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Old 11th January 2004, 12:23 AM   #1
matjans is offline matjans  Netherlands
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Default sub xo design questions

hello all,

sorry to bother you guys with this newbie question but here i go....

I am planning to build a sub to match my speakers. Building an amp and the sub itself won't pose a problem (i think )

Designing a crossover, however, will be as I have never done this.

Any hints/links to suggested reading/schematics ? I've been searching for a couple of hours now but almost everything I find is either pretty complicated (for a newbie to filter design anyways) OR has something to do with digital filters.
A "howto - build passive xo's" would be great...


What i'd really like is a variable passive xo.
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Old 11th January 2004, 03:45 AM   #2
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Matjans,

Checkout Rod Elliot's writeup in x-over design here:
http://sound.westhost.com/lr-passive.htm
The problem with passive x-overs for subs is the components need to be very large (read $$expensive$$). Than to try and make it variable on top of that will send you to the poor house. You can get much better results from bi-amping with an active x-over for not much more money (depending on what you buy).
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Old 11th January 2004, 03:48 AM   #3
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Crossovers for subs are usuall in the 70-120Hz range. For a passive network the inductor values are large, the losses high and the expense high.

It is more practical to bi-amp and for this you'll be looking at active crossovers. They are easy to calculate and build and I believe there are some PC boards available. I don't have the proper links but I'm sure someone can jump in here and provide them.

There is no such thing as a variable passive crossover.
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Old 11th January 2004, 04:04 AM   #4
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Quote:
Originally posted by Bill Fitzpatrick

There is no such thing as a variable passive crossover.
Sorry Bill,

This one was designed by the Pass Labs crew.
http://www.vidsonix.com/vidsonixnew/..._audio4ind.htm
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Old 11th January 2004, 12:05 PM   #5
matjans is offline matjans  Netherlands
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i see that my first post was pretty unclear.

I am building a separate sub for HT purposes. All i need info on is a line-level filter design. Be that active or not.

I'll bridge an opa or a lm3886 or anything as an amp.

sorry for the confusion
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Old 11th January 2004, 12:16 PM   #6
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here is a good link to get you going on active crossovers:
http://www.linkwitzlab.com/filters.htm
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Old 11th January 2004, 12:45 PM   #7
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Quote:
Originally posted by matjans
i see that my first post was pretty unclear.

I am building a separate sub for HT purposes. All i need info on is a line-level filter design. Be that active or not.

I'll bridge an opa or a lm3886 or anything as an amp.

sorry for the confusion

Doesn't your av receiver have a built in x/o ?

Rob
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Old 11th January 2004, 12:45 PM   #8
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Hi, I want to build a sub crossover too, and was wondering if this would work. It is off the site Joe Dirt sent us to. I would build it as just a lowpass, not even building the highpass part. Would the frequency cutoff be 99hz as in the schematic, or is that something else?


Thanks, Mike
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Old 11th January 2004, 12:50 PM   #9
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oops!

heres the pic.

-Mike
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File Type: gif lr2.gif (6.0 KB, 124 views)
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Old 11th January 2004, 12:57 PM   #10
matjans is offline matjans  Netherlands
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rob: i'm not using an a/v receiver, my (philips) dvd player has rca outs for front/rear/sub. No center though.
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