Good points to bring up. Basically jaxvon is correct. We do hear logarithmically. The 20Hz - 20KHz range is composed of 10 octaves with the highest being 10,000Hz - 20,000Hz. So if we laid out the whole frequency spectrum in a linear fashion that one octave (just as an example) would give a reader a terribly distorted picture.
I picked the 20Hz - 500Hz logarithmic scale on LMS for several reasons:
1. LMS will not, to my knowledge, convert to a linear scale. Their algorithyms for testing are written for the logrithmic scale.
2. The logrithmic scale really does graphically explain two aspects of low bass.
a) As you go lower each individual hertz lower becomes a harder and harder target to attain. (So the Hz are spread out more and more.)
b) The resulting curve, if hand-drawn (like I needed to do for the AV123 UFW10) gives an accurate representation of what type of rolloff the sub is actually doing. i.e. A sealed sub will show its shallower 12dB charactristic roll-off and a ported sub will show its 24dB/octave rolloff.
3. Correct me if you've seen otherwise, but all of the print mags I know of use the log scale.
Regarding the scale going up to 500Hz:
1. I wanted show an example of a well thought out and engineered design which (as I mentioned in my article) has an added bit of EQ boost to give a shallow roll-off, extended response. This type of curve will work okay for:
a) eliminating the frequency gap that will occur with those "cube type" speakers when playing music or TV programs which have no software-applied 4th order roll-off like DD or DTS.
How many hundreds of thousands of systems has Bose sold? Okay I admit that you'll hear stuff coming out of the sub that should be in the sats but my point is that if the consumer is smart enough to be stepping up to a single sub like this they will hopefully also be aware (by reading the many articles available on Audioholics) that a receiver with suitable bass management would also be part of the next step up to higher quality sound. (And that "suitable" bass management could then be intelligently applied to fit, for example, 2.1 music listening with a roll-off of 140Hz handing off to tiny satellites.)
b) Most subs DO NOT have a boost curve applied to the upper end of the scale to bring the response up closer to flat. In fact, if you pay close attention some of the third-party-tested subs in the print mags, like Tom Nousaine does for S & V, you'll see that many of the subs rolloff way BEFORE 100Hz so there are always lost frequencies (i.e. 60Hz to 100Hz) which can never be reproduced even when you've got DD or DTS software electronically adding their 4th order roll-offs (most times at 80 -100Hz, though the spec for both reads "up to 120Hz")
c) If you have a natural or electronically designed-in roll-off at frequencies around 80Hz-100Hz, plus you have the software-imposed rolloff for DD or DTS, you are, in effect cascading one roll-off curve on top of another. This many times results in an 8th order curve which is audible and which also makes the sub-sat blend or splice much more difficult to achieve.
The pro audio sub I designed for Alesis had an in-out, 4th order in>flat response out switch on its front specifically so sound mixers could hear what they were starting with (as far as upper bass frequency content) before they applied the software equalization in their DD or DTS encoders. Velodyne among others has also had such a feature on many of their more "serious" subs over the years.
Hope this helps....
