3rd order HIgh pass filter - explanation?

APaddy · 16th January 2006, 05:10 PM

hi guys

can anyone give a detailed description of what a 3rd order high pass filter is???

what is the 3rd order part ???

and also how to calculate the cut of frequency???

thanks guys

richie00boy · 16th January 2006, 05:33 PM

A high-pass filter lets the highs pass and attenuates the lows.

The filter order represents the number of poles in the system. Basically the higher the order the steeper the cut-off slope.

I don't have the formulas to hand, but you should be able to find them in books such as Don Lancaster's Active Filter Cookbook (assuming an active filter).

APaddy · 16th January 2006, 05:48 PM

thanks richie00boy for clearing up the 3rd order explanation!!

does anyone know a good website for this stuff...?

need this info for my project report!!!

thanks

AndrewT · 22nd January 2006, 10:09 AM

Hi,
I think ESP has a couple of sections on active filter cutoffs and poles(slope), maybe also passive?
http://sound.westhost.com

For passive try Nelson Pass at http://www.passdiy.com

APaddy · 23rd January 2006, 02:43 PM

thanks andrew

will check em out!!!

Ouroboros · 23rd January 2006, 02:45 PM

Download 'Filterlab' from the Microchip website. A wonderful little program for filters up to 7th order.

phase_accurate · 23rd January 2006, 02:53 PM

Quote:

The filter order represents the number of poles in the system. Basically the higher the order the steeper the cut-off slope.

Another way of expressing this is: The order is the same as the amount of components that show a frequency-dependant behaviour (i.e. inductors and/or capacitors) in a filter.

Regards

Charles

MosfetOwner · 23rd January 2006, 04:07 PM

Quote:

Originally posted by APaddy

what is the 3rd order part ???

The other people have already answered most of your questions. However, the 3rd order part means that below the cutoff frequency, the level will roll off at 18dB per octave. A first order filter rolls off at 6dB/octave, a second order at 12dB/octave and so on. An octave is a halving (or doubling) in frequency.

APaddy · 23rd January 2006, 05:34 PM

thanks guys

does anyone have on hand the calculations used to caclulate the cut off and 3 rd order part.

thanks

Cal Weldon · 23rd January 2006, 08:12 PM

Are you looking for a passive filter calculator?

If so, here's one: http://www.mhsoft.nl/spk_calc.asp

16th January 2006, 05:10 PM	#1
APaddy diyAudio Member Join Date: Jan 2006 Location: London	3rd order HIgh pass filter - explanation? hi guys can anyone give a detailed description of what a 3rd order high pass filter is??? what is the 3rd order part ??? and also how to calculate the cut of frequency??? thanks guys

16th January 2006, 05:33 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	A high-pass filter lets the highs pass and attenuates the lows. The filter order represents the number of poles in the system. Basically the higher the order the steeper the cut-off slope. I don't have the formulas to hand, but you should be able to find them in books such as Don Lancaster's Active Filter Cookbook (assuming an active filter). __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

23rd January 2006, 08:12 PM	#10
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Are you looking for a passive filter calculator? If so, here's one: http://www.mhsoft.nl/spk_calc.asp __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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16th January 2006, 05:48 PM	#3
APaddy diyAudio Member Join Date: Jan 2006 Location: London	thanks richie00boy for clearing up the 3rd order explanation!! does anyone know a good website for this stuff...? need this info for my project report!!! thanks

22nd January 2006, 10:09 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, I think ESP has a couple of sections on active filter cutoffs and poles(slope), maybe also passive? http://sound.westhost.com For passive try Nelson Pass at http://www.passdiy.com

23rd January 2006, 02:43 PM	#5
APaddy diyAudio Member Join Date: Jan 2006 Location: London	thanks andrew will check em out!!!

23rd January 2006, 02:45 PM	#6
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	Download 'Filterlab' from the Microchip website. A wonderful little program for filters up to 7th order.

23rd January 2006, 05:34 PM	#9
APaddy diyAudio Member Join Date: Jan 2006 Location: London	thanks guys does anyone have on hand the calculations used to caclulate the cut off and 3 rd order part. thanks

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