Whats the different between a high pass filter and a low shelving EQ?”
Trying to explain this in non-technical terms, but likely gonna fail. A high pass filter, ideally, passes any signal of frequency above the cutoff without any gain or loss. It passes it with a gain of 1, i.e. 0 decibels (dB). Any frequency below the cutoff is not passed at all. It has a gain of 0, i.e. -infinity dB. Realistically, there’s not a perfect cutoff; there’s a slope and the farther below the cutoff the better the signal’s filtered out, but that’s the idea. A shelving filter, such as an equalizer, is designed not to completely remove some frequencies, but to pass them more or less than others. A hypothetical, ideal, shelving filter might pass signals above a certain frequency with a unity gain (0dB) and lower frequency signals with only a gain of 0.5 (-3dB). Again, a real filter would have some slope near the cutoff frequency that would asymptotically approach the high and low gains.
In the ‘old days’ 😉 it was easy to tell the difference. A high pass was usually a switch with no control over frequency or depth and a low shelf was that knob at the bottom of the EQ section that allowed you to add or cut the ‘bass’ (or low tones). These days with digital mixers and DAW’s it’s easy to understand why the line has blurred. With DSP it is easy to design both a high pass and a low shelf with nearly all the same properties. Here are some general differences: The pass filter is a ‘cut-only’ type of EQ while the shelf may be used to add or cut frequencies. Generally a pass filter has a much steeper slope than a shelf. With out being too technical, both filters have a slope that starts at a given frequency. This slope represents how the frequencies below the filter point are affected. Usually the slope for a pass filter is measured by a number of db per octave. The larger the number, the steeper the slope the more dramatic the effect. In practical application, a pass filter
