Originally Posted by desertdome
There are basic acoustic principles that can be applied to every theater construction project. The difficulty is in determining the absorption coefficients of various materials and designs. The professionals use modeling software that I don't think can account for things such as soffit bass traps, DIY materials, custom stage/riser sizes, etc. The rooms are designed using know products (Quest), known dimensions, and a standard riser/stage layout. Once you deviate from these, then the model doesn't work as well. Without the ability to predict what will happen, I think some might be hesitant to make recommendations even though standard acoustic principles will still apply.
One example is FoLLgoTT's Single Bass Array
with subs up front and heavy absorption in the rear. He achieves almost perfect bass response with very little EQ. I haven't seen any professional builds utilize this method. Its probably because it can't be modeled in their current software.
The challenge is balancing the different elements in the theater to deliver the end results. One cannot just apply all the 'rules of thumb' seen on AVS (soffit traps, riser traps, use 1" linacoustic, no use 2" linacoustic with a poly sheet inbetween, no use 4" minimum absorbers everywhere...and the rest of them!) and expect a superb end result.
When you are aiming for very good all the design elements have to be considered together. For example designing a multi-sub array
to cancel all axial room mode activity in the sub's passband (below 80Hz typically) and using a double drywall / green glue wall on channel and clips as a bass trap (yes the wall becomes a very good bass trap under 60Hz) together with designing in a suitable digital signal processor from the get go (yes it's fine to EQ if seat to seat variability is low, which is achieved through the multi-sub design) will mean that no special effort is needed in adding acoustical treatment to 'trap' bass below 100hz.
Another example is in the high frequencies. What we hear is some combination of direct + early reflected + late reflected sound
. Different speaker designs will throw out different amounts of energy in the high frequencies and therefore have different issues that need addressing. JTRs, for example, have very narrow high frequency dispersion due to the waveguide (they don't publish their numbers but I know the waveguide they are using and it is around 60 degrees from memory....not all waveguided speakers have that narrow a pattern, Procella's for example are 80 degrees horizontal). It would be very easy to overdeaden a room with this type of speaker - ideally the acoustic design for such a room wants to keep as much energy in the late reflected field as possible. Contrast this with the off axis performance of a wide dispersion speaker such as a cone/dome
and one would have a very different approach to the overall acoustic treatment design, with more absorption outside the major reflection points in the room. The acoustic treatment design for the frequencies above the room's modal area (300Hz for sake of argument) starts, or should start, from the speaker outward. Anyone using the same design and approach for speakers as different as Triads and Procellas is not taking into account the speaker's off axis performance. Speaker outwards!
Unfortunately there is no magic single 'home theater acoustic modeling software'. What we have is a collection of tools that can be used to predict results. Optimally we would do some combination of low frequency modeling using either a basic room mode calculator or boundary element modeling software, reflection point analysis using ray tracing, speaker boundary interference analysis using mostly proprietary in house tools (Excel spreadsheets in my case), T60 estimators, real on / off axis measurements of the speakers in use, geometric modeling of the speaker / room interaction, WOW this is a long list and I don't think I've captured everything either!
Of course all of us designers latch on to things that seem to work well and reuse them as design elements in future projects. That's real world experience.