So why can't I just record everything in my bedroom? Well... you can. There's nothing stopping you getting the most out of the sounds you need with a reasonable representation, which can be enhanced in post production. However, taking some simple steps to prepare your room, or choosing a room dependant on the source can improve your recording immensely. Below, I'll go over what you might use for the appropriate desired effect on your recordings.
Dampened and Clean - If you plan to go the route of a reflection/reverberant-less recording that will allow you to add any and all effects afterwards, you'll want to use a room that is smaller and with as little hard surface as possible. The most typical setup for a studio recording is to have a reasonably sized room (4l x 6b x 3.5h metres) that incorporates lots of foam tiling for sound absorption and texturing that would reflect sound in all directions (to reduce reflections and possible phasing on microphones). There's no reason you can't get this effect at home though. A bed duvet pinned against the length of a wall will provide a sufficient amount of dampening. Some even choose to keep egg cartons and line their walls with them, which also helps. The thing to remember, which even I've forgot to consider in the past, is your floor and ceiling. These reflect sound as much as walls, especially when you have a laminate flooring. The easiest way to resolve this is by having carpeted flooring and the means to pin a duvet or carpet-like material to the ceiling, as well as your walls. And if you're budget can take it, definitely invest in some high-density acoustic foam tiles - you can easily buy a pack of these from ebay for £35/$55 which would be sufficient for even a professional environment.
Reverberant - It may be the case that you want to record your source with some natural reverb, which is perfectly fine if you know that this is the desired effect for your production. As reverb has unlimited potential in sound and effect, it's good to play around with this if you haven't had experience before. I'll go over a few examples and what they might add to your recording.
Music: If you're a guitarist who wants to have a huge reverberant sound for a lead solo part, you might want to have your amp and mics in a large church-like hall. The time at which the sound reverberates is usually between a second or two, creating a large sustained sound. This can also be true if you want a large drum sound, but i'd advise to have at least a little dampening to control this; otherwise, the sound isn't as precise, which won't help in the mixing stage.
Sound for TV/Film: A lot of sound effects and dialogue in this instance are recorded in a dampened/clean studio. However, you may not be able to bring a church bell or a huge crowd into your tiny recording studio. Instead, you can record them in their natural environment, or one which will reflect (pun not intended) the scenario on the screen. As long you perform some test recordings to ensure it sounds fine, you can save some time in post-production (as well as some CPU power from those plugins!).Let's now consider the source sound. Much like with microphone choice, you have to understand how your source is creating sound physically, in order to find the best placement and gain level. For example, if you're recording an acoustic guitar, there isn't a lot of physical movement in the air apart from the musicians hand moving up and down to strum the strings. On the other hand, when you're trying to record a vocal, there's a considerable amount of air moving around with the singer breathing, shouting, as well as the troublesome popping caused by 'b's and 'p's. If you don't know what I mean, just place your hand about 2" in front of your face and say "Barry and Peter": you should feel the air shoot out more on the 'b' and 'p'.
Another consideration, especially for music, is how it may hinder the musicians ability to play their instrument. The worst thing you could do for any musician is to place a microphone or stand in a position that would mean they aren't comfortable and therefore can't perform in what should be their top form. From personal experience, this means microphones on drums that I would catch with my sticks when moving around the kit, or stands behind me that I would catch with my elbow. In short, always consider the musicians needs before placing microphones to get what may technically be the best sound; if they aren't playing their best, you wouldn't get the best sound from them anyway.
Linking in with musicians, but not exclusively relating to them, the proximity effect is also something you would need to think about. I say linking in with musicians, because the proximity effect can add a sense of intimacy with a vocal or guitar. I won't go into too much detail (as it's quite complicated), but due to the physics involved with the diaphragm and the short distance between the source and the microphone, a bass boost occurs naturally. You can test this yourself: just get someone to say a few words into one of your ears a few feet away, and then have them say it up close to your ear - you should hear it. This is used a lot in music and movies to emphasise a voice, but it's really up to you what you want to use it for: after all, if you use it and don't need it, you can (for the most part) EQ out the effect in post production.
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General Microphone Placement: I think the best (and only) way to describe microphone placement is through several different examples. These examples will work around a single instrument or source, and then detail different scenarios in recording them:
Vocals / Voice Over
As mentioned briefly, the human voice is quite varied in terms of both dynamic range and frequency. The way to work out the best microphone placement and gain is what you'll be using it for.
Music: I would always try and go for a studio-type acoustically treated room and have the microphone set up at mouth level with your singer. Generally you want the mic to be around 6" away. However, you won't have to worry about distance too much as an engineer, because the singer will (or should) move back and forth depending on the volume and effect. As with the proximity effect discussed earlier, they may move in to about 2", or for very loud singing, they may choose to back up to 8-10". Gain wise, you'll want to get them to sing a few lines repeated at as loud a level as necessary for the song or section, making sure the pre-fade level is touching about -3dB. This gives plenty of head room for short loud bursts. You can also consider the polar pattern, which would probably be cardioid to avoid capturing the room tone, but if you do want this, use a figure-of-8 pattern to control it.
ADR (Automatic Dialogue Replacement): This one has always fascinated me. I must clarify what this is first: all ADR is recorded in the studio after filming (hence dialogue replacement); this is common practice in many films. Basically, a film set is usually very noisy and, even though the sound is usually recorded regardless, you wouldn't get a seamless transition between shots. So instead, they record dialogue afterwards in a studio which gives them more control. So in terms of mic positioning, you want to try and record it as if you we're listening to them in the scene. For example, if they happen to be very close to the screen, you want quite an intimate recording similar to vocals as described above. If they're stood in the middle of a room a few metres away from the camera, you want to record them from a few feet away, usually above them. To get a better idea of this, just check out some DVD extras of films: Lord of The Rings has a dedicated feature on sound, and animated films usually have a section devoted to ADR (although not as direct as recording technique).
Electric Guitar/Bass
If you're either a guitarist of bassist, these tricks are so easy for you to have a mess around with. Both are pretty much the same, but guitars amps tend to have a slightly more direct sound from the speaker.
Live: When you don't have much control over where the amp goes, you tend to have to put up with what you have (especially in smaller venues). If you can, try and have the speaker unit in a reasonably open space with the back exposed; otherwise, you'll get exaggerated peaks and troughs in the bass frequencies. However, the key to remember for live sound is that you will never have as much control as the studio; always concentrate on suiting the sound for the venue. So moving back to the guitar amp; if you have a single cone, place your dynamic mic facing towards the centre of the cone, either directly or at a slight angle. If you have a 4/6 speaker cab, pick a cone and mic it up the same way. After all, you'd expect the amp/cab to be doing most of the work.
Studio: Because you will have more control, you can be much more specific about your mic placement to change the sound to your needs. The best way to find the guitar sound you want is to work out where it will lie in the mix. Are you recording a rhythm part? Is it a scorching solo? Fat power chords? All of these encompass different microphone positioning, because moving the mic around the speaker cone can dramatically alter how the recording turns out. The centre of the cone is where you get a very precise sound because it's where the most movement occurs. On the other hand, the edge of the cone is where the least movement occurs, so you get a bassier rounder sound with less high frequency content. Therefore, if you want to record a rhythm guitar part for example, you'll want to keep the microphone away from the centre of the cone so it doesn't take all the attention in the mix. Similarly with a lead guitar part, you want to place it in the centre to capture as much of an intimate in-your-face sound as possible.
Loud One-Shots
This one isn't very specific, but describes basic technique for anything in the nature of loud sounds that could potentially cause distortion. One particular example is fireworks. They have a whizz and then a very loud short bang. I'd say record the firework from a normal distance (8-10m) and follow the firework with your microphone; swinging it upwards as it lifts off. Gain wise, I would recommend keeping it low for a test recording, check what level came out and then alter accordingly. If it was recorded right, you'll have a very quiet whizz and then the bang heading towards 0dB (ideally -0.5dB). If your recorder has a very low noise profile and there isn't too much back ground noise, you can use a transient designer to bring out the whizz and tail of the bang which will make it sound a lot sweeter. More on that in another post though!
Traffic/Public/Machinery
This all lies on the application you'd use it for. For sound and film (or music if you chose to include something like that), recording in stereo in the best way to go about it. If it's not the focus of the mix (which is usually the case), you can always get away with recording 2 mono tracks and summing them to stereo panned hard left and right. For games which would use point sources, you can either record in stereo and sum to mono/split the tracks, or record in mono. This is especially important for ambience which I'll detail in a later post when I get to game audio implementation in UDK.
Regardless of this, if it's background noise you want, try and record the sound from a distance. With the public, this is vital, as the listener is drawn to the human voice and a particularly apparent one will stick out like a soar thumb. Mic placement is pretty simple: just point it at the crowd; for gain, keep it at about -3dB so you get a healthy signal if possible. If you're pushing your recorder though, back it off a little to avoid a high noise floor, as you'll more than likely pull this sound down in the mix anyway. I'd also recommend a cardioid polar pattern, as hyper-cardioid may be too precise for a 'crowd' sound, where omni-directional wouldn't give you much control over what you were recording.
Conclusion: Microphone placement and gain is a bit of art in itself. You really have to be forward-thinking and reflective, based upon the image you're portraying or the overall mix. As long as you have a good plan, you should be able to make the right decisions. And before I forget, I would go over Drum mic placement and gain, but I think that's big enough for it's own post! So I'll leave it here for now.
Thank you very much if you've read this far, it was a big one today. Next time, we'll go over some experimental things and the endless possibilities of recording your sources! I'm rather excited about this one I must say...
Alex.
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