Originally Posted by RayGuy
I have that chart too, and I have always used it to refer to the frequency range of various musical instruments. But, FWIW, I think there is a difference between the frequency ranges often used for audio/HT purposes and the terms used to describe the properties of musical instruments in charts like that one. And, I have also seen a lot of variation in charts like these. This one just happens to be my personal favorite, as well.
In his earlier post, Darth was referring to some demarcations of frequencies which may be commonly used for audio/HT systems. And, even there the ranges vary, depending on the source. I offer one approach below, which I believe makes some sense.
For instance, the tweeters crossover from the mid-range driver in many three-way speakers at about 2500Hz. So, it seems useful to think of high-frequencies as starting at 2,500Hz, and covering the three octaves up to 20,000Hz. The mid-range could be thought of as covering the roughly three octave range from 2,500Hz to about 500Hz.
Most three-way speakers may crossover from mid-range driver to woofer at about 400Hz to 500Hz. And, bass frequencies are typically thought of as starting at about 500Hz (480Hz actually), because that is where our perception of loudness changes, according to the Equal Loudness Contours.
I personally find it useful to further subdivide bass as follows. Upper bass would cover the two octaves from about 480Hz to 120Hz. And, mid-bass would cover the roughly one octave down to about 50Hz. That range from about 50Hz to about 120Hz is the average range where most people feel the mid-bass sensation known as chest punch. 120Hz is also a useful dividing line for mid-bass, as it was the frequency chosen to be the max frequency for the LFE (low-frequency effects) channel in the original Dolby/THX standards.
Low-bass would typically be thought of as covering the frequencies from about 50Hz down to about 20Hz. That's just slightly more than an octave, and below 20Hz would be the ULF (ultra low-frequency) range. That can comprise another full octave, down to 10Hz (for instance, most systems of automated room EQ only set filters down to 10Hz), or it can go a little lower than that for some systems and some usages.
There is nothing hard and fast about any of the demarcations I have listed, but they do make some sense. And, they do correspond pretty well to speaker and subwoofer design averages, to changes in the way we hear and feel certain frequencies, to the way that bass behaves in most rooms (frequencies tend to radiate omnidirectionally below about 500Hz), and to Dolby/THX standards.
I don't think that any two people in the audio profession would be likely to use exactly the same dividing lines, especially if they started at 10Hz and just began multiplying by two for each octave. But, the method listed above does offer a pretty rational and consistent way to carve-up the 11 octaves from 10Hz to 20,000Hz.