Didn't really see any threads that pointed this out, but thought some of you may be interested.....new to me at least 
Elliptic Crossovers
Elliptic Crossovers
http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1032037028&openflup&29&4#29
According to Joseph Audio: "The Infinite Slope design we employ is absent of any ringing.
None. Nada. Don't believe me?
Go look at the review of the RM33si in Stereophile, see the waterfall plot of the RM33si. (it's online now)"
To find this, go to the above link and look for the post which begins, "This topic comes up every few months...."
According to Joseph Audio: "The Infinite Slope design we employ is absent of any ringing.
None. Nada. Don't believe me?
Go look at the review of the RM33si in Stereophile, see the waterfall plot of the RM33si. (it's online now)"
To find this, go to the above link and look for the post which begins, "This topic comes up every few months...."
Group Delay
5th order elliptical LPF
Butterworth
Courtesy of www.filter-solutions.com
5th order elliptical LPF
An externally hosted image should be here but it was not working when we last tested it.
Butterworth
An externally hosted image should be here but it was not working when we last tested it.
Courtesy of www.filter-solutions.com
Where Chebychev filters give a steeper slope by allowing ripple in the passband, an eliptic filter has an even steeper slope by allowing ripple in the stop band as well. This is illustrated by the graphs shown by jackinnj. I'm sure that the bloke who first analysed eliptic filters saw applications in the RF communications field and not quality audio.
On the other hand, I have a speaker made by Castle, and the tweeter crossover is second order, but also has a notch filter tuned to the tweeter resonant frequency. It is an old design, there are no resistors at all in the crossover. The frequency response shape is just like the eliptic response shown in the graph above. If this was deliberate, then maybe the use of eliptic filters is not new, and was used commercially decades ago.
On the other hand, I have a speaker made by Castle, and the tweeter crossover is second order, but also has a notch filter tuned to the tweeter resonant frequency. It is an old design, there are no resistors at all in the crossover. The frequency response shape is just like the eliptic response shown in the graph above. If this was deliberate, then maybe the use of eliptic filters is not new, and was used commercially decades ago.
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