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Distance in meters between wall and acoustical center of speaker.
dB SPL relative to free-space response.
SPL vs. Distance to Boundary
As we have seen on the previous page, the placement of a
USW-1P on a floor or against a boundary significantly changes
the low frequency response when compared to free field
measurement of the same speaker.
The graph below represents the change in dB SPL for frequen-
cies under 125 Hz of a single USW-1P as it is moved away
from a boundary. Distance measured in meters, is based on the
distance from the wall behind the speaker to the acoustical
center of the USW-1P. All dB SPL measurements are made
with the microphone on axis to the speaker.
To better understand the graph above, imagine a USW-1P
with a wall behind it. As you move the USW-1P away from
the wall the graph above shows how the response of the
speaker will change. For example if the USW-1P is placed 1
meter from a wall and is measured on axis to the speaker, you
will see a -5 dB change in the low frequency as illustrated by
the dotted lines on the graph.
Polarity
With the USW-1P in close-proximity to, and coplanar with,
the UPA-P, or other Meyer Speakers, both speakers should be
set to the same polarity. Separating the subwoofers and main
cabinets in a speaker system by more than 5 feet may require
polarity reversal or a delay line to compensate for the propa-
gation delay between the speakers and the measurement posi-
tion.
Measurement and Correction Tools
It is recommended that even the most carefully assembled
sound systems be analyzed with precise measurement tools.
We recommend using the Meyer SIM® Sound Analyzer
and CP-10 Parametric Equalizer to
• choose, place, and array speakers;
• measure propagation delays between speakers to set
the correct polarity and delay times;
• measure and equalize variations in frequency re-
sponse caused by the acoustical environment and the
placement and interaction of speakers.
The VX-1:
The VX-1 is an ideal control option for USW-1P systems. The
VX-1 is a stereo virtual crossover which allows the user to
adjust the gain, switch between stereo and mono distribution
of two inputs and make shelving EQ adjustments to the left
and right sides of the system.
USW-1P with the UPA-P
The USW-1P and UPA-P can be configured in a wide variety
of array configurations to suit specific application needs.
Refer to the UPA-P Operating Instructions for recommended
arrays; or for additional system design ideas, contact Meyer
Sound for the following TechNotes documents on UPA-P
array design:
• Two UPA-1Ps @ 70° Horizontal Splay
(Doc #: 01.990.101.90 A)
• Two UPA-1Ps @ 85° Horizontal Splay
(Doc #: 01.990.101.91 A)
• Two UPA-2Ps Tight-pack (Doc #: 01.990.101.92 A).
• Three UPA-2Ps Tight-pack (Doc #: 01.990.101.93 A).
These documents are also available on the Meyer Sound
website: http://www.meyersound.com.
Distance to Boundary vs. dB SPL below 125 Hz