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Low Pass Filter - Still Hears The Voice

Suraj143

Active Member
I have made a sallen key low pass filter for my Subwoofer amplifier.I can still hear the voice a little bit.I need without voice.How to cancel the remaining voice in below circuit?

1624547053009.png
 

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danadak

Member
Just for the heck of it I did this with DSP wizard on a PSOC -

1624550425442.png

The phase response thru this not linear. And clock noise may/may not be an issue,
although a simple RC might take care of that.

This is a complete example project in tool, PSOC Creator, you use the wizard to customize it.


1624550775373.png

Tool and compiler free, example project you write no code, its already done.

Configed as a BiQuad -

1624551094706.png


Regards, Dana.
 

AnalogKid

Well-Known Member
Most Helpful Member
You cannot completely remove all voice frequencies using a simple lowpass filter. The fundamental oscillation frequency of adult vocal chords can be 125 Hz or lower, and the energy in the 2nd and 3rd harmonics is significant. I think that by the time you have a filter than can "completely" remove these frequencies, there will be little left for the sub-woofer to reproduce.

ak
 

Suraj143

Active Member
Thanks Danadak for the simulations.Adding more stages little bit harder to check at this moment.Because I'm experimenting it on a PCB.

You cannot completely remove all voice frequencies using a simple lowpass filter. The fundamental oscillation frequency of adult vocal chords can be 125 Hz or lower, and the energy in the 2nd and 3rd harmonics is significant. I think that by the time you have a filter than can "completely" remove these frequencies, there will be little left for the sub-woofer to reproduce.

ak
That is a very Nice point.Never heard on this brfore...
 

rjenkinsgb

Well-Known Member
Most Helpful Member
I have made a sallen key low pass filter for my Subwoofer amplifier.I can still hear the voice a little bit.I need without voice.
Also remember that a SUBwoofer is supposed to be for frequencies below what a normal "woofer" in a speaker cabinet is capable of - it should really start to have noticeable effect at somewhere below 100Hz, possibly below 60Hz even with decent main speakers.
 

danadak

Member
FYI, the OpAmp version done with TI Filterpro is two stages, same # as you are using,
which creates a 4 pole or 4'th order filter.

The digital filter entirely different approach, something to consider for design in future
projects.

Regards, Dana.
 

crutschow

Well-Known Member
Most Helpful Member
You might try a 3-pole filter (here) which requires just an added resistor and capacitor at the input, which will give an added 6dB/octave rolloff.
You should adjust the corner frequency to be about 80Hz.
 

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