You didn't say which Mic capsule you have fitted to the SLX-2.
Looking at the spec. there is an option to fit several different mic capsules. As far as I can see, the popular option is the SM58.
The SM58 cartridge has a Cardiod (Unidirectional) response which helps to combat feedback. If you are using a cartridge which has a Omnidirectional response, then you are more likely to get feedback problems, when the mic is close to the KN7000 speakers.
In the past, I have used the KN7000 mic system without any problems and still use it occasionally - purely for announcements - not vocals!!
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Willum
After silence, that which comes nearest to expressing the inexpressible is Music.
Aldous Huxley
( especially when the music is played on a KN7000....)