Subwoofer wont produce low frequencies - KLH HT-9900 System

A subwoofer is a low frequency device so it is designed to amplify low frequencies <200 herts to play on a speaker designed for low frequencies. You want low frequencies to pass to the amplifier while high frequencies do not enter the amplifier to cause damage to your amplifier or sub woofer speakers plus it will sound terrible. Anothher reason may be to not have to worry about a crossover filter on the speaker system..

Hum is a constant low-frequency buzz, usually at about 60 Hz or 120 Hz, which results from voltage differences between true "ground" (what you'd get shoving a copper pipe into the ground) and the electrical "ground" of your receiver's chassis When this voltage differential exists, it's called a "ground loop," and the hum it produces is darned annoying. You'll hear the hum mainly from the subwoofer because it's a low-frequency noise, you will need a ground loop insulator they are about $20 at any electronic store

Yes, for best results. Your subwoofer should have a seperate amplifier because it has low pass filter that produces low frequency signals. It is done by connecting the sub woofer output to the input signal of the amplifier and then connecting the output signal to the subwoofer speaker terminals. Hope this helps.

H?,
You have a very good system...one of the best of SONY..SUB does not get activated automatically especially on STEREO mode.DIRECT STEREO Notes • No sound will be output from the subwoofer.
.your system has Dedicated Power Amplifier for 2 Externally Driven Sub-Woofers (200W RMS x 2)..in order to activate the sub woofer amplifier you need to make a selection on the surround modes while you are switching the modes of the surround you will see the speaker position on the display of receiver as well..if you do not see the sub woofer it wont be activated..Sound Field Program (A.F.D) is a good example to test it..
Take care and please Remember to rate/vote and give me 4 Thumbs Up
for Helping out the Community :)
Hope this helps!
--------------------
Additionally please follow the instruction on your user manual to activate the SUB ,as is follows..
-----------------
BASS-OUT
Low-frequency (bass) signals can be directed to the
subwoofer and/or the front left and right speakers
according to the characteristics of your system. This
setting also determines the routing of the LFE (low-
frequency effect) signals found in Dolby Digital or DTS
sources.
Choices: SWFR (subwoofer), FRONT, BOTH
• Select SWFR if you connect a subwoofer. LFE and
low-frequency signals from other channels are directed
to the subwoofer according to the speaker settings.
• Select FRONT if you do not use a subwoofer. LFE and
low-frequency signals from other channels are directed
to the front speakers according to the speaker settings
(even if you have previously set the front speakers to
SML).
• Select BOTH if you connect a subwoofer and you want
to output low-frequency signals from front channels to
both the front speakers and subwoofer. LFE and low-
frequency signals from other channels are also directed
to the subwoofer according to the speaker settings. Use
this function to reinforce low-frequency signals using
the subwoofer when playing back sources such as CDs.

H?,
You have a very good system...one of the best of SONY..SUB does not get activated automatically especially on STEREO mode.DIRECT STEREO Notes • No sound will be output from the subwoofer.
.your system has Dedicated Power Amplifier for 2 Externally Driven Sub-Woofers (200W RMS x 2)..in order to activate the sub woofer amplifier you need to make a selection on the surround modes while you are switching the modes of the surround you will see the speaker position on the display of receiver as well..if you do not see the sub woofer it wont be activated..Sound Field Program (A.F.D) is a good example to test it..
Take care and please Remember to rate/vote and give me 4 Thumbs Up
for Helping out the Community :)
Hope this helps!
--------------------
Additionally please follow the instruction on your user manual to activate the SUB ,as is follows..
-----------------
BASS-OUT
Low-frequency (bass) signals can be directed to the
subwoofer and/or the front left and right speakers
according to the characteristics of your system. This
setting also determines the routing of the LFE (low-
frequency effect) signals found in Dolby Digital or DTS
sources.
Choices: SWFR (subwoofer), FRONT, BOTH
• Select SWFR if you connect a subwoofer. LFE and
low-frequency signals from other channels are directed
to the subwoofer according to the speaker settings.
• Select FRONT if you do not use a subwoofer. LFE and
low-frequency signals from other channels are directed
to the front speakers according to the speaker settings
(even if you have previously set the front speakers to
SML).
• Select BOTH if you connect a subwoofer and you want
to output low-frequency signals from front channels to
both the front speakers and subwoofer. LFE and low-
frequency signals from other channels are also directed
to the subwoofer according to the speaker settings. Use
this function to reinforce low-frequency signals using
the subwoofer when playing back sources such as CDs.

a sbwoofer is ment for producing bass by playing low frequency notes at an amplified power. subs move air vibrating off of your trunk and creating bass. a speakeris ment to produse high and midbass frequencies. thus having a tewwter and a small woffer cone. trying to get bss out of a door speaker usually results in very bad distortion which will actually blow a speaker very easy

On the amp there should be High pass and a low pass setting. Put it on low pass cause if its on high pass or in between it produces normal noted like a speaker. Low pass will filter out all the high frequencies.

Make sure the subwoofer is set to low frequency, make sure subwoofer and bass are enabled on the headdeck. Make sure the gain is turned up on the amp, make sure the rcas haven't come out of the back of the head deck.

Hey i'm no expert either but maybe just maybe your amp has a subsonic filter on it which cuts out the lowlow bass maybe check that and either disengage it or turn it all the way down if it even has one thats all i can think of unless you have a ported box and going below the boxes tuning frequency other than that im as stumped as you are-good luck with it

Low-pass crossover
Both sets of inputs sum the left and right channels together and the
resulting signal is passed through an adjustable low-pass crossover before
being amplified. The crossover control allows you to adjust the upper limit
of the subwoofer's frequency response from 40 to 120 Hz. The subwoofer's
response will begin rolling off above the frequency you set this control to.
You should set the crossover frequency to obtain a smooth and seamless
transition from the subwoofer to the main speakers in your system. If your
main speakers are smaller units with limited low frequency output, you
may wish to choose a higher frequency (such as 100-120Hz) than you
would with larger speakers which have greater low frequency output. With
larger speakers, you might start with this control set lower, such as 80Hz.