Thank you Wayne for that very in-depth paper on House Curve.
It was quite interesting. Your really have me thinking now.
I will start up-front by saying that I don't consider myself a true-believer in the House Curve for home use - yet. I will also say that I still have an open mind and am considering all options.
In doing a little research of my own, I ran across an article written for Surround Professional by Tomlinson Holman of THX fame. Curiously, the x-curve quote attributed to Mr. Margouleff in your article appears word-for-word in the last paragraph of Mr. Tomlinson's (without any credit). Mr. Tomlinson's article was written in 2000.
http://www.micasamm.com/publications/surround_0100b.htm
I would be interested in your thoughts on the following statements:
The rolled-off house curve has a good basis in psychoacoustics, because a soundfield originating at a distance is "expected" to be more rolled-off than one originating nearby. It is a little like optical illusions in vision that show, despite occupying the same area on the retina, pictures look bigger on a larger screen, even when a small screen is closer and takes up the same horizontal and vertical angles. As it turns out, both spectrum and level are affected by the perception of the size of space you are in, and "getting it to match" perfectly from large to small room in physical sound pressure level and response does not result in sounding the same.
The issue we are dealing with in a home setting does not appear to be based on the same cause or does it?
"Another development of the X curve is how it should vary with room volume. Although a variation in the response with room volume was written into the original standard, further work shows that the response should be "hinged" at 2 kHz, and turned up at high frequencies in smaller rooms. Curves that extend the range out to higher frequencies before breaking away from flat do not seem to interchange as well."
What do you make of this given your theories on the subject?
Although a bit off topic, I was also surprised to see this:
"The largest variations among different practitioners are in the use of microphones. The problem is that the soundfield seen by a microphone in a large room is a mixture of direct sound, early reflections, and reverberation. Standard measurement 1/2-inch microphones demonstrate very different high-frequency response when measured anechoically on axis and with a diffuse field. Differences are on the order of 6 dB in the top octave between the two, and response in rooms is highly affected by the differences between these two. Only by the use of small, low-diffraction microphones, such as 1/4-inch or smaller diaphragm mics, are the differences kept small."
My SPL meter has a 1/2" mic as I suspect the majority of meters out there do. I wonder if a smaller mic would actually be more acurate for measuring SPL for home theater? I wonder if the key is the size of the room?
I understand Mr. Tomlinson's suggestion to measure
"grazing incidence across the diaphragm rather than perpendicular to the soundfield" do to the diffuse nature of the surround channels but I don't really understand the need to use a smaller mic.
Mike