Question: It is said that as it is not permissible to perform salat by following anyone other than the imam it is not permissible, either, to perform salat by following the sound emitted from a loudspeaker. Then why is it permissible to follow the voice of a muballigh even though he is considered someone else?
Muballigh is a person who performs the same salat with followers and who repeats the takbirs that the imam says for the followers behind when there is a large number of followers and when the voice of the imam cannot be heard from all directions. If a person from the outside says takbir, it is not permissible to follow his takbir. The muballigh is not someone from the outside, but the helper of the imam among followers. Our religion permits the muballigh to help the imam. Following the words of the muballigh is to follow the imam. However, giving an answer to a person from the outside or doing an action at the behest of him nullifies salat.
The sound emitted from a loudspeaker is neither a transmission of sound nor an echo. When the imam speaks into a loudspeaker, his voice is converted into sound produced by electricity and the magnet. That is, the sound emitted from the loudspeaker is not the original voice of the imam, but the sound produced by the iron plate vibrated by magnetic forces activated by electricity. The image of the imam on TV is not the imam himself, but only an image. His voice on TV is not his original voice, but only similarity. So is the case with sound emitted from a loudspeaker. I will give some examples for cases when salat is nullified:
1. Saying "Amin" to the du'a of someone else other than that of the imam nullifies salat. For example, if some people are performing Salat al-Maghrib while one is performing it individually, one's saying "Amin" to the imam of those followers when he completes Surat al-Fatiha nullifies one's salat because he is not the imam one is following. Similarly, if a person says “May Allah forgive your sins" to a musalli and if the musalli says "Amin," the musalli's salat will be nullified.
2. Correcting the mistake of someone else other than that of the imam nullifies salat. For example, if one or an imam a musalli is not following recites the Qur'an al-karim wrongly and the musalli corrects it, the musalli's salat is nullified because he is considered to have given an answer to an imam he is not following. If the imam the musalli is following recites wrongly or if he is unable to complete a verse, the musalli's correcting it does not nullify his salat because the person correcting the mistake is the one among the followers of him.
3. If the wudu' of the imam breaks, he can appoint a substitute in his place among the followers of him, but he cannot appoint someone who is not of the followers as a substitute. If a person from the outside comes and wants to lead salat instead of the imam when his wudu' has broken, he is not allowed to lead salat for those followers.
4. If a person comes and tells the musalli to move a little to make room for the former and if the latter moves at the behest of the former, the musalli's salat will be nullified because he has moved by order of someone else in salat.
The muballigh cannot be compared to the loudspeaker. He is the helper of the imam who transmits his voice by order of our religion. As for the loudspeaker, it converts the voice of the imam into some other sound, so they are not similar in any way.