To ensure that your speaker cabinets are properly sealed, you can follow these steps:

1. Inspect the cabinet for any visible gaps or cracks. These can often be found around the edges of the cabinet and around any joints or seams.
2. Fill any gaps or cracks with a high-quality wood filler or silicone sealant. Make sure to smooth the filler or sealant out so that it is flush with the surface of the cabinet.
3. Once the filler or sealant has fully cured, sand the surface of the cabinet with fine-grit sandpaper to ensure a smooth, even finish.
4. Use a sealant or paint specifically designed for speakers to seal the surface of the cabinet. This will help to protect the wood and ensure that it is properly sealed.
5. Repeat these steps as needed to ensure that all areas of the cabinet are properly sealed.

It is important to make sure that your speaker cabinets are properly sealed in order to prevent air leaks, which can affect the performance of the speakers.