Frequency Splitter

Frequency Splitter allows you to separate audio into low and high, or low, mid, and high frequency bands. Bands may be routed to independent audio outputs for advanced multi-band effects processing. For example, Frequency Splitter is exceptionally useful in Patcher! Frequency splitter also offers zero latency, Minimum Phase crossovers, or high fidelity and responsive Linear Phase crossover filters, for perfect recombination with the dry or other signals. A wide range of crossover slopes from 6 to 96 dB/Oct are available to suit all mixing tasks. Each band can be cut, boosted, muted and soloed, for precise monitoring and quick equalization. Finally, the frequency response input and output display modes allow quick decision making, removing guesswork.


  • Crossover - Control the frequency crossover point and slope of the filter for the bands.
    • Slope (Menu) - Choose between -6 and -96 dB/Octave slopes independently for the Low and High Cutoff Frequencies. NOTE: Filters do not instantly stop audio at their Cutoff Frequency. Rather frequencies trail off to silence at a given rate, specified in dB (decibels) per octave. Minus means the level is falling. -6 dB is a very shallow slope, allowing many frequencies past the cutoff. -96 dB is extremely steep and will quickly filter frequencies past the cutoff. The slope you choose depends on the sound you want to achieve. If you are at all confused, just look at the Equalization curves for the various settings (slopes). The reason for all this detail is that manual writers are paid by the word.
    • Cutoff Frequency (Knobs) - Choose filter band Cutoff Frequencies between 30 Hz and 16 kHz for the Low and High Bands.
    • Bands (Switch) - 2 or 3 Band mode. In 2 band mode, the Low Cutoff Frequency controls for the Low/High frequency split point.
    • Link (Icon) - When selected the movement of Low and High FREQ knobs are linked. Moving one will move the other by the same amount. When the limits of the frequency range are encountered at either end, the gap will compress to minimum.
  • Main Output - Control band levels, mute or solo them. Main outputs to the host Mixer Track.
    • Low, Mid, High (Knobs) - Band level controls. +18 dB to -∞ (muted).
    • Mute / Solo (Switches) - Below the knobs, use the switches to Mute (Left-Click) or Solo (Right-Click).
    • Bands (Visualization) - Show the Low, Mid and High Main filter bands.
    • Equalization curve (Visualization) - Display the resulting EQ curve for the Main output in response to Low, Mid and High level changes.
  • Sends - Sends are Pre-Fader to the destination Mixer Track. That is, they will be audible on the destination Mixer Track, even if the host Mixer Track send is of type Sidechain or its fader is set to zero. For Send destinations to be available here, first create links between the Host Mixer Track and the Destination Track/s you want to Send to, from Frequency Splitters Send Outputs.
    • Target mixer track (controls) - These integrate with the Mixer Track Send feature. To use them, first send the Mixer Track hosting Frequency Splitter to additional Mixer Track/s then (Left-Click) and drag or (Right-Click) and directly select the target Mixer track from the pop-up list. NOTE: Naming Mixer tracks will make identifying the correct target Track easier.
    • Low, Mid, High (Knobs) - Send / Sidechain band level controls. +18 dB to -∞ (muted).
    • Mute / Solo (Switches) - Below the knobs, use the switches to Mute (Left-Click) or Solo (Right-Click).
    • Bands (Visualization) - Show the Low, Mid and High Send filter bands.
    • Equalization curve (Visualization) - Display the resulting EQ curve for the Send output in response to Low, Mid and High level changes.

    NOTE: If you want to use the Sends to split an audio signal for independent processing, you may want to prevent Frequency Splitters Main Output reaching the Send Tracks. Do this in one of four ways (choose the method that best suits your preferred workflow):

    1. Use Sidechain Sends - For all Host Track to Destination Track links, use Sidechain sends. This prevents the audio from Frequency Splitters Main Output reaching the destination Mixer Tracks via that route. Optionally, disable the Host to Master Track Send to ensure only the split audio is audible.

      Figure (above): The Master Send is deselected AND Sidechain Sends are used for Send Tracks, to avoid the Main Out making it to the Master by either route.

    2. Turn down the Host Mixer Track fader - Frequency Splitter internal Sends are pre-fader, so the audio will still reach the linked Mixer track/s (similar to how Fruity Send works).
    3. Mute Main Outputs - Use the Mute switches for the Low, Mid and High Main Outputs.
    4. Turn down Main Outputs - Set the Low, Mid and High levels to -∞ (muted).
  • Filter controls - Change the filter type, precision and responsiveness to Automation.
    • Filter type - Choose between Normal and Linear Phase filter mode.
      • Normal - Near zero-latency Infinite Impulse Response (IIR) filters tuned for an Analog Response curve. IIR filters allow near real-time processing and audio pass-through (see PDC).
      • Linear phase - Frequencies are split while maintaining perfect Phase alignment with respect to the input signal. This comes at the expense of additional processing latency (between 12 and 290 ms depending on the Precision setting).
    • Precision - Higher precision in selection of the Low cutoff frequency, particularly the slope of the low frequency range as it is moved to the lowest end of the range. The tradeoff for this precision is higher processing delay (see PDC).
    • Speed - Maximum parameter modulation slew-rate. Higher values allow faster automation, at the expense of greater plugin latency. Frequency Splitter features a proprietary engine based on advanced FFT filtering, that allows fast parameter changes (cutoff frequency and level), not possible with conventional FFT Linear Phase filters.
  • Monitor - Frequency monitoring. From left to right....
    • - Disable monitoring.
    • - Monitor the Input signal (pre-Equalization)
    • M (Main) - Show the Main output visualization.
    • S (Sends) - Show the Send output visualization.
    • O - Monitor the Output signal (post-Equalization)

    NOTE: When both M and S switches are OFF, the Input frequency visualization is shown.

  • Options (Menu) - Visualization options:
    • High precision - Increases the resolution of the background frequency spectrum monitoring at the expense of display latency (plugin audio latency remains unaffected).
    • Legacy monitor - Switches to the frequency-spectrograph algorithm used prior to FL Studio 12. The 'legacy' algorithm tends to blur the lowest frequency bands, but has the advantage it can be easier to identify the center frequency of these low frequency bands.
    • Monitor input - Choose the source for the background visualization.
      • MID - Center panned signal. Technically the MID signal = Left Channel + Right Channels / 2. NOTE: SIDE signals are invisible or less visible in this mode, as adding the L and R Channels will cancel out any differences between the L and R Channels. See Fruity Stereo Shaper for a delailed discussion of MID signals.
      • SIDE - Stereo signals. Technically the SIDE signal = Left Channel - Right Channel. NOTE: SIDE visualization is useful if you are mixing a phase inverted L or R Channel into the other side. MID will not display in these circumstances, as the center panned (Mono) information cancels to zero. See Fruity Stereo Shaper for a delailed discussion of SIDE signals.
      • Left / Right - Left or Right Channel.
    • Histogram Enabled - Show a frequency histogram display on the background. In this display the line (creating a series of peaks), represents the level of frequencies from 20 Hz to 20 kHz.
    • Range - Lowest dB activity metered. Choose from -60, -90 or -120 dB.
    • Pivot slope - Choose slopes of 1.5, 3, 4.5 and 6 dB/octave. These slopes pivot the spectrum around 1 kHz, visually increasing the height of high frequency peaks and reducing the height of low frequency peaks. A setting of 4.5 dB/oct shows a spectrum that is closer to how you hear it. All frequencies sounding at a similar loudness will look flat. This can be useful for looking at the frequencies of your final mix. Use 1.5, 3 dB settings if you find you are aiming for a mix with less bass and more highs. A setting of 6 dB/oct shows the frequencies of a basic saw oscillator as flat. This may be useful during sound design. When set to 0 dB 'white noise' will look flat.
    • Frequency precision - The number of bands used in the frequency spectrum. Higher settings come at the expense of visual display latency (although plugin audio latency remains unaffected).
    • Time smoothing - Depending on the Average mode setting, Time smoothing has different effects on peak reactivity and persistence.
      • Average mode OFF: The spectrum reacts to peaks. Smoothing sets how slowly the frequency peaks fall over time.
      • Average mode ON: The spectrum shows the average of peaks over time. Smoothing sets how long the averaging time window is.
    • Average mode (RMS) - Shows the average peak level rather than the instantaneous peak level.
    • Heatmap Enabled - Shows the intensify of frequencies from 20 Hz to 20 kHz as changes in the intensity of vertical line. You can think of this as the 'top-down' view of the Frequency Histogram view (above).
    • High precision - Shows more precise vertical lines. Switch this off to use an alternative algorithm that tends to blur the lowest frequency bands, but has the advantage it can be easier to identify the center frequency of these low frequency bands.
    • Enhanced frequency - Thinner lines are used to represent frequency.
    • Heatmap position - When the Heatmap is used together with the Frquency Histogram view, the Heatmap can be displayed above (Top) below (Bottom) or over (Full) the Histogram.

Plugin Credits: Daniel Schaack (Code), Miroslav Krajcovic (GUI).