EQ matching
Posted: Mon Apr 25, 2016 12:51 am
Here's the basic idea... As you probably know, you can emulate an EQ by capturing its impulse response and use it in a FIR filter. You can capture the IR in various ways, most common being passing known testing signal (usually a sine sweep or white noise) through the filter and then calculate the IR using deconvolution.
Problem is, FIR filters tend to be ridiculously CPU expensive and have poor precision in the low-end, because their frequency resolution is linear (instead of logarithmic like human ear).
Lately I've been working on different method. From the known dry and wet testing signal it is possible to estimate coefficients for a IIR filter. They can be much more CPU friendly and do not have the frequency resolution problem. In future I can even add non-linearities estimation, which would allow to emulate wide variety of devices (including guitar amps, analogue EQ's etc.). Kind of like Acustica Nebula or Kemper profiling amp.
Now, my current schematic is rather sparse. It contains a makeshift filter (coded in code component). The schematic passes a testing signal through it (impulse) and then estimates the coefficients from the captured wet and dry signals. You can compare (just numerically, not visually, sorry for my laziness) the original vs estimated coefficients, as well as original vs. estimated impulse response.
I've been kind of burned out lately with this project and flowstone in general, so I'm hoping to catch a fresh wind from your opinions and ideas guys...
Problem is, FIR filters tend to be ridiculously CPU expensive and have poor precision in the low-end, because their frequency resolution is linear (instead of logarithmic like human ear).
Lately I've been working on different method. From the known dry and wet testing signal it is possible to estimate coefficients for a IIR filter. They can be much more CPU friendly and do not have the frequency resolution problem. In future I can even add non-linearities estimation, which would allow to emulate wide variety of devices (including guitar amps, analogue EQ's etc.). Kind of like Acustica Nebula or Kemper profiling amp.
Now, my current schematic is rather sparse. It contains a makeshift filter (coded in code component). The schematic passes a testing signal through it (impulse) and then estimates the coefficients from the captured wet and dry signals. You can compare (just numerically, not visually, sorry for my laziness) the original vs estimated coefficients, as well as original vs. estimated impulse response.
I've been kind of burned out lately with this project and flowstone in general, so I'm hoping to catch a fresh wind from your opinions and ideas guys...