SMS1
Instruction Manual Rev B
Page 8
Bi-Amp and Bi-Wire Operation
Bi-Amp Operation
Set the switch to
BI-AMP
when driving the tweeter and woofer from separate amplifiers. In
BI-
AMP
mode, two amplifier channels will be required for each speaker. A four-pole NL4 cable is
required for all
BI-AMP
applications. In
BI-AMP
mode, the passive crossover is split into separate
high and low frequency sections. Both drivers still receive the proper range of frequencies and no
external crossover is required. This topology simplifies the use of the
BI-AMP
mode while
protecting the drivers from incorrect wiring.
Bi-Amp Operation May Reduce Power Amplifier IMD
BI-AMP
connections use separate amplifiers to drive the woofer and tweeter. With many
amplifiers, this will reduce IMD (intermodulation distortion) and may improve the sound quality.
Please note that it is not necessary to use a Benchmark
AHB2
in
BI-AMP
mode. The
AHB2
is
virtually distortion free, and the use of bi-amplification will not reduce distortion. However, bi-
amplification can offer an opportunity to add separate active filters for the high-frequency and low-
frequency drivers. In such a system, a
Bi-AMP
connection from an
AHB2
will allow fine-tuning of
driver and room response.
Using Bi-Amp Mode to Add Correction Processors
BI-AMP
connections provide an opportunity to fine-tune the frequency-domain and time-domain
response of the speakers and room using external active processing. This processing can be added
as an analog process (between the DAC and power amplifier), or as a digital process (before the
DAC). If the correction is digital, two channels of D/A conversion and two channels of amplification
will be required for each speaker. If the correction is analog, there is no need to duplicate the
number of D/A channels, but two channels of amplification will still be required for each speaker.
When using a Benchmark
AHB2
for
BI-AMP
connections, connect the four-pole NL4 cable to the
"
1&2
" output connector on the
AHB2
. Channel 1 drives the woofer, channel 2 drives the tweeter.
Bi-Wire Operation
The
SMS1
supports Bi-Wire connections when the speakers are set to
BI-AMP
mode. Bi-Wire
connections use separate conductors for the woofer and tweeter. Unlike
BI-AMP
connections, both
sets of conductors are driven from a common amplifier channel. Bi-Wire connections offer no
advantages when high-quality cables are used over relatively short runs. Bi-Wire connections may
be useful for long cable runs. Special four-pole cables are required for Bi-Wire connections. The
high-frequency and low-frequency conductors must be connected together at the power amplifier,
but must be connected to separate pins in the NL4 plug. Pin assignments are shown on the rear
plate of the
SMS1
.