High-Low Cut PlugIn Sound Laundry™ 2.5

Linear-Phase High-LowCut Filtering 

In a typical mastering low-cut or high-cut filter, the attenuation rate (slope) can be adjusted to 6 dB per octave (1st order filter) or 12 dB per Octave (2nd order filter) and its cut-off frequency usually to some fixed values. In addition, a typical audio filter is a non-linear phase filter. That means different frequencies are delayed differently when passing the filter. The phase shift may spread the attack edge of impulse-like signals (e.g. drums) and blur the sound. 

It is practically impossible to implement a linear-phase filter in analog technology. Digital signal processing technology made it a reality. Until now this type of filter has been used only in exotic high-end professional audio equipment. One reason for that is the high complexity of this filter; another is the actual studio praxis driven by the analog predecessors. 

For the first time in digital audio technology, the High-Low Cut PlugIn uses low-cut and high-cut filters with continuously adjustable slope ranging from 0 to 24 dB per octave. Even the most advanced filters used in the digital audio domain have only fixed slopes of 6, 12, or 18 dB per octave. Slopes lower than 6 dB per octave and slopes like 9, 13, or 16 dB per octave are impossible to implement with common filter architectures; slopes higher then 12 dB per octave (but still in 6 dB steps) are normally achievable only by cascading more filters. The High-Low Cut PlugIn is a novel audio processing tool, allowing a filter with any slope you like between 0 and 24 d per octave. A slope of 24 dB per octave corresponds to a classical filter of the 4th order

The cut-off frequency of the low-cut filter can be continuously adjusted in the range from 20 to 600 Hz, the cut-off frequency for the high-cut filter in the range from 700 Hz to 20 kHz. 

Changing the parameter of the filters during playback causes no audible artifacts. Therefore you can safely start your wave-file player and look for the best sounding result while adjusting the filter parameters live.

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