Monitors / Monitoring

I produce electronic dance music. Much of the time I work with headphones on, to help me focus on detailed sounds in repetitive loops. However, I often notice that when I switch to listening on speakers (to check the actual mix and so on) the track seems a bit faster. What could be the cause?

These active monitors can have their responses tailored to suit their environment when used with the powerful four-band DSP equaliser option.