091HPDoctor

Precision low-frequency processing
Most high-pass filters stop at 20 Hz and offer a limited set of slopes and filter types. HPDoctor goes down to 1 Hz, covers fractional slopes from 1 dB/oct up to 24 dB/oct, and includes seven filter types for different sonic and phase characteristics. A focused utility for situations where a regular HPF isn't precise enough.The idea and the design was provided by Ronny Pries.

Applications:

• Removing DC offset without touching the audible low end.
• Cleaning up subsonic energy before compressors.
• Shaping kicks and bass with resonance around the cutoff.
• Console-style high-pass emulation.
• Mastering cleanup where precision matters.
• Phase manipulation and alignment via the allpass mode.

Features:

• Frequency range: 1–150 Hz.
• Slopes from 1 dB/oct up to 24 dB/oct (type-dependent).
• Seven filter types: Butterworth, Elliptic, Chebyshev I, Chebyshev II, Bessel, Ladder, Allpass.
• Optional "Const -3 dB" mode for consistent cutoff behavior across filter types.
• Full 64-bit double-precision internal processing.
• Click-free transitions for all parameter and filter changes.
• Formats: VST3, AU.
• Platforms: Windows, macOS (signed), Linux.