitar on the front of the mic while capturing the room ambience with the back.
Multi-pattern microphones are not tied to any one polar pattern but offer a switch to change between the polar patterns listed above. This obviously makes them extremely versatile – switch to omni-directional if you want to capture the ambience of the room, to cardioid for a tight, focussed recording, or to figure-of-8 for recording a pair of vocalists. Basically, you get the best of all worlds!
Understanding mic frequency response charts
Often on manufacturer’s websites and in microphone manuals, you’ll see a diagram like this:
Although this may give you terrible flashbacks to GCSE maths, these images can in fact be very useful in helping you decide which mic will be most appropriate for a given recording task. If you are familiar with graphic EQs, the graph basically shows the effect of the mic on the different frequencies of whatever you’re recording. For example, in the chart above (using the dotted line which means bass roll-off is engaged), the mic doesn’t record at full volume until about 100Hz (around the bottom E of a guitar), records a bit louder at around 500Hz, and has a “peak” (i.e. records louder) at around 10kHz (above the range of most instruments but in the region where a lot of the harmonics can be heard).
Small versus large diaphragm microphones
Another basic difference between mics is whether they are large diaphragm or small diaphragm. The diaphragm is the bit of the mic that wobbles in response to the sound you’re recording. Although most people’s first microphone will have a large diaphragm (as they can record a wider range of sounds), it is always worth having a small diaphragm mic in your collection. The broad differences are as follows:
Large diaphragm mics
You can use a large diaphragm mic to record pretty much any sound source: vocals, guitars, percussion etc. They can generally reach quite low in terms of frequencies and offer a flattering sound. As large diaphragms are more prevalent on commercially available mics, they are also more likely to have features such as multiple polar patterns and a pad switch.
Small diaphragm mics
Generally less popular than large diaphragm mics because they’re less versatile (and maybe because they’re generally smaller!), small diaphragms should nevertheless not be overlooked. Because of their smaller, lighter-mass diaphragms, they offer a more detailed recording on sounds with high frequencies, sharp transients, and extended harmonic overtones such as acoustic guitar, cymbals, harp and more.
What are microphone “pad” and “bass roll-off” switches for?
One last couple of things you need to know about are a pair of functions available on quite a few recording microphones: the pad switch and the bass roll-off switch.
All the pad switch does is lower the output of the mic by a specified amount (generally either -10dB or -20dB). You would use this in instances where your source is particularly loud (e.g. a guitar amp) and you don’t want to overdrive the input of your mixer.
The bass roll-off switch, on the other hand, just lowers the volume of a pre-defined frequency range, generally under about 100Hz. This is useful if you are mainly recording in higher frequencies and don’t want to unnecessarily record e.g. the rumble from a mic stand moving around, or the thump from a vocalist tapping his or her foot.
Hopefully this article should have gone over any questions and issues you may have when looking to buy a recording microphone. The only other things to think about are what’s included with the mic – a shock-mount is a must with a large diaphragm mic, and it is worth investing in a pop shield.
If you have any questions, anything to add, or if you see any inaccuracies in the article, please do not hesitate to comment below. Happy hunting!