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Old 19th June 2010, 05:44 AM   #1
asbn369 is offline asbn369  Dubai
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Default designing simple low pass subwoofer filter

hi,
can anyone help me in designing simple low pass filter for subwoofer.(8 ohm around 150 w)is it possible to make low pass subwoofer filter only with capacitor and resistor?if yes what will be the values?????i dont neeed all those advanced circuits.just simple one so that only low frequencies can be heard.please help!!!!!
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Old 19th June 2010, 05:57 AM   #2
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You can build a 1st order (6 dB/octave) Low Pass with a C+R.

PLLXO

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Old 19th June 2010, 09:09 AM   #3
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Is this at speaker level, or to drive the amplifier?
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Old 19th June 2010, 10:36 AM   #4
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by asbn369 View Post
I don't need all those advanced circuits. Just simple one so that only low frequencies can be heard.
A single pole (=6dB/oct = 20dB/dec) will let through a lot of intelligible upper frequencies.
A 2pole will let through less but still hearing too much of the midrange.
A 3pole may be satisfactory, but I would recommend a 4pole low pass filter.

A simple circuit of just a R+C can only give you single pole.
An L+C can give you a two pole.
Both of these can be passive filters, either attached to the speaker input or attached to the power amp input.

If you want 3 or 4 pole you really need to go to an active filter. This is no longer simple. Choose.
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Old 4th July 2010, 06:29 AM   #5
asbn369 is offline asbn369  Dubai
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thanks for all the replys.is there any subwoofer filter designs that can be placed after power amp ie, directly amp to sub woofer.im new to audio and i dont know more about this.any replys could be a great help!!!!!!!!
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Old 4th July 2010, 07:21 AM   #6
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Just a big 10mH coil;then 100uF (to O V );then another big coil 8 mH and maybe a 50uF cap (those caps need to be electrolytics ,BP,Bi-Polar ). These components will stop anything over 100 Hz.
Coils can be home made ,just wind enamelled copper wire around a bolt or reel.
Search for a tutorial around the net..if it exists ..
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Old 5th July 2010, 10:00 AM   #7
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Quote:
Originally Posted by asbn369 View Post
hi,
can anyone help me in designing simple low pass filter for subwoofer.(8 ohm around 150 w)is it possible to make low pass subwoofer filter only with capacitor and resistor?...
No. If you don't want (the use of) an inductor filter, use only 4/6th order bandpass enclosures. It works as an acoustic filter (You can also use smaller coils). Now it all depends on the type of driver/enclosure/frequency.
The Subwoofer DIY Page v1.1 - Projects : An INF10 Bandpass Subwoofer
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Old 2nd August 2010, 11:40 AM   #8
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Quote:
Originally Posted by AndrewT View Post
A single pole (=6dB/oct = 20dB/dec) will let through a lot of intelligible upper frequencies.
A 2pole will let through less but still hearing too much of the midrange.
A 3pole may be satisfactory, but I would recommend a 4pole low pass filter.

A simple circuit of just a R+C can only give you single pole.
An L+C can give you a two pole.
Both of these can be passive filters, either attached to the speaker input or attached to the power amp input.

If you want 3 or 4 pole you really need to go to an active filter. This is no longer simple. Choose.
I want a 4 pole active filter for the input of amplifier (TDA2050 and TDA 7293)
I wonder if there is a circuit to do this
Anyone ?
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Old 2nd August 2010, 12:55 PM   #9
AndrewT is online now AndrewT  Scotland
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there are many filters for your amplifier.
Just google filter or active filter or audio filter, or simply search this Forum.
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