Please add a useful/switchable lowcut!

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This topic contains 20 replies, has 8 voices, and was last updated by Profile photo of vilddyr vilddyr 8 years, 2 months ago.

Viewing 6 posts - 16 through 21 (of 21 total)
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  • #33056
    Profile photo of Jens-Droessler
    Jens-Droessler
    Participant

    For reasons established in other threads subs off aux or even LR Sub is not recommendable, unless you use the aux or the Sub mix per channel only as a switch. If you change the level of the sub mix per channel to be different from the main mix, it will have negative impact on the phase coherence and the linearity of your overall system.

    Of course making the lowcut switchable to higher orders of filtering will be a DSP problem. The higher the order/steepness, the higher the DSP usage.

    Anyways, I’d like to see that feature too. Making it global, setting it for ALL channels from preference, would make it pretty useless again. You’ll need to decide PER CHANNEL what the right order/steepness is.

    #33057
    Profile photo of mervaka
    mervaka
    Participant

    Would you be happy to lose one of your other filters in order to create a 4th order filter? That’s an easy implementation possibility. You’d just gang the filter coefficients to its neighbour, and they’d already be cascaded. To make a 3rd order filter, a 1st order filter could instead be calculated, and that would run at no extra DSP cost. I am of course making the assumption that we’re using biquad filters here :)

    eg: you want a 4th order HPF:
    your MF bell filter would disappear, and its coefficients would mirror that of the LF filter, creating a cascade of two biquad filters.

    eg: you want a 3rd order LPF:
    your HM bell filter would disappear, and its coefficients would be recalculated for a first order LPF with the same frequency parameter as the HF filter. This creates a cascade of a 1st and 2nd order filter.

    While on the subject, I don’t think you need higher order filters to create shelving filters with an adjustable transition bandwidth (or slope).

    EDIT: After a quick look at this in MATLAB, the downside of cascading two 2nd order filters would be that the centre frequency would sit at -6dB, not -3dB, which is what standard 4th order Butterworth polynomials would give. Same applies between a 1st/2nd order cascade and 3rd order Butterworth polynomials.

    #33062
    Profile photo of Jens-Droessler
    Jens-Droessler
    Participant

    Losing an EQ band is not an option.

    And yes,cascading two butterworth filters of the same order and frequency results in a filter with 6dB point as edge. This is how Linkwitz-Riley filters are constructed.

    But maybe the shelving EQ bands could be done with selectable slopes (at least 6dB in addition to the 12dB standard?) and the locut/highpass EQ could be with selectable Q?

    #33066
    Profile photo of mervaka
    mervaka
    Participant

    Thinking about it, a dedicated fourth order LPF/HPF would actually require the same number of coefficients (and therefore multiplications and additions/subtractions) as a biquadratic filter, so 3rd and 4th order filters could be implemented without additional DSP processing cost if dedicated HPF/LPF algorithms were implemented for each filter order. However, extra unit delays are used, so an additional 50%/100% extra data memory would be required for each filter.

    #33118
    Profile photo of SteffenR
    SteffenR
    Participant

    Is the low cut not placed in the preamp? I mean as hardware?
    Just asking….
    I would prefer a changed EQ… with Q Control in the shelving filters.

    SRV-AVB
    R-72, iDR-16, xDR-16, Dante

    #33134
    Profile photo of vilddyr
    vilddyr
    Participant

    That really would not make sense. That would be The same as just loosing a band in The parametric.

Viewing 6 posts - 16 through 21 (of 21 total)

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