Here's an excellent article that dispels some myths of first reflections.
http://www.madronadigital.com/Library/RoomReflections.html
Regards,
Wayne
Interesting article. I have my own theory on how a room should be treated. First reflections are important but all reflections are more important.
The reality is there will always be reflections... you could never eliminate them ever. You can absorb them, or deflect them in other directions or break them up by diffusion. Lower frequencies benefit from passing through the walls/floor/ceiling so there is little to no need for me to do much to them. I have major echo in my room from bare walls bouncing back and forth. This is fact. The article said you don't see echo in small rooms but you do... because the distance the bouncing back and forth is so large. Absorption can be bad and I have a theory where you could essentially treat only half a room as treating one wall affects how the other wall sounds.
They say our ears are most sensitive around the 1,000-4,000 frequency range. I say only treat a room for these levels first then see if you even need to treat for lower frequencies which are less sensitive in comparison. Your telling me these ultra sensitive higher frequencies don't overpower the lower end? I think it does. Everyone says bass traps etc but in the end you suck the life from the room. Bass is suppose to be room filling for a reason, it's natural. I'm treating my room for 1,000-4500 and will leave it alone and see how it sounds.
First reflections is a joke because the entire room is reflecting everything from all angles back to you. Your responsibility is to treat the entire room equally but not entirely. What that article said is correct. Our brains need comb filtering for things to sound natural. It's in our everyday lives. If you listened to a stereo in an anechoic chamber it would sound bad. But... people always want to do minimal treatment due to economic reasons so first points are the first picks. The 2nd can be almost as strong as the first reflection. Treat the whole room.
This is why I think you shouldn't treat more than 50% of any wall space. You need reflections for natural sounding playback. Take my back wall for example it's 20.5'x7.75' tall or ~160sqf total. I already have a couch taking up the back wall space by around 34sqft. I don't want to treat any more than 80sqft of wall space. I'm placing two 1x8 diffusion strips, one 4'x7' qrd panel and two 2'x2' absorption panels which will total 52sqft of space... then add the couch and I'm at 86sqft of wall wall covering.
This alone leaves enough wall space to keep some comb filtering in affect to keep the wall sounding as naturally as possible yet reducing the decay to a reasonble level. This further reduces the front wall interaction by breaking up the back wall reflections. I'll move onto the ceiling where I have the same 160' area that will need the same 80sqft of treatment. Of this I'll do about 30% absorption (24sqft) and 70% diffusion (56sqft) so I'll make 6 panels 1'x4' and make 4 - 2'x4' diffusion panels and 4 - 2'x3' poly diffuser panels.
My other half of the front ceiling will mimic the back ceiling but in an alternating panel type fashion and the side walls will get 1'x6' tall qrd strips about 4 of these placed alternating distances with some 1x4 diffusion strips mixed in and then the area above the ceiling line in the cathedral part with get similiar covering.
