Asterisk connects slowly


I’m having a little problem with asterisk. I have 2 SIP clients configured, and when they call each other it takes some time to be actually bridged together (after they picked up) and be able to talk.

Its like i pick up the ringing phone, and i can’t hear the other party for 1-2 sec.

Any ideas?

Edit: strange, i tried two soft phones (x-lite) and the delay is gone. So probably it has to do something with the hard phones. They are D-link DPH-300S phones, no idea which setting could be wrong.