Studio Display audio latency when using GarageBand

I am running my guitar through a digital audio interface (Pyone), then throughGarageBand to add effects, and then to a studio display speakers. I get a small but annoying delay in the output. The delay is NOT noticeable when I switch the output to Mac Mini speakers. I conclude that the processing in the studio display is causing the delay but I can't see any way to decrease the delay. Any suggestions??