i would like to know is there any solution for this to make it good.

If you mean will Dell do anything, the answer is no. If you mean how to repair it, download the XPS L502x Service Manual from this page. The service manual is available in a variety of languages (click the blue "more languages" button), and it will provide step by step instructions for replacing the speakers.

Note: when you follow the links to the manual, you will be able to view it in your browser; however you should perform an additional step and open it in Adobe Reader in order to view the manual properly. When you are working on your laptop you should have the manual open in another computer within viewing range. If that is not practical then you should print out the manual after opening it in Adobe Reader.

The part you need is this:

http://www.parts-people.com/index.php?action=category&id=143&subid=340&refine=speake

You might be able to find the part on ebay or some similar site.