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The bass range of frequencies and the
"bass instruments" of kick drum and bass guitar give the mixing engineer the
most mixing challenges. This range is very important to many productions but hard to
obtain clarity in mixdown It is equally hard to judge how much of this range that
you have in the mastering process. How do we get a clear yet powerful low-end
in the mix and on our final master? In this article we will find that bass clarity
in mixing depends on several factors, including how the instruments were recorded.
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The Difficulty With Bass:
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The lowest octave that can be heard (20Hz to
40Hz) virtually has no energy in most music. The lowest note on a bass has a
fundamental frequency of about 41 Hz. So this first octave contains such things a
"room rumble" and the lowest notes of a pipe organ.
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The second octave (40 Hz to 80Hz) contains
the fundamental frequencies of the low bass notes and the foot drum. So this is the
first octave we are really concerned with, unless we are reproducing earthquakes and the
like.
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This second octave is
very difficult to
judge, even for the most-experienced engineers. This is largely due to the speakers
we use in listening.
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The Difficulty With Speakers:
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The average speaker that people listen to,
does not reproduce the frequency range from 40 Hz to 80Hz. This is true even for
many expensive "powered" speakers. You really can't hear this range of
frequencies unless you have awfully big speakers or a sub-woofer on your system.
But the difficulties don't end there.
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Because speakers don't reproduce this range,
speaker manufacturers often "enhance" the low-end by boosting the sound output
for the next octave (80 Hz to 160 Hz). This makes the speaker sound like it
has more bass response but they are actually substituting extra energy in this octave for
a lack in the lower octave (40 Hz to 80 Hz). This makes it hard to judge the sound, add
equalization, etc.
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When subwoofers are added to speakers, there
is still the boost in the higher bass octave and additionally there can be a
"hump" around the point where the subwoofer and the speakers are both
reproducing sound (around 100 Hz). The "truest" speakers are those huge
studio monitors that no one can afford except large studios.
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Difficulty With Rooms
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In addition to all of these problems, you
have problems with standing waves that
make the bass uneven in the room. As you walk around most rooms, you will
hear more bass in some spots and less bass in other areas. Usually the bass is louder near
the walls and in the corners of a room. Also, speakers against the wall or in
corners increases bass output.
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So - What to do?.
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It is very necessary that you judge the amount of energy in both octaves
that we have discussed. It is all to easy to "accidentally" have an
abundance of energy in the low bass octave (40 Hz to 80 Hz) that goes
"unnoticed" in your mixing but which makes the whole mix sound "muddy"
on a big system and "low in level" on a smaller system.
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| My advice for judging energy in this range are: |
| 1. Always choose a "reference" cut from some national
artist that "sounds good" and has good "bass clarity" on all systems.
When trying to judge your bass clarity, compare the sound on your recording with
the "reference." |
| 2. Listen to the mix on as many different systems as possible,
including a "big" system or a system with a sub-woofer. |
| 3. Consider strongly adding a subwoofer system to your monitors,
unless the specifications on your speaker show that you have adequate 50 Hz energy. |
| 4. Set up your "near-field" monitors in the room so that: |
| a. Your speakers are away from the wall by at least18 inches or so. |
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FIGURE 1 -
ROOM SETUP |
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| b. There should be sound-absorbing material on the wall behind the
speaker to prevent reflections from interfering with the "direct sound."
This is especially important if the speaks cannot be 18 inches away from the wall. |
| c. Set up your "listening chair" so it is not against a
wall, or in a corner. |
| d. I have developed a set-up that can be
used in many small rooms that keeps the speakers working well for you (see right) |
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Advanced Tip
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Another way to judge the amount of energy in the bass ranges of your mix
involves using a Spectrum Analyzer. The spectrum analyzer shows the energy
distribution in each octave. You play both your mix and the reference mix through
the device and compare energy between the two for the ranges we have discussed. There are
many models and many computer programs that will do this for you. The unit we use is
a Wave plug-in called "PAZ" (probably short for "program analyzer").
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The Clarity Frequencies:
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These bass-frequency instruments have harmonic frequencies that are in the midrange.
This doesn't mean that you can generate these harmonics with your
equalizer. It does mean that when you record you have to capture the harmonics of
the instrument. When you do this, the amount of equalization you have to use will be
less and clarity on your bass will automatically be better.
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