Might be due to the expensive shipping...they are only willing to ship me 6 items...3 each...for 6 months!!! Meaning I have to wait another 6 months before I can get another batch of samples...dohz
Matttcattt said:
Slope for starters. 1st order is 6db/octace, 2nd order is 12, 3rd 18 and so on. This means a 2nd order rolls off fasters than a first order. But, I think a 2nd order will invert the signal, where a first order won't (either that, or it's the other way around)
Randy
Actuallya 2nd order will invert the signal, a 180 degree phase shift while a 1st order will induce a 90 degree phase shift, 3rd 270 degrees and 4th 360 degrees, that's why it's often to her that 4th order networks are "phase coherent". And yes, I know that it's much more complicated that this, but I just wanted to provide a brief explanation, there are other threads explaining it more i ndetail.
JoeBob said:
Hi JoeBob,
Thanks for the correction, I did not know it changed 90 degrees per order like that.
Randy
what do you mean by faster rolloff? do you mean that the sound will be cut off nearer to the cutoff frequency?
Matttcattt said:
What you call the cutoff frequency is really the corner frequency. The signal does not just stop at that frequency, it is the point where the amplitude of the signal starts to get smaller.
The higher order the filter, the faster the amplitude of the signal will get smaller.
A picture may help show this.
Go here
http://www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/filter/filter.html
Select the "mag-phase" button (it's next to the circuit button). Then change the order of the filter, and see what happens to the graph as you do it.
Randy
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