sub xo design questions

[matjans]

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.

 

[roddyama]

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).

 

[Bill Fitzpatrick]

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.

 

[roddyama]

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/vidsonix_audio4ind.htm

 

[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

 

[JOE DIRT®]

here is a good link to get you going on active crossovers:
http://www.linkwitzlab.com/filters.htm

 

[SpeakerBob]

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

 

[soundNERD]

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

 

[soundNERD]

oops!

heres the pic.

-Mike

 

[matjans]

rob: i'm not using an a/v receiver, my (philips) dvd player has rca outs for front/rear/sub. No center though.

 

[SpeakerBob]

Ok in that case the link to the linkwitz site given above will give you most info you need for opamp based x/o.

Also look at this site - John doesn't seem to be answering e-mails but theres lots of info there:

http://www.snippets.org/filters/crossover.htm

Good luck!

Rob

 

[roddyama]

Matjans,

Ohh, line-level. Here a site that can help with a PLLXO.
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
If you're really sharp you'll recognize the home page of one of our more prominent members.

Take a look at Rod Elliot's site for information and boards for some simple active line-level filters. The xover stuff is here:
http://sound.westhost.com/projects-3.htm

I use a first order PLLXO as a hi-pass to the mid-bass and a third order active lo-pass for the sub. Beyond a second order PLLXO and the losses become too high.

 

[matjans]

ah thanks (and yes i know who you're talking about )