It's a place of gathering for worship and sermon.
We will use a keyboard, percussion pad and 5 microphones connected to a 8 channel mixer.
Based on reading some articles I narrowed it to 12" 125w speakers. I am yet to decide on the make / model. The dimension of the hall will be 60Lx40Bx15H in feet.
Will this be used on a recurring basis? If so, I would suggest hiring a sound company so you can rent a system and have them set it up for the first time- that way, it should work as planned
if they know what they're doing and you won't be on the hook if it doesn't. In the long run, it would save headaches, financial loss and frustration because this isn't a typical application of making things loud and not caring as much if speech is intelligible.
Describe the interior of the space- are all of the walls flat with no bumps or small outcroppings, is the ceiling flat, slanted and is it supported by trusses or large beams? What surfaces- carpeted floor, or tile/wood? What about the walls- are they very smooth, or does the building have small columns at regular intervals?
For speech, the requirements are different from what's needed for music, partially because the sound level isn't as high- this falls under the category of 'House of Worship' sound systems, which you can look into online and it's a big part of commercial sound contracting.
Where are you located?
The first link shows large installations and they don't apply to your needs, but the information and details do- it will also give you information to mull over and some of that will be good for clues as to what you need to look for.
A Look at Some Recent Audio Upgrades This year, most sectors of the live event industry have been hit hard, yet there has been activity on the installation front, particularly in the house of worship and educational markets, as schools and religious organizations take this opportunity to prepare...
fohonline.com
The second link is for a manufacturer of audio equipment that's used extensively in this area- you might contact them for help in selecting equipment.
www.qsc.com
Don't overthink this, but don't underthink it, either. You need to define the needs-
- High sound levels, or more moderate?
- Who will operate the system? Do they have experience with this, or will it be operated by various people with different levels of knowledge about how it works and how it should sound?
- Will the system need to be expanded at any time? It might be better to buy a mixer with more channels now, rather than find out that you need more without time to address the problem.
- The world has changed greatly in recent years- it's no longer necessary to use a huge mixer with a sea of knobs and sliders- a decent mixer that uses a laptop/desktop computer or tablet for control is now available for a very affordable price and the best part is that the controls won't need to be cleaned or maintained.
Here's a 12 channel mixer from SoundCraft- I used one of their non-IP models in 2018 for a school gym and it fit their needs nicely. The videos might be more technical, but they give you something to chew on-
The Ui Series mixers feature cross-platform compatibility with iOS, Android, Windows, Mac OS, and...
www.soundcraft.com