Cut off frequencies up to 34Hz

Discussion in 'Effects and the DSP' started by blitter2, Feb 25, 2011.

  1. blitter2

    blitter2 New Member

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    Hi.

    Using kx dsp I would like to cut off frequencies until 34Hz.

    Because my subwoofer can play frequencies from 35Hz and upwards undistorted.

    I have tried with EQ P5, but I haven't managed to completely disable this range.

    Bear in mind I have no LFE output, just stereo.

    Please help.
     
  2. blitter2

    blitter2 New Member

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    Ok I have done it.

    I used a 2nd order crossover with 35 hz frequency, and only connected h1 and h2.
     
  3. Russ

    Russ Well-Known Member

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    How are you testing this?

    EQ P5 should give better results than a 2nd order crossover.

    e.g. (with EQ P5)
    Enable all 5 filters
    Set each filter to High-Pass, 35 Hz, BW = 1.01
    (not necessarily optimal settings)
     
    Last edited: Feb 27, 2011
  4. blitter2

    blitter2 New Member

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    Russ I have't had done any test.

    I assumed that it would do because l1 and l2 that was whats below 35hz wasn't sounding, because I haven't had it connected on kx dsp. Only h1 and h2.

    Russ thank you for the advice, it sounds nice.
     
  5. Russ

    Russ Well-Known Member

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    Just remember that a 2nd order crossover is not a brick wall at the crossover point. It will perform like other 2nd order filters (final slope is 12 dB per octave).
     
  6. blitter2

    blitter2 New Member

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    Russ Thanks.

    Russ for a 2nd order crossover among, does it matter if its connected before or after EQ P5, for the sound to be correct?
     
    Last edited: Mar 4, 2011
  7. Russ

    Russ Well-Known Member

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    Sorry, I think I probably did not explain good enough.

    In your first post, you said "I have tried with EQ P5, but I haven't managed to completely disable this range.". My response was meant to show that EQ P5 can disable more of that range than the 2nd order crossover (h1/h2 outputs).

    e.g.
    EQ P5 with only 1 filter enabled (or EQ P1), set to Highpass with BW (Q) = 0.71 will give pretty much identical results (frequency response) to the 2nd order crossover's h1/h2 outputs.

    What to use would depend on what you want the final result to be, but there is probably no point using the 2nd order crossover, if you are not using all if it's outputs (as you can get the same result with EQ P1, etc.)

    [edit]
    BTW: I do not mean to make you think using the 2nd order crossover is bad, it just seemed (from your first posts) that you thought it was like a brick wall at the crossover frequency, and I was trying to explain that it is not (but there is nothing wrong with using it, if it gives you the results you want).
     
    Last edited: Mar 5, 2011
  8. blitter2

    blitter2 New Member

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    Russ, if I keep 3 or 4 instances of HighPass BW=1.01 - FREQ=35Hz filter on EQ P5, pease what other 1 or 2 filters could I add to enchance the sound?
     
  9. Russ

    Russ Well-Known Member

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    I am not sure what you mean by enhance the sound (e.g. could mean EQ, or Reverb, etc). Do you mean general EQ for all frequencies? You could use the 10 Band EQ, etc. (if you have enough DSP resources).

    Just do what you would normally do... but do not do too much near the frequencies affected by the highpass filters.

    BTW: You might try a program like HOLMImpluse.
     
    Last edited: Mar 8, 2011
  10. blitter2

    blitter2 New Member

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    I mean to insert 1 or 2 new filters via EQ P5 to make the sound more pleasant.

    Up to now I have only attenuated frequencies below 35hz.

    Maybe I can use some settings for sound industry standard filters like butterworth or any else :)

    On this case I can keep 3 instances of HighPass filter for frequency attenuation below 35Hz. And add 2 new ones.

    Russ please any recommendation for 2 good ones to have?
     
    Last edited: Mar 8, 2011
  11. Russ

    Russ Well-Known Member

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    Yeah, you can use the remaining filters to add some EQ for the other frequencies...

    I cannot really offer any recommendation... EQ settings are a subjective thing (and results can be different for different people (e.g. can depend on your speakers, and the style of music you listen too, and your own personal preferences, etc)). For a graphic equalizer (e.g. EQ G10), there are some common settings, but for 2 filters of a parametric EQ... I do not know (ideally, you would not need to use any EQ, right?)

    You mention Buttorworth, but that just describes the frequency response of the filter... it can be lowpass, highpass, bandpass, etc, and can be different orders (1st/2nd/3rd,..., etc), with different cuttoff frequencies, etc.
     
    Last edited: Mar 8, 2011
  12. blitter2

    blitter2 New Member

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    Russ if I added a Lowpass filter with fcenter=80Hz, what is a good value for BW?

    Would BW=1.01 be any good?
     
  13. Russ

    Russ Well-Known Member

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    I think you mean highpass? (you do not want to block frequencies above @80 Hz, right?)

    You would probably want Q (BW) values in the range of 0.25 to 0.71. Above that you start to get a little boost near the cutoff frequency. What setting to use depends on what you want... e.g. See this picture (Note: Shows expected results with a single highpass filter, if you use multiple filters, they may interact with each other and give different results).

    Edit:
    BTW: With a single (2nd order) highpass filter, Q=0.71 will give response like Butterworth.
     
    Last edited: Mar 29, 2011
  14. blitter2

    blitter2 New Member

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    I use 2.1 with LFE now.

    I wanted to put an EQ P1 (LowPass) before EQ P5 (4xHighPass-35Hz-BW=0.71) for the bass range (35Hz and above).

    Or it can be better for the range above 80Hz (satelite speakers)?

    I use rear output of Live 5.1 for subwoofer, and front output for satelite speakers.

    You have sugested a LowPass filter before, but I haven't asked you details.

    Yes. Please tell me how to block frequencies above 80Hz for the subwoofer.
    HighPass with BW=0.71 but with what value for fcenter?
     
    Last edited: Mar 29, 2011
  15. Russ

    Russ Well-Known Member

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    Ahh, I see...

    Yeah that (Lowpass @80 Hz) should be OK (to block frequencies above 80 Hz for the subwoofer).
    Settings are the same as I said with highpass (same settings give same curve, just in the opposite direction (i.e. mirror image (at the cutoff frequency))).

    BTW: Now that you have a (discreet) subwoofer, a crossover is more of an option (previously you were only using half of it), so you might consider that again (e.g. maybe 4th order crossover (and you can add EQ P1 (or whatever) for additional filtering if wanted, etc)).
     
    Last edited: Mar 29, 2011
  16. blitter2

    blitter2 New Member

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    I have read this the net but I don't know if it is true : That 4rth order crossover is for subwoofers with an air hole, and 2nd order is for ones without.

    Mine has no hole for air.

    Is it true?
     
  17. Russ

    Russ Well-Known Member

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    Again, I am not an an expert...

    AFAIK, the difference between 2nd order crossover and 4th order is the slope and phase.

    e.g.
    2nd order has slope of 12 dB per octave, and there is a phase difference of 180 degrees between the outputs.

    4th order has slope of 24 dB per octave, and the outputs are in phase with each other.
    (I only mentioned the 4th order crossover because it will block more unwanted frequencies (than the 2nd order crossover), and from your original post I thought that is what you wanted).

    I have no idea about the air holes, etc.
     
    Last edited: Mar 29, 2011
  18. blitter2

    blitter2 New Member

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    Russ thank you.
     
  19. blitter2

    blitter2 New Member

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    Speakers are advertized by its brands for reproducing a certain frequency range.

    Does it as well reproduces frequencies outside advertized range with distrorsion?

    Or it doesn't reproduces it at all?
     
  20. Russ

    Russ Well-Known Member

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    Sorry for the late reply, but again I am not a speaker expert, and thought maybe someone else would respond....

    In any case, I think it would depend on the speaker... e.g. Some cheap speakers are just junk... Some speakers have components that block frequencies that the speakers cannot handle, etc. I think in most cases (with decent computer speakers operating at nominal volume levels, etc), you probably wouldn't notice... But if the speakers are operating near it's limits (e.g. at extreme volume levels, with treble/bass cranked up, etc), then it will probably not sound so good and might even damage something. Again, not an expert, such questions might be better asked in the diyAudio forums or maybe some forum specifically about speakers, etc.
     

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