Audio Info Base
Microphones & Sound Recording Equipment Explained
In some ways the sound is more important than the visuals in any given video production, why? Allow me to explain.
Your hearing is the first sense to develop in the womb and as such makes it one of the most sensitive. When it comes to watching movies and TV programmes, your ears are a lot less forgiving than your eyes. We can all tolerate a slightly questionable picture, slightly under or overexposed shots, the odd bit of picture noise, shaky camerawork or images recorded on lesser formats such as the old Hi8. In fact some footage is deliberately shot this way! However, as soon as the sound starts to deteriorate it is a different story. When we hear poor audio, be it crackles, static pops, distorted peaks, or simply audio that was recorded using very poor audio equipment, we cringe and reach for the remote control. One of the main reasons for poor quality audio in video productions is because the person operating the camcorder at the time was using the cheap built in mic and probably had the audio levels set to auto on the camcorder. Because many of today's modern DV, HDV and HD camcorders are more than capable of producing broadcast quality images, the audio should be taken very seriously. So if you don't want your footage to stand out as blatant 'amateur night' then please, take some good advice and turn off the automatic settings, invest in some decent audio equipment and read up on location sound recording techniques. If it were a choice between watching a programme with perfect pictures and dodgy audio, and a programme with very iffy and questionable pictures and perfect audio, I would take the latter any day. It is for this reason that every self-respecting video producer should give just as much (if not more) attention to the audio side of their productions. Good audio is a combination of technique as well as using the correct equipment. I have compiled this audio info base to be informative without being too geeky; I hope you find it useful.
BALANCED & UNBALANCED
All modern professional audio equipment use balanced audio line inputs and outputs. Unbalanced signals are carried via two-core cable (one inner core and one outer shield) and are susceptible to hum and interference, whereas balanced cables use a three-core cable (two inner cores and one outer shield) and are interference and hum free depending on the quality of the cable. Balanced XLR come into their own when long cables are used as longer cables are more susceptible to picking up interference as they can act as an aerial (similar to a wire aerial that comes with radio tuners). The most common connectors used are XLR plugs but sometimes a ¼ inch TRS jack plug is used. If you are plugging directly into a camcorder, which does not have balanced inputs, you can convert the signal using a Beachbox connected to your camera. A Beachbox takes a balanced line-in with an XLR socket and a line-out terminating in a mini-jack plug. A Beachtek beachbox will cost around £160 or £260 if you also require phantom power for the microphone.
Rifle mics (also referred to as shotgun mics) are the most commonly used on-board camcorder microphones and come in various guises. Professional shotgun mics are usually condenser style mics, which require power to operate them, as opposed to dynamic mics, which do not. Dynamic mics use a diaphragm against a moving coil with a permanently charged magnet, much like a loudspeaker in reverse, whereas condenser mics use a thin metallic coated membrane placed close to a stationary backplate. A total electrical charge is then placed between the membrane and backplate, either from a battery or 9v to 48v (phantom) power supplied from the equipment to which the mic is attached, using the same audio cable, hence the term 'phantom'. There are also some electret mics available, which are similar to condenser mics, although they use permanently charged electrostatic or polarized material, which does not in itself require power, however, electret mics usually contain an integrated pre-amplifier which does require power. While there are some very good electret mics on the market, condenser mics are more commonly used in rifle mic design, as they have a better low-noise characteristic combined with a wider frequency response and a greater dynamic range making them more suitable for rifle mic applications.
Microphones that come supplied with new camcorders are rarely taken seriously, more often than not they will be discarded and replaced with a decent mic. There is a vast array of mics on the market ranging in price, quality and specifications. As with your choice of camcorder it should depend on your criteria. The term 'you get what you pay for' is not always true and a good example is the entry-level professional mics from an Australian company called Rode. They produce two rifle mics, the NTG-1 (phantom power only) and the NTG-2 (both phantom power and AA battery power) they retail at around £141 and £160 respectively. Both mics have a super-cardioid polar pattern, which is biased toward the front and sides making them very directional and ideal for on-camera use.
In the £250-£600 price level there are many makes and models to choose from. Manufacturers such as Sony, Beyer Dynamic, Sennheiser and Audio Technica all produce various models with differing specifications. For example, at £260 the Beyer Dynamic MCE86S-II is an excellent quality hyper-cardioid mic. This mic has recently been tweaked to have a higher output signal making it more suitable for plugging directly into a camcorder, as is the most popular mic in this class, the Sennheiser K6/ME66 combination, which has a very high output. The Sennheiser K6 system has a unique modular design in that the K6 or K6P (phantom power only) power supply module is sold as a separate unit for approximately £230. Once you have the K6 power unit, you then have a choice of five different mic capsules and three lavalier (tie-clip) mics to choose from. The ME66 mic capsule is approximately £210 and has a super-cardioid polar pattern and the ME67, at approximately £250, has a (hyper-cardioid) polar pattern for a more extreme directional pick-up pattern. Other capsules available are the ME62 (omni-directional), ME64 (cardioid) and the ME65 (super-cardioid) reporter's mic. Sony produces two popular mics in this category, which are the ECM674 at approximately £300 and the ECM678 at approximately £600. Both are super cardioid and are electret condenser mics. The main difference between the two is that the ECM678 has a better frequency response and dynamic range.
Finally we come to the high-end professional microphones from makers such as, Sennheiser, Sony, Neumann and Schoeps. Prices start from £850 upwards with some Neumann and Schoeps models costing £2000 plus. So what do you get for that sort of money, well? Absolute quality and precision. One such example can be found in the Sennheiser MKH416 - a long-standing model in the market, which Sennheiser once replaced with the MKH60, but it has since been brought back into their catalogue due to public demand; now the classic MKH416 and the newer MKH60 are available from Sennheiser's current product catalogue. The MKH416 has been a favorite of sound engineers for over 30 years and has earned the right to be acclaimed as the 'industry standard'. Costing around £850, it is an interference tube mic with a super cardioid polar pattern and uses transformerless circuitry, which in short, means it is very sensitive and has extremely accurate reproduction. All this is built into a rugged, brass housing making it suitable for adverse climatic conditions. The mic that was to replace it was the Sennheiser MKH60 and, although it has a better low noise characteristic, sound recordists still wanted the MKH416, hence Sennheiser bringing it back into production.
As you are now aware, there are many mics out there, all of which have their own characteristics or 'flavour'. Whether we have a small or a large budget, we all want the best that our money can buy. So what microphone do you choose? Your choice will depend on the cost and specifications that best suit your criteria. Reading all the technical data and advertising blurb is, frankly, no substitute for actually trying a mic with the equipment it has to work with, as your personal taste will probably differ from that of the next person.
When you need to close-mic a subject and using a lavalier or rifle mic is impractical, a reporter style mic comes in very useful. It may be a situation where too many lavalier mics and radio kits would be required and your rifle mic on a boom cannot get close enough. The reporter mic gives the user freedom to place the mic wherever it is needed for the best result. A good quality reporter mic can also deliver good results for voice-overs in post-production. What separates a specially designed reporter's mic from a regular hand-held mic? A reporters mic needs to be rugged and weather resistant if it is to last. You may find that the mic is physically very long in design. This long design allows you to get the mics head nearer the subject with less reach and effort on the reporter's part and it also allows the use of flags, which fit around the top of the mic and usually has the production company logo or name of the programme.
There are different polar patterns to choose from, although most reporter's mics are omnidirectional. A cardioid polar pattern will be more directional and give a more focused sound. A decent reporter's mic will set you back between £150 and £250. Some of the best makers include Shure, Beyerdynamic (MCE-58) and Sennheiser, but there are many other excellent companies who also make reporter's mics.
You might have also seen sports commentators on TV using a microphone wedged firmly between their top lip and just below their nose. The mic they are using is aptly called a 'lip mic', the industry standard model is made by a company called Coles. These are ribbon mics and are designed to be close-talking. Noise cancelling and positioning of the mic is important, hence the use of positioning bars. They are fitted with windshields for both mouth and nose breath. Unlike condenser or dynamic mics, ribbon mics work on the principle of a corrugated metal ribbon suspended within a magnetic field. They detect gradient pressure unlike condensers, which detect sound pressure and have a bidirectional polar pattern (figure of eight). Do not use lip mics with phantom power as they do not require it and the voltage can sometimes damage them.
PZM (PRESSURE ZONE) OR BOUNDARY MICS
These unusual flat mics are a type of condenser mic. They work by taking advantage of a phenomenon called 'the boundary effect'. A very small condenser mic is placed face down, close to the boundary plate which creates a pressure zone between plate and mic. The mic detects the changes in pressure as opposed to conventional mics which use air (sound) pressure. Best results are achieved by placing the mic against a flat surface i.e. table-top or wall. They are often used in conferences as they can be placed unobtrusively in the centre of a table. Boundary mics pick up direct sound and very little reflected sound (reverberation), which can be taken advantage of. Prices start from around £40 for a Tandy Realistic PZM mic which is surprisingly good for the price. A better quality Beyerdynamic boundary mic will set you back around £150.
LAVALIER MICS & RADIO MICS
Lavalier mics (also referred to as tie-clip mics) are miniaturized electret or condenser mics. Their compact size makes them very useful for placing close to the sound source while maintaining a very low profile. Obvious applications include, interviewers and interviewees, front-of-camera announcers, presenters and commentators. They can also be invaluable when a rifle mic, attached to a boom pole cannot get close enough to the sound source without appearing in-frame. The further a mic is away from the subject the more ambience (room sound) is included, the closer a mic is to the subject the less ambient sound i.e. the subject will be more isolated and dominant, resulting in clearer audio. This is usually referred to as 'the proximity effect'. Good technique often utilizes a mixture of both, close miking for detail and distant miking to add atmosphere. When combined with a radio kit, the lavalier mic becomes an indispensable and useful tool in your audio kit.
Prices start from as little as £50 for the Audio-Technica ATR35s, which has an integrated 20 foot lead terminated with a 3.5mm mini-jack plug. If your equipment has XLR inputs, a 3.5mm mini-jack to XLR adapter is available from Rode for £10. Generally lavalier mics at the lower end of the market tend to produce a rather harsh and unpleasant sound in my experience. So, swiftly moving on to the mid-range lavalier mics. £190 will buy you a Beyerdynamic MCE5 lavalier mic and CV18 preamp. This model has an omnidirectional polar pattern and the preamp is equipped with a mini XLR connector. Although an omnidirectional polar pattern is more common, other polar patterns are available from manufacturers such as Sennheiser. If you have already invested in their Sennheiser K6/ME66 rifle mic system and have a K6 power module, you can purchase a K100-60 lead, to which you can connect most of their lavalier mic capsules costing £200 upwards. Sony produces the much-acclaimed ECM77B mic at around £350. It is an omnidirectional mic with combined battery and preamp.
Lavalier mics are more commonly used in conjunction with radio transmitters and receivers, and having no trailing cables in-shot or to trip over is a huge benefit. Wireless mic systems are widely available and are becoming more and more sophisticated. Be careful if you plan to purchase from abroad as the legal bandwidth will be different from one country to the next. There is a choice of UHF or VHF, and of the two, the UHF band has become the most popular as it offers more interference-free frequencies. You will come across three distinct types of radio system. Single channel receivers have one antenna and one receiver circuit. Diversity receivers have two antennae and a circuit which selects the strongest signal. True Diversity or Dual Diversity receivers have two totally independent receiver modules and a circuit which selects the best channel for both signal strength and signal-to-noise ratio. Other functions available on some models include, Multiple banks, which allow the user to choose a different frequency if more than one set is being used, or you are sharing space with another videographer using wireless mics. Pilot tone squelch, which will eliminate pops and clicks when the equipment is switched on and off, it will also automatically mute the equipment when the signal is either too weak or erratic. Auto-scan, is a feature that will search for the best available frequency, while Presets will memorise your favourite or most often, used settings.
You will find all these features on both Sony's UWP system and Sennheiser's ew100 G2 system, which are in the £450 to £560 price bracket. Apart from body packs (which are supplied with a belt-clip or accessory-shoe clip), there are also plug-in transmitters designed for reporter's hand-held mics, these plug-in transmitters are compact units with a built-in female XLR socket. Any self-powered mic can be plugged directly onto the transmitter and used with a receiver. You can for instance, plug one onto your rifle mic or reporter style mic, so they can be used wireless. Top of the range radio mic kits tend to be dual or true diversity and are of a module type design. They can be inserted directly into the body of high-end camcorders and body pack cases are purchased as optional accessories. For these systems you should expect to pay £1000 plus, depending on what configuration is needed.
WINDSHIELDS & SOFTIES
A microphone will never realise its optimum performance without a good windshield being fitted to it. The foam windshields that are usually supplied with the microphone are as good as useless and should be ignored. The mic capsule picks up wind noise when air travels across it, so if you want to stop wind noise, a pocket of still air needs to be created around it. It also helps when physical contact with the mic is kept to a minimum. Zeppelins or Cages give the best results as they fit all the afore-mentioned criteria. The microphone is held in a suspension mount and then the windshield cage is constructed around it. A furry zip-up windjammer cover can also be added to the zeppelin to further stop air and eliminate rustling of the inner foam lining. The Rycote full windshield system is by far the biggest seller and will set you back around £400. The drawback is that zeppelins tend to be large and not usable on-camera, they are more suited to sound recordists operating the mic on the end of a boom pole. For use with an on-board camera mic there are more compact systems that work on the same principle. The Rycote softie is a push-on windshield and can be used with a separate suspension mount and pistol grip. Rycote softies sell for around £170 for a kit, which includes the windjammer, suspension mount and pistol grip, the pistol grip allows it to be handheld or fitted to a boom pole, or the suspention mount alone has a hot-shoe adaptor that allows for direct mounting to the camcorder's accessory hot-shoe. A less expensive option is the Lightwave Equaliser windshields, which retail for £60. These zeppelins and windjammers have a very simple but effective design. When the windshield costs nearly as much as the microphone it may seem expensive, but I strongly advise anyone to budget for a decent windshield when purchasing a mic if you want good results.
BOOM POLES (OR FISH POLES)
There is not an awful lot to say about microphone Boom Poles. They are usually telescopic and come in various lengths; the most common being around 10 feet when fully extended. There are a few factors that determine the price of any given boom pole. First there are the raw materials they are made from. A cheaper boom pole will generally be made from aluminium whilst the more expensive ones are made from carbon. Carbon is lighter so it is easier on the arms of the person who has to hold it above their head for long takes. There are two ways for the microphone cable to travel down the boom pole. The cheaper boom poles will simply have Velcro straps that allow you to strap the microphone cable to the outside of the pole every two feet or so. More expensive boom poles might have the cable running down the inside of the pole so no Velcro strips are required, this is tidier and keeps the cable out of the way.
Boom poles are manufactured by several different companies. The industry standard has always been Panamic, whose boom poles are top quality telescopic carbon models that cost around £250. Gitzo are also a superb boom pole maker, again, high quality carbon models are on offer for around £150. In 2006 Rode brought out a great aluminium telescopic boom pole with internal cable feature for just £60. Finally, if you are budget conscious, but want a good quality low-priced boom pole, B-Hague have two models on offer for around £25.
There is a very useful gadget you can buy called the Boom-Buddy (cost around £59.95 inc vat). The Boom-Buddy will fit on top of almost any stand/tripod etc. So if there is no need to follow an actor/presenter around and you boom is okay locked-off, the Boom-Buddy is a great little device; especially for the one-man outfit.
The use of headphones for monitoring is a must in my book. Would you trust the footage in your camera without checking it on playback? The only way to know for sure that your audio is being recorded correctly is to monitor it with good quality headphones. Cheap headphones are better than no headphones, but good monitoring headphones will give you a better representation of the audio being captured. Headphones will have either an open back, which can have a more natural sound or a closed back, which are better for stopping sound leakage as well as providing isolation of the outside world. For use with a camcorder the closed back type is a better option and there are many on the market. Sennheiser, Beyerdynamic and Sony all produce headphones in the £20 to £50 price range. Sennheisers HD212 and Beyerdynamic DT231 give very good value for money. With a Beyerdynamic DT250 (closed back) at £90, you can expect more accurate reproduction, comfort and durability. They are available in regular 80 Ohms or 200 Ohms for equipment with a weaker output. The velvet ear-pads are user replaceable and so is the coiled cable which terminates in both mini-jack and ¼ inch stereo jack. An alternative would be the Sennheiser HD25, which at £120 has proved a best seller. As with the Beyerdynamic DT250 these are closed back, over-ear headphones and are particularly good in the field. Monitoring of the audio via headphones in postproduction would be better with open or half-open reference headphones although the HD25 or DT250 will do at a pinch.
DIGITAL FIELD RECORDERS
Technology has come along in leaps and bounds and no more so than with audio. Tape recorders are almost a thing of the past with the advent of digital recorders. The two main types of digital recorder in the video market are hard-drive or solid-state flash style recorders. Hard-drive recorders offer more capacity while solid-state recorders offer compactness. You will come across many recording formats, some are compressed to allow longer recording times and some are uncompressed for better audio quality. Some small solid-state card recorders such as the Edirol R-1 or Marantz PMD660 record directly onto a compact flash card and as they have no moving parts they are extremely quiet in operation making them ideal for reporters recording interviews and the like. The Edirol R-1 cost £280 and the Marantz cost £375, for compactness the Edirol wins, but for versatility it's the Marantz. The Marantz can also record onto microdrives for extended recording time and it also has balanced XLR inputs with 48v phantom power. One step further, HHB produce a Sennheiser hand-held mic with a 1GB flash recorder built in for £700. With the press of a switch it is ready to record and afterwards you simply download the audio files onto your laptop or computer via the built-in USB interface. Further up the range are the field recorders such as the Fostex FR2 and the Tascam HD-P2 at £785 and £850 respectively. Both machines are 2 track and capable of giving professional 24 bit sound quality. They also incorporate timecode allowing them to be synchronised to video recorders and other external devices. The Edirol R-4 at £1000 is a 4 track, 40GB hard-drive recorder and records 17 hours of high quality 24-bit audio. Also featured is a limiter, which prevents sound peaks from overloading and becoming distorted, plus 5 different effects. At the top of the range you will have a choice of machines like Sound Devices 744T at £3000 or even up to the HHB Portadrive at £7000. These fully equipped recorders are designed for the professional sound recordist to deal with any given audio situation.
FIELD MIXERS & POSTPRODUCTION MIXERS
It is becoming more and more common these days for mics to be connected directly to a camcorder, relying on the cameras pre-amps and then mixing in post-production. It has to be said that the cameras on-board pre-amps are not exactly audiophile quality and cameras rarely if ever have any mixing facility, enter the soundman with a field mixer. With the use of a field mixer the soundman is able to not only mix several sources at the same time, but also shape the sound so that what goes into the audio recorder or camcorder is as near to the final product as is possible. The American company Sound Devices make a small mixer called the Mixpre, at £650 this is one of the best small 2-channel studio quality field mixers available. It has a built-in limiter which will stop sound peaks clipping and overloading the system. It can be powered either by mains or battery. As you step-up in price, you will then be looking at three, four, five and six channel mixers from makers such as, Sound Devices and SQN, these can cost anywhere between £2500 and £4500 and will deliver the very best professional sound quality.
If it is a small mixer for post-production then there are several good quality, inexpensive mixers on the market. The Alesis MultiMix-8 Firewire is one such mixer. It has 8 channels with XLR inputs with phantom power. All channels have three band EQ and gain controls. There are 100 built-in effects such as reverb and echo etc. It has Firewire out as well as the more usual phono and jack making it a perfect little mixer for home based NLE suites and it cost just £189. A USB version is also available.