Microphones - a brief insight

Keith Scott FRPS DPAGB AV-AFIAP

Knowing that I’m a collector of such items a friend asked advice on buying a new microphone. His question to which there is no simple answer “what’s the best” mic? Without quantifying certain criteria there is no such thing as `the’ best mic. Different mics have different purposes and properties.

To ascertain the best mic for a specic purpose, we need to know the intended sound source, its proximity, location, and acoustic conditions. On a technical note we need to know into what equipment it is connecting to ascertain compatibility, and suitability. Leaving aside the technicalities of pre -amps and other audio recording equipment let’s consider the following different mic requirements:

Recording the buzz of a bee on a countryside ower, recording distant bleating of lambs on a fellside, a choir in a cathedral, rock singer on stage, a single musical instrument e.g. violin, guitar, or trumpet, high pitched singer, deep voiced orator, birds in trees, or actors on a location lmset. Perhaps the sound of machinery, trains, planes, cars, crowds, or other background noises. Each of these sound sources may have different mic requirements.

Before purchasing any mic, you need to answer the following: Does this mic need to be xed or portable? Does it require external power? Do I need a large or small condenser, or dynamic mic? Is it suitable for recording close or distant sounds? Which polar pattern do I need? Does the technical spec and price fall within my essential parameters?

In the world of AV it’s easy to think that a mic would primarily be used to record voiceovers, and this may be true, but would such voiceovers be recorded close up in a controlled acoustically treated studio, someone’s lounge, village hall, sports event, or will it be a remote mountainside whilst interviewing a goatherder?

No `one’ mic, not even the most expensive can properly full such varied requirements. Talk to any sound engineer and he/she will tell you that they have a mic armoury, a cupboard full of many different types, makes, and models to suit different recording situations, including subtleties of voice and different musical instruments.

Many AV workers already use portable digital recorders with in-built mics, either as their sole recorder or as secondary recorders for location work. These may prove more than adequate for some workers. However, for rened, convenience, or specialist purposes the ability to connect high-quality separate mics of diverse types can have distinct advantages.

Professional studio recorders and good quality eld recorders have 3 pin XLR (Extra Low Resistance) connectors to allow connection of professional quality mics. Recorders with such connectors will usually provide 48V phantom power capable of driving condenser mics of either large or small diaphragm type, or simply provide connection for dynamic mics that do not require external power; as dynamic mics generate their own tiny current.

More than two hundred manufacturers produce mics, yet most readers will be familiar with only a few company names e.g. Audio-Technica, Neumann, AKG, Rode, Sennheiser, Shure, etc. Nearly all major manufacturers produce technically different types and numerous models, therefore thousands of mics are available. The cost of mics varies from just a few pounds for a cheap and cheerful Chinese mass-made low ender, to many thousands of pounds for a very high end Blackspade, Brauner, Schoeps, Neumann, Sony or Telefunken.

In the eld of audio there is unnecessary snobbery regarding equipment, but what matters in respect of a mic is performance, sensitivity, build quality, and how it sounds. Without making any recommendation the following descriptions should be regarded as indicative of type and price range.

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You don’t have to pay a fortune for a decent mic, for around £100 (at time of writing) you can buy an AKG C100s (right). This is regarded by audio engineers as the Swiss Army knife of mics. Ruggedly built, sounds good on various sound sources including instruments and speech. It can be powered by either phantom power or battery therefore it can be used in a studio or on location. Its biggest drawback as a condenser (back-electret) mic is low sensitivity at only 6.0mV/Pa, but it does have an impressive frequency range of 50Hz to 20kHz. It requires close use for speech, not good for distance.

Probably the world’s largest selling mic in a similar price bracket is the Shure SM58 (left). This is a dynamic mic that doesn’t need external power. This is robust, built like a tank and suitable for touring and live stage performances where it could suffer abuse. It is great as a singer’s mic, emphasises proximity effect on low frequencies quite strongly. Typical of dynamic mics it has very low sensitivity of 1.9mV/Pa and therefore needs to be used very close to mouth. Its frequency range is limited between 50Hz-15kHz however, this is more than enough for vocals.

If buying an SM58 ensure you buy from a reputable dealer in preference to eBay. The is the most ripped off and cheaply copied mic worldwide. Pirated copies are numerous, dreadful quality and completely useless. Although we’ve mentioned condenser and dynamic mics both of which work with a diaphragm capsule, there is another type i.e. ribbon mic. For the purpose of this article we’ll leave out ribbons because they’re delicate, usually expensive, and least likely to be of common use to most AV workers.

Condenser mics come in two types, those that require external power to energise the capsule, and those that can be energised from an internal battery, frequently referred to as `back electret’. In many cases the back electret can also be energised from external phantom power. This makes the back electret versatile and suitable for location work whereby a standard large diaphragm condenser mic requiring external power is more likely (but not necessarily) studio based. Large diaphragm condenser mics usually have diaphragms of 25mm to 32mm diameter, whereas small diaphragm (pencil mics) are usually about 12mm to15mm.

Rode is an Australian company that makes different types of mics, including a range of very good large diameter studio condensers.

The latest iteration of their NT1 (right) provides a frequency range of 20Hz to 20kHz, lowest selfnoise in the industry at only 4dB-A and high sensitivity of 35mV. This is an affordable studio mic at around £210, it can handle musical instruments and voices, either singing or speech. It’s a good mic for voiceovers with a smooth at response with a subtle colouration of +2 or +3 dB around the vocal frequency range.

We can hardly consider large diaphragm studio mics without mentioning the highly regarded name of Neumann of Berlin. Their reputation for superb build and sound quality is second to none. Pictured left is their model TLM103 at around £900-£1000. Introduced in 1997 this mic is often used by professional voiceover artists. It also has low self-noise at only 7dB-A, noise to sound ratio of 87dB, and sensitivity at 23 mV/Pa, max sound pressure level of 138dB. Neumann mics can be found in all good recording studios, but many of their sophisticated studio models are beyond the technical need or cost parameters of AV workers.

The cost of some microphones exceed £10,000, but many of sophisticated studio models are beyond the technical need or cost parameters of AV workers.

All types and models mentioned above have one thing in common, they’re all cardioid pattern mics. This is roughly a heart shaped polar pattern from the front of the mic. Not all sound sources are suitable to this pattern of mic, especially sounds at some distance. For such sound sources a super cardioid, hyper cardioid, or lobar mic is required. These are generally described as shotgun mics. These can be short, medium or long shotguns and are usually recognisable by their `slotted interference tube’ construction.

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Most of the major manufactures offer various shotgun mics but Sennheiser has for many years supplied their MKH-146 industry standard short shotgun for the lm and video industry, frequently used on a pole over the top of actors on set. Whilst this is an excellent mic producing superb sound it’s also a bit pricey at between £900 -£1000, probably more than most AV workers would want to pay.

Fortunately, Sennheiser produce an excellent alternative named MKE-600 at a more palatable price of £200–£249 depending where you purchase. This mic can be operated by either 48V phantom power or with battery. It has a super-cardioid lobar polar pattern, frequency response of 40 Hz-20 kHz. A maximum sound pressure level of 132 dB at 48 Volts phantom power and 126 dB when operated from internal power which can last up to 150 hours from a single AA battery. What’s impressive is its sensitivity at 21 mV/Pa with phantom power and 19mV/Pa with battery.

Sennheiser market this as a professional video mic and because its weight is only 128g without battery it can comfortably sit on either video or SLR camera. Its versatility allows use on location or in the studio. It certainly doesn’t have to be mounted on a camera. It’s great at recording mid distant sounds but also voices. Because of its versatility if I were to own only one mic it would be this, or one of an equivalent spec from another manufacturer.

Before buying any mic always check the compatibility with your intended recorder, or camera, ensure that impedance and power parameters match those stipulated in the manual. To get the best from a good mic it needs connecting to a recorder or interface with high quality mic pre-amps.

The Zoom F4/F8 or Sound Devices MixPre series recorders have excellent pre -amps with plenty of head room and negligible self-noise. If recording indoors directly into a computer or DAW a good interface with high quality pre-amps is essential. Focusrite Scarlet 2i4 is an example of a decent interface at an affordable price.