Two of Salmon's victims were in the public gallery and cried as the summary of facts was read.
Crown prosecutor Claire Boshier said they would suffer lasting trauma.
"There were serious effects, with some victims considering suicide and self-harm, and others will continue to be affected by this for quite some time."
A psychiatric report found there was a high risk of Salmon carrying out further sexual offending.
Ms Boshier told the court Salmon had shown next to no remorse.
"His insight into the impact of his offending on his victims appeared to be lacking, and he appeared to minimise this."
Salmon said he would have never followed through with his threats.
* On September 11, 2015 the Herald stated that Karl Salmon had pleaded guilty to a charge of rape in the proceedings reported above. In fact he pleaded guilty to a charge of sexual connection with a girl under the age of 16 years after having intercourse with her.