I’ve recently come across this website/tool that makes finding speaker to listener reflection points really simple, great for working out where to place acoustic treatment in your home theatres
The site is https://amcoustics.com/tools/amray
The below demonstration is for my home studio, sound design and mixing room. My speaker and listening postions will be different than a home theatre but the same process applies
Draw the walls of the room as accurately as you can. (If you have angled walls/ceiling like 123toid has in his new theatre and the flat part of the wall stops below seated ear height try and use the dimmentions of the room at listening position head height/speaker height)
Add the soundsource in the position of your first speaker
Change the ray tracing algorithm to triangular and add the listening position
Change the reflection order to 1 and you will now see the first reflection points drawn out for that speaker. Make a note of the positions or take a screenshot, this will be where acoustic treatment wants to be placed
Move the soundsource to the position of your next speaker and make a note of/screenshot these new reflection positions
Repeat this for each speaker you want to treat reflection points of. This is likely going to be your main LCR and side/rear surrounds. Atmos overhead speakers can probably be ignored for this process
When you have done this for all of your speakers you can take the noted reflection points/screenshots and using tape mark them out on your walls at listening position head height, blue painters tape is a good option for this.
These tape marks are the places you want to add acoustic treatment, you can decide how big each panel needs to be based on the dispersion of the tape e.g. if you have several tape marks landing near each other you can make a single larger panel to cover all of them
If after placing your treatment you can still hear some annoying reflections from certain speakers or for those just wanting to take their room treatment to the next level you can change the reflection order to 2 and find any secondary relfection points.
A word of warning: This could start to get a bit confusing and/or overwhelming for those less experienced with room acoustics and acoustic treatment as you start to get an exponentially complex spiders web of lines
For most people in home theatre setting only playing back content (not recording and mixing audio) just focusing on the first reflection points (reflection order 1) should be enough to significantly improve the audio experience of your theatre and by spending the time to carefully calculate reflections and plan the size and position of your treatment you can help keep the costs down by not wasting time and money on putting extra treatment in unneccessary locations
@123toid Maybe this could make a good YT video topic explaing the principles and going through an example how to use the tool
Josh Evans, Professional Live Sound Engineer, High End Commercial AV Install Technician