Toa HB-1 - Manual (Page 10)

10
8. CROSSOVER CONNECTIONS WITH A FULL-RANGE SPEAKER
8.1. Recommended Filters for the HB-1
• Because the HB-1's enclosure construction is designed to create an acoustic band-pass filter, the mid and
high frequency audio ranges are cut even if the input signal band is not limited with a low-pass filter.
Therefore, the HB-1 functions as a sub-woofer with no filtering.
• The speaker driving efficiency can be increased by inserting a low-pass filter before the power amplifier to
cut the mid and high frequency components of the input signal to the sub-woofer.
• The following filter settings are recommended
when using a digital signal processor for the
HB-1's signal system:
High-pass filter (– 12 dB/oct):
Cut-off frequency=40 Hz, Q=1.0
Low-pass filter (– 12 dB/oct):
Cut-off frequency=100 Hz, Q=1.0
8.2. Level Balance and Polarity
When using the HB-1 in combination with TOA's F or H series Full-Range Speakers, adjust their level balance
or polarity depending on the conditions of the installation location.
8.2.1. Level balance adjustment
Adjust the level of the sub-woofer or full range speaker depending on the number of units to be installed or
installation conditions.
8.2.2. Polarity adjustment
• Acoustic energy increases at the crossover band for the sub-woofer and full-range speaker if the two
speaker are in phase with each other, and decreases if out of phase. Because the phase characteristics of
both the sub-woofer and the full-range speaker vary continuously depending on frequency, simply matching
the connector polarities of the sub-woofer is not always the best procedure.
• To confirm how much the acoustic energy increases or decreases, reverse the polarity of the sub-woofer's
"+" and "–" connectors and select the connection polarity that results in the largest output of acoustic energy.
(The use of a real-time spectrum analyzer to check the degree of energy increase is highly recommended.)
[dB]
+20
+10
-10
-20
-30
-40
0
20 50 100 500 1k 5k 10k 20k
[Hz]
Frequency-to-gain relationship
HB-1's cross section
[dB]
110
100
80
70
60
50
90
20 50 100 500 1k 5k 10k 20k
[Hz]
Frequency-to-SPL relationship
(1 W 1 m, 1/2 free sound field)