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Old 9th March 2011, 10:56 PM   #11
JrmEng is offline JrmEng  United States
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Clarified transfer function for Fig. 14 & 15.

JRM
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Old 1st May 2011, 08:05 PM   #12
JrmEng is offline JrmEng  United States
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More clarifications.

Additional info can be found here:
http://xenotron.home.comcast.net/~xenotron/xover.htm

JRM

Last edited by JrmEng; 1st May 2011 at 08:12 PM.
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Old 16th September 2012, 03:22 PM   #13
JrmEng is offline JrmEng  United States
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Updated 15-SEP-2012.
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Old 11th November 2013, 03:29 PM   #14
JrmEng is offline JrmEng  United States
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Updated 4-Nov-13 to include analysis of 11th order filters, 2-, 3-, 4-way.
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Old 13th November 2013, 06:03 PM   #15
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Interesting article. Just when I'm thinking i may have overcooked the BSC on my first attempt at a 5th order sallen key lowpass, this arrives. Interesting food for thought.
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Old 13th November 2013, 07:49 PM   #16
JrmEng is offline JrmEng  United States
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That's right, 3rd order is the practical limit for 3-way and higher. Non-inverting Sallen-Key will have unacceptable distortion.
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Old 14th November 2013, 04:08 PM   #17
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Quote:
Originally Posted by JrmEng View Post
That's right, 3rd order is the practical limit for 3-way and higher. Non-inverting Sallen-Key will have unacceptable distortion.
What's the basis for that? Q too high? There are other topologies besides the SK... MFB for instance or leapfrog.

I really can't see any reason why 3rd order is any kind of limit. I'd like to see this explained in detail without a reference to your product page or proprietary technology. This is a DIY site...
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Old 14th November 2013, 05:10 PM   #18
JrmEng is offline JrmEng  United States
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Originally Posted by CharlieLaub View Post
What's the basis for that? Q too high? There are other topologies besides the SK... MFB for instance or leapfrog.

I really can't see any reason why 3rd order is any kind of limit. I'd like to see this explained in detail without a reference to your product page or proprietary technology. This is a DIY site...
What web site? The analysis is too extensive to be contained within DIY, so an external link is provided. The answer to your question(s) are addressed there if you had bothered to look and read. All of the technical information used in the analysis is readily available in textbooks, technical journals, and on the internet for DIY'ers to find. The analysis is what it is, can't help if you don't like the results.
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Old 14th November 2013, 05:54 PM   #19
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Originally Posted by JrmEng View Post
What web site? The analysis is too extensive to be contained within DIY, so an external link is provided. The answer to your question(s) are addressed there if you had bothered to look and read. All of the technical information used in the analysis is readily available in textbooks, technical journals, and on the internet for DIY'ers to find. The analysis is what it is, can't help if you don't like the results.
What web site you say??? It's the very one you linked to! Oh yes, I bothered to looked at your links before. One goes to a product you are selling and the other to a bunch of SPICE sims (your "Cascade" web page) that is such a random torrent of info that is is difficult to determine much of anything from it. And then you have the balls to say "its in the textbook"! This is a DIY web site where you are supposed to enter into discussions about these kind of things, not point to some unnamed textbook and say that the analysis is "too extensive"...

One thing I can say: It would be a bad idea to use crossovers with filters having 11th order. Have you heard of group delay? You should calculate that for your filters and system sum, and then compare that against the studies of GD audibility. There is a reason why the telephone company spent a lot of time investigating this phenomonon... 11th order will definitely be audible, so you are introducing a bad effect in your effort to reduce distortion. Why not just use a better suited driver in the first place? This is one of the main reasons why you don't see crossovers at orders higher than 5 or so (already 5th has pretty peaky GD).

It would be beneficial to all if you described the point of what you are simulating in your SPICE models instead of just posting "Oh hey everyone I just some more stuff, come take a look" which I can only assume is just another attempt to drive traffic to your crossover product page, which is one of the links you posted under the guise of "Additional info can be found here" although the only content on that page is for your $2,950.00 3PX8 crossover box. I find that pretty distasteful.
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Old 14th November 2013, 06:47 PM   #20
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There is no link to a commercial web site, or any external site, on the original analysis page. JRM Engineering does not have a web site.

I have noticed there are numerous threads which reference Linkwitz commercial web site, as well as other manufactirers, in order to clarify some technical point.

Spice simulation has no way to display group delay; group delay is calculated for 2nd and 3rd order topologies, Fig. 6,7,11,12,13. The term "excessive phase shift across the spectrum" implies group delay too high.

A local audiophile has built an 11th order 4-way system that has received some favorable observations, and that analysis was done to see if measured response agreed with theoretical. Another audiophile wanted to see results if implementing a 3-way version with 1st or 3rd order for the tweeter resulting in tweeter signal now only having 1 active gain stage = lower distortion in tweeter.

The purpose of the original post was to demonstrate the properties of various xover topologies which might be beyond the capabilities of average DIY'ers, to help them make a more informed decision about which design might yield acceptable results.

One cannot twist the math to justify one design over another. Given the facts, one has to decide which parameters one is willing to compromise.

An additional topic "Conclusions" has been added to the analysis. You may choose to agree or not.

Last edited by JrmEng; 14th November 2013 at 07:09 PM.
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