homemalow pass filter ??'s

binsky3333 · 14th September 2010, 09:41 PM

Hey guys, im building my own subwoofer amp. Most subwoofers do frequencies from like 80-200hz. I know in order to achieve this, i must create a low pass filter. Would this work? Is this really all that a low pass filter is? http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/experiment/lowpass/lpf.html

Just a simple resistor and capacitor? Also where does the low pass filter go? Before the amp, or after it?

richie00boy · 14th September 2010, 09:52 PM

Subs typically do 20-100Hz.

That is a low pass filter, but it's not suitable for you because the rate of roll off is too shallow - it is a 1st-order filter. You need at least 2nd-order. It should go before the power amp as an active filter.

binsky3333 · 10:18 PM

Quote:

Originally Posted by richie00boy

Subs typically do 20-100Hz.

That is a low pass filter, but it's not suitable for you because the rate of roll off is too shallow - it is a 1st-order filter. You need at least 2nd-order. It should go before the power amp as an active filter.

Crap, dont know what happened to the title, but what do you mean by 1st-order and 2nd-order? Could you elaborate a bit more?

Do you mean, those are the wrong cap and resistor values for my filter?

Thanks in advance!

richie00boy · 12:27 PM

It couldn't be more wrong. Well actually that is a bit harsh I suppose.

Read up about active filters, ESP site is a good one. I also have a sub-woofer controller project on my website.

binsky3333 · 04:56 PM

Quote:

Originally Posted by richie00boy

It couldn't be more wrong. Well actually that is a bit harsh I suppose.

Read up about active filters, ESP site is a good one. I also have a sub-woofer controller project on my website.

Wow, thats exaactly what im looking for, thanks! Ill look at that, and come back here if i have any questions.

Also where does the low filter go, before or after the amp? Is this the kind of filter i need?

OR

Thanks!

binsky3333 · 17th September 2010, 01:44 AM

Bump, i need this answer ASAP and cant find anything i can understand on the internet.

richie00boy · 17th September 2010, 03:11 PM

I couldn't open those pictures.

binsky3333 · 06:49 PM

They're on this site.

Active Low Pass Filter

Also would this work? http://www.mouser.com/ProductDetail/...knB80IXw%3d%3d

Also is this a second order? http://freecircuitdiagram.com/wp-con...lter_lm833.gif

binsky3333 · 17th September 2010, 08:04 PM

Sorry for the double post, it wouldnt let me edit mine, but what kind of caps do i use?

Ceramic, electrolyte? Polarized or non-polarized?

richie00boy · 17th September 2010, 10:38 PM

It covers the basics quite well, but it's still not quite what you need as it's only 1st-order. Did you look at the ESP site?

14th September 2010, 09:41 PM	#1
binsky3333 diyAudio Member Join Date: Sep 2010	homemalow pass filter ??'s Hey guys, im building my own subwoofer amp. Most subwoofers do frequencies from like 80-200hz. I know in order to achieve this, i must create a low pass filter. Would this work? Is this really all that a low pass filter is? http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/experiment/lowpass/lpf.html Just a simple resistor and capacitor? Also where does the low pass filter go? Before the amp, or after it?

14th September 2010, 09:52 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Subs typically do 20-100Hz. That is a low pass filter, but it's not suitable for you because the rate of roll off is too shallow - it is a 1st-order filter. You need at least 2nd-order. It should go before the power amp as an active filter. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

15th September 2010, 12:22 PM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	It couldn't be more wrong. Well actually that is a bit harsh I suppose. Read up about active filters, ESP site is a good one. I also have a sub-woofer controller project on my website. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more Last edited by richie00boy; 15th September 2010 at 12:27 PM.

17th September 2010, 03:11 PM	#7
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I couldn't open those pictures. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

17th September 2010, 06:37 PM	#8
binsky3333 diyAudio Member Join Date: Sep 2010	They're on this site. Active Low Pass Filter Also would this work? http://www.mouser.com/ProductDetail/...knB80IXw%3d%3d Also is this a second order? http://freecircuitdiagram.com/wp-con...lter_lm833.gif Last edited by binsky3333; 17th September 2010 at 06:49 PM.


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17th September 2010, 01:44 AM	#6
binsky3333 diyAudio Member Join Date: Sep 2010	Bump, i need this answer ASAP and cant find anything i can understand on the internet.

17th September 2010, 08:04 PM	#9
binsky3333 diyAudio Member Join Date: Sep 2010	Sorry for the double post, it wouldnt let me edit mine, but what kind of caps do i use? Ceramic, electrolyte? Polarized or non-polarized?

17th September 2010, 10:38 PM	#10
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	It covers the basics quite well, but it's still not quite what you need as it's only 1st-order. Did you look at the ESP site? __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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