There's seems to be no way to do that (change time delay between rings) directly from the phone settings. However, the user may always create a custom ringtone with a custom duration of silence and then just copy that tone from PC to the phone.
Putting a delay between when the phone rings and when the phone actually receives a call may increase the risk of missing calls.
Try using a custom ringtone with a louder output volume instead. Phone speakers seems to be most responsive/efficient for tones within the 4,000 - 6,000 Hz range, so it would be beneficial to use a ringtone that has sounds within that frequency range.