Choosing A Microphone

Transcript

Choosing a microphone This is a brief guide to the kinds of microphones available. Unfortunately, I do not have wide experience of the market, so I advise you to consult someone who has—a good shop, for example. Forums and blogs are another source of information, but be aware that most of the discussion is about recording bands and music rather than speech, and that the professional gear they are discussing costs a lot more than you can probably justify. If, however, you can beg or borrow such equipment or get it second-hand, you will get excellent results. The first thing to ask yourself is whether you need to buy. Perhaps you already have something serviceable. A dictaphone, for example. Laptops, tablets and video cameras often have microphones, but you need to be sure they are up to scratch – you can probably assume that your webcam’s or laptop’s built-in mike isn’t. Or you could enquire whether your local talking newspaper (TN) or hospital radio has a studio they could let you use. Many such organisations hire out their facilities on a commercial basis, so some delicate negotiations may be required. There is a directory of TNs at the Talking News Federation (www.tnf.org.uk/). Or if your employer makes training videos, there may be some equipment you could use after work. Secondly, you need to decide budget. Unless you are lucky enough to drop on some quality second-hand gear, you get what you pay for. You need to balance quality against the fact that you may be called on to record a small number of items for Cycle only every two editions. Unless you need a microphone for other purposes, it would be hard to justify spending a lot; on the other hand, a cheap £10 mike or headset will sound muffled and lacking the high frequencies necessary to understand speech. Microphone Technologies There are two main sorts: dynamic and condenser mikes. Dynamic This is the most common sort and is standard for concerts, outside recordings and most uses. It does not require any power and is fairly robust. With the exception of some studio mikes, most mike formats are based on this technology. Their simplicity of use makes them my recommendation. Condenser Microphones Also called capacitor mikes. Electret mikes are a kind of condenser mike. These microphones are the ones you see in studios and are usually mounted vertically in front of the performer (unlike the cigar shaped dynamic mikes that point towards the performer). They require a 48V power supply known as phantom power. They are very sensitive, have a wide frequency range and produce very good quality. You won’t find this type of microphone at the cheap end of the market (and if you do, avoid them!) though budget models are not out of reach. However, their strengths are also their greatest weaknesses; you will find they pick up every extraneous sound: you will often see them mounted in frames suspended by rubber bands to stop them picking up every vibration; you may need a pop screen to stop them seemingly magnifying your every breath; and some filtering may be required. In addition, supplying power means feeding them from a suitable mixing desk or using a power inserter. With care, you can get excellent results, but for our purposes are generally overkill. Microphone formats You need to hold the mike steady and reasonably close to the mouth without blocking your view of the copy, and that can be done in a variety of ways. Stand mounted. On a free standing stand or desk stand. The former is preferable as sound travels better through solid material than air, so a desk stand picks up your wrist and elbow on the table surface. The resourceful might improvise a stand from a standard lamp or similar. Headset. Either pop-star style behind the ear or as part of a pair of headphones. Very convenient because the mike is close to the mouth but does not get in the way of your reading the copy. But there are pitfalls. You may catch the boom with your hand when you adjust your spectacles; the cable can rub against your clothes, causing a loud noise; and it is more subject to wear and damage than a stand mike, so crackles from damaged connections creep in. Also bear in mind that if you buy headphones, much of the price goes on the headphones rather than the microphone. While cheap ‘Skype’ headsets are available from supermarkets, they should be avoided. By comparison, standard office telephone headsets start at around £120 (and are only suitable for phones, by the way). Lapel mikes. Similar to the above but clip to the clothing. All the disadvantages of the above, but are not so close to the mouth – they therefore have to be fairly omnidirectional and pick up a lot of noise, especially rustling clothing and cable rub. We have all seen them used successfully in TV broadcasts, but my local TN’s experience is that they don’t work well. You have no need for your mike to be discreet. My advice is to avoid. Directionality The ideal for recording Cycle is a unidirectional microphone, which picks up sound from the front but is insensitive to the rear and sides. If you use an omnidirectional mike, you will be surprised how echoey even your well furnished room sounds. I will briefly run through the main patterns, starting with the one most suitable for us, the cardioid. Cardioid This is the most common unidirectional pattern. Cardioid means heart-shaped, and is so called because a graph of its sensitivity shows virtually none to the rear, a bit more to the sides and the maximum to the front. With good rejection of rear echoes, this is ideal. Not so directional that your voice is lost if you move your head slightly, but you do still need some care to avoid sounds and echoes from the side. Supercardioid Supercardioid microphones offer a narrower pickup than cardioids and a greater rejection of ambient sound. But they also have some pickup directly at the rear. Hence it is important to shield them from unwanted echoes. Omnidirectional Great for picking up the ambience of an event, but too echoey for us. Figure of Eight Like it sounds, this is two cardioid patterns back to back. With reasonable rejection from the sides, this is useful for doing interviews across a table, but picks up too much echo for our use. If you get one of these, make sure it is switchable to unidirectional mode. Be aware that this pattern is only available in expensive microphones. Other specialist microphones, like the extreme unidirectional mikes used for wildlife recording over a long distance (shotgun mikes), or the mikes that sports broadcasters press to their upper lips, need not detain us here. What do you do if your microphone is the wrong sort? The answer may be to shield the mike so it behaves like a unidirectional one. Such shields can be bought (expensive version pictured to the right), but you could improvise using some thick foam (try your local market or soft furnishings firms) or egg trays. Shield the back, sides and top. Proximity Effect Every directional microphone (i.e. cardioid, supercardioid) has a so-called proximity effect. This is created when the microphone moves closer to the sound source resulting in an increase in bass response and, hence, warmer sound. Beware of its becoming ‘boomy’ though, or getting too much breath pressure. To test this out, experiment with bringing the microphone closer to your lips when recording and listen for the change in sound. Pops When we speak, we do not only emit sound but also breath. This is particularly noticeable when you say the letters known as plosives: P, T and K. Dangle a piece of tissue in front of your mouth and say a sentence. It flutters in the breath but the plosives give it quite a kick. The force of those plosives badly affects mikes, blowing the diaphragm that picks up the sound to the limit, causing a pop. How do we prevent it? Professional broadcasters learn to minimise the effect but cannot eradicate it. The most important thing is mike positioning. Do not place the mike right in front of the mouth but slightly to the side, above or below, but still facing at the mouth. Imagine the burst of breath passing by the mike but the sound being picked up. Remember this each time you readjust your headset microphone boom. Secondly, use a pop filter or windscreen. Filters consist of one or two layers of fine mesh that is acoustically transparent but blocks most of the excess wind. Most general purpose mikes incorporate a pop filter, and if your mike comes with a foam shield, use it. If that is not enough, you can purchase a pop filter for a fiver on eBay or Amazon, or impro- vise your own from a wire coat hanger bent into a loop (or an embroidery frame, old sieve, or whatever) and an old stocking. All about plugs Most microphones for domestic use have either a 3.5mm jack plug or USB plug. Outside the home, ¼ inch jacks or three-pin XLR plugs are used, which usually plug into a mixing desk or digitiser. But the difference is not just the size and shape of the plugs. The three systems – XLR, jacks (of any size) and USB – are fundamentally different from each other and require extra equipment if they are to be mixed. The trouble with cables is that they not only carry signals: they also act as aerials and pick up unwanted electrical noise – hum from other equipment, pops and crackles from refrigerators starting up and passing trucks, static in the atmosphere and even radio signals. I was once in a church when the PA started picking up Radio 2, much to the amusement of the congregation. There are two different ways of dealing with this problem. The simplest to understand is shielding. Just as batteries have two ends, and require a complete circuit to work, so mikes too have two wires: one for the signal and a return wire (which is earthed). Shielded cables have the signal wire in the centre surrounded by insulation, and a wire mesh or foil surrounding that, which is both the shield and the return. Most of the noise will be caught by the shield and sent to earth, though it may be ineffective with high noise levels or low signal levels. These cables generally have jack plugs and are termed unbalanced. XLR outputs are balanced, and have three wires: two for the signal and a common return. The two signals are a negative, or mirror image, of each other. The signal is ‘flipped’ so that when one wire has a positive voltage, the other is negative and vice versa. Either wire could be used to connect to your equipment and they sound the same, but if you added the two together, you would get silence because they cancel each other out (though that would be pointless). There is no shielding so both wires pick up any noise in the environment. Of course, both wires now carry the same noise. So the equipment it is plugged into flips one of the wires again. Now, its signal is the same as the other wire, but its noise is the negative of the other wire. We add together the two signals and the noise is cancelled out, but the signal is actually doubled. Compared to unbalanced cables, balanced ones give better noise rejection and permit longer cable runs, so are preferred by professional studios and for concerts etc. The XLR plugs are also robust and have a clip to stop them being accidentally pulled out. So you will understand why you cannot mix balanced and unbalanced cables. While simple adapters (cables with XLR on one end, jack on the other) that just use two wires of the three-wire balanced cable are available, their use introduces hum or worse. Something more sophisticated is needed. USB is different again. Microphones are analogue devices. The analogue signals need to be converted to digital in order to be recorded by the computer, which is performed by analogue to digital converters (ADCs). When you plug in a jack, ADCs on the computer’s sound card convert it; but USB is a digital interface. In this case, the ADC is in the mike itself. Like everything else, ADCs – especially good ones – cost money, and the ones in a cheap soundcard or a laptop may not be the best. A good quality USB mike might be an improvement, and will be consistent regardless of which computer it is plugged in to. And USB mikes are not subject to problems that beset ordinary mikes like hum, mismatched impedances and scratchy connections. It gives guaranteed compatibility. But equally, if you buy a USB mike you are paying for the mike and the ADC, and anything less than £50 may be a false economy – if the ADC introduces hiss, say, you can’t just change the soundcard to solve the problem. When Sandbach TN replaced a fairly cheap soundcard with a standalone digitiser that cost over £100, the improvement in quality was very noticeable. But most soundcards and laptops are acceptable for Talking Cycle, so your decision may be based as much on the convenience of USB as anything. Just be aware that USB mikes cannot be plugged into a mixing desk. What I say about USB also applies to other interfaces, i.e. Firewire and Thunderbolt. Connecting up The first thing is to find out what plugs you have on your computer or recording device. Most desktop or tower PCs will have at least three stereo ‘mini- jack plugs’ which are small (3.5mm) and round. They will generally be for headphone/speaker, mic in and line in. They may be on a separate soundcard or – more commonly these days – on the motherboard together with the other sockets round the back. Laptops will usually have the same, but may only have two sockets: headphone and mic. Most PCs these days have more sound sockets, typically 6, and offer surround sound, 5.1 etc. In these cases the sockets may have different purposes depending on how they are configured. You will need to consult the computer manual to work out what does what. You can also use other devices such as a tablet, iPad or iPhone to record, and the sockets they have will vary, so inspect your machine. They may only have USB, often marked with this symbol: For example, first generation iPod Touch models do not have a mic input but later ones do. Secondly, look at what your microphone has. • If it is a ‘computer microphone’ it will have a 3.5mm jack for the mic in socket on your computer or laptop. • If it is a USB mike or headset, it will have a USB plug. As we have seen, these either cost more or have lower quality than a mike of the same price. • A professional mike will have a large XLR socket to take a balanced cable, which has XLR plugs at both ends. The first two are usually fine just to plug in and use. It has to be said that computer microphone inputs are not as standardised as they should be, so there is a chance you will get some problem like hum or finding it too soft. In the latter case, make sure you have turned on ‘microphone boost’ in the Sound control panel. If you are lucky enough to have a good mike like a Shure SM57 or SM58, you need something to interface between the mike and the computer. In the studio, this would be the mixing desk, a standalone digitiser or an audio interface. These items are often more expensive than the microphone. Here are some possibilities. • If you only have a USB socket, you will have to obtain some sort of digitiser. An example is the Shure X2U, whose RRP is £99. It would be cheaper to buy a USB mike like the Samson Meteor. Or there’s the Blue Microphones Icicle XLR-USB Microphone Adapter at around £43 or the StudioSeries one at £40. Even cheaper devices are available on Amazon. You will probably need an XLR cable too. • You can obtain a Balanced / Unbalanced Converter such as the Studiospares RED502 (£28). You will also need a ¼” jack to 3.5mm jack cable for that. • For ‘classic’ mikes like the Shure SM57 and SM58, which like to be fed into low impedance inputs rather than the high impedance inputs you find on modern equipment, use a Line Matching Transformer, e.g. Shure A85F, from about £20. You will also need a ¼” to 3.5mm jack adapter. An excellent solution for these mikes. • If you have a line in socket, you have more options. Line inputs need a higher signal than mic in. Microphones are not amplified so those inputs have preamplifiers. Line inputs are far more standardised, however, so are a reliable option. ◦ You could use an audio interface, e.g. Focusrite iTrack Solo, £65. You also need a cable with twin phono plugs to 3.5mm jack. Audio interfaces are available with a wide range of prices and features. ◦ You can use a mike preamp. I can’t vouch for the quality of cheap ones like Fame Mic 10, £15. Needs mini-jack to mini-jack cable. • If you have an iPhone, iPod Touch or iPad there are dedicated interfaces available. The IK Multimedia iRig Pre costs about £30. All prices are approximate and you should shop around. A mention is not necessarily a recommendation as I have not personally used any of these items. Note that if any device offers phantom power it should be switched off (unless you are using a condenser mike). And while we’re talking about wire, always check the length. The wire on headsets designed for portable MP3 players and mobile phones are quite short and may not reach to a computer on the floor or placed out of the way behind some furniture. Testing What if you already have some equipment? How do you make sure it is good enough? Here are some very unscientific tips. • Always listen to your recordings through a good set of speakers or headphones. If you use a device like a dictaphone, laptop or tablet, do not only listen on the same device—it will give you a very misleading impression. • Record some silence and listen to it. Include some normal speech so you can set the volume to ordinary levels (even hi-fi will have hiss if turned up enough). • Record someone whose voice you know well and listen to it dispassionately. Use a script you are not familiar with. Try to include pairs of words that are easily confused1. Is it reasonably realistic and easy to understand? 1 • Record yourself and get someone else to listen critically. • Compare, if you can, with a studio recording of yourself or your partner. For example, spell out words which differ by only one letter, where the letters are easily confused like B/P, B/V, F/S etc. Appendix – Product lists These links are provided for your convenience. Please shop around and check all details, cables needed etc. All prices rounded. Check out suppliers’ reputations before ordering. USB microphones Samson Meteor £53. http://www.amazon.co.uk/Samson-Meteor-USB-Microphone-Chrome/dp/B004MF39YS £45: https://www.bax-shop.co.uk/usb-microphone/samson-meteor-mic-usb-microphone Samson Meteorite £20 www.amazon.co.uk/Samson-SAMETEORITE-Meteorite-Condensor-Microphone/ Blue Microphones Snowball iCE £47 http://www.amazon.co.uk/Blue-Microphones-Snowball-iCE-Microphone/ Samson CO1U £42 (also CO3 etc) https://www.bax-shop.co.uk/large-diaphragm-condenser-microphones/samson-c01-largediaphragm-studio-microphone See also: http://www.gear4music.com/Microphones/USB.html Digitisers Shure X2U £80 http://www.canford.co.uk/Products/93-549_SHURE-X2U-XLR-TO-USB-ADAPTERMICROPHONE-PREAMPLIFIER-USB-single-channel-headphone-output-phantom Citronic XLR to USB Adaptor Interface £14.50 http://www.amazon.co.uk/Adaptor-Interface-Convert-Microphone-Digital StudioSeries XLR to USB Adapter £40 http://www.amazon.co.uk/XLR-Adapter-Phantom-Power-Preamp Blue Microphones Icicle XLR-USB Microphone Adapter £43 http://www.amazon.co.uk/Blue-Microphones-XLR-USB-Microphone-Condenser/ Lexicon Alpha Studio USB Audio Interface £41 http://www.amazon.co.uk/Lexicon-Alpha-Studio-Audio-Interface Balanced / Unbalanced Converters Studiospares RED502 Bi-Directional Balanced / Unbalanced Converter £28 https://www.studiospares.com/Microphones/DI-Boxes/Studiospares-RED502-Bi-Directional-Balanced-Unbalanced-Converter_458210.htm Shure A85F line matching transformer £20 http://www.shure.com/americas/products/accessories/microphones/microphone-problemsolvers/a85f-line-matching-transformer https://www.bax-shop.co.uk/special-microphone-adapters/shure-a85f-line-matching-transformer Audio Interfaces Focusrite iTrack Solo £65 http://www.gear4music.com/Recording-and-Computers/Focusrite-iTrack-Solo-Interface-Inc-RedPlugins/MQF See also: • http://www.gear4music.com/Audio-Interfaces.html • http://www.andertons.co.uk/Products/Products.asp? keyword=interfaces&type=search&attributeXML0=||||#1447274880374page-1 Microphone preamp Fame Mic 10 £15 http://www.dv247.com/studio-equipment/fame-mic-10-microphone-preamp--200835 XLR to iPhone/Pod/iPad IK Multimedia iRig Pre £35 www.dawsons.co.uk/ik-multimedia-irig-pre £30: http://www.andertons.co.uk/mobile-device-interfaces/pid22994/cid794/ik-multimedia-irigpre.asp Tascam iXZ Interface £33 http://www.andertons.co.uk/mobile-device-interfaces/pid22092/cid794/tascam-ixz-interface-foripad-iphone-38-ipod-touch.asp