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About a Nelson Pass phase coherent crossover
About a Nelson Pass phase coherent crossover
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Old 1st October 2007, 08:24 AM   #1
gaetan8888 is offline gaetan8888  Canada
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Default About a Nelson Pass phase coherent crossover

Hello

I did found a nice active crossover plan in the document; Phase coherent crossover networks, by Nelson Pass, and it's 2 khz center frequency are righ for me.

I would use the 18 bd / octave schematic.

Is it a butterworth or a bessel type ?

Anybody did a simulation of the summed phase and square wave output on that circuit ?

Thank

Gaetan

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Old 1st October 2007, 02:33 PM   #2
jackinnj is offline jackinnj  United States
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About a Nelson Pass phase coherent crossover
Here's a sim, the center plot is the summed magnitude or phase:

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Old 1st October 2007, 05:27 PM   #3
gaetan8888 is offline gaetan8888  Canada
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Hello

That's look quite good and phase coherent.

Which simulator did you use ?


Thank you very much

Gaetan
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Old 1st October 2007, 06:47 PM   #4
jackinnj is offline jackinnj  United States
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About a Nelson Pass phase coherent crossover
Multisim -- now that National Instruments has taken over it doesn't crash and burn -- EWB was a Canadian company I believe.

Here's the 18dB/8vo

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Old 1st October 2007, 11:44 PM   #5
Nelson Pass is offline Nelson Pass  United States
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About a Nelson Pass phase coherent crossover
I should point out that 1 Megohm resistors in the voltage
divider are unrealistically high values for op amps.

Also, it's a lot easier to realize these with ordinary Sallen-Key
filters than with cascaded values of passive components. Just
build the desired filter and use a differential amplifier comparing
the input and output, scaling for gain differences in the pass band.

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Old 16th November 2018, 04:32 PM   #6
Nikolas Ojala is offline Nikolas Ojala  Finland
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Lightbulb Possible applications for phase coherent crossovers

I think that a WAW (Woofer Assisted Wideband) would be kind of a natural application for a phase coherent crossover. A coaxial speaker driver would be another, perhaps even more obvious. I would be also tempted to use current drive for both the widerange and the woofer.
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Old 16th November 2018, 04:38 PM   #7
Lingwendil is offline Lingwendil  United States
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About a Nelson Pass phase coherent crossover
Yep. a fullrange top with a helper woofer is a great application for most of these sorts of phase-coherent electronic crossovers, since you are likely to cross pretty low, time alignment tends to be a non-issue, and biamping makes matching different driver sensitivities a breeze.

coax may need time alignment, or it may not. depends on the actual application and crossover point.
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Old 16th November 2018, 06:05 PM   #8
planet10 is offline planet10  Canada
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About a Nelson Pass phase coherent crossover
We have used phase coherent, 1st order PLLXOs with many/mpst of out WAW. Driver C-C under quarter wavelength and the phase coherence of the XO means that little to none of what a good FR does gets lost. I will be getting a B4 kit when they come and will wire it up as 1st order, meaning i know longer have to worry about amp input impedances.

dave
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Old 16th November 2018, 07:00 PM   #9
adason is offline adason  United States
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Or just put two buffers on the output of your PLLXO now, no waiting
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Old 16th November 2018, 10:25 PM   #10
Nelson Pass is offline Nelson Pass  United States
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About a Nelson Pass phase coherent crossover
Written a long time ago, the piece should have identified the distinction
between "phase perfect" and "phase coherent".

My bad.

The circuits in the article are phase perfect in that they sum to form
a perfect replica of the original amplitude and phase, so they do a
perfect square wave.

Phase coherent means that there is a constant phase difference
between the two outputs.

You can make a phase perfect crossover which is not phase coherent.

You can make a phase coherent crossover which is not phase perfect.

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