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Acoustical Parameters (cont.) - Bass Control Filters
Bass Summing
The subwoofer(s) is an essential speaker in an advanced home theater system. You can use
one or more subwoofers in any home theater system. It is designed to provide sound rein-
forcement of the low frequencies (below 80Hz). With AC-3 encoded source materials, the
subwoofer takes on a whole new dimension. While it is typically used as a specialized "low
frequency" speaker in standard Pro Logic or Stereo playback, with AC-3, the subwoofer acts
more as an effects channel. The term "5.1" (Digital Discrete Home Theater) refers to the main
five speaker channels ("5") and the ".1" refers to the channel more commonly called the "LFE"
Channel or "Low Frequency Effects" Channel.
The LFE Channel, when playing an AC-3 and DTS encoded source (i.e. AC-3 Laser Disc),
receives specialized bass information in addition to the standard bass information. This LFE
signal contains information as its name would indicate, low frequency effects, such as explo-
sions, drums, bass, rumbles, impacts, and others. This aspect of AC-3 and DTS Digital
Surround makes the encoding format unique and more dramatic. Some material may have
no LFE information or LFE channel. The SSD-66 (5.1) provides two means to determine the
presance of LFE. The six quadrant vector-scope will indicate bass information with illumina-
tion of the outer segments on the right & left side of the scope. Also, when playing AC-3
material, the AC-3 Status Feedback (bottom of page 54) will indicate whether the source was
encoded with an LFE channel. With DTS decoding, the bass is enhanced. For Input Labels
set to the Multi-Pin Input (MUTI PIN/V#), the LFE information needs to be lowered 10 dB.
The SSD-66 (5.1) permits the subwoofer to receive either the LFE Channel (only), the LFE
Channel summed (combined) with the bass information from all of the other five channels, or
the summed bass information and the LFE were the LFE is lowered by 10 dB. Unless you are
using large, full-range speakers for all of the speaker channels, you will want to sum the bass
information from all of the speaker channels with the low frequency effects channel. Thus the
subwoofer will pass not just the ".1" encoded special effects, but also the bass information
which would normally be lost, as the other speakers in the system cannot properly handle low
frequencies.
We will set the subwoofer's bass-sum filter for each Input Label in the following pages. Thus
the bass-sum filter, bass redirect filter, and bass level control will all be set at the same time.
Bass Redirect
Bass redirection refers to the SSD-66 (5.1)'s ability to transfer the bass information of one
speaker to another speaker(s) better capable of playing low frequencies. This option is es-
sential, especially when the center channel speaker is relatively small in size and in adequate
for playing heavy bass audio segments.
While the bass redirection option is typically associated to the global speaker setup, the SSD-
66 (5.1) is flexible enough to permit each input its own redirect position. This permits you to
setup the SSD-66 (5.1) where each source and even further, each Input Label, has its own
bass redirection setting. Please note, that if you wish to use the same bass redirection setting
for each source, you will need to set it for each Input Label individually. The available bass
redirection options include:
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