A type of
compression where the onset of compression is gradual. In normal or hard knee compression when the signal reaches the
threshold the unit immediately begins to compress at whatever
ratio is set. In some situations the compression becomes very easy to hear (which is often not desirable) as the signal
amplitude moves above and below the threshold. This is usually made worse when using high compression ratios. The solution is to have the compressor gradually enter into compression at a lower ratio prior to the signal reaching the threshold. The ratio is gradually ramped up as the signal gets louder until, at some point beyond the threshold, the full compression ratio is reached. This slower onset often makes the compression much more difficult to detect. The process is called “soft knee” because of how the compression ratio looks when plotted on a graph. In normal compression the knee (which is the point where compression begins) is an abrupt angle (how steep depends on the ratio) whereas in soft knee it is more of a curve.
