Hi, Tom.
Please forgive me for not fully understanding your question. From what sense do you mean, "a true series crossover has to to pass all the information sent to it by the amplifier, unlike most every other crossover design?"
To be honest, I really have no idea why the series crossover is not used more. Despite the "black magic" that surrounds crossovers, this one even being on another plane, it is no more complex or difficult to understand than a parallel network. Though, I would allow that the most simple first order parallel network (cap inline with the tweeter, plus coil inline with the mid/woofer) is probably the most easy for folks to envision.
What I think sometimes scares people is when they see the schematic of a series network. It looks all wrong on paper, as our minds have grown accustomed to seeing the cap go with the tweeter, and the coil go with the mid/woofer. With a series network, the same is true, but it took a very simple parable that talked about what was actually happening before it clicked for this dunderhead. Of course, I sound ridiculous in this post, because I cannot draw out a parallel and a series network, and I wish I could. Suffice it to say that it looks odd, with the coil in parallel to the tweeter, and the cap in parallel to the woofer.
Bud got started down the series crossover road while at one of his visits to Dynaudio. In talking to someone, he noticed two crossovers on their desk. Bud being Bud, he asked about them. The employee mentioned, "Oh, they're different. These are the series crossovers and these are the parallel." Bud asked what was different about them, to which the reply was, "Well the series crossovers are just better. Both from a sonic and measurement standpoint." Of course at that point, Bud's question was, "Well then why the hell do you even offer the parallel crossover?!?" The answer was, "Nobody wants the series crossover because they've never seen them before, and whenever we send them a diagram, they run away."
Again, Bud being Bud, he didn't run away. He built them, tested them (and saw their much superior dynamic range), listened to them (musicality plus cohesion - less sense of listening to individual drivers), and soon after never built another parallel network outside of to have something to show as a comparison for testing or at shows for dealers, customers, friends.
What was even a surprise to Bud was when I used to discuss them with him last year. He never heard of Zeta, which is the means to alter the rolloff and sonics of a series crossover. The traditional first order Butterworth (6 db/octave) values of the parallel network yield the same 6 db/octave rolloff have a Zeta value of 1.0. By altering the cap/coil values in relation to each other, one can lower the Zeta (for example - 0.7, slower rolloff - more laid back sound) or raise it (1.2 faster rolloff - more upfront sound). He never heard of this before, and nothing made him more happy than discourse he found interesting. It was something that he wanted us to experiment with together. Alas, he fell ill before we got to play...
I hear in the series crossover a sense of cohesiveness that I instantly noticed each time I listened to the Roman Audio Centurions. The Centurions use Ray Kimber's patented DiAural Crossover, which is just a simple series crossover - though I have never looked at the patent. As Ray was another one of us Bud Fried proteges, I consider it a homage to Bud. Anyway, the sound of these speakers just knocked my socks off. They were creamy, smooth, yet detailed and dynamic. Musical, and I realize that is a vastly overused term. The cohesiveness in the sound haunted me. I could not stop thinking about them. I later understood why, it was the series crossover, the drivers act in unison, as opposed to working on their own.
Please forgive me for not fully understanding your question. From what sense do you mean, "a true series crossover has to to pass all the information sent to it by the amplifier, unlike most every other crossover design?"
To be honest, I really have no idea why the series crossover is not used more. Despite the "black magic" that surrounds crossovers, this one even being on another plane, it is no more complex or difficult to understand than a parallel network. Though, I would allow that the most simple first order parallel network (cap inline with the tweeter, plus coil inline with the mid/woofer) is probably the most easy for folks to envision.
What I think sometimes scares people is when they see the schematic of a series network. It looks all wrong on paper, as our minds have grown accustomed to seeing the cap go with the tweeter, and the coil go with the mid/woofer. With a series network, the same is true, but it took a very simple parable that talked about what was actually happening before it clicked for this dunderhead. Of course, I sound ridiculous in this post, because I cannot draw out a parallel and a series network, and I wish I could. Suffice it to say that it looks odd, with the coil in parallel to the tweeter, and the cap in parallel to the woofer.
Bud got started down the series crossover road while at one of his visits to Dynaudio. In talking to someone, he noticed two crossovers on their desk. Bud being Bud, he asked about them. The employee mentioned, "Oh, they're different. These are the series crossovers and these are the parallel." Bud asked what was different about them, to which the reply was, "Well the series crossovers are just better. Both from a sonic and measurement standpoint." Of course at that point, Bud's question was, "Well then why the hell do you even offer the parallel crossover?!?" The answer was, "Nobody wants the series crossover because they've never seen them before, and whenever we send them a diagram, they run away."
Again, Bud being Bud, he didn't run away. He built them, tested them (and saw their much superior dynamic range), listened to them (musicality plus cohesion - less sense of listening to individual drivers), and soon after never built another parallel network outside of to have something to show as a comparison for testing or at shows for dealers, customers, friends.
What was even a surprise to Bud was when I used to discuss them with him last year. He never heard of Zeta, which is the means to alter the rolloff and sonics of a series crossover. The traditional first order Butterworth (6 db/octave) values of the parallel network yield the same 6 db/octave rolloff have a Zeta value of 1.0. By altering the cap/coil values in relation to each other, one can lower the Zeta (for example - 0.7, slower rolloff - more laid back sound) or raise it (1.2 faster rolloff - more upfront sound). He never heard of this before, and nothing made him more happy than discourse he found interesting. It was something that he wanted us to experiment with together. Alas, he fell ill before we got to play...
I hear in the series crossover a sense of cohesiveness that I instantly noticed each time I listened to the Roman Audio Centurions. The Centurions use Ray Kimber's patented DiAural Crossover, which is just a simple series crossover - though I have never looked at the patent. As Ray was another one of us Bud Fried proteges, I consider it a homage to Bud. Anyway, the sound of these speakers just knocked my socks off. They were creamy, smooth, yet detailed and dynamic. Musical, and I realize that is a vastly overused term. The cohesiveness in the sound haunted me. I could not stop thinking about them. I later understood why, it was the series crossover, the drivers act in unison, as opposed to working on their own.