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Subsonic Filter and Port Tuning
Your new SVS Subwoofer not only comes with
our “Tri-Power” port flares, but custom port
plugs and variable subsonic filter which allow
your sub to produce 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 include a
custom “port plugs” which, when inserted into a port, allows you the user to experi-
ment with a substantially deeper response.
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
plugs 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’s amp which coincides correctly with
your new bass extension mode. NOTE: We strongly recommend you do NOT run a
different subsonic filter setting than your port plug configuration would dictate —
especially if you are running the subwoofer at high sound pressure levels. This
simple table indicates the settings 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 one, and then two port-blockers to your SVS (along
with addition woofer excursion needed to keep up with the lower frequencies). The
bottom line? Many customers feel the slight loss in upper bass output to be insig-
nificant compared to the deeper response the port block gives. We let you decide.
PB12-NSD/2 Subsonic Filter Knob
Stock (no ports blocked) 25Hz
With one port-blocked 20Hz
With two ports-blocked 16Hz