Basics for Microphone use
The tone of a microphone changes
as you get closer to it. Mostly the low frequencies increase in
relation the higher ones. You can use this "proximity effect" to get
the sound you want. Keep in mind that as you get closer the dynamics
and vocal popping increases. Using a pop filter (or some nylon stocking
spread over a wire loop) in front of the mike is a must for close
miking vocals. Learning to turn your head when you hit a loud or high
note can be very useful.
Avoid open sound holes. Placing
a mike in front of a guitar sound hole will allow the body frequency of
the guitar to dominate the sound. (which is a bad thing) Using the mike
at an angle to the guitar face (10 to 15 degrees) and pointing it at
the area between the sound hole and the neck is a better practice.
Stuffing a towel in the guitar is also a good way of balancing the tone.
Multiple mikes -
Mikes are often used as a stereo
pair by crossing 2 mikes at 90 degrees and having the heads as close as
possible. The reason they have to be close is that sound waves are
spherical waves of compressed air separated by decompressed air. If 2
mikes are different distances from the sound source some of the waves
will be pushing on one mike while pulling on the other. When the output
of the 2 mikes is added together the result is that the frequency of
that particular wave disappears. (the outputs cancel each other out)
It is very hard to hear when
there are missing frequencies cause by phase cancellation, which is why
there are 2 simple rules used with multiple mikes that are going into
the same mix.
Rule 1 - When there are 2 mikes
near an instrument. The distance of the sound source to the further
mike should be at least 3 times the distance of the source to the
closer mike. (This is often an issue when using 2 mikes on someone who
is singing and playing the guitar at the same time.)
Rule 2 - When you are recording
near a wall or a surface that can reflect sound, The distance from the
sound source to the wall should at least twice the distance as the
source to the mike.
Recording in a small space -
In the room you are recording in
you have to be aware of what noise sources are inside and outside the
room. You will not be able to remove all noise sources in a home studio
enviroment. Mostly you deal with it by keeping the mike as close as
possible to the sound source you want to record.
For noise sources inside the
room (like a computer or other gear with a cooling fan) you need to aim
the 'dead spot' of the mike towards that source. Recording mikes
usually have a cardioid or figure 8 (bi-directional) sensitivity
pattern. Which means that the dead spot is either at the back or at the
side of the mike.
Another important consideration
is the sound of the room. When you clap your hands are there any
reflections? A dead sounding room is no problem as you can always add
reverb. If you have audible reflections you have to consider that this
is going to be there on everything you record. Sometimes you can use
ambient reflections to your advantage. (Some of Elvis Presley's
classics had the vocals recorded in the studio toilets as they didn't
have reverb devices.)
Preamps and A/D Converters
These are 2 important links to
getting the microphone signal to a storage device and
like the microphone, they will determine the quality of the sound.
There are 3 considerations for
Power - It needs plenty of gain
so you have the option of not being close to the mike.
Noise - A well made preamp will
increase the volume without adding any noise to the signal.
Phantom Power - many good mikes
require phantom power to make the mike function.
You don't neccessarily need to
spend a lot of money to have a decent preamp but you will have to check
the specs and read some reviews to make sure you are getting the best
in the price range.
Analogue to Digital Converter -
The next thing that has to
happen to the signal coming from the microphone is that it has to be
changed from a complex waveform into a numerical representation of that
waveform. The short name for this device is a A/D converter. It has 2
parameters of quality or resolution.
1st parameter - Sampling rate
This is how many times per
second (Hz) the waveform is looked at and recorded as a number. The
sampling rate of CDs is 44.1 kHz (44,100 samples per second) Because
this is just over twice the frequency of human hearing, the highest
waves are represented by only 2 points, which is rather poor definition
for something as complex as a sound wave. For recording purposes it is
best to use high definition as there will be a lot of mathematical
processes done to the wave during processing and mixing. I either use
48 or 96 kHz depending on how much processing I intend to do.
2nd parameter - Bit rate
When the the A/D converter looks
at the sound wave coming from the mike, it records the voltage as a
number. The bit rate refers to how accurate that number will be. Each
added bit means twice as many numbers to choose from. CDs are 16 bit
but most good converters now go up to 24 bit. Once again the higher
resolution will result in more accurate processing even if the end
result is going to be a CD.
Types of preamp and A/D units
Although home computers have
preamps and converters built in they are very noisy just from being
inside a computer which has a lot of components that produce electronic
noise. For this reason any quality recording requires that the preamp
and converters are outside the computer.
There are some nice cheap units
that put the preamp in the same box as the converters which is a great
idea. The digital data is then sent to the computer via usb of
firewire. I would avoid units that use usb1 because the interface has
low bandwidth whereas usb2 and firewire have heaps of headroom.
I use a small mixer with a firewire
output that has 10 channels in and 2 coming out of the computer.
There are also some good small interfaces with a couple of mike
preamps. The highest quality one for the price is probably the Emu 0404
which for some reason are not sold in Australia. This is not
necessarily bad, as many items of recording gear are half the price
when ordered from the US.
Another option that I don't
personally have experience with is using a usb mike. These
have a converter in the actual microphone and simply plug into the usb
port of your computer. Originally designed for podcasting, it's a
simple and cheap way to start out digital recording. There are some
high resolution usb mikes
beginning to appear with 24/96 A/D conversion that might be considered
Computer, Software etc
Any computer that has usb2 is
more than adequate for digital audio recording. The main thing is to
keep the computer from being cluttered with too much software. Regular ghosting
or cleaning the registry is a
good routine. Sometimes installing the whole operating system from
scratch is the best way to clean a computer.
There is a lot of multitrack recording
software to choose from, free and otherwise. The most important
qualities to look for are:
visual feedback - like seeing the waveforms appear during
to use plugins
- small third party inserts that can be applied to individual tracks
I have recently been using Reaper. It's a very
professional, low cost program that puts many other high cost programs
to shame. I won't be doing a software tutorial as this program is huge,
but it's layout is well worth getting used to. An excellent user manual
can be downloaded as well.
There are also some nice free
programas like Audacity
which are good for those who just want to get used to recording