If you are placing speakers in a small room, in a cabinet, or near side or back walls, you may be experiencing an effect called boundary reinforcement, which gives you too much mid-bass sound in your speakers.
The solution? Try a port plug! Perfect for both bookshelf and floorstanding speakers, a port plug can help to reduce boundary effects and give you clearer, faster imaging.
If you're using port plugs in a speaker with more than one port, add one plug to each speaker and listen for a few days. If your room or listening preferences are saying that there is still too much mid-bass, try adding another port plug. Experimenting is the key! Port plugs are sold and packaged in pairs.
If you would like more information, read Andrew Welker's post When Should You Use Port Plugs? or watch his video below.