Short answer
Gathering to remember Allah is virtuous: authentic hadith say angels surround such gatherings. On doing dhikr aloud, the Hanafi texts say quiet dhikr is better in general, and loud dhikr is allowed as long as it disturbs no one praying, sleeping or reciting and is free of showing off. Scholars differ on fixed forms of dhikr in unison.
Gatherings of dhikr are mustahabb. Quiet dhikr is better in general; loud dhikr is permissible when it harms no one and is not done for show, and is makruh when it disturbs others. Treating a particular invented form or time as a required sunnah is not allowed.
The four schools agree on this.
Explanation
Gathering for dhikr. The Prophet ﷺ said Allah has angels who roam the roads looking for people of dhikr, and when they find them they surround them up to the lowest heaven (Bukhari). He also said no group gathers in a house of Allah to recite and study the Quran without tranquillity descending on them (Muslim). Sitting together in a halaqah of Quran, dhikr and learning is clearly good.
Loud or quiet? Both have evidence. On a journey the Companions raised their voices with takbir, and the Prophet ﷺ said: "Go easy on yourselves, you are not calling someone deaf or absent" (Bukhari). Allah says to remember Him "without being apparent in speech" (7:205). On the other side, Ibn Abbas said raising the voice with dhikr after the fard prayers was done in the Prophet's time (Bukhari). Ibn Abidin brings these together: dhikr aloud is allowed and can be better where it wakes hearts and encourages others, and quiet is better where there is fear of showing off or of disturbing others.
Where scholars differ. Many Hanafi scholars, including those of Deoband, allow loud dhikr in Sufi circles as a means of training the heart, provided it is not believed to be a required sunnah in that form and does not disturb others. Other scholars consider dhikr in a single voice at fixed times an innovation. This is a matter of legitimate difference; it should not divide a masjid.
For ordinary practice, quiet personal dhikr is safe for everyone. See the best dhikr and Quran khatam gatherings.
The evidence
Quran, Surah Al-A'raaf 7:205
وَٱذْكُر رَّبَّكَ فِى نَفْسِكَ تَضَرُّعًۭا وَخِيفَةًۭ وَدُونَ ٱلْجَهْرِ مِنَ ٱلْقَوْلِ بِٱلْغُدُوِّ وَٱلْءَاصَالِ وَلَا تَكُن مِّنَ ٱلْغَٰفِلِينَ ﴿٢٠٥﴾
And remember your Lord within yourself in humility and in fear without being apparent in speech - in the mornings and the evenings. And do not be among the heedless.
Quiet remembrance is praised.
Sahih al-Bukhari 6408
Sahih... إن لله ملائكة يطوفون في الطرق يلتمسون أهل الذكر ...
"Allah has angels who roam the roads seeking the people of dhikr."
Gatherings of dhikr are loved by Allah.
Sahih al-Bukhari 2992
Sahih... اربعوا على أنفسكم فإنكم لا تدعون أصم ولا غائبا ...
"Go easy on yourselves, for you are not calling one who is deaf or absent."
Shouting in dhikr is not required.
Sahih al-Bukhari 841
Sahih... أن رفع الصوت بالذكر حين ينصرف الناس من المكتوبة كان على عهد النبي ...
"Ibn Abbas said that raising the voice with dhikr when people finished the obligatory prayer was done in the time of the Prophet."
Some audible dhikr has a basis in the Sunnah.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, discussion of raising the voice in dhikr. Reconciles the reports on loud and quiet dhikr.
- Fatawa Mahmudiyya, Chapter on dhikr and Sufi practice. Deobandi view on loud dhikr in circles of spiritual training.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.