It is obligatory
that the Ma'mum recites Al-Fatihah. It will make no difference whether the Ma'mum recites it in a loud voice simultaneously with the Imam, while the Imam is reciting the Surah or during the period when the Imam is silent, if there is any, after reciting Al-Fatihah and before reciting the Surah. Actually, it is a multiple choice. However, reciting it during the period when the Imam is silent, if there is any, is preferable so as to reconcile the seemingly conflicting proofs on the issue.
Q: Should the person offering Jahri Salah (Prayer recited out loud) individually recite out loud or in a low voice?
It is recommended to recite it out loud for there is no evidence to the contrary.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.