5
CONTROL SETTINGS
The following settings and adjustments for the QM75.4 and QM500.1 models are provided to allow
customized tuning for a wide variety of system applications. Read each feature description carefully to
understand its application and function in order to the make the proper adjustments to maximize your
system's sound performance while minimizing the possibility to over-drive the connected speaker(s) or
subwoofer(s). For sensitive bandwidth limited speakers such as tweeters, be sure to set high-pass crossover
points appropriately for protection from lower frequencies before powering on the amplifier and then start
the tuning process at low to moderate sound levels.
Gain Adjustment (LEVEL):
This adjustment is for matching the input sensitivity of the amplifier with
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the maximum unclipped signal provided by the source. Follow proper gain setting procedures to ensure
optimum source volume range with minimum chance for clipping or over-driving the
speaker(s)/subwoofer(s). Aside from music, a -10dBfs sine wave tone at a frequency between the chosen
crossover points may also be used during the tuning process to ensure proper headroom and gain
overlap for typical music recording levels. Readjustment may be necessary after any changes to
crossover or bass boost settings.
Input Channel (MODE INPUT):
This switch is available in the QM75.4 model only and selects the input
mode for either a 2-channel or 4-channel source. When 2CH is selected, input signal connections to
CH1/2 will be copied to CH3/4 inputs.
Crossover Mode (HPF/LPF/FULL):
This switch is available in the QM75.4 model and is for selecting the
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crossover mode. For CH1/2, it is selctable as a high-pass filter (HPF) or bypassed for full-range operation
(FULL). For CH3/4, it is also selectable as a low-pass filter (LPF) and band-pass (BP), which enables both
LPF and HPF frequency adjustments.
High-pass Filter (HPF):
This adjustment is available in the QM75.4 model and sets the HPF cut-off
frequency (Fc) from 15Hz to 3.5kHz with a slope of -12dB/oct. For smaller full-range or component
speakers, use the high-pass (HPF) setting to filter out unwanted lower frequencies. Note that when set to
a very low frequency, this high-pass will act as a subsonic filter.
Low-pass Filter (LPF):
This adjustment is available in the QM75.4 for CH3/4 and QM500.1 model, which
sets the LPF cut-off frequency (Fc) from 35Hz to 3.5kHz with a slope of -12dB/oct. For woofers or
subwoofers capable of reproducing only low frequencies, use this setting to filter out unwanted higher
frequencies. For the QM75.4 model, note that when CH3/4 crossover mode is set to LPF it will also
enable the CH3/4 HPF frequency adjustment for band-pass (BP) filter applications, such as a
woofer/midrange in an active 2-way component set, or act as a subsonic filter for a subwoofer when
used in 3-channel configuration.
Subsonic Filter (SUBSONIC):
This adjustment is available in the QM500.1 model, and sets the subsonic
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filter cut-off frequncy from 15-55Hz with a slope of -12dB/oct. Use this adjustment to optimize
subwoofer performance by limiting the frequency response to what they can effectively reproduce and
minimize the chance of being over-driven. Very low frequencies can also waste amplifier power but this
setting is especially important for preventing damage to subwoofers from over-excursion in ported
enclosures below the tuning frequency.
Bass EQ (BASS BOOST):
This provides level adjustment of a single EQ band centered at 45Hz from 0dB
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up to +12dB. It is available in the QM75.4 for CH3/4, and in the QM500.1 model. Use this setting to
achieve desired bass response without over-driving the speaker(s)/subwoofer(s) or causing excessive
amplifier output distortion.
Phase Adjustment (PHASE SHIFT):
This adjustment is available in the QM500.1 model, and provides
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the ability to shift the signal phase from 0
° to 180
°. Unlike a typical polarity switch, this adjustment
allows variable adjustment of the output phase that can be used to alleviate bass cancellations with
other speakers in the system for improved frequency response.
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QM75.4
QM500.1