Originally Posted by AndreYew
Room dimensions can cause a disaster (eg. cubical, concrete room), but they will never solve acoustic problems, because a room will always have modes. The real question is what you do with those modes.
So if I have a mode at 40 Hz, which has a wavelength of 28 feet, what kind of physical room treatment will fix that?
Depends. Need the whole picture. How many rows of seating? Need room plans/dimensions both inside and out. Are you at a peak or null for your listening position? There are 4 ways. Move the seating, move the sub, add resonator, or fork out for construction. You think Auto-EQ will fix it? I would first look into a resonator (looks like Noah posted before I could finish typing). Next question is it aesthetically pleasing? Not sure. You could possibly add a sub to help cancel the effects. There isn't a one answer fixes all problems. Every room is different. It takes trial and error while thinking outside the box. Witnessed one installation with subs in the ceiling. Not sure that is the safest method, but it worked. Just don't sit underneath one.
And sometimes you can't eradicate it. If you have a single row of seating, then you have a better chance of removing the effect at your listening position. That would not "remove" it from the room, but it would improve your listening position. I've not seen where you can buy off the shelf "products" tackling room modes. Custom solutions would most likely be required.
Maybe stop building rectangular or square rooms. Try different shapes. Who wrote a rulebook that all rooms have to be only be 4 walls?
From what I've seen with AUTO-EQ methods, if you are dealing with a peak it will lower the mic area neutering the next row. If you are at a null, then the next row gets lots of bass. If you use multi-mics for averaging, then you get a compromise with neither position being perfect in most "average household rooms".
Question: Did you try to fit a home theater into an existing room, or did you design a custom room with the assistance of an acoustic engineer, architect, interior designer, along with your custom cinema designer? Most don't want (or have) the money to do it right. Usually it's- Lets fit a theater into an existing room. I for one am not afraid point out the good and bad. And propose solutions to do it right. Sometimes it means moving walls, or changing the shape of the room.