Here's what Ashdown say about the Studio One Compressor:
As a hardworking bass player – and at the detriment of your reputation – the demand for a perfect recording session is paramount.
By nature, studio compressors are widely used for levelling the audio signal, limiting to prevent unwanted distortion and for dynamic range preservation. Generally, a good studio compressor, if used correctly, should really only be noticeable to the player and imperceptible to those listening to the performance.
Designed with the studio bass player in mind, the Ashdown Studio Compressor tames the dynamic range of your signal so that there is less inconsistency between the loudest notes and the quietest notes and also providing a way for you to control the manner in which it does this.
The Studio Compressor has controls for “Threshold”, which sets the level at which the unit starts to limit the signal, “Ratio” which sets the amount of compression and an overall “Gain” control which allows the signal level to adjusted.
A low threshold ratio vs a high threshold ratio means how much (or little) the signal will get compressed. Typically, a low threshold compression comes in earlier, capturing the signal and wrapping it sooner before putting it to the amplifier. High threshold compression comes in later - enabling more of the signal from the path to be put out to your amplifier before being compressed.