Filters -> poles, order, Q, slope, bandwidth, WTF?

[Tricky-Loops]

Generally high Q -> low bandwidth and the filter design is based on resonance, so higher Q (also called quality) produces more resonance, because that's the only way the filter could satisfy the "low bandwidth" requirement, speaking of normal language, a little normal at least .

Let's show it in a picture:

[CableChannel]

Ahhh so I think where I am wrong is that for me bandwith = order. That is wrong. Bandwidth = Q, and order is just order. Right? That would fit with these images:

low Q, low order


low Q, high order


high Q, low order


high Q, high order

[Tricky-Loops]

"Order" is about the steepness of the curve!

As I said:

1st order = 1-pole = 6 db/Oct
2nd order = 2-pole = 12 db/Oct
3rd order = 3-pole = 18 db/Oct
4th order = 4-pole = 24 db/Oct

and so on...

[CableChannel]

You sound like teaching me, but this is exactly what I said!

[manducator]

Ahhh so I think where I am wrong is that for me bandwith = order. That is wrong. Bandwidth = Q, and order is just order. Right? That would fit with these images:

low Q, low order


low Q, high order


high Q, low order


high Q, high order

Is it me, but I can't see a difference between the last two pictures?

[Tricky-Loops]

You sound like teaching me, but this is exactly what I said!

Sorry, if I tried to help you...

[CableChannel]

@manducator: there is a difference in the rolloff but due to the large Q you can't recognize it on that scale, so yeah they seem almost identical but they arent.

@Ticky: Sorry maybe we were miscommunicating but you were telling me stuff that I already know so it felt a little strange.

If you think about it both things have something to do with steepness it seems. Q defines some kind of local steepness at cutoff frequency, and the order defines the long range steepness over the spectrum.