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Author Topic: Tell me what you see in these phase response graphs  (Read 9056 times)

Art Welter

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Re: Tell me what you see in these phase response graphs. Updated measurments
« Reply #20 on: February 07, 2018, 02:28:45 pm »

Thanks Art

Here's a few I did a couple days after the others I posted, my fingers were frozen numb after I was done!

I normally flip the polarity on the high freq. and tweak the mid/woofer time delay to find the deepest null point.
After I flip the high freq back to normal I go back and forth a little with the mid/woofer delay watching the amplitude and phase response.
Next time out I'll see what happens trying some different crossover slopes and even some asymmetrical slopes.
Nothing quite like outdoor testing in cold weather!

Looks like the polarity was correct, as well as slopes you might try overlapping the crossover points, that is bringing the LF point higher or HF lower to compensate for the acoustical roll-offs. That said, 1600 Hz is already pretty high for a 15"...
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Mike Caldwell

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Re: Tell me what you see in these phase response graphs. Updated measurments
« Reply #21 on: February 07, 2018, 04:43:13 pm »

Nothing quite like outdoor testing in cold weather!

Looks like the polarity was correct, as well as slopes you might try overlapping the crossover points, that is bringing the LF point higher or HF lower to compensate for the acoustical roll-offs. That said, 1600 Hz is already pretty high for a 15"...

Yea I kind of scooted the crossover up a little higher for a little more driver protection for when they get pushed sometimes.
To be honest I need to build another preset for "less demanding" use with a lower crossover.

fedele de marco

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Re: Tell me what you see in these phase response graphs
« Reply #22 on: February 11, 2018, 04:41:35 pm »

(Why not? Yes...you can
Also check your measurement setup and signal path.


REW does not have set or find delay like Smaart, it does have loop back delay finder or a use acoustic source to set delay, using both showed the same results.
« Last Edit: February 11, 2018, 04:51:56 pm by fedele de marco »
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Jean-Pierre Coetzee

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Yea I kind of scooted the crossover up a little higher for a little more driver protection for when they get pushed sometimes.
To be honest I need to build another preset for "less demanding" use with a lower crossover.

I'm not sure what DSP you have but you should be able to get a little better phase response if you have the DSP power available. Also don't just check the response on axis, if you plan to use the box with say a 60 degree horn then check it at points in between as well up to 60 degrees, you may find that crossing over a 15 that high will have detrimental effects as you move further out of the coverage pattern. designing a loudspeaker is about more than just on axis response as I'm sure that Ivan can tell you.
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Merlijn van Veen

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Re: Tell me what you see in these phase response graphs
« Reply #24 on: March 24, 2018, 10:50:18 am »

I'd love to hear a more in depth explanation of this statement.  By my understanding both electronic and acoustical manipulations will cause a delay of low end, represented by an upward sloping phase plot towards the low frequency.  How does one achieve a downward slope on the low freq?  Please set me straight.

Correct me if I’m wrong, but if there were to be such a thing as a “perfect” phase trace for loudspeakers, I imagine it would be flat. Like a microphone cable. Preserving the impulse response. Evidently, trying to achieve this, comes with its own set of tradeoffs.
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Mike Caldwell

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I'm not sure what DSP you have but you should be able to get a little better phase response if you have the DSP power available. Also don't just check the response on axis, if you plan to use the box with say a 60 degree horn then check it at points in between as well up to 60 degrees, you may find that crossing over a 15 that high will have detrimental effects as you move further out of the coverage pattern. designing a loudspeaker is about more than just on axis response as I'm sure that Ivan can tell you.

Now that it's warming up a little I'm going to do some more measurements and test. The last time out my fingers got so numb I couldn't feel the keys on my laptop.

My DSP's are DBX Venue 360's
« Last Edit: March 26, 2018, 08:32:21 pm by Mike Caldwell »
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Ivan Beaver

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Re: Tell me what you see in these phase response graphs
« Reply #26 on: March 26, 2018, 08:15:54 pm »

Correct me if I’m wrong, but if there were to be such a thing as a “perfect” phase trace for loudspeakers, I imagine it would be flat. Like a microphone cable. Preserving the impulse response. Evidently, trying to achieve this, comes with its own set of tradeoffs.
I have always believed that the "perfect phase response" would be as follows.

It would "fall" below the lower knee of the response, be flat across the operating passband of the loudspeaker, then fall as the HF response falls.

So it would kind of look like a "S" that was turned 90* to the left. Kinda
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Chris Grimshaw

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Re: Tell me what you see in these phase response graphs
« Reply #27 on: March 27, 2018, 04:46:44 am »

I have always believed that the "perfect phase response" would be as follows.

It would "fall" below the lower knee of the response, be flat across the operating passband of the loudspeaker, then fall as the HF response falls.

So it would kind of look like a "S" that was turned 90* to the left. Kinda

I believe that's only a function of the rising/falling frequency response at each end of the passband of the speaker.
If we're talking about ideal speakers, then it'd be good for 1Hz-50+kHz anyway, putting those phase shifts well outside of the audible range.

Chris
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