This month’s header: October 2015

This month’s header picture is a variation on Mandelbrot’s set (M set) done on Xaos. If you have a Mac or Linux machine and some interest on fractal geometry, you should try GNU Xaos. This small program let’s you explore several known fractals interactively. It will also record your explorations in video, or take snapshots.


The original Mandelbrot’s set is defined as the set of complex numbers for which the iteration z ↔ z²+c  is convergent (the symbol should be a double harpoon, but I cannot make it render on all browsers). Contrary to other programs, Xaos let’s you edit the formula that generates the fractal (you are still limited within certain families of fractal, I think). Just for fun, I put the formula z ↔ z²+ 0.99*c and this resulted on a distorted M set, that still resembles the original one, but lack much of the original symmetry.

The image was then edited in GIMP: the colour space was altered, the low contrast area was blurred and darkened, and a brighter blurred overlay was added to make the picture  “glow” a little bit.

Characterizing Volca Sample’s Low Pass Filter

I’ve been preparing a couple of Volca Sample tutorials before going on vacation, and this question came up when presenting the low-pass filter. What kind of filter does the Volca Sample ships with? in order to test it, I used sample 27. This sample is a small snare with not too much bass and quite a lot of white noise. I recorded this sample being played with the filter at 127, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10 and all closed. At first glance, the filter sounds like a 12dB/octave one. Figure 1 shows the wave shape of those samples (A), and their corresponding spectrogram (B).

Figure 1: Wave shape (A) and spectrogram (B) of sample 27 using different [HI CUT] settings. Form left to right: 127, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, and 0.
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This month’s header

This month’s header was made with GIMP, using the Fractal Explorer. It is a fairly large area or Julia’s set (CX = 0.322; CY=0.416). The bottom left corner is near (0.25,0.25), and the top right is close to (0.5,0.35).