K(a)-nip-ex, with the a after the K barely, if at all, audible. Go from the K right to the n, produces a kind of very short, breathy "H" sound. Takes some practice but there's plenty of German words like that: Knauf, Knödel, Knie, Knopf, knabbern, etc.
Another of life's mysteries solved. Thanks.
Happy to help :) Updated my original reply with more of the subtle details. When it's your mother tongue, you don't really pay attention to those until you really think about it.
Looked for a German video where it's pronounced the way we do. 'Khnee-pex' might be a good approximation. https://youtu.be/JIhBuHr5jtM?t=22