Tilt Triple Spectral Balancers

Tilt module is designed to provide useful and convenient noise shaping, especially useful for for percussion and breath synthesis.

A single input (typically from an external noise generator) is fed into three “tilt” filters, each with its own own tilt EQ control knob to determine the noise tone, centred at 1kHz, 224Hz, and 65Hz, and each with its own output.

For example, you can use the the Low tilt to emphasize sub-bass and kick drums and subsonic noise (when tilted to bass) or reduce microphone thumps (when tilted treble). The High tilt can be used to make different high-hat and snare sounds from noise. The Mid tilt can bring an instrument forward or back in a mix.

Operation

Tilt filters were devised in the 1970s by the British Quad electro-static speaker company. With a single control, you balance between higher and lower frequencies. At 50%, the output is flat. However, at other settings it tilts the frequency response around its particular mid-frequency: for example when fully right, the frequencies starting an octave above the mid will be twice as loud as the mid, while the frequencies the octave below the mid are half as loud.

What is special about tilt filters, compared standard low- or high-pass filters, is that (by selecting the correct components)

you can maintain a more constant signal power: the High tilt filter, for example, will boost (or cut the highs) more than it cuts (or boosts) the lows; and
the filter has a shelving action, so that the signal which avoids the dull or tinny excess of simple low-pass or high-pass filters.

Rationale:

Most noise generators provide coloured noise: this is, in effect a simple low pass or high pass filter on White noise. For example pink noise has is called 1/f noise, as the relative level of any frequency component is in reverse proportion to its frequency. Brownian noise decreases at 1/f² or a 6db/8ve low-pass filter. Violet noise, in contrast, is like white noise through a 6db/8ve high-pass filter.

However, this simple coloring is not the only kinds of noise possible, and goes too far: pink or brown noise will have very little high content, while blue or violet nose will have very little low content.

Each section of the Tilt module has a different mid frequency and scaling, to provide a good variety of distinct noise distributions.

Pimp my Tilt:

Tilt was designed for noise shaping. But if you prefer different parameters, use this online ca lculator for different resistor and capacitor values: the schematic you will receive with the product is laid out the same way, so substituting your own values should be straightforward. (Or, you feel free to email me.)

The schematic has some other values you could use:

if you want to use it for percussion noise, you might build the 600 Hz instead of the 224Hz;
if you want to use it for bass EQ, build the 158 Hz instead of the 64Hz;
for extra presence, build the 1488Hz filter instead of the 1022Hz.

The current low-frequency tilt filter, for example, is aimed at boosting subsonic noise and sub-bass: you may decide to double the tilt frequency to 110Hz to make it more useful for general bass (when tilted to bass) or to simulate how many lead instruments have a “weak” low end due to their size.

Pots: The values given are calculated for 100k pots: however, you can use 47k/50k pots if you prefer: use the online calculator to adjust the other values accordingly.

Audio Examples

In each of these, the sound source is plugged into the Low then Mid then High filters, and each time the tilt is varied from middle (none) to low to high. In some cases, the low filter will not have an audible effect if you are using speakers that do not produce low bass.

Chuff: Pink noise through through a low-pass gate. Note that you may perceive some of the effect as being a change in distance.
Solar Storm: Self-oscillating filter frequency modulated by (pink) noise. This causes various storm and instability effects.
Sweeping VCO signal through filter: you can hear how the volume differences during the sweep can help audio sit in the mix better, by preventing clashes.

(Note: these samples were made with a prototype. The production version will have slightly stronger boost-cut.)

Details:

High
- 1022 Hz, +/- 11.3dB above, +/- 4.2dB below
Mid
- 225 Hz, +/- 2.7dB above, +/- 12dB below
Low
- 65 Hz, +/- 3.4dB above, +/- 30dB below

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