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Recording Handbook
Chapter 3: The Sound Source

 3. The Sound Source

There are only two ways to get your sonic information onto the tape, through a microphone or directly from an electronic output. In general, the quality of what comes back is affected by the quality of the equipment the signal passes through.

a. Voices, Horns and Acoustic Piano

While the human voice is the most dynamic, all of these instruments present a similar problem to the engineer. How can we preserve the performance, that is the soft and loud of it, and get it accurately on tape? With these instruments, we usually have to use a microphone.

The two main types of microphones are "dynamic", which have no active electronics involved in amplifying the input signal, and "condenser", which require either batteries or "phantom power" to power their electronics. Both types have a thin membrane, called the diaphragm, that vibrates and that physical vibration is translated into an electronic signal. In general, condenser mikes are brighter and have a broader frequency response, but they are more fragile. That's why you usually see an SM57, a general purpose dynamic mike, in the lead singer's hands at a concert. They can withstand a lot of abuse.

Classic condenser microphones like the Neumann U-47 and AKG C-12 use vacuum tube electronics and are treasured for their unique sound. They are rather large and have diaphragms 2 inches in diameter. Ribbon microphones are another vintage design that incorporates a thin rectangular strip as it's diaphragm, hence the name. PZM designs are a relatively new invention. They work on a completely different principle and don't look anything like traditional microphones.

The signal created by the microphone is very small and it is the microphone pre-amp that increases this level to what is known as "line-level" for interfacing with the mixing board. This is yet another link in the chain with it's opportunity to affect the sound, and they do.

Everyone has their favorite microphones and pre-amps for different situations and most do color the sound. The important thing is whether you like that color and if it's appropriate for the particular situation at hand. Here again, we run into the concept of "flat frequency response" and again it is relatively meaningless. Most microphones are not "flat" and some are better suited for certain jobs than others. As always, you need a reference and in this regard, frequency response charts and the like can be useful. Rules are made to be broken.

Signal processing is another powerful weapon for your sonic arsenal. The judicious use of compression can be a big help in lots of situations. Compressors were originally developed to compensate for the limited dynamic range of analog tape. Basically, they make the soft parts a little louder and the loud parts a little softer. This performs the dual function of keeping the soft passages higher above the "noise floor" and preventing the loud parts from getting too loud and peaking into distortion. Most compressors allow you to change the "range" (1:1, 2:1, 4:1, etc.) and the "attack time" and "release time" of the effect.

Expanders and Limiters are related to compressors. Expanders make the soft parts softer and the loud parts louder. Like compressors, you can set the range, and attack and release times of the effect. With limiters you can set a threshold that cannot be exceeded. Noise Gates simply do what their name implies by shutting off the signal path when there is no input.

b. Guitars, Basses and Things With Strings

String instruments can be recorded acoustically with microphones or directly if they have pickups. There is a different sound to each and in different situations, one may be more appropriate than the other. Often, both are recorded simultaneously and blended together in the mix. Electric guitars and basses are recorded through microphones on the amplifiers and direct to be blended or used seperately later in the mix. All the just mentioned signal processing definitely applies here, too.

The Rockman headphone guitar amp, invented by Tom Scholz in the mid 1980's, started the revolution in small, electronic amp simulators. Rackmount guitar pre-amps have gotten very sophisticated in the last few years, offering tube pre-amp stages, multi-effects, MIDI and memory capabilities. There's still nothing quite like a Gibson Les Paul into a 100 watt Marshall stack, but that can get dificult for the neighbors!

c. Samplers, Synthesizers and Drum Machines

All of these devices have direct outputs and can be connected straight to your mixer. A lot of them also include built-in effects and it's up to you whether you want to print them "wet" or "dry". It will probably depend on how many tracks you've got to play with, but you can print sounds and their effects seperately. This way if you change your mind about that "big reverb", you're not locked in.

Playing one sound at a time to tape has never been a problem but these days, there's a lot of sequencing going on and most of these boxes only have 2 or 4 outputs. In 4 or 8-track recording, this is an asset and you just have to mix the sounds from inside the box. In a professional 24 or 48-track situation, you'll want individual sounds on individual tracks. Two ways to do this are mute the sequencer tracks and record each sound in successive passes or turn down the internal volumes of all the sounds and turn one on at a time as you make passes.

Drum machines are a powerful tool and have become a mainstay of modern music making. They all have unique sounds and many have become associated with specific types of music i.e. the Roland 808 and EMu SP-12 with rap and the Roland 909 with dance. Some also have sampling capabilities and built-in audio triggering for replacing sounds off tape. Earlier models were designed with pads for programming, and some people still prefer that. Now most are available as sound modules like any other synth and the programming is simply done from the keyboard and sequencer.

Samplers are basically digital recorders. The earliest models could only record and playback one sound at a time. In the early 80's, many a snare was replaced by hand with a steady index finger and the AMS sampler. Two of the earliest MIDI samplers were the Akai S-612 and Ensoniq Mirage. They were 8-bit, which refers to their sampling resolution. Technically, the higher the resolution, the more accurate the sample. Again, specs are one thing and sound is another. These boxes all sound different and they do what they do, differently. If you like the sound of your old 12-bit box, then go for it.

Polyphonic samplers began to appear in the mid 80's, among them the Casio FZ-1 and Akai S-900, S-950 and stereo S-1000 units. Resolution evolved to 12-bit and then 16-bit and MIDI made these boxes even more powerful. In the studio, samplers are great for quick repairs, flying vocals around or moving tracks. A sequencer and a sampler locked to tape in the mix can be real handy for those last minute repairs and arrangement changes.

d. Real Drums and Real Drummers

There are two things that you need to get good live drum sounds, a properly tuned, great sounding kit and a properly tuned, great drummer. If you can only get one, go with the human. You can always replace the sounds.

The basic approach to drum miking involves a separate mike for the kick, the snare, the hat, the toms and one or two overheads to get the cymbals and the room sound if there is one. Another snare option is to put one mike underneath and one on top. Some of the great drum sounds from classic rock records were recorded with two mikes on the whole kit! The miking techniques should reflect what kind of drum sound you're going for.

Compression can be a big help when recording drums because of the transient nature of the instruments. Depending on the parts being played, use it as needed. Sometimes gates can be helpful as well, especially when the rhythm section is being recorded in the same room. Noise gates with "sidechain" capability allow you to select what frequencies will open the gate. Another excellent device for this application is the "Kepex" expander/gate whose operation is frequency dependent.

Many engineers like to slam high levels on to analog tape to get the natural "tape compression" sound. Some even go to the lengths of recording drums on 2" 16-track analog and then transferring that to another format to complete the project. Hey, if you've got the budget and the time, go for it.

 

     
     
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