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Old 28th November 2011, 04:55 PM   #1
diyAudio Member
Join Date: Nov 2011
Default Help with filter?


To start, I don't even know what a filter does, can some one please explain it very short?

I am going to build a "halfinator", and someone pointed out that a need 2 filters, because I am going to use 1 piezo and 1 subwoofer per chanel. How do I build/buy a filter? How do I know how to builde it?

Thanks for your time!

/a fresh builder
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Old 29th November 2011, 12:44 AM   #2
Enzo is offline Enzo  United States
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Join Date: Sep 2004
Location: Lansing, Michigan
Filter is a generic term meaning something that lets one thing pass and not another. We often refer to filter capacitors as filters, they are there to smooth away the ripple from the rectified AC before sending the now smooth DC to the circuits. But a filter can also mean a circuit to block an unwanted noise. a hum filter would allow music but block hum.

And sometimes people misuse the term, even though it is a very flexible one. If I read you correctly, you are probably thinking of what we would call a crossover. One could consider the crossover a filter, I suppose, but I wouldn;t expect to call it by that name.

A crossover takes the overall sound signal from an amplifier, and splits it into highs and lows for the tweeters and woofers. Or I guess you could say the subwoofer part filters out the unwanted high frequencies and so on.

You haven;t quite specified your need. WHen you say subwoofer, do you really mean just woofer? In other words, a typical speaker cabinet might have a woofer and a tweeter. A subwoofer would be a separate speaker designed to put out sounds at lower frequencies than teh regular woofer can. Hence the name sub-woofer.

A basic speaker can be made with a piezo and a woofer. But you will have to decide of you need a crossover for both or just to limit what goes to the piezo. Piezos themselves don;t respond below a certain frequency anyway, and can act as their own crossover to some extent. In some speaker systems with piezos, the woofer is run full range, while in others, the woofer is cut off at the point the piezo takes over.
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Old 29th November 2011, 06:42 AM   #3
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Sorry, of course I meant a woofer, I am too used to hi-fi, haha.

So basically I don't need a crossover?

Do you build your own crossover, or do you buy a complete one?

I also wonder how you connect the speakers. Do you do it in serie oct parallel (just plug in the 2 cables in each hole)?
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Old 29th November 2011, 08:37 AM   #4
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
The woofer and piezo will work together without a crossover, but that doesn;t mean your needs will be met. That is why I mentioned we need a few more specs from you.

SImple crossovers are, well, simple - a few components. You have to calculate the part values or look them up on a chart. I run a maintenance and repair type operation and don;t get into building such things. But if I did, I'd probably look at the selection at Parts Express or a similar supplier. They sell complete crossovers, or they sell the bare circuit boards, and you install your own parts, which they also sell individually.

I think what you ought to do is find a book or online tutorial about how speakers work, and the basics of designing them. If you just want something to make sound, there is not much to it. But the better you want it to sound, the more thought you must put into it.
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