newbie, help with low-pass filter - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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
Reply
 
Thread Tools Search this Thread
Old 28th June 2005, 01:24 PM   #1
micfly is offline micfly  United States
diyAudio Member
 
Join Date: Jun 2005
Location: houston, tx
Default newbie, help with low-pass filter

I just want to ad a simple filter to a pair of small mid-bass speakers. These are in the rear doors of my truck. The rear seats stay folded down basically covering the speakers so all I want back there is bass. The speakers are 4 ohm 6.5" drivers rated at 50Hz-5kHz. These are drivers only with no built-in tweeters.

I would like to just cut out the highs to these speakers anywhere from 1-5kHz. I can only find select components at my local electronics store so not sure which way to go. What I bought was a choke rated at .68mH. This could be used for a simple first order filter by what I can figure should cut out about 1kHz and up.

Or, I can use a 10uF capacitor with a .33mH choke for a simple second order filter. What I can figure is I needed a 9.95uF cap with a .636mH choke. Will the 10uF/.33mH be close enough? If I use this should I swap the +/- wires for correct polarization?

Also, the capacitors are non-polarized and the chokes are RF Filters. Are these the correct parts?

Which way should I go, the first order or second order filter? Thanks for all help!
  Reply With Quote
Old 28th June 2005, 07:55 PM   #2
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
You can start with just the chokes you bought and if that doesn't do it then design it for a 12dB at say 1000hz. Remember your drivers are 4 ohms so:

20 uFd caps
1.3 mH chokes

If you use a 10 and a .6 your cut off will be 2kHz.

Are you using one of these?

http://www.mhsoft.nl/spk_calc.asp

Cal
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 29th June 2005, 12:24 AM   #3
micfly is offline micfly  United States
diyAudio Member
 
Join Date: Jun 2005
Location: houston, tx
Heh, thanks for the help. Yea, actually I was using this one: http://www.apicsllc.com/apics/Misc/filter2.html

2K is probably too high, eh? I was kinda thinking that. If I can find the right combo of caps/chokes what should I really shoot for? 1k or lower? Like I say, I just want bass back there. Thanks again for the help!
  Reply With Quote
Old 29th June 2005, 12:33 AM   #4
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
If bass is your desire then 500 with a 12 dB might be a good target. At the same time keep in mind, the lower you go the bigger and more expensive the components are. Is this your permanent set up in the truck?
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 29th June 2005, 03:40 AM   #5
micfly is offline micfly  United States
diyAudio Member
 
Join Date: Jun 2005
Location: houston, tx
Yes it's permanent. I replaced the front two speakers with a good set of co-axils that sound fine. It has a good sounding set of tweeters up front, too. And the factory 6-disk changer is also fine with me. I just thought in the back, with the speakers covered, just do the bass deal. When I ordered the drivers for the back I didn't realize they would not come filtered...duh :-( When I installed them they sounded terrible (distortion). So, on when my jorney for filters. I'll try the parts store again for the 500 range components. Thanks again for the help!
  Reply With Quote
Old 29th June 2005, 03:58 AM   #6
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
Quote:
Originally posted by micfly with the speakers covered,
Now there's an idea. Why don't you stuff a blanket or pillow up against them and see what you think of the sound. Just don't impede the cone travel. The thicker the blanket, the lower the frequency.

Quote:
When I installed them they sounded terrible (distortion)
Distortion?
What kind of distortion were you hearing?
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 29th June 2005, 11:17 AM   #7
micfly is offline micfly  United States
diyAudio Member
 
Join Date: Jun 2005
Location: houston, tx
I'm sure the distortion is from all the highs these speakers can't reproduce. It's just when I open the doors and stick my ear up near them, otherwise up front most people wouldn't notice.

BTW, still wondering, If I go with the 2nd order should I swap the +/- wires? Also, if I get close on the part specs is that ok?

Click the image to open in full size.
  Reply With Quote
Old 29th June 2005, 11:45 AM   #8
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
If you're using RF chokes they will probaly saturate as soon as any real power goes though them and the result will sound bad and possibly be a fire hazard.

The distortion you can hear is because your amp/headunit is clipping. Fitting a low-pass filter will help this to some extent by rounding off the waveform, but it will not do sod all for the fundamental problem that you are overdriving your amp/headunit.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
GIC low pass filter? capslock Digital Source 19 4th May 2011 04:24 AM
Low Pass filter for sub? cathode_ray Subwoofers 9 25th April 2007 05:04 PM
low pass filter AudioAddicted Car Audio 17 2nd November 2006 06:44 AM
low pass filter crazyant Car Audio 3 15th September 2005 06:15 PM
D1 DAC from Pass 20 KHz filter? promitheus Digital Source 2 15th September 2003 05:22 PM


New To Site? Need Help?

All times are GMT. The time now is 11:30 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2