Maybe you're comparing your EV speakers to your Desktop's 5.1 Altec Lansing speaker system? ;)
Are you on a broadband connection with your Scribbler? My <s>Scribbler </s>, Acer, works fine on broadband Skype but not on dial up.
Do you have an array mic? If so change settings.
Just some initial thoughts, since your "Other sound/mic/voice features are working fine."