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Terms:
1.
LFE:
Low Frequency Effects, AKA: Low Frequency Enhancement, AKA: The .1 channel.
2.
Redirected Bass:
This is all information contained in all 5 satellite channels that is below
80 Hz., which is redirected to the SW (subwoofer) output of the Pre/Pro or Receiver.
3.
SW Output:
This is the output of the Pre/Pro or Receiver that sends a combined, single
signal comprised of the LFE channel and the Redirected Bass from all 5 satellites (or, any
satellite that's set to 'small' in the speaker setup menu) to the subwoofer(s).
4.
SPL:
Sound Pressure Level. This is the unit of measurement used to calibrate the channel
levels of all of the 5.1 channels. SPL is measured in Decibels, which is abbreviated as dB.
5.
Subsonic:
This is the description used for any sound that is below the threshold of human
hearing, or below approximately 20 Hz.
6.
T
ight, fast, articulate, etc.:
These are adjectives that describe a subwoofer that is capable of
delivering low frequencies on-time with the rest of the system, without any peaks in
response.
7.
Boomy, muddy, slow, etc.:
These adjectives describe a subwoofer that lacks the capabilities
of the subwoofer described in item #6, and/or is misplaced or badly calibrated, resulting in
peaky response.
8.
Polarity:
Better described as Absolute Phase. Usually, this adjustment is made by
comparing 0 degrees to 180 degrees. If 2 speakers are 180 degrees 'out of phase', then
there will be gross cancellation of sound waves in the region of audio information that the
2 speakers share the reproduction of. In the case of satellites and a subwoofer, this will
be at and around the crossover point.
9.
Relative Phase
:
Phase is time. It's measured in degrees. If you can visualize a sound
wave that curves upward to it's peak and then downward to its bottom--that is one cycle
of the wave. Since degrees of angle are not curved, there are infinite degrees along this
wave. As the frequency is lowered, the phase changes. Some subwoofer designs change
more drastically than others.
Distance disparity between speakers and subwoofer also changes the time that it takes for
the shared audio information to reach your ear. Because these situations result in infinite
phase differences between speakers and subwoofer, there is no perfect phase setting that
works for all frequencies through the crossover region. This is why it's important to keep
distance to the listening position and infinite phase control in mind when setting up any
subwoofer.
10.
Crossover Region
:
A typical multi-channel audio controller has crossover options that are
based on a Linkwitz/Riley 24 dB per octave network. This means that the subwoofer is
stopped from playing above the crossover point and the satellite is stopped from playing
below the crossover point. This stoppage of the speaker's natural response is not a brick
wall. It is a gradual braking from the crossover point and then beyond that at a rate of 24
dB per octave.
The idea is that across 2 octaves (from the crossover point to one octave below that point
the satellite has a brake applied that ends up being 24 dB lower, and from the crossover
point to one octave above that point the subwoofer has a brake applied that ends up being
24 dB lower, a total region of 2 octaves), the sum of the 2 signals at any point in the
crossover region should sum to unity, or, in other words, result in a frequency response
curve that is a flat line. This 2-octave area of overlap between the satellites and the
subwoofer is the crossover region.
