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Multi-Way Conventional loudspeakers with crossovers

A little addition to multiway crossovers a la Linkwitz: multi-cascading
A little addition to multiway crossovers a la Linkwitz: multi-cascading
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Old 15th January 2019, 02:55 PM   #11
CharlieLaub is online now CharlieLaub  United States
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I commend you on your analysis, however, I must point out that you have developed an improvement on a solution for an "invented problem".

It really bothered me that SL made such a big deal about the cascade arrangement of filters on his web site. His analysis seemed rather pointless, because...

HE DID NOT INCLUDE THE DRIVER RESPONSES!

This is after all a loudspeaker crossover, not a purely electronic transmission system. How you connect or cascade filters and the phase relationships at the filter output(s) are not of prime importance to the task at hand because the phase relationships between filter outputs is internal to the system. What is of paramount importance is the phase relationship of the ACOUSTIC output from the drivers at the listening position. The phase response of the acoustic radiation is a product of the input (the electrical signal, which you have modeled), the driver's inherent phase response due to its bandpass character, and the phase rotation due to the propagation delay (because the acoustic output must travel from the driver's acoustic center to the listener and this takes some time).

Time alignment is helpful to some extent because it evens out the propagation delays from each driver to the listening position. Unfortunately, time alignment does not "flatten" the frequency-dependent phase response of the driver that results from the driver's own acoustic passband character (it's inherent in the driver itself). You cannot accurately know the phase angle for each driver around the crossover point unless you measure it, and without that information your model (in CAD) is incomplete.

Only by including the phase (and amplitude) response of each driver's output, which should be as observed from the listening position with the drivers installed in the final loudspeaker enclosure, can an accurate model of the loudspeaker system output be created.
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Last edited by CharlieLaub; 15th January 2019 at 03:09 PM.
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Old 15th January 2019, 03:06 PM   #12
minkuni is offline minkuni  Norway
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Omitting the driver responses for the sake of discussing the core matter is a valid approach.


Of course the actual responses need to be considered in an actual design, but jumping directly to that stage introduces complexity that hides the main point of the filtering structure being discussed.
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Old 15th January 2019, 03:13 PM   #13
CharlieLaub is online now CharlieLaub  United States
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Quote:
Originally Posted by minkuni View Post
Omitting the driver responses for the sake of discussing the core matter is a valid approach.


Of course the actual responses need to be considered in an actual design, but jumping directly to that stage introduces complexity that hides the main point of the filtering structure being discussed.
No, its not a "core matter". It matters no more and no less than other "phase modifiers" in the reproduction chain. That was my point. The filters are simply passing their outputs to the drivers, which further modify the response before spitting out the signal from their acoustic center as sound, and then the propagation through the air further modifies the phase (and amplitude) of that sound.

Let me as you this: do you listen to the electrical signal or the acoustic one?
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Old 15th January 2019, 03:37 PM   #14
Juhazi is online now Juhazi  Finland
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Someone who can use Vituixcad or some other simulation with measured response, phase and timing parameter,s could make an example how this cascading affects a real multiway loudspeaker. Charlie is absolutely right, pure electric simulation with ideal signal is worthless in context of loudspeaker design.

I have been fiddling with a 4-way speaker and minidsp for more 6 years now, and I never faced problems that SL describes. But finding nice xo is river deep, mountain high! Linkwitz was an EE and a deep tinkerer, and he put many of his open questions on his webpage as teasers and for discussion.
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Last edited by Juhazi; 15th January 2019 at 03:40 PM.
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Old 15th January 2019, 03:37 PM   #15
adason is offline adason  United States
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not discussing response flatness...

just want to ask different question
in typical parallel crossover, tweeter will see only one or two capacitors

in cascading crossover, tweeter will see multiple, including very big value capacitors, like 50Hz first filter, probably some bipolars, then 200Hz, maybe not bipolars, but some big caps, before the 2kHz filter cap...
would not that degrade heights more then in typical parallel crossover?
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Old 15th January 2019, 03:47 PM   #16
CharlieLaub is online now CharlieLaub  United States
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Quote:
Originally Posted by adason View Post
not discussing response flatness...

just want to ask different question
in typical parallel crossover, tweeter will see only one or two capacitors

in cascading crossover, tweeter will see multiple, including very big value capacitors, like 50Hz first filter, probably some bipolars, then 200Hz, maybe not bipolars, but some big caps, before the 2kHz filter cap...
would not that degrade heights more then in typical parallel crossover?
We're talking about active crossovers... no bipolar caps here (I hope!).
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Old 15th January 2019, 03:51 PM   #17
Davey is offline Davey  United States
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This configuration has been discussed many years ago. Most recently over on the OPLUG forum.
ORION/PLUTO/LX... Users Group • View topic - Phase consistent crossover topology

Dave.
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Old 15th January 2019, 03:52 PM   #18
adason is offline adason  United States
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Quote:
Originally Posted by CharlieLaub View Post
We're talking about active crossovers... no bipolar caps here (I hope!).
ok, my bad...should have read the thread more carefully
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Old 15th January 2019, 04:00 PM   #19
CharlieLaub is online now CharlieLaub  United States
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Originally Posted by Davey View Post
This configuration has been discussed many years ago. Most recently over on the OPLUG forum.
ORION/PLUTO/LX... Users Group • View topic - Phase consistent crossover topology

Dave.
One of the first few replies is this one:
Quote:
Do not forget that each driver adds a high pass filter.
SL
That's really only half the story... in addition to the near-resonance high pass rolloff there is also a low pass filter regime at the top end (no driver has infinite bandwidth). The high-pass and low-pass parts of the response create a "bandpass character" to the driver, and each impart phase rotation to the acoustic radiation.

SL included a model of the resonance high pass filter here:
Woofer crossover & offset
The crossover point was 100Hz. In that case the drivers were too far away from the low-pass end of the passband to bother to include that part of the phase response, however, it does influence the overall phase response of every driver.
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Last edited by CharlieLaub; 15th January 2019 at 04:04 PM.
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Old 15th January 2019, 04:02 PM   #20
pixelpusher is online now pixelpusher  United States
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This can be done with "Ultimate Equalizer" by the maker of SoundEasy. I've not tried it but if you believe phase coherency is important you should check it out.

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