Originally Posted by LTD02
"I agree with Bosso that's its about constructive waves at very long wavelengths."
it is not according to drs. rienstra and hirschberg who are at one of the most prestigious technical universities in europe. one is a physics and math professor, the other is a physics and fluid/gas dynamics professor.
see sections 2.2.3. on compactness and 4.1 on plane waves (read through to the first footnote, about one page) where it is discussed how below the critical frequency, air, which is normally a compressible fluid, behaves as an incompressible fluid and pressure is pretty much uniformly increasing and decreasing everywhere at the same time.
if you'd like to discuss it some more, revive the other discussion thread.
Apparently you haven't read that paper or much about propagation of sound pressure waves in general. Plane waves (surface waves, however they refer to them in whatever paper, all being the same 1-D waves) are not relevant to the discussion. You have to skip to the Spherical Waves section, where you see the appropriate disclaimer:
The paper even takes the spherical wave and reduces it back to a plane wave. ^^ Well and good for the purposes of the paper, but sadly, irrelevant to us.
In our rooms there are no "hard walls" (which don't exist except to make a formula work), there is no "far field", which means there are no plane waves to discuss and this rather lengthy paper does not address boundary reinforcement, transmission losses through various boundaries (that relate to us) and there is no such "critical (sound) frequency" formula for a lossy listening space.
This is a no-brainer. If the "critical frequency" is simply derived from the rooms longest dimension, why does that not jive with the actual responses posted by members here?
Twice the longest dimension in my room works out to below 20 Hz. So, why does room gain begin at nearly an octave above that, and why does everyone else's, regardless of the huge disparity in the "longest dimension" (the critical) part of the equation?
Here's the bottom line:
We have data posted by members. In order for the data to be of any use, we have to find a global explanation with variables resulting in a window, sized by the weight of the evidence (an average).
The facts are that progressively constructive reflections fits nicely with the data, the variables being (a) transmission losses variability due to the construction of the boundaries (which also works toward simplicity because there aren't infinite methods employed in the construction of boundaries in the national building codes) and (b) signal chain roll off.
This makes it simpler to predict in-room performance when attempting to expand the BW of your system. This is why I can predict the in-room response of a sealed system given only (a) the signal chain roll off, (b) the systems naked response and (c) the construction method of the boundaries far better than anyone else can with the PVG critical frequency, sealed vs open stuff, and will be happy to prove that any time someone is interested.
If we site white papers and endlessly discuss the irrelevance of them, we end up where we began... at Best Buy, or we throw displacement and amplification at the problem. Neither approach is illegal, but they certainly aren't optimal or a guarantee of success.
BTW, I really don't want to get into a generalized "everyone is right, everyone is wrong" circle jerk. I'd rather use the thread we end up in so that our discussion may be related directly to the OP's room/system/results. That's how we learn something of value, IMO. The OP has the right to yell "scram" anytime he wishes.