Originally posted by JT Clark:
The more the excursion, the more the distortion. The better subs will have more control of themselves at the higher excursion. That is, they have a larger linear region. One way of looking at xmax is where the sub goes from linear to non-linear. Also known as where the distortion becomes audible. Hearing this exact point varies from person to person, but there is a generally accepted measurement that extrememly few may be able to detect it below.
IIRC, it's necessary to have 4 times the displacement to create a frequency an octave down. So bass, especially the bottom end, takes a lot of displacement.
There is some more, but I'm not sure if I can explain it without getting technical. If you keep popping specific questions, I may be able to avoid that. I'll explain what I can.
you are saying two different things here. excursion does not CAUSE distortion and really by itself does nothing negative at all to the sound, it is, as you said, at the point where the movement becomes non-linear that distortion occurs. one would argue that if there was no point (or so small as not to be detected) of non-linearity, you could have any amount of excursion that you wished. you could have an excursion of 1 foot and it could have as much distortion as 0.1 inches if it is controlled correctly.
the reason why subs need to have large excursions in the first place is to move more air, which is i guess what you were saying in that 2nd paragraph.
to say that more excursion means more distortion is not true, because while it could, if controlled properly it will not. good subs control the movement well, while others do not.
my post about something needed for a good sub was servo control. servo control (which i explained above) basically negates any artifical output of the sub and keeps the movement along a linear path so as to minimize distortion. that is obviously watered down, but as you can imagine it makes a big difference.
its good to read up and find out a lot of cool stuff, but make sure you know how to apply it and what it means.
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