Passive Line Level High Pass

noodle_snacks · 26th January 2006, 03:40 PM

I need a temporary high pass filter or rumble filter for a subwoofer set at 40hz until i can get something active sorted out.

I had a look at: http://en.wikipedia.org/wiki/High-pass_filter Which seems to give the circuit and the equation, however i have no idea what sort of resistor value to use in order to derive the capacitance required.

Any help as to what sort of resistor value i should be looking at for a line level filter?

Nigel Goodwin · 26th January 2006, 03:46 PM

It depends entirely on what impedance feeds the filter, and what impedance it in turn feeds. Also, a crude passive filter isn't really steep enough, get a dual-opamp and build an active filter!.

planet10 · 26th January 2006, 07:16 PM

More info

http://www.t-linespeakers.org/tech/f...ssiveHLxo.html

dave

noodle_snacks · 27th January 2006, 12:50 AM

I do indeed intend to build an active filter, i just want a quick and easy passive one until i have the time to do so.

How can i calculate my amplifiers input impedance and preamps output impedance?

pinkmouse · 27th January 2006, 12:56 AM

There is a thread in SS showing you how to calculate the input impedance.

sreten · 27th January 2006, 08:36 AM

Hi,

a temporary solution is to drastically reduce the
input coupling capacitor value of the sub amplifier.

As prevously stated, won't work that well.

/.sreten.

noodle_snacks · 27th January 2006, 11:19 AM

Thanks for the help, however i found a digital 250 band equaliser plugin for winamp which i will be able to use when i need the high pass filter. The filter can be set for flat response at 39hz and to be 60db down by 35hz.

http://coyote.freeweb.hu/winamp/dsp.cgi

I will probably build a steep opamp filter however since it just so happens the sound source for this little event is a computer running winamp. I have tested the plugin with a spectrogram and it does work effectively at cutting out low bass.

26th January 2006, 03:40 PM	#1
noodle_snacks diyAudio Member Join Date: Mar 2004 Location: Hobart, Tasmania	Passive Line Level High Pass I need a temporary high pass filter or rumble filter for a subwoofer set at 40hz until i can get something active sorted out. I had a look at: http://en.wikipedia.org/wiki/High-pass_filter Which seems to give the circuit and the equation, however i have no idea what sort of resistor value to use in order to derive the capacitance required. Any help as to what sort of resistor value i should be looking at for a line level filter?

26th January 2006, 03:46 PM	#2
Nigel Goodwin diyAudio Member Join Date: Jul 2005 Location: North Derbyshire	It depends entirely on what impedance feeds the filter, and what impedance it in turn feeds. Also, a crude passive filter isn't really steep enough, get a dual-opamp and build an active filter!. __________________ Nigel Goodwin

26th January 2006, 07:16 PM	#3
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 5	More info http://www.t-linespeakers.org/tech/f...ssiveHLxo.html dave __________________ community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

27th January 2006, 12:56 AM	#5
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	There is a thread in SS showing you how to calculate the input impedance. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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27th January 2006, 12:50 AM	#4
noodle_snacks diyAudio Member Join Date: Mar 2004 Location: Hobart, Tasmania	I do indeed intend to build an active filter, i just want a quick and easy passive one until i have the time to do so. How can i calculate my amplifiers input impedance and preamps output impedance?

27th January 2006, 08:36 AM	#6
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, a temporary solution is to drastically reduce the input coupling capacitor value of the sub amplifier. As prevously stated, won't work that well. /.sreten.

27th January 2006, 11:19 AM	#7
noodle_snacks diyAudio Member Join Date: Mar 2004 Location: Hobart, Tasmania	Thanks for the help, however i found a digital 250 band equaliser plugin for winamp which i will be able to use when i need the high pass filter. The filter can be set for flat response at 39hz and to be 60db down by 35hz. http://coyote.freeweb.hu/winamp/dsp.cgi I will probably build a steep opamp filter however since it just so happens the sound source for this little event is a computer running winamp. I have tested the plugin with a spectrogram and it does work effectively at cutting out low bass.

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