Hi there JM, and Welcome!
Where should I place the speakers (horizontally)? in the center of the baffle/front wall? how to determine this? is there any calculation or formula involved?
The center is not the best place, as it can lead to "focusing" or "lobing" of some frequencies. It's better to have it off-center. I have read that the ideal location is about 2/5 of the width of the soffit, but that often isn't possible, as it would put the speaker very close to one edge. So offset it as much as you can while still leaving a good margin.
Is it relate to where the spot of the mix position? so the meeting point of both speakers (60°) not fall in the half length of the room?
No, not really. First, forge the "60° equilateral triangle" that you see in so many places. That only works if the room is big and the speakers permit it. For most home studios it's NOT a good layout. The best layout is to start by placing your mix position at somewhere between 33% and 43% of the room length (in other words, somewhere around 38%, give or take 5% either way). Then position the speakers in the soffits so that they are NOT directly lined up with the corners of the room, and roughly as far apart from each other as the distance from the mix position (your ears) to the front wall, or preferably a bit more: So if, for example, the distance form the from wall to your ears is 180cm, then try to keep the speakers at least 180 cm apart. At the same time as you are doing that, angle the speakers so that they are both aiming at a point about 25 to 50 cm behind your head. If the angle is not 30°, that's fine. As long as it is somewhere in the range 25° to 35°, that's great. You can even go as much as 45°, but that's the limit. I try to not go more than about 40°, maximum, but 25 to 35 is good for most rooms.
So play around with those parameters until you get something that works: mix position 33% to 43% of room depth, speaker location about 20% to 40% of room width, and about 2/5 of the width of the soffit, speaker separation as large as possible, but at least the same as the distance from front wall to mix position, and speaker angle in the range 25° to 35°, aimed at a spot around 25cm to 50cm behind your head. For most rooms, that should give you a pretty decent geometric layout. If you do it correctly, you'll find that the axis of each speaker is pointing roughly at the tips of your ear lobe, or maybe a bit further out (a few cm, max).
2. If I go with heavy stand (brick stand) for the speakers, do I still need decoupling mechanism under the speakers?
It's better, yes. If that's what you plan to do, then consider using Sorbothane pads to decouple the speakers from the stand.
will it still vibrate the rest of the structure?
It is possible, yes. Unlikely, but possible.
3. Relate to #2, if I go with heavy stand, do I still need the bass hangers? since I think the space below is reduced.
That's one reason why I don't use brick stands inside soffits: It takes up all the space where you need bass trapping (hangers)! In my soffit designs, I use a very rigidly framed "shelf" that the speaker sits on (with a floating suspension system), and that shelf just runs across the inside the soffit, from side to side and front to back. There is a large slot in the shelf, to allow cooling airflow up past the rear of the speaker, and the framing under the shelf provides the support for hanging the hangers.
Hope I you guys understand my question.
They are all very good questions! It shows that you have been thinking about this carefully, which is a good sign!
- Stuart -
wow 