Rane THX Room EQ - Manual (Page 4)

Home THX Equalization Manual Rev. 1.5
4
Test Equipment Requirements
1.) Real Time Analyzer
This procedure requires the use of a real-
time (spectrum) analyzer and a pink noise source.
The analyzer approved for use is the R-2 THX
Audio Analyzer. The R-2 analyzer contains the
following:
• a 4 input real-time analyzer with measurement
bands at ISO one-third octave and ISO octave
intervals
• four calibrated omnidirectional microphones
• spatial averaging through microphone multi-
plexing
• averaging over time (10 seconds up to 2
hours)
• a calibrated internal pink noise source
Along with real-time analysis, the R-2 Analyzer
can measure room reverberation (RT-60) and
background noise (NC levels).
If the R-2 Audio Analyzer is unavailable, the
following equipment may be used with care:
• A real-time analyzer with measurement
bands at ISO one-third octave intervals and a
display range of ± 5 dB (minimum)
• A calibrated omni-directional microphone, or
microphones.
• The analyzer must be capable of defeating
any weighting which may be applied to the
real-time display
• The real-time analyzer must be also capable
of correctly storing and averaging a minimum
of four measurements and have a slow re-
sponse mode.
The use of a single RTA, a large number of
multiple measurements, and the averaging of
these measurements is a time consuming
process and can be subject to a high degree
of operator error. It is therefore highly recom-
mended that R-2 be employed whenever
possible.
2.) Pink Noise Sources
Pink Noise can be obtained from one of the
following sources:
• the R-2 analyzer
• the “Wow!” laser disc Chapters 8-10
• the Delos/Stereo Review Surround Sound
Test CD
• any calibrated true pink noise source (this can
be verified by measuring the noise source into
the line input of the analyzer for flat response)
Why Pink Noise
What is Pink Noise and why choose it over
White Noise? Simply put, white noise is a ran-
dom signal with equal amplitude per frequency,
and pink noise is a random signal with equal
energy per octave. Let’s look at two octave
bands; say from 500 Hz to 1 kHz and 1 kHz to 2
kHz. If each of these bands had equal amplitude
per frequency, it’s apparent that the 1-2 kHz band
would contain more energy than the 500 Hz to 1
kHZ band because it contains twice the number of
frequencies. Consequently white noise sounds
very bright. Pink noise, however, containing equal
energy per octave, closely reflects our psycho-
acoustic expectations of flat response. Because
of this perception of flat tonal balance, pink noise
is a very useful tool when using a spectrum
analyzer with 1/3 octave or octave measurement
intervals, and when comparing loudspeakers for
spectral similarity by ear .
One element of caution is necessary,
though. Because pink noise has a random ele-
ment to it, when you measure pink noise using a