Trinary crossovers??? Looking for more information...

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Hi, I stumbled on this website: http://www.orchid-precision-audio.co.uk/page6.html

They claim perfect phase, time, power linearity anywhere in the audio band because of this crossover design. So, they have a almost perfect square wave response.

More explanation here: http://www.1388.com/articles/tech_lwo/page2/page2.html

I want to know if it's ******** or not, because I don't see these crossovers used even on the EgglestonWorks Ivy or on the Wilson Audio X-1 Grand SLAMM.

If there's more information about this way of designing a crossover, I would like you to point me at the information, even Google doesn't like the term... :D

Thank you very much,
Simon
 
Sounds like a 'filler driver' concept. I'm slightly sketchy on the formalities,but the basic idea:
generate a 2-way xover for the woofer and tweeter so that they are in phase at the xover. I *think* it's typical to use 2nd order acoustic slopes, but 4th might work as well. Now invert one.This creates a deep null, but due to the differing delay in the xover legs, they are actually 'time aligned'. Now, 'fill in' the null with a third driver using first-order acoustic slopes centered on the xover freq used in the original 2-way.

Done properly, this is in fact a linear-phase xover and will pass a square wave.

John Kreskovsky who usually hangs out at the Madisound board (but does post here occasionally) has (or used to have) a paper on his site covering this.
 
nuuk put a very interesting design on decibel dungeon here
The crossover sums dead flat in both magnitude and phasel, I built, measured and simulated one. The only problem I had was that if the high - pass filter has a -12dB slope, the low - pass filter has a -6dB slope. You need very good drive units to use it.

If a low - pass filter was similarly treated, and the outputs of the summing opamps combined then maybe this is the kind of thing they mean. I don't know how they do it passively though.

:)
 
This xover concept was originally described by Bang and Olufsen back in the late '70's. It was called the "filler driver".
Basically if you look at the summation of a 2nd order low pass and high pass filter, the magnitude response sums to unity, but not the phase response. The result is an all-pass response.
The difference between the all pass response and a unity response is a 1st order bandpass response. This is the filler driver, a driver/filter whose response is centered at the xover frequency and which rolls off at 6dB/oct either side.
B&O sold many models using this principle.
The drawbacks are that the filler driver must cover a wide frequency range with low colouration. Thus it must be of high quality. It also runs in parallel with the main drivers so you have to watch impedance. Also, off axis response, particularly in the vertical direction becomes very untidy.
In the end, I believe that the potential benefits of fixing the phase were overwhelmed by the drawbacks, and the reality never lived up to the potential.
This is one of the aspects of correcting phase response that I believe is too often overlooked. Nearly all practical implemantations of "linear Phase" results in very poor off axis response. The phase is only correct at one point in space, yet the sound we hear from a loudspeaker in a room is a combination of many things, the direct sound, the early reflections and the late reflections. Only the direct response, along one narrow axis, is phase linear.

Andrew
 
This xover concept was originally described by Bang and Olufsen back in the late '70's. It was called the "filler driver".

That's correct.
But nowadays by using subtractive techniques one can do such tricks without an additional driver. But your system has to be active therefore.

The phase is only correct at one point in space, yet the sound we hear from a loudspeaker in a room is a combination of many things, the direct sound, the early reflections and the late reflections. Only the direct response, along one narrow axis, is phase linear.

I still prefer a speaker that is transient-perfect one one axis only over the one that is bad everywhere.

Regards

Charles
 
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