Has anyone got experience of building bass traps into the ceiling? We're about to replace our listening room ceiling (that is also our living room), and wondering if I should consider integrating some sound treatment at the same time. Am specifically looking at treating a 50Hz peak in a room ~11m x 5m.
my whole drop ceiling was one huge bass trap. pictures of my room show inset chambers and then dropped areas. the walls of those drops were open behind the fabric coverings.
over a 7-8 year period i slowly closed up all the openings.
the last step was 3 years ago when my speaker designer measured the room and found a narrow 10db suckout around 30hz, his opinion was that it's cause was the remaining ceiling openings mid room. 6 months later my son and i closed those openings and magically the 10db suckout was gone. which forced me to completely re-adjust my active bass towers.
so careful what you wish for.
Very good advice here. I've seen many efforts to attack one room problem with tuned traps, and more than 1/2 the time they create as many issues as they solve, and many times they don't end up in a useful place. Unless someone doing the modeling of your room has verified their model with measurements in your room, I would always suggest looking for more broad absorption which is focused in this range, where it most often becomes diffusive or reflective at high frequencies. Companies market under different names, but the general concept is to use some size perforation vs area with absorption behind the perforated layer.
Pegboard over absorption is the most basic example, where the thickness of the board, area of the holes, and trapped air volume determine the absorption vs frequency. To get low in frequency, you will most likely need a bit thicker board to lengthen the openings (similar to longer port length), larger and less area of holes to admit more low frequency, and more distance to the hard boundary behind the perforated layer.
One example of this would be say a pattern of wider spaced 3-5" diameter holes in a 1/2" thick sheet of plywood or MDF with 6-12" space behind the plywood stuffed with rockwool, fiberglass, or cotton insulation. There are calculators online and some programs will model such assemblies/cavities. There are a few limited range products that aren't resonant devices which are focused at lower frequencies using related concepts. GIKAcoustic has items like the
Soffit Trap with added Range Limiter, or their
Scopus Tuned Traps which are more targeted in frequency, but still broader in effect than a Helmholtz resonator.