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Features

KFilter6 combines electrical, electro-acoustic and measurement-oriented tools in one desktop project.

Loudspeaker and enclosure model

  • Four independent driver slots
  • Thiele/Small parameter editing
  • Voice-coil resistance and inductance
  • Effective diaphragm diameter
  • Enclosure parameters including Vb, Fb and Ql
  • Open-baffle, sealed, vented and band-pass enclosure states
  • Enclosure-dependent controls that disable parameters not used by the selected model without discarding their values
  • Ql loss damping for sealed, vented and band-pass calculations
  • Per-driver gain and polarity
  • Simplified and full-circuit calculation paths
  • Bidirectional bass-reflex tube helper: edit diameter to calculate length, or edit length to calculate diameter

A driver with Fs = 0 can also be used without the acoustic Thiele/Small path; its impedance then remains the electrical voice-coil model.

Passive crossover network

Each driver provides eight network sections. Every section contains a series and a shunt branch with R, C and L elements.

KFilter6 calculates the effect of the passive network on both SPL and impedance and provides an interactive graphical network preview with direct click targets for driver, active-filter, baffle and network editing.

SPL and impedance analysis

  • Individual driver SPL curves
  • Individual impedance curves
  • Phase-sensitive vector SPL sum
  • Energetic SPL sum
  • Total loudspeaker impedance
  • Configurable plot colours
  • Project PDF export with network and response plots

The vector sum is useful around crossover regions where relative phase matters. The energetic sum provides a complementary view without cancellation from phase opposition.

Measurements and correction curves

KFilter6 can import absolute SPL measurement files and convert them into relative correction curves using calibration and a selectable correction window.

Supported workflow includes:

  • absolute SPL measurement import
  • 0 dB calibration
  • selectable correction-frequency range
  • optional logarithmic fades
  • editable correction curves
  • per-driver measurement hide state
  • optional merge of measurement corrections into individual and summed SPL results
  • FRD export of stored relative correction points

Measurement correction is applied after the complex active-filter, baffle and floor stages.

Active filters

Each driver can have an ordered complex active-filter chain.

Supported sections include:

  • Butterworth low-pass and high-pass, order 1–8
  • Bessel low-pass and high-pass, order 1–8
  • Linkwitz-Riley LR2, LR4, LR6 and LR8 low-pass/high-pass
  • second-order generic/Q low-pass and high-pass
  • Butterworth band-pass
  • Notch
  • Parametric / Peaking EQ
  • Low Shelf and High Shelf
  • first- and second-order All-pass
  • Gain
  • Delay
  • Polarity

Both magnitude and phase are retained in the complex response. An invalid or unsupported enabled section causes the complete active-filter stage to be bypassed rather than silently applying only part of the requested chain.

Baffle / diffraction

Two productive baffle models are available per driver:

Simple Baffle Step

A width-based engineering shelf with approximately:

  • 0 dB at low frequency
  • +3.01 dB around 115 / width[m]
  • +6.02 dB at high frequency

Rectangular Edge Diffraction

A geometry-aware on-axis edge-diffraction model using:

  • baffle width and height
  • driver centre position
  • finite-piston spatial averaging (M = 73)
  • optional full-height 45° chamfer on the left and/or right edge

For the productive free-field response, the low-frequency magnitude is blended conservatively toward the Simple Baffle Step result while retaining the geometry-driven rectangular phase. This avoids encouraging excessive electrical compensation of low-midrange cabinet gain.

A separate Rigid floor contact (diffraction only) boundary model is also available for an idealized cabinet standing directly on a rigid floor.

Floor Reflection — Experimental

KFilter6 also contains a separate first-specular floor-reflection stage using image-source geometry. It is deliberately marked Experimental because the resulting comb filtering changes strongly with listener and loudspeaker position and therefore is not a good target for fixed loudspeaker equalization.

Current surface choices include:

  • Hard / rigid floor
  • experimental porous-floor Miki reference

This feature is retained as a useful analysis tool, but it is intentionally isolated from the core baffle/diffraction model.

Project and driver files

.kfp projects

  • current JSON format: version 10
  • legacy text-based .kfp files remain readable
  • current projects persist driver, network, measurements, active filters, baffle and floor-reflection settings

.kfd driver slots

Driver format version 2 stores a complete driver slot, including:

  • driver and enclosure values
  • passive crossover network
  • measurement/correction curve and hide state
  • active-filter chain
  • baffle settings
  • floor-reflection settings
  • relevant dialog metadata

This makes it possible to move a complete configured driver between projects instead of exporting only its raw Thiele/Small parameters.

Desktop workflow

KFilter6 is a native Qt6 desktop application. No account, cloud service or online connection is required for simulation work.