Third party wireless sub-woofers will not work with the Smart soundbar 300, we do have bass modules that are available to expand your soundbars ability.
The Bose Bass modules 500 and 700 were designed to be fully compatible with the Smart soundbar 300 for wireless connection.
If you have any further questions, let me know!
Feel more. Do more. Be more. Come check out my profile here. New to the community? Check out the Getting Started board. Help others find answers to your questions by clicking on 'Accept as Solution' at the bottom of a reply. If you see a post you like, make sure to give it a thumbs up!