Contact the speaker manufacturer. They built em. They may suggest sanding and refinishing. They will know the finish product to use.

This may or may not help you. I bought a used oak coffee table (in great shape and cheap) on FB, but it had a watermark on it. I’ve treated it several times and the mark is almost gone. Here’s hoping once more will do the trick.

I dip out a 1/2 teaspoon of Hellman’s real mayonnaise onto a paper plate and dribble in several drops of Old English furniture polish. Mix well with a qtip and smooth it over the watermark with a paper towel. Don’t leave enough on there so it looks goopy but still enough so it’s obviously there. Let sit for 3-4 days and then lightly smooth it out with a clean paper towel.

This worked for me:

AI Overview

To clean a furniture spill with a hair dryer, first blot the area dry, then use the hair dryer on a low or medium heat setting, held a few inches away from the stain. Move the dryer in circular motions and avoid keeping it in one spot for too long to prevent damage. Monitor the stain and, once it fades, allow the wood to cool before applying a furniture polish or oil. 

"By its shape a bourbon bottle is likely" . I have never been successful removing stains caused by alcohol as it typically penetrates the finish, unlike water. I'm fairly certain you will not be able to remove it and it will require sanding to bare wood.