Crossover freq. DSP wanted

Discussion in 'Effects and the DSP' started by gribelu, Nov 11, 2003.

  1. gribelu

    gribelu New Member

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    Hello there. I was wondering if anyone would be in the mood to code something that would act like a crossover. That is, it would let the user select a frequency between 1 and 20000hz, and split the input channel into 2 channels, one with the low end, and the other with the high end.
    There are some DSPs that are supposed to do that but with any of them low frequencies are still present in the high frequency output channel and viceversa... try it with the Wavegen.. i have and got all disappointed and stuff :/

    If no one will code this... thanks for reading the thread even :)

    Edit: In case anyone is wondering, i'm trying to send the all the low frequency sound to the front speakers (because they have a woofer) and leave the rear speakers with only the mid and high range (because they suck).
     
  2. Daniel Drummond

    Daniel Drummond New Member

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    Just use the FREQ SPLITER plugin available in KX DSP menu...
     
  3. gribelu

    gribelu New Member

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    Last edited: Nov 12, 2003
  4. Max M.

    Max M. h/h member-shmember

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    Last edited: Nov 12, 2003
  5. gribelu

    gribelu New Member

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    well, if i only wanted lower volume low frequencies i would've used an EQ or whatever... I guess i'll solder a few things together and make myself a crossover for the rear channels...

    Thanks for your input
     
  6. Max M.

    Max M. h/h member-shmember

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    (try, i hope you'll then find out the thing you've misunderstood)
     
  7. akinkhoo

    akinkhoo New Member

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    so did anyone manage to get a crossover done? :hmm:
     
  8. radiocolonel.it

    radiocolonel.it New Member

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    If u want u can try this, don't expect to much but it works for me:

    http://www.radiocolonel.it/files/ColHQ_CROSSOVER.zip


    It's done in dane, so the control goes from 0% to 100% (so u can't read the cut frequency but u can figure it out with a FFT vst or other) and there is no "cool" skin ( i look for beauty in woman and in nature, not in skins)
     
  9. Nappylady

    Nappylady New Member

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    I'm using the latest 3538h, and I have option for 2nd-order crossover, and 4th-order crossover in the "add effect/plugin" list. I'm not sure if it came with 3538, 3538h, or with ProFX, which I also have installed.

    There are some really good crossovers available for kX... where to find them?
     
  10. -zerodb

    -zerodb New Member

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    I JUST noticed the crossover filter from 3538h... need to try that out. Currently I'm using cascaded multiple "freq splitter" filters to get a steep enough cutoff for my application (I'm using my SB2ZS in my car, splitting between a set of compression horns, midrange drivers, and subwoofer, and need at least a 24db/octave slope for the horns in particular to sound decent).
     
  11. -zerodb

    -zerodb New Member

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    No crossover provides a "brick wall" to lower frequencies. If you look at crossover specs it will read something like "12 db/octave slope"

    This means if you set a high-pass xover at, say, 100 hz... and at 100 hz your sound level is 100db, then at 50 hz (one octave down) the sound will be 88db. At 25 hz (another octave down) it will be 76db output.

    If it were a 24 db/octave xover, it would be 76db at 50 hz, and 52db at 25 hz. You will never build a xover that just "stops" everything below 100hz, at least not in the analog domain. It might be possible with a DSP but I've never seen one, and it would probabaly produce some very undesireable results.
     
  12. augustw

    augustw New Member

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    forward+backward filter: how to?

    First let me congratulate the kx project with their magnificent work.
    This is precisely what I've been looking for: finally a good driver for the relatively nice creative hardware.
    At last I can try to use the multiple outputs in labview and matlab.

    The question I have: I would like to implement a forward/backwards double IIR filter like the matlab statement [filtfilt] does. It does: filter an array, reverse it, filter it again with the same filter, and reverse it again to get a double filtered result with some nice characteristics.
    The downside is that it only works correctly for relatively large chunks of data with considerable overlap.

    Could the DSP apply this [filtfilt] to chunks of data (say 48000 samples) by using tram; or to put it in other words: can a chunk of data be filtered and stored in a tram and then be reversed?

    greetings from a new user @ netherlands
     
  13. Nappylady

    Nappylady New Member

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    -zerodB, did you know that the freq splitter plugin has an option to make the slope steeper without cascading plugins? The plugin has two controls--frequency, and "order". If "order" is set to 1, it'll be a 6dB/octave crossover. As I recall, it goes up to 10th order, but I could be wrong about that. I do know that it's a substantial crossover.

    Also, be aware that freq splitter does not compensate for humps or notches at the crossover frequency due to the filtering.

    augustw, IIR filtering is really hard to do on 10kx hardware; it really wasn't made for that application. There have been some implemented, but they're very limited in the number of taps (is that the right word?) they can have. You might have better luck importing audio data over ASIO, processing it, and then sending it back over ASIO. This will give you low latency, at the very least... dunno if that helps you at all.
     
  14. eyagos

    eyagos New Member

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    Nappylady & zerodB:
    Instead of freq splitter, you should use 4th-order crossover. It has a very better slope and uses aproximately the same resources (it is stereo).

    Nappylady:
    IIR filtering is perfectly possible in KX. Probably you were talking about FIR filtering...

    Augustw:
    I think that what you say is possible. For 48000 samples you'll need:

    - A circular counter from i=1 to i=48000.
    i=i+1
    - A tram of 96000 samples for invert the input.
    TRAM1 = input
    INVERTED = TRAM1[(i-48000)*2]
    - An IIR filter.
    - Another tram of 96000 samples for invert inverted & filtered input.
    TRAM2 = inverted & filtered input
    INVERTED = TRAM2[(i-48000)*2]
    - Another IIR filter (with the same coeffcients).

    All these things can be done in dane.
     
  15. Nappylady

    Nappylady New Member

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    FIR filtering, yes, I'm sure that's what I was thinking of...

    I'm sure glad you're here to straighten things out :) Thanks for the useful info...
     
  16. -zerodb

    -zerodb New Member

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    The version I'm using isn't labeled "order..." I think it's "width" or something obscure lik ethat. I recall some discussion of the actual effect of this setting and nobody seemed to be able to put it in clear terms as you have above. If that's the case, I should experiment with it further. Some people running FFT analyzers on the filter didn't seem to be able to correlate "width" to actual crossover slope. Otherwise I suspect the new 4th order crossover filter is a better option.
     
  17. Maddogg6

    Maddogg6 Tail Razer

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    Even tho I assume the use for such a filter is when watching DVD's or some other 'single source' audio stream - but for those musician out there that tihis may not be obvious to...

    You *could* assign your low frequency instrument (wave or DXi ot VSTi) to the ASIO channel that coresponds to the LFE output and have a 'natural' way of seperating the highs and lows - BEFORE thay are mixed.
     
  18. augustw

    augustw New Member

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    That would be great!
    Thanks for your extremely fast answering: I did not even find time to install the kx drivers yet.

    By the way: I am still using Windows ME; will uninstall the audigy drivers be enough to succesfully install kx or would you suggest starting from a freshly installed OS (XP?)
     
  19. -zerodb

    -zerodb New Member

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    For anyone interested, I switched all my "freq splitter" filters to "4th order crossover" filters (I'm running kX in my car audio system) and it sounds VASTLY different. Seems to be much cleaner, but output levels are way off as well, going to take some readjustment but I have no doubt the end result will be far superior.
     

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