Low pass filter

[funky2x]

my question is that I used the low pass filter topology sallen-key with tda2030 and ne5532 to use as 2.1 system for computer and when tested the sound still coming out from the woofer , is that right or am wrong that should hear only the low frequency ( boomy ) and the result isnt what what I wanted , is there way to move around to get the deep bass ???? and stop the music coming out the woofer ?????


thank you all

 

[PullaEmu]

Hi,

You are correct, low pass filter lets only low frequencies pass unaffected (as they were). Low pass filters attenuate (weaken) frequencies above their cut-off frequency. The cut-off frequency does not mean "sounds above are cut-off", it only means "sounds above will be weaker".

Sallen-Key filters attenuate by 12 dB / octave (doubled frequency), so if your cut-off frequency is 150Hz, you'll have -12dB @ 300Hz, -24dB @ 600Hz, -36dB@ 1200Hz and so on. That's why you still hear other than low frequencies from woofer. You can cascade (put many in a line) filters to achieve stronger attenuation.

 

[funky2x]

thank you , but why with products you cant hear any music coming ... what is the difference here. even I looked at many diagrams with almost the same BOM but not achieved that result .

An externally hosted image should be here but it was not working when we last tested it.

 

[AndrewT]

If you have a two way speaker with dual speaker terminals, just remove the drive from one driver and listen to the other.
Now swap the drive to the other driver.
Both versions are quite intelligible. You can hear signals that are way outside the passband of the filter+driver.

 

[funky2x]

used in 2.1 system for computer .

 

[JMFahey]

Your schematic is fine, but ... are you sure you are only sending its ouput and nothing else to the woofer amp?
Sound should be real boomy, and although, say, a voice might be softly heard in the background, it should be very weak and un intelligible.
Recheck your wiring.