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Author Topic: Polar Phase Representation  (Read 1518 times)

Barry Singleton

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Re: Polar Phase Representation
« Reply #10 on: April 06, 2019, 10:40:34 pm »

  Hi Frank;

  Thanks for the corrections. I was feeding a machine when I read and posted in broken increments. Divided attention is never good.

  In my experience the little “whorls”  as Richard I think, or maybe Don Davis called them are typically resonances in loudspeakers.

  What’s the old joke? I showed an EE a Nyquist plot of a loud speaker and asked him what he thought. He said I don’t know what it is, but it’s broken.

  Barry.

  I should shoot a JBL M2 and see what it looks like.
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Frank Koenig

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Re: Polar Phase Representation
« Reply #11 on: April 07, 2019, 04:48:35 pm »

In my experience the little “whorls”  as Richard I think, or maybe Don Davis called them are typically resonances in loudspeakers.

I think that's right. I ran the transfer functions of a number of simple filters to get a feel for how they are represented. A bi-quad makes a perfect (looking) circle irrespective of its Q. Changing the Q simply changes the rate at which the locus moves along the (normal-to-our-view) frequency axis. Changing the gain changes the radius of the circle, as one would expect. Example below is of a 1 kHz bi-quad with +6dB and Q=1 (by my definition) and the same with 1 cycle of delay at the max freq of 8 kHz.

Hi- and low-pass filters make spirals. Not surprisingly, all-pass filters make circles around the origin, and a straight wire makes a point at 0 or 180 deg depending on the polarity. Delay winds up whatever is there like a clock spring.

So are the whorls useful in identifying simple (2nd order) resonances that can be corrected with bi-quads?

--Frank





« Last Edit: April 07, 2019, 04:51:48 pm by Frank Koenig »
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Barry Singleton

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Re: Polar Phase Representation
« Reply #12 on: April 10, 2019, 05:38:31 pm »

....So are the whorls useful in identifying simple (2nd order) resonances that can be corrected with bi-quads?

--Frank

  I haven’t dug deep in this sandbox for a while and my memory sucks but counter clockwise whorls indicate that part of the measurment is a-causal. Easy to otherwise miss in an acoustic measurment of a chaotic system with added delay for filtering.

  I am interested in what you are doing. Just so busy I can’t see straight and get back here often.

  Thank you Frank
Barry.
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Frank Koenig

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Re: Polar Phase Representation
« Reply #13 on: April 12, 2019, 10:48:27 am »

Traveling now and away from my beloved desktop. I'll be back on in due course. --Frank
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Re: Polar Phase Representation
« Reply #13 on: April 12, 2019, 10:48:27 am »


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