Based on your description of the problem with
muffled sound, it's possible that your center speaker is blown. However, there could be other potential causes as well.
One thing you can try is to disconnect the center speaker from your setup and test it with a different amplifier or receiver. This can help you determine whether the issue is with the speaker or with your equipment.
Another possibility is that the issue could be caused by a damaged or loose wire. You might want to check all of the connections between your speakers and your amplifier to make sure everything is secure and in good condition.
If you've tried these steps and you're still having the same issue, it's possible that your speaker is indeed blown. You can try replacing the speaker or taking it to a professional to have it repaired.