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SATELLITE/SUBWOOFER PHASING TEST
(WITH BOTH THX AND NON-THX COMPONENTS)
Before you can sit down to enjoy your new subwoofer, you need to perform one simple Phasing Test.
This test insures optimum sound in the critical bass frequencies where your subwoofer and Satellite
or L/C/R speakers overlap.
When using the subwoofer with a THX controller and THX L/C/R speakers, the crossover slopes are
linear phase. When the subwoofer is placed along the same axis as the front speakers, the system
will tolerate a plus or minus 28 inch offset before significant losses at the crossover point are seen.
Here are two methods of setting the correct phase with your subwoofer.
PHASING TEST METHOD ONE
Set the switch labelled "SUBWOOFER PHASE" to the "+" position. Then, play a familiar CD, LP,
laserdisc or tape with steady, consistent bass content. Listen carefully to the "mid-bass" region of
70 - 125 Hz. This is the part of the spectrum where electric or string basses and drums predominate.
Then, reverse the position of the "SUBWOOFER PHASE" switch. If it is set to the "+" position, set
it to the "-" position. If it was set to the "-" position, set it to the "+" position. The best way is to have
a partner work the switch while you sit in the main listening position and listen.
Now listen to the same music, concentrating on the mid-bass. If you hear less bass, set the
"SUBWOOFER PHASE" switch to the opposite position. If you hear more bass, leave the switch where
it is; the new position is correct.
PHASING TEST METHOD TWO
First, set the toggle switch labelled "SUBWOOFER PHASE" to the "+" position. Then, feed wideband
pink noise (found on test CDs, the "Wow" disc, or a pink noise generator) through your front channel
speakers and your subwoofer. You can do this test by listening, but it is best to use a spectrum analyzer
and look at its display in the "mid-bass" region of 70 - 125 Hz.
Then, reverse the position of the "SUBWOOFER PHASE" switch. If it is set to the "+" position, set
it to the "-" position. If it was set to the "-" position, set it to the "+" position. The best way is to have
a partner work the switch while you sit in the main listening position and listen.
Now, listen to the same wideband pink noise or look at the spectrum analyzer output in the mid-bass
region. If you hear/measure less bass, set the "SUBWOOFER PHASE" switch to the opposite position.
If you hear/measure more bass, leave the switch alone; the new position is correct.
This test is necessary because the different distances from each speaker to your ears mean that it
is possible that the Subwoofer's output may arrive at your ears out of phase with the Satellites' output.
When this happens, the midbass is cancelled. Re-do this test any time you move any of your speakers
or the listening position.
If you want to experiment, move the main speakers or subwoofer towards or away from your listening
position, in small increments. When you hear the best combination of stereo image localization and
focus with solid midbass impact and output, you have the ideal location.
If you have two subwoofers, perform one test for each subwoofer. When you perform each test,
make sure the other subwoofer is not operating by either unplugging its input cable or its power cord. |
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發表於 2009-8-12 22:36
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