Low Pass Filter - Still Hears The Voice

[Suraj143]

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?

 

[danadak]

Design done with TI Filterpro -

68 db down at 1 Khz.


Regards, Dana.

 

[danadak]

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

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.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-059-psoc-5lp-prototyping-kit-onboard-programmer-and

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

Configed as a BiQuad -

Regards, Dana.

 

[AnalogKid]

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]

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]

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]

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]

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.

 

[danadak]

This one as well -

**broken link removed**

Regards, Dana.