Sounds like a Sampling rate mis match from your Studio One project settings to your audio device settings.
Example. If you recording at 96khz Sample Rate within Studio One, mixdown to wav or mp3 file, then play that file back with say iTunes or Windows Media Player while your audio device is set to 44.1khz Sample Rate, it will sound slow, distorted and other anomalous audio artifacts/aliasing. Conversely things would be faster if playing a mixdown at 44.1khz with an audio device set to 96khz.
Make sure that you have your Audio Device set to the "same" Sampling Rate as your DAW and or mixdown file.
I'm pretty sure this is what going on for you. Search around online for any additional information about Sampling Rate Mismatch issues.