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I have seen a couple of case that did not have a speaker fitted. I have also had to replace a couple of case speakers because they were to quiet. I just grabbed one from and old case and swapped them over. If you look at the two links below you will see an example of both types (that I know of) one large one small. Check them out and then see if you have either in the case.
large = http://www.directron.com/casespeaker.html
small = http://www.directron.com/d500speaker.html