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Multi-Way Conventional loudspeakers with crossovers

An exercise in converting a speaker to time-phase coherent
An exercise in converting a speaker to time-phase coherent
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Old 3rd December 2019, 03:07 AM   #81
andy2 is offline andy2  United States
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The more you want from God, the more he's like a devil.
This is probably the last example. I here use a three way design but using first order. It's a non-coherent design with the mid being inverted polarity, while the woofer and tweeter are positive polarity. So I guess you would expect that being a first order design, the step response should not be complicated right?

But I guess as anything in life, as you want more and more, things start get complicated. The step response now looks a bit of a mess. Interestingly, the step response looks a bit like a 2way using 3rd order filters. I don't know if it's a coincidence or not, a 2way using second order looks the same as a 2way using first order filter. Looks like anything 3 or above is where HE's starting to get real pissed.

Anyway, I'll leave it to the consideration of the readers (if there's any lols).
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Last edited by andy2; 3rd December 2019 at 03:14 AM.
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Old 3rd December 2019, 04:46 AM   #82
andy2 is offline andy2  United States
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“So where does that leave us?” from “The Lovers”.
After looking at various step response of various designs – coherent and “transient perfect”, first order non-coherent, third order, 2way, 3way and so on … you can see the elegance of the coherent design with a proper step response. The non-coherent design step response does make me feel a bit uneasy.

On the one hand, there are a lot of speakers that are designed that use high order filters (infinite slope … for example) that sound just fine.

But on the other hand, we also know phase shifts do affect the sound quality such as MP3, early 1980's digital music.

I also talk to a lot of people who have said that they “do” hear difference in first order filter speaker vs. higher order speaker, me included. The consensus is that in high order filter speaker, the most difference comes from the treble. In first order design, the treble is more integrated with the music, whereas in high order filter, the treble seems more like it's riding on top of the music.

So should we ask which is better? Maybe we should leave it at it between the listener and his lover ….. errrrr ….. I meant his speakers lols.

More to come ...
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Old 3rd December 2019, 09:45 AM   #83
kimmosto is offline kimmosto  Finland
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Originally Posted by john k... View Post
It's a complete waste of time and effort. It doesn't not lead to a better speaker.
Tuning was successful if performance did not drop more than 15 %.
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Old 3rd December 2019, 12:05 PM   #84
john k... is offline john k...  United States
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Originally Posted by andy2 View Post
I also talk to a lot of people who have said that they “do” hear difference in first order filter speaker vs. higher order speaker, me included. The consensus is that in high order filter speaker, the most difference comes from the treble. In first order design, the treble is more integrated with the music, whereas in high order filter, the treble seems more like it's riding on top of the music.

So should we ask which is better? Maybe we should leave it at it between the listener and his lover ….. errrrr ….. I meant his speakers lols.

More to come ...
Again, if you take two or 3 drivers and build a speaker with passive crossover, it will sound different with different crossovers, regardless of whether they are TP or not, because when you change the crossover order and type you change more than just the axial frequency response (amplitude and phase). You change the polar response, driver overlap, driver excursion, distortion, etc., and that leads to different sounding speakers even if the axial amplitude response is identical.

This thread is a perfect example. Here Andy2 has designed numerous different TP system that all produce relatively similar step responses. Do they all now sound the same because they are TP? Of course not.

Another thing to consider with a multiway system is that it is the sum of the output of all the drivers that yields the TP response. Each individual driver is introducing a phase shift in its band pass that cancels the phase shift introduced by another drivers. Using the B&O concept as an example, if you keep Fc of the HP and LP 2nd order response the same fc(hp) = fc(LP) and design systems where the Q of these filters are different (there is no requirement that Q = 0.5, nor is there a requirement that Q(LP) = Q(HP) ), they will all be TP. But how the drivers sum will be different resulting is different polar response because the phase of each driver will have a different frequency dependence. This difference in phase leads to other factors as well. Consider the sum of the woofer + filler. This sum must then sum to the tweeter to yield zero phase. With one selection of Q the woofer + filler sum may have an amplitude of 0.707 @ 45 degrees at a given frequency which will sum to the tweeter which has an output of amplitude 0.707 @ -45 degrees at the same frequency. The sum is amplitude 1@ 0 degrees. A different selection of Q may yield the woofer + filler output = 1@ 60 degrees while the tweeter output is 1 @ -60 degrees. Again, the sum is 1 @ 0 degrees. So the same result is achieved but the individual drivers are behaving very differently, reproducing their component with different amplitude and phase.

The point, again, is that just because you have achieved a TP response on axis doesn't mean that differences in what you hear, compared to a system built with the same drivers but not TP, can be attributed to the TP nature of one of the systems, better or worse.
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Old 3rd December 2019, 05:39 PM   #85
ernperkins is offline ernperkins  United States
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Originally Posted by john k... View Post
I admire Andy2 for the effort he is making. Having been through it I know the effort. But having done it, other than for the exercise, it's a complete waste of time and money to pursue this approach for a quality speaker.
John – Glad to see you’re still active here in your retirement. A few years back I discovered the work you did on TP and quasi-TP passive crossovers in the early 2000’s. At that time your “It’s Just a Phase I Am Going Through” paper was my design inspiration. So it was it was very interesting to see your response when it finally became possible to do an apples-to-apples comparison of linear phase vs non-linear phase crossovers using tools like Ultimate Equalizer. After all that work it must have been difficult to conclude that linear phase crossovers aren’t the magic bullet that many make them to be.
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Old 4th December 2019, 12:52 AM   #86
mark100 is offline mark100  United States
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Originally Posted by ernperkins View Post
John – Glad to see you’re still active here in your retirement. A few years back I discovered the work you did on TP and quasi-TP passive crossovers in the early 2000’s. At that time your “It’s Just a Phase I Am Going Through” paper was my design inspiration. So it was it was very interesting to see your response when it finally became possible to do an apples-to-apples comparison of linear phase vs non-linear phase crossovers using tools like Ultimate Equalizer. After all that work it must have been difficult to conclude that linear phase crossovers aren’t the magic bullet that many make them to be.
Hey guys, I read this and have to ask again....

were your (John K) listening tests phase linearization on top of crossovers already in place..what I call global FIR on inputs..

or were they drivers individually flattened with minimum phase EQ and then put together with linear phase crossovers.. ????

There is a world of difference....the first method just doesn't add anything ime, whereas the second rocks, again ime......that's why i ask...
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Old 4th December 2019, 05:59 AM   #87
andy2 is offline andy2  United States
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I put together a 3way xover using ideal drivers so it's a little better to see how the phase of the woofer, mid, and tweeter matched up in a "B&O" filter setup. Of course, the woofer and the tweeter are using 2nd order filters. The mid is using first order filter.

1. The first one is with all the drivers on. Overall system phase is 0 degree phase shift. The system shows proper step response.

2. The second one is with the mid off. The tweeter is inverted to show that without the mid, the system is basically a 2way system using 2nd order filter roll off. So the phase shift is -180 degree at 20KHz.
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File Type: png BO_ideal.png (57.0 KB, 108 views)
File Type: png BO_midoff.png (54.7 KB, 90 views)
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Old 4th December 2019, 06:33 AM   #88
andy2 is offline andy2  United States
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And in contrast to the "B&O" type filter, the first order filter version does show some very similarities. The only difference is the woofer and tweeter are using 1st order roll off.

1. Again with all drivers all, 0 phase shift. Proper step response.

2. With the mid off, the tweeter inverted polarity, then you have a typical 2way system with the phase shift also at -180 degree at 20KHz.
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File Type: png FirstOrder_Ideal.png (56.4 KB, 101 views)
File Type: png FirstOrder_Midoff.png (57.4 KB, 97 views)
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Old 4th December 2019, 07:30 AM   #89
AllenB is online now AllenB  Australia
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@Mark100, if I understand you those two should be the same thing, yes?
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Old 4th December 2019, 08:16 AM   #90
phase_accurate is offline phase_accurate
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If I understood him correctly he was using FIR correction before the crossover. This way he could switch back and forth between transient-perfect and "normal". This way no other properties of the system were changed for the listening test.

When I find the time I will do something different: I willl use a transient-perfcet crossover and switch an allpass in and out before the crossover in order to hear whether it makes any difference. The test will be purely subjective of course but the decision whether I like a topology or not is also a purely subjective one.

Regards

Charles
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