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Old 3rd February 2011, 08:38 PM   #1
Elbert is offline Elbert  Norway
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Default Shelving 2nd order high-pass?

Just a Qick one;

I'm looking for information (or a calculator) on how to design/ calculate a 2nd Order shelving High pass filter.

Anny ideas/ links anyone?
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Old 3rd February 2011, 09:10 PM   #2
AEIOU is offline AEIOU  United States
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Default ?

Quote:
Originally Posted by Elbert View Post
Just a Quick one;

I'm looking for information (or a calculator) on how to design/ calculate a 2nd Order shelving High pass filter.

Anny ideas/ links anyone?
I'm not quite sure what you mean by "shelving" Filters are either high pass, low pass, band pass or band reject.
Passive line level low and high pass filter help
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Old 3rd February 2011, 09:29 PM   #3
Elbert is offline Elbert  Norway
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Ah,

I was actually of the impression that shelving filters were a distinct type of filters, but what I'm referring to is perhaps only a variation of one of the types you mention?

I did build a filter stage described as a shelving high-pass described on The linkwitz-lab web page.

Active Filters

For this circuit, one could choose a start frequency, and filter gain. As the filter is 1st order, magnitude will rise with 6dB/ oct up to the set gain, and then flatten out, not continue the slope as with a "ordinary" high-pass filter.

The problem is that the slope I get with this filter is not steep enough, so I'm looking for a similar filter but with 12/dB oct slope in stead of only 6.

Does this make any more sense??

Last edited by Elbert; 3rd February 2011 at 09:35 PM.
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Old 3rd February 2011, 09:53 PM   #4
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Default OK, I understand now.

Maybe you could email Mr. Linkwitz and he could help you or suggest something.

Quote:
Originally Posted by Elbert View Post
Ah,

I was actually of the impression that shelving filters were a distinct type of filters, but what I'm referring to is perhaps only a variation of one of the types you mention?

I did build a filter stage described as a shelving high-pass described on The linkwitz-lab web page.

Active Filters

For this circuit, one could choose a start frequency, and filter gain. As the filter is 1st order, magnitude will rise with 6dB/ oct up to the set gain, and then flatten out, not continue the slope as with a "ordinary" high-pass filter.

The problem is that the slope I get with this filter is not steep enough, so I'm looking for a similar filter but with 12/dB oct slope in stead of only 6.

Does this make any more sense??
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Old 3rd February 2011, 10:01 PM   #5
Elbert is offline Elbert  Norway
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You think so?

I sort of have the feeling that it is a bit below a person of Mr Linkwitz position to answer simple/ stupid questions like that.. The answer is probably right there in some theory or textbook, but being a mere amateur, I'm not the best at translating analogue theory to working circuits...

Last edited by Elbert; 3rd February 2011 at 10:06 PM.
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Old 3rd February 2011, 10:20 PM   #6
AEIOU is offline AEIOU  United States
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Quote:
Originally Posted by Elbert View Post
You think so?

I sort of have the feeling that it is a bit below a person of Mr Linkwitz position to answer simple/ stupid questions like that.. The answer is probably right there in some theory or textbook, but being a mere amateur, I'm not the best at translating analogue theory to working circuits...
I still would ask, not expecting him to do all the math for you, but he may know a source or an online link.
I've actually met and talked with Mr. Linkwitz on two separate occasions. I even called him "Siggy." He came to attended our DIYs here in Northern California and demonstrated his loudspeakers for us. He was pleasant to talk to, not all self important or anything like that. A very nice gentleman, so don't worry about it.

Last edited by AEIOU; 3rd February 2011 at 10:28 PM.
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Old 3rd February 2011, 10:40 PM   #7
Elbert is offline Elbert  Norway
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Well,

Perhaps I'll give it a shot then?

As long as I get a schematic and some formulaes for working out the values, I'll be able to work something out!

.. that is, if I cna find his e-mail address.. ?

Last edited by Elbert; 3rd February 2011 at 10:42 PM.
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Old 3rd February 2011, 11:16 PM   #8
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It's on his website linkwitzlab.com...look under ordering information for Orion DIY. As noted above SL is very down-to-earth & approachable. Before you ask search his website (which is very extensive) as the answer is likely to be there already. If you don't find it then e-mail him & state your question clearly and succinctly.
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Old 3rd February 2011, 11:50 PM   #9
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Quote:
Originally Posted by AEIOU View Post
I'm not quite sure what you mean by "shelving" Filters are either high pass, low pass, band pass or band reject.
Passive line level low and high pass filter help
There are infinitely many kinds of filters.

I think (not sure, just think) "shelving filter" sometimes refers to high-Q filters. That is my interpretation "shelving filter" from a "digital filter cookbook" article that I read. For example, the typical bass boost function in a subwoofer amp is a second order high pass filter with a big Q, which gives it a bump near the nominal boosted frequency. The nominal bass-boost in decibels is equal to 20*log10(Q).

A "shelving filter" may also refer to a filter such as is used for baffle step correction or "loudness" compensation, where frequencies above a "knee" frequency are attenuated relative to those lower than the "knee" frequency. Alternately, lower frequencies might be attenuated, for example to compensate for effect of a constant directivity horn. That is the way Linkwitz uses the term.
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Last edited by Dave Jones; 4th February 2011 at 12:01 AM.
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Old 4th February 2011, 03:20 AM   #10
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A biquad (AKA Linkwitz transform) can also be used as a second order high shelf. http://www.linkwitzlab.com/images/graphics/f0Q0fpQp.gif

You can also string two first order filters together with a bit less flexibility.
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