You should self-troubleshoot if your computer has 2 of the 3.5mm jacks. When you want email support, please include the test result.
Can I use it with a smartphone or tablet/iPad?
No, the 3.5mm output connector of K667 is a TRS plug, and the mic itself needs 5V power to work. It means that you can only hook it up with a computer that has a dedicated 3.5mm MIC jack.
Can I use it with a speaker that has a 3.5mm AUX jack or plug it into a 6.5mm jack via an adapter?
No, neither input jacks mentioned above on the speaker provides a plug-in power supply. While K667 needs 5V power to work, it will not perform at all, even though the size of the input jack fits.