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Old 28th November 2008, 04:05 AM   #1
Buzzy is offline Buzzy  Singapore
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Default Active filter for subwoofer

I would like to build an active filter for my vented subwoofer. Would Rod Elliot project 71 be suitable for this purpose ? http://sound.westhost.com/project71.htm

There are many circuits shown on the page. Is figure 4 the circuit i should be building ? I dunno if it is complete or if some stuff is missing.
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Old 28th November 2008, 05:22 AM   #2
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What do you want the filter to do? The circuit you linked to is typically used to extend bass response below resonance in a sealed box - it would be useful, for example, if you chose to seal the port on your current sub and then wanted to reclaim bass extension.

I don't think that's what you're trying to do. Perhaps you were looking for a rumble filter? http://sound.westhost.com/project99.htm

Or maybe you're after an active crossover? http://sound.westhost.com/project09.htm

Or perhaps you were after a graphic subwoofer equaliser? http://sound.westhost.com/project84.htm

Please elaborate on what you're trying to achieve.
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Old 28th November 2008, 10:39 AM   #3
Buzzy is offline Buzzy  Singapore
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oops sry. What i want is to cutoff the low frequencies to save my sub from over-excursion.

Btw is it ok to supply opamp with just +12 and -12V dc instead of the +15 -15V ?
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Old 28th November 2008, 11:10 AM   #4
AndrewT is offline AndrewT  Scotland
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look up sixth order alignment.
It adds a little bit of equalisation and a 12dB/octave high pass filter to a vented enclosure.
However the enclosure/driver needs to be designed in conjunction with the filter.
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Old 28th November 2008, 12:41 PM   #5
BWRX is offline BWRX  United States
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Quote:
Originally posted by Buzzy
Btw is it ok to supply opamp with just +12 and -12V dc instead of the +15 -15V ?
If you're using TL072 op amps that will be perfectly fine.
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Old 30th November 2008, 04:20 AM   #6
Buzzy is offline Buzzy  Singapore
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Quote:
Originally posted by AndrewT
look up sixth order alignment.
It adds a little bit of equalisation and a 12dB/octave high pass filter to a vented enclosure.
However the enclosure/driver needs to be designed in conjunction with the filter.
Thanks for all the replies. AndrewT I don't need any equalisation in the active filter as i have a separate EQ. All i want is just to cut off freq below 16Hz so that i do not go over the excursion limit. Should i be looking at project 9 or project 99 on Rod Elliot's page ?
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Old 30th November 2008, 04:48 AM   #7
BWRX is offline BWRX  United States
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The one you want is Project99 - the rumble filter.
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