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Subsonic Filter and Port Tuning
Your new SVS subwoofer not only comes with our
efficient “Tri-Power” port flares, but custom port
plugs and variable subsonic filter which allow
your sub to be “tuned” to even lower frequencies
than its stock configuration. For most people and
most rooms, your SVS is already configured for
the best blend of extension (how deep/low your sub goes) and output (how loud it
gets at a variety of bass frequencies). However, we know that bass is a very personal
taste and no two rooms will react exactly the same with any subwoofer. So we in-
clude a custom “port plug” that, when inserted into a port, allows you the user to
experiment with a substantially lower “tune”.
As with all such devices, there are compromises when tuning a sub lower. Installing
a port block takes some capacity from upper reaches of bass, installing two port
blocks naturally limits upper bass response even more. So while you will indeed get
more bass down low (where DVD and music bass is more rare, but quite exciting),
you’ll sacrifice total output capacity above the stock tuning point of the sub (where
bass is more common). You should decide if the effect is pleasing on the sorts of
movies and music you enjoy.
How to do it? To insert a port plug, simply squeeze the foam on one end and press
the plug into a port flare until it is about 1” lower than the edge of the surface of the
sub. You can remove the plug by inserting your fingertips into the port flare and
squeezing and pulling on the foam plug at the same time. Be sure to select the sub-
sonic filter point on the back of your SVS amp which coincides correctly with your
new “tuning point”. NOTE: We strongly recommend you do NOT run a lower
subsonic filter point than your port plug configuration would dictate — especially if
you are running the subwoofer at high sound pressure levels. Moderate levels are
doubly important if you put the subsonic filter into the 12Hz mode (* contact SVS
about details on the use of this deepest mode). This simple table indicates the set-
tings you should use in setting up your sub blockers and the subsonic filter knob.
Look to the next page for a computer simulated response chart showing the reduc-
tion of upper bass when adding a port-plug to your SVS (along with additional
woofer excursion needed to maintain lower frequencies). The bottom line? Many
customers feel the slight loss in upper bass output to be insignificant compared to the
deeper response the port block gives. We let you decide.
SVS PB12-Plus Tuning Chart Subsonic Filter Knob
Stock tune (no ports blocked) 20Hz
With one port-blocked 16Hz
With two ports-blocked * 12Hz