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SP-8000 Subwoofer Preamplifier

Instruction Manual

Subwoofer Placement

Single Subwoofers

If you are using a single subwoofer, then, generally speaking, the ideal
location would be in the front of the room, between the LRs, or close
to or in a corner (see Figure 8). Every room has its own unique sound
characteristics, and flexibility in the exact placement of subwoofers is
always desirable. The closer a subwoofer is placed to a wall and especially
a corner, the more and deeper the bass response you will hear. However,
in some rooms, corner placement can produce too much bass or a “one
note” boomy effect. Under such circumstances the subwoofer may work
better away from the wall or corner. You should experiment to find the
best position in your room.

Placement & Setup

Figure 8

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Helpful Hint:

A particularly useful experiment is to place the sub-

woofer right at the prime listening position (move the couch or chair
out of the way and put the sub in its place). Then play something
with lots of good bass (preferably music), and walk around the room,
listening to the subwoofer’s response. When you locate an area that
has ample amounts of well-defined bass, you have found a potentially
good place to locate the sub.

Dual Subwoofers

When two subwoofers are used you may wish to place them asymmetri-
cally; that is, in slightly different positions in the room (Figure 9). This will
reduce common mode room resonances that typically occur with sym-
metrically placed subwoofers. Another good option is to place the sub-
woofers in the same corner. Several tests have shown this to be a viable
means of producing smooth bass response in many rooms.

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Figure 9

System Setup and Operation

When using the SP-8000, your subwoofer's controls are of a secondary
nature. They will be left at a nominal position, and all adjustments to
your system will then be via the SP-8000. Preset your subwoofer as fol-
lows:
Level - THX / Preset or approx 1/3 up from minimum
Lowpass - THX / External or set to highest frequency
Phase - Normal / 0 Degrees

The LOW PASS Control

When used with a complete THX Certified speaker
system, the Sp-8000's system’s LOW PASS control
should be set to 80Hz,

unless you are using a pro-

cessor with a built-in crossover. If your processor is
THX certified or has a built-in crossover, bypass the

Preamplifier's amplifier’s LOW PASS control by setting it to the THX/EXT
setting.

All THX certified satellites have been optimized to work with an

80 Hz crossover point.
If your Processor/Receiver has no internal crossover (a fairly rare occur-
rence these days) the SP-8000's Low Pass Control should be used to opti-
mize the performance of the system, by ensuring that the subwoofer and
satellites produce a cohesive and well integrated sound picture.
Higher crossover frequencies pass more bass to the subwoofer but can
quickly begin to sound boomy. They also make it easier to localize the
subwoofer sonically, which is highly undesirable. Higher crossover fre-
quencies may be suitable, however, when using very small satellites that
have no real low frequency performance. Settings lower than 80Hz should
be employed if you are using larger speakers that have extended bass
response. This way, the subwoofer will only reproduce the very lowest
bass frequencies that are in the range where the main speakers begin
to roll off. It’s generally undesirable to have the main speakers and the
subwoofer overlap too much. Larger speakers means a lower LOW PASS
crossover frequency, smaller speakers means a higher LOW PASS cross-
over frequency. You may also contact the manufacturer of your satellite
speakers for their specified low frequency response to determine the
appropriate LOW PASS setting on your subwoofer amplifier. In the end,
however, a little time spent experimenting will generally result in dra-
matically better bass response.

A Word About Bass, Center Channel Modes, and
System Setup:

Many Dolby Pro Logic surround processors and

surround receivers provide a choice between “Wide” (full fre-
quency range) and “Normal” (restricted low frequency) mode for
the center channel speaker. Atlantic Technology recommends that
the center channel be operated in the Normal mode when using
a powered subwoofer. The center channel speaker will sound
more dynamic and the intelligibility of the system will generally be
improved when in the Normal mode.

Bass Management

Today, many processors and receivers offer Bass Management capa-
bility. If yours does it will ask you to choose between Large and Small
loudspeakers during the system setup procedure. When speakers are set

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