Low Pass Filter
Printed From: Community Theater Green Room
Category: Producing Theater
Forum Name: Lights and Sound
Forum Discription: Technical discussion
URL: http://www.communitytheater.org/forum/forum_posts.asp?TID=2805
Printed Date: 5/23/25 at 9:38am
Software Version: Web Wiz Forums 8.05 - http://www.webwizforums.com
Topic: Low Pass Filter
Posted By: mark_j
Subject: Low Pass Filter
Date Posted: 11/13/07 at 7:01pm
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I want to hook up a low pass filter to a bass speaker we have. I found a simple diagram on how to make one, but one of the two components aren't available around here- namely a load coil. I don't have my cheat sheet with me but I know the numbers for the coil and capacitor are 113 and 14.4 (not sure which is which without looking it back up.) Now I found out I don't need a coil if I have a resistor, but I can't find a cheat sheet on the internet that tells me the Ohms I need for the resistor. Does anyone know where I can find a chart showing resistor/capacitor pairs for a low pass filter? Is there a way to convert a load coil rating to a resistor rating? At the moment the speaker is hooked to a 200 wat amp. It may go to 400 down the road. The speaker (a Bose Accoustic Cannon) should handle 600. It has 8 ohms resistance. I'm looking to filter out frequencies over 125hz with a 12dbl fall off. Does anybody have any ideas or am I spouting internet induced foolishness?
Mark J.
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Replies:
Posted By: JoeMc
Date Posted: 11/13/07 at 9:32pm
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G'day Mark Not being a niose boy, just a Sparky & I did electronics back in the days of Valves, about 50 years ago. Try these links & especialy the 'Blueroom' in the UK which has heaps of audio techies there. Blueroom;-
http://www.blue-room.org.uk/index.php - http://www.blue-room.org.uk/index.php ?There is a numbers of topics & sites covering low & high pass filters that may help. Low Pass Filters;-
http://www.freqdev.com/products/filters/lowpass.html?gclid=CKnZ3qKh248CFR0yhgodsBH60w - http://www.freqdev.com/products/filters/lowpass.html?gclid=CKnZ3qKh248CFR0yhgodsBH60w
Low pas Filter Bose 302;- http://www.blue-room.org.uk/index.php?showtopic=9548 - http://www.blue-room.org.uk/index.php?showtopic=9548 Low cost filters;-
http://www.pfinc.com/products/modules/filter_modules.htm?gclid=CNWtqO-h248CFQgZhgodZlad0w - http://www.pfinc.com/products/modules/filter_modules.htm?gclid=CNWtqO-h248CFQgZhgodZlad0w
I'd hate to lead you up a gum tree, although there are a number of techies here that may give you an answer or at least piont you in the right direction. Best of luck! ------------- [western] Gondawandaland "Hear the light & see the sound! TOI TOI CHOOKAS {may you always play to a full house!} |
Posted By: vickifrank
Date Posted: 11/14/07 at 10:51am
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Hi Mark,
It sort of depends on what type filter you are creating. Is it a butterworth, chebysheve or bessel configuration? Then comes the gain (or attenuation) that you want. Each filter has different formulas for the gain, so you can compute what resistance you need for a given gain and capacitor size. If you can read the caption on the diagram and it contains the circuit name, then you can find the formula online.
Some of you Noise guys might want to weigh in here. I'm an EE, but the wrong type of EE (computers, software manager, etc..) so my filter experience is a couple of decades rusty...and confined to keeping up with my big brother (an antenna specialist), and old tales of idiot fellows in college spot-welding circuits to the power supplies by forgetting to turn off the juice when changing circuits. Ah yes, egghead mistakes. One of several ways to get fried in college, not the most pleasant way with your comrades laughing their heads off.
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Posted By: JoeMc
Date Posted: 11/14/07 at 12:07pm
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Gawd the wombats one encounters at times! Or watching a sparky straddling a live overhead power gantry, in a sudden rain deluge, bouncing along the girder, like Roo without a parachute & walking rather 'ows ya father' for a week! Then the idiot sparkie who wondered what the big red button was on a CO2 Fire Panel did & shut the Power House Generation Turbines down & the whole of a large Alunimium Refinery for a day. The moron he ended up cutting my first weeks holday, after 3 years short & I had to drive 300kms to fix it. Also coping two speeding tickets on the way! All he had to say was "I only wanted to see what would happen" I suggested "he hit the road & on the way call into the Hospital & ask the power house attendant, who was sleeping in the duct at the time, that question? Funny he never came back? ------------- [western] Gondawandaland "Hear the light & see the sound! TOI TOI CHOOKAS {may you always play to a full house!} |
Posted By: vickifrank
Date Posted: 11/14/07 at 1:20pm
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Yes, those wombats will always be with us. Which explains (plus litigation) why ladders come plastered with warning stickers: "Don't set on ice patches!" "Don't reach out beyond the ladder!" "Don't use aluminum ladders in rainstorms!" Recently in the news near us a fellow that couldn't get a lag bolt off of his car went inside for his shotgun and had at it. Needless to say the bullet didn't succeed in loosening the bolt, but did succeed in loosening his nuts when it bounced off the car. Ouch!! Either
 or  . Last I heard the docs were separating soup from nuts without specifying the likely outcome. I'm sure you've heard of the Darwin awards. I think if you die in the act of being a wombat you qualify--or if you lose certain abilities to propagate your wombat-ness can also qualify.I've never done anything wombat-ish myself!
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