Lowshelf Filter Node

The Lowshelf Filter Node is a standard lowshelf filter. Frequencies lower than the frequency get a boost (or an attenuation), frequencies over it are unchanged.

It’s also called a bass booster (or can be used to build one), because of how it can increase the amplitude of lower frequencies.

How to Use

The Lowshelf Filter Node needs a source audio signal connected to its audio input, to which it can apply the effect, and then output the result. The input audio signal can come from anywhere, as long as it's audible: an Audio File Node, Oscillator Node, Noise Generator Node all work. Click their output, then click the audio input of the Lowshelf Filter Node to establish a connection.

Connect to an Audio Destination Node to listen to the output, and play your project if your audio source needs it.


Audio Input

An audio signal to filter. You can also connect a control signal, but it will be largely unchanged.

Frequency-Control Input

A control signal to control the Frequency setting. You can also connect an audio signal, but keep in mind that it can cause the Lowshelf Filter Node to become unstable and reset. See the technical details section below.

You can enable this input from node properties, or by connecting to it.

Gain-Control Input

A control signal to automate the Gain setting, in dB, from -40 dB to 40 dB.

You can enable this input from node properties, or by connecting to it.



Frequencies below this setting will receive a boost or attenuation, depending on the Gain setting. The value is in Hz.


The boost to be applied, in dB. If set to a negative value, an attenuation is applied instead.

Filter Order

The order of the differential equation describing the filter. In simpler terms, when you increase the filter order, it’s essentially the same as chaining multiple Lowshelf Filter Nodes.


Audio Output

The filtered audio signal (or whatever is left of the control signal if that’s what you connected).

Technical details

The Lowshelf Filter Node is a digital biquad filter, and as such, it's possible for it to become unstable, e.g. in response to rapid frequency modulation. When this happens, the Lowshelf Filter Node will attempt to reset itself every few seconds, to avoid remaining unstable forever. This auto-reset is done in real-time mode (i.e. when you play your project), but not during exporting. That is, if the filter becomes unstable while exporting, it may remain unstable until the end of the exported audio.

Note: the behavior of this auto-reset is mostly non-deterministic, and depends on several undocumented factors. Don't rely on it to produce "glitchy" audio. Instead, use a Gain Node with an LFO-controlled gain, or a similar amplitude modulation technique.

Node conversions

★ With AudioNodes HD

Node conversion is available from the node menu.

Convert to: Highshelf Filter Node

When converting, FrequencyFilter Order and Gain values are transferred to the new Highshelf Filter Node