Ruling on installing additions to loudspeakers in Mosques

If the installation of this equipment does nothing more than
improve the sound inside the mosque, there is nothing wrong with it, but if
it makes the sound of the letters reverberate then it is haraam, because it
means that it is adding a letter or two to the recitation, and changing the 
words of Allaah to something other than that which was revealed. It says in
al-Iqnaa’: Ahmad regarded it as makrooh to recite in a wavering
choice and he said: it is an innovation. If it also results in changing the
pronunciation of the Qur’aan and making the vowels sound like letters, then
it is haraam. End quote. 

But if the sound comes out of the mosque from the top of the
minaret and there are no other mosques around whose worshippers may be
disturbed, or dwellings whose people will be disturbed by the sound, then I
hope that there is nothing wrong with that. But if there are other mosques
around whose worshippers will be disturbed or dwellings whose  people will
be disturbed by the sound, then it should not be done from the top of the
minaret, because that is annoying and disturbing others. It was narrated
that Abu Sa’eed a-Khudri (may Allaah be pleased with him) said: The
Messenger of Allaah (peace and blessings of Allaah be upon him)
observed i’tikaaf in the mosque and he heard them reciting Qur’aan out loud.
He drew aside the curtain and said: “Each one of you is conversing privately
with his Lord, so do not disturb one another and do not raise your voices
above one another in reading Qur’aan, or in prayer.” Narrated by Abu Dawood.
A similar report was narrated by al-Bayaadi Farwah ibn ‘Amr, as was narrated
by Maalik in al-Muwatta’. Ibn ‘Abd al-Barr said: The hadeeths of
al-Bayaadi and Abu Sa’eed are saheeh. Shaykh al-Islam Ibn Taymiyah said: No
one should recite Qur’aan so loudly that he annoys others such as those who
are praying. End quote. 

Majmoo’ Fataawa Ibn ‘Uthaymeen,
15/160.