audioXpress
2007 3
off. The digital RS SPL meter has a less
steep low-frequency rolloff compared to
the new RS SPL meter, but still a few
decibels off relative to the old RS SPL
meters. The digital RS SPL meter also
does not show the correct C-weighting
high-frequency rolloff behavior above
10kHz.
For all four RS SPL meters, the re-
gion above 550Hz deviated from a flat
frequency response by as much as +18dB
(!) for the digital meter, resulting in vari-
ous peaks and dips. Although the old
RS SPL meters mostly met the man-
ufacturer’s claimed frequency response
of 32Hz ~10kHz (±3dB), the new RS
SPL meter’s early low-frequency rolloff
and large peaks in the high frequencies
demonstrated large deviation (±7dB)
from the manufacturer’s claim. The digi-
tal RS SPL meter fared even worse, with
a huge peak at 6kHz that resulted in an
even larger deviation (±10.4dB) from
the manufacturer’s claim.
Based on the calculated response of
the RS SPL meters, comments regard-
ing the appropriateness of using this
device for common usages can be quali-
fied:
• Home-theater speaker level match-
ing—It is perfectly fine to use the
RS SPL meter for this usage, be-
cause you are only level matching
main, center, and surround speakers,
the speakers are subject to the same
frequency aberrations of the RS SPL
meter, and it shouldn’t make a differ-
ence whether you use the old, new, or
digital model.
• Subwoofer level matching to main
speakers. Matching subwoofer lev-
els to main speakers is probably ac-
ceptable for the old RS SPL meter,
but perhaps questionable for the new
meter and the digital meter. Because
the old RS SPL meter has a low-fre-
quency response that extends down
to 24Hz (-3dB), using a test CD
such as the
Stereophile
Test CD’s
1/3-octave warble tones to level
match a subwoofer to main speak-
ers shouldn’t pose a problem. This is
especially true with the commonly
used 80Hz subwoofer crossover fre-
quency of home-theater receivers.
With the old meter, you can play
four 1/3-octave spaced tones below
80Hz (63, 50, 40, and 31.5Hz) with
FIGURE 2: Calculated RS SPL meter frequency responses, relative to calibrated
Mitey Mike II and associated electronics.
FIGURE 3: A, B, and C weighting response characteristics for sound level
meters. [F. Alton Everest,
Master Handbook of Acoustics
(McGraw-Hill, New York,
2001), pp. 39, Fig. 2-3].
20Hz -4.2dB -4.8dB -9.8dB -6.3dB
25Hz -2.5dB -2.9dB -7.2dB -4.5dB
31.5Hz -1.1dB -1.6dB -4.8dB -2.9dB
40Hz -1.1dB -1.0dB -3.3dB -2.0dB
50Hz -0.4dB -0.3dB -2.1dB -1.1dB
63Hz 0.0dB -0.3dB -1.3dB -0.7dB
80Hz -0.4dB -0.1dB -0.7dB -0.3dB
100Hz +0.2dB +0.3dB -0.2dB 0.0dB
OLD RS SPL
METER (A)
OLD RS SPL
METER (B)
NEW RS SPL
METER
DIGITAL RS
SPL METER
TABLE 3: 1/3-octave spaced low-frequency rolloff of the four RS SPL meters.
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Commentaires sur ces manuels