Here is some information presented by P. D'Antonio, with a PhD in diffraction physics - he knows a 'bit' about the science of absorption and diffusion. I think that means he does not depend solely on reading forums or searching online for opinions regarding the understanding of absorption and bass traps in particular. He also owns a small company called RPG, Inc.
From Acoustic Absorbers & Diffusers by D'Antonio & Cox
1.3 Modal control in critical listening spaces
...Particularly prominent modes are usually treated with bass absorption, often referred to as bass traps or bins. (It is not usually possible to treat this problem with diffusion because the sizes of the diffusers become prohibitively large, although Section 2.2.3 discusses a case where this has been done.) Porous absorbers are not usually used, as they would have to be extremely thick to provide significant bass absorption. Porous absorption is most effective when it is placed at a quarter wavelength from a room
boundary, where the particle velocity is maximum. For a 100 Hz tone, this would be roughly 1 m from the boundary.(At the 1/4 wavelength of the lowest frequency to be absorbed...)
Placing porous absorbers directly on a room boundary, while the most practical, is not efficient, because the particle velocity at a boundary is zero. Too often, many people place porous absorption in corners of rooms thinking this will absorb sound, since all the modes have a ‘contribution’ in the corners. However,
while the modes have a maximum pressure in the corners, the particle velocity is very low and so the absorption is ineffective. For these reasons, resonant absorbers are preferred for treating low frequencies.
Resonant absorbers are mass spring systems with damping to provide absorption at the resonant frequency of the system. The mass might come in the form of a membrane made of plywood or mass-loaded vinyl. Alternatively, the vibrating air in the neck of a hole might form the mass, as is the case for a Helmholtz resonant absorber. The spring usually comes from an air cavity. Damping is most often provided by sound being forced through a porous resistive material: mineral wool, fibreglass or acoustic foam.
The problem with resonant absorbers is that they usually only provide a narrow bandwidth of absorption. To cover a wide bandwidth, a series of absorbers are required, each tuned to a different frequency range. Alternatively, double-layered absorbers can be used, but are expensive to construct. In recent years, a new resonant absorber has been constructed where the vibrating mass is a metal plate and the spring is formed from foam or polyester, and this provides absorption over a broader bandwidth.
1.11 Summary
This chapter has outlined some absorber applications, and touched on some of the issues that will be important in future chapters. It has also introduced some necessary mathematical principles. The remaining chapters concerning absorption are as follows:
• Chapter 3 discusses measuring absorber properties from the microscopic to the macroscopic.
• Chapter 5 discusses the application, design and theoretical modelling of porous absorbers.
• Chapter 6 discusses the application, design and theoretical modelling of resonant absorption, especially Helmholtz and membrane devices.
• Chapter 7 sets out some miscellaneous absorbers, which did not obviously fit into Chapters 5 and 6. Seating in auditoria, turning Schroeder diffusers into absorbers, sonic crystals, trees and vegetation are considered.
• Chapter 11 discusses hybrid diffusers, and as these cause absorption, they are also an interesting absorber technology.
• Chapter 12 discusses how to use predictions and laboratory measurements of single absorbent properties (mainly absorption coefficients), in room predictions, including the role of absorption coefficients in geometric room acoustic models.
• Chapter 13 rounds off the work on absorbers by looking at active impedance technologies.
Its your choice.
We can give you general guidelines for bass traps if you like. Or you can simply serendipitously copy all of the advice on the web and 'experiment'. Of course part of the 'fun' of doing that is discovering how much of what so many says is correct, is actually wrong. But hey - I certainly wouldn't want to be accused of stifling anyone's 'creative' intuition.
And seeing as you are already complaining about that, it seemed prudent to refer you to THE definitive source on the subject.
The current 'best of breed' porous corner trap is to build a 2foot by 2foot (or 2.5 foot) by ~34inch (or 38 inch) face covered with a minimum of 6mil thick plastic. The interior is divided into several sections with plastic orchard netting to minimize compression of fluffed 'pink fluffy' Fiberglass fill and the front netting stapled closed. This is then covered with >=6mil plastic and an aesthetic cloth face cover. These are typically needed in a minimum of all four vertical corners...
But hey, its your choice.
And don't ignore resonant absorbers...
Good luck.