Recording tools: The Microphone

As with any other process, the tools used are all important, but if I had to decide which tool was the most important (a futile act, seeing as all the components need eachother to function) it would have to be the microphone.

Microphones are the physical "ears" of the recording session. Their purpose is to transate the physical sound waves from the air, into an electrical signal that can then be recorded. Sound is actually the movement of air molecules, or rather the movement of regions of denser and less dense particles. When a 1kHz tone is heard, you eardrum is actually picking up density changes in the air inside the ear, oscillating at 1000 times per second.

A microphone works in a similar fashion. Just as the ear drum vibrates with the air and transfers this energy into nerve impulses, the membrane of a microphone vibrates and translates this energy into electrical impulses.

There are three major types of microphone:

Dynamic microphones are by far the cheapest and most common microphones, especially in project studios and on the stage. These microphones consist of a membrane with a coil of wire attached on one side. In the center of this coil there is a stationary magnet.

Now, when the soundwaves hit the membrane they casue it to vibrate. The vibrations are the same as found in the soundwave. Physics tell us that when a coil of wire moves within a magnetic feild a current in the wire is induced, proportional to the movement. When the membrane moves, the wire moves and a current is induced. now, due to the membrane vibrating in the same way as the soundwaves, the induced current will also be proportional to the soundwaves, with voltage changes representing the wave. Positive voltage peaks are the same as wave peaks, while negative voltages are the same as troughs.Dynamics are good because they are cheap to make. They are also robust which means you can easily put them in more dangerous places, like a kick drum or the top of a snare drum. One of the problems with them is their relatively low sensitivety, seeing as the membrane and the coil are slightly heavy and therefore heavy to move. This also means that they often have a reduced responce in the high frequency bands. Common dynamic microphones are f.eks. the Shure SM57, SM58 and SM7B. Or the Sennheiser MD421's.

Condenser Microphones use a slightly different princial, though the basics are the same.

A condenser microphone uses a condenser, two plates of metal with a gap between them. A current is passed from one plate to the other, and the gap between them has a resistance, which affects the voltage of the current. When the soundwaves hit one of these plates it vibrates (in the same way as the membrane on the dynamic), thus changing the distance between the plates and therefore changing the resistance. The Resistance changes affect the voltage of the signal proportionally to the vibrations of the membrane.Condenser microphones require a current to work, and this current is usually provided by the preamp on either the desk or the interface. Most condenser microphones operate on a 48V current. The current is led through the same cable as the sound signal, so on condensers it is not the overall signal which is recorded, but rather the difference in Voltages from 48V. These differences are proportional to the soundwave and can therefore be recorded.

Condenser Microphones are a tad more expensive to manufacture than dynamics. You can however pick one up for around 2000kr (350USD norwegian prices) new at a store that are acceptable. The good thing with condensers is that their membrane is very light. This means they have an extended frequency pickup range and also react faster to changes in volume (transients.) These characteristics make them the microphone of choice for vocals, overheads on drums and acoustic instruments. In professional studios there are often more condenser microphones than there are dynamics, for this very reason.

The last type of microphone are called Ribbon Microphones. These microphones use a strip of very thin metal that vibrates within a magnetic feild. They are not as commonly used as condensers and dynamics due to their high pricetag and vulnerable ribbon. Ribbons also usually have a diminished pickup of the higher frequencies, usually dipping off at 16kHz. They do however excell at giving the source a very warm and mellow, natural sound amking them a good choice for strings, choirs and very often guitar amps. They are often very good on kick drums, but caution has to be made when placing them. Try to angle them at 45 degrees to the membrane of the drum (meaning pointing at the top of the drum with front angled down). This positioning makes sure the pressure from the air rolls off along the length of the ribbon without stretching or braking it.

As allways, leave a comment if you have any questions. I will be writing a post on common microphones, and microphone characteristics soon. Stay tuned!

The importance of monitors

Far too many under estimate the absolute importance of monitoring. Would a specialist in photography use a PC monitor which distorted and changed the color balance of the image? This would lead to decisions being made that would ultimately be different from the ones that would be made in an ideal situation.

The fact is, my friends, that the quality of monitors you use when mixing and indeed recording audio plays a huge part in the final outcome of the track. I know many who think that they can mix effectively with hi-fi speakers. I myself must admit that I was a part of that deluded fraternity. But when I started mixing in a good monitoring environment it was like being able to see for the first time. Details that are unnoticeable on conventilonal speakers became shockingly apparent, and I was forced to rethink alot of my previous work.

The fact is that conventional speakers colour the sound, to make whatever you are listening to as comfortable as possible. Studio monitors aim to do the opposite. In an ideal world a set of studio monitors must have a completely linear frequency curve between 20-20 000Hz because their aim is not to disguise and change the sound to your liking, but to reveal the bitter and eventually unavoidable truth and therefore give you the chance to improve it.

Please, do not do yourselves the injustice of cuting down on monoitor costs. There is nothing that is truly "good enough" and when it comes down to it, save on other aspects of your studio. It doesn not matter how much fancy outboard gear, or how wonderful you microphones and preamps are if you cannot hear enough to make them work. Do not work blindfolded!

Yours truly,
Robin

MIxing Tools: Compression

Compression is one of the more vague mixing tools, yet the one that few mixes can use without. A compressor is a dynamic prosessor. This means that it processes the dynamic range of a signal. In music dynamics is defined as the difference between the loudest and the quietest parts of the song. A compressor does what the name suggests, and compresses the dynamic range of a signal.

A compressor is actually an automatic gain rider, doing the job that sound engineers had to do with fader riding in the studio/stage/broadcasting studio so as to have a good overall level without letting the peaks overdrive the tape machine/cirquitry and recently AD converters. A compressor takes on this job by reducing the gain of a signal whenever the signal passes a threshold level. This means that all the dynamics over the threshold are reduced, therefore reducing the dynamics of the overall track, enabling the engineer to have a louder average signal without clipping (overdriving the cirquitry).


Well, thats cool I guess. So how does a compressor work? A compressor is one of the most useful tools in mixing when used correctly, and as all tools, can be destructive if used incorrectly. To the right there is a basic software compressor. The controls are the ratio, threshold, attack and release. The ration determines the rate of gain reduction. On the graphical representation the ration determines the slope of the upper half of the curve. A ratio of 1:1 will rueslt in no change while 1:1000 (or infinity) will result in a horizontal curve. The threshold control determines the level at which the gain reduction kicks in. Graphically the threshold is represented as the "break" in the curve. The attack and release controls are the most important controls to understand, as they determine how fast the compressor reacts and when the gain reduction ceases after the signal goes below the threshold again.

In Use
A compressor is most commonly used to create a balance in a mix without having to automate to much. It can "tighten" up a performance that is uneven because it brings the peaks closer to the "valleys." Getting a controlled vocal track for instance, where there is alot of dynamics, you can pull up the quiter sections without having the loud sections become overpowering.

For percussive instruments a compressor can be very useful. By playing around with the attack and release settings on a compressor you can let the initial attack of the snare (f.eks) pass through, while the gain reduction kicks in and dampens the ring of the drum. This method also works the other way round, by having a short attack time and a short release time the attack of the snare will be attenuated while the ring will be left unaffected. Compressors are good as transient shapers, and if used properly can really help a track become punchy, in your face, or pull it back and move it away from the focus point.

PLay around with them, more info will follow. Meanwhile you can send me a mail to robin.bjerke@gmail.com or post a comment if you have any questions.

Peace