Re: HPF

> Another way could be to implement a single pole filter using a DelayNode and feeding it back through a GainNode. I haven't experimented with that yet, but will try it out sometime this week. I believe with a combination of the BiquadFilterNode and a Single Pole filter we should be able to get a filter with a slope of any power of 6dB/octave.

I think that won't work. There is a minimum 128 sample delay in any feedback loop in the web audio api by spec.

-Srikumar

On 7 Apr, 2014, at 5:56 am, Chinmay Pendharkar <notthetup@gmail.com> wrote:

> Hi Jory,
> 
> The Biquad topology allows for a filter with two poles and two zeros. Each pole gives a 6dB/octave slope. So with 2 poles, biquad can either get 6dB or 12dB slope. To get more than 12dB, one can just cascade multiple Biquad filters and the slopes add linearly. So 2 BiquadFilterNode in series will give you 24dB etc. But you're indeed limited to multiples of 12dB/octave.
> 
> Another way could be to implement a single pole filter using a DelayNode and feeding it back through a GainNode. I haven't experimented with that yet, but will try it out sometime this week. I believe with a combination of the BiquadFilterNode and a Single Pole filter we should be able to get a filter with a slope of any power of 6dB/octave.
> 
> -Chinmay
> 
> 
> On Mon, Apr 7, 2014 at 3:46 AM, Jory <me@jory.org> wrote:
> Hi,
> 
> I need to implement a highpass filter with a 24 dB/octave slope, but
> the Biquad filter node only does 12 dB/oct. I would imagine this
> shouldn't be hard to do, and perhaps I have to do it with a
> ScriptProcessorNode, but I also wonder why the Biquad.highpass is fixed
> at 12 dB/oct, rather than allowing the user to select 6, 12, 18, or 24
> dB?
> 
> Any help on how I can implement this would be greatly appreciated.
> Thanks!
> 
> Jory K. Prum
> Sound Guy
> 
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