Filter Query

mashypie · 13th December 2010, 04:05 PM

Hello,

What determines one type of filter from another in crossovers?

Is it the way the components are arranged, or their values?

I'm quite interested in a Bessel arrangement but am struggling to find any schematics (or the ones I do find all seem to be active)

I can get my head around 1st order, 2nd order and their roll off, just not how one would design one type over another

:-/

John Sheerin · 13th December 2010, 04:58 PM

To increase the order of your filter, typically you need to add more parts. For example a first order high pass filter would be a single capacitor in series. To make it second order, you would add an inductor in parallel. 3rd order would add another series capacitor. 4th order another inductor in parallel, etc. However, note that this is just for the ideal electrical response. When you change from a resistive load to a loudspeaker which has an impedance that changes with frequency, to get a particular transfer function (such as bessel), you need to consider the frequency response and impedance of the loudspeaker along with the filter components. The acoustic transfer function is ultimately what you care about.

mashypie · 13th December 2010, 05:17 PM

So all HP filters are arranged in that way, regardless of whether its Butterworth, Bessel or L-R etc?

John Sheerin · 13th December 2010, 05:42 PM

As far as I know, yes. You vary the values of the components to get different roll off shapes (bessel, butterworth, etc.).

13th December 2010, 04:05 PM	#1
mashypie diyAudio Member Join Date: Nov 2010	Filter Query Hello, What determines one type of filter from another in crossovers? Is it the way the components are arranged, or their values? I'm quite interested in a Bessel arrangement but am struggling to find any schematics (or the ones I do find all seem to be active) I can get my head around 1st order, 2nd order and their roll off, just not how one would design one type over another :-/

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
query	Professor smith	Multi-Way	2	5th May 2009 01:47 AM
Just one big filter cap or more smaller filter caps ...	beppe61	Power Supplies	2	18th July 2006 05:46 PM
active filter from rod elliot and sub filter questions	wuffer	Parts	0	2nd October 2005 01:12 PM
Marketing query	KT	Chip Amps	2	20th March 2004 07:20 AM
chassis-mounted filter or IEC plug filter	jarthel	Solid State	7	11th March 2002 10:17 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

13th December 2010, 04:58 PM	#2
John Sheerin diyAudio Member Join Date: Nov 2003 Location: Pittsburgh, PA	To increase the order of your filter, typically you need to add more parts. For example a first order high pass filter would be a single capacitor in series. To make it second order, you would add an inductor in parallel. 3rd order would add another series capacitor. 4th order another inductor in parallel, etc. However, note that this is just for the ideal electrical response. When you change from a resistive load to a loudspeaker which has an impedance that changes with frequency, to get a particular transfer function (such as bessel), you need to consider the frequency response and impedance of the loudspeaker along with the filter components. The acoustic transfer function is ultimately what you care about.

13th December 2010, 05:17 PM	#3
mashypie diyAudio Member Join Date: Nov 2010	So all HP filters are arranged in that way, regardless of whether its Butterworth, Bessel or L-R etc?

13th December 2010, 05:42 PM	#4
John Sheerin diyAudio Member Join Date: Nov 2003 Location: Pittsburgh, PA	As far as I know, yes. You vary the values of the components to get different roll off shapes (bessel, butterworth, etc.).

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)