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PostPosted: January 10th, 2018, 5:24 pm 
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DaveR wrote:
Cogito wrote:
brombo wrote:
It should reduce 2nd harmonic distortion due to asymmetries in the cone suspensions since the restoring force of the suspension will not be exactly symmetrical (not purely kx where x is the displacement and k the spring constant).


That reminds me of J. Gordon Holt’s experiment on audibility of absolute phase. He found that one can identify the polarity reversal only in the drivers that do not have linear excursion on both sides.

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https://www.stereophile.com/content/absolute-phase-fact-or-fallacy


A servo controlled driver should have the same excursion characteristics for both directions if the servo circuitry is doing its job.


Dave:

That is only true if the motor strength at large excursions is symmetrical. I have seen many drivers that for several reasons have a BL curve that is not symmetrical around center. At some point no matter how much power the servo forces into the voice coil there is not enough motor strength to control the nonlinearities. That point will vary in the in and out directions if the BL is not symmetrical. What is worse, the non symmetry of the suspension compliance (Kms) often is worse in the same direction that the BL is weakest making the job of the servo even that much harder. I'm including two graphs of a good driver that illustrates the case where the BL decreases faster in the same direction that the suspension stiffens faster.


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Non symmetrical BL.png
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Non symmetrical Kms.png
Non symmetrical Kms.png [ 30.33 KiB | Viewed 2709 times ]
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PostPosted: January 10th, 2018, 5:36 pm 
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Tom,

That patent application seems to be a whole lot of nothing. We are discussing impact of distortion in acoustic environment, while the paper seems to addressing the issue electrically.
Moreover, I do not see a single product on Miller And Kreisel website with reverse mounted drivers.

Patent applications are processed by patent clerks who are mostly fresh out of college law graduates who work there for few years, learn the tricks of the trade and start their legal practice.

The patent applications have to be convoluted and technical to increase the chance of approval. An easy to read patent application can be easily understood and rejected by young clerks.

_________________
Shashi


Last edited by Cogito on January 10th, 2018, 5:49 pm, edited 1 time in total.

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PostPosted: January 10th, 2018, 5:40 pm 
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Well the beauty of these H-Frame cabinets is that they are reversible. Just flip the bottom one around if you want.

The original design is the opposed version as I built them.


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PostPosted: January 10th, 2018, 8:38 pm 
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Cogito wrote:
Tom,

That patent application seems to be a whole lot of nothing. We are discussing impact of distortion in acoustic environment, while the paper seems to addressing the issue electrically.
Moreover, I do not see a single product on Miller And Kreisel website with reverse mounted drivers.

Patent applications are processed by patent clerks who are mostly fresh out of college law graduates who work there for few years, learn the tricks of the trade and start their legal practice.

The patent applications have to be convoluted and technical to increase the chance of approval. An easy to read patent application can be easily understood and rejected by young clerks.


What happens in the electrical and electo-mechanical domain has a significant impact on everything after, like acoustic environments.


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PostPosted: January 11th, 2018, 5:55 pm 
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Once I have the updated servo amps, will try distortion measurements and see what I find with a nearfield mic. Might be interesting and Pocket CLIO supports the measurements with their calibrated omni mic.


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PostPosted: January 19th, 2018, 8:41 am 
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The update from Rythmik Audio today is they have received the HX300-8OB for mod to HX300-12OB and should be completed and shipped by Monday.

Should have them next week and start new measurements for the digital crossover design.


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PostPosted: January 25th, 2018, 11:18 pm 
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Update today is the HX300-12OB amps will be here next Tuesday. Another day. I hate waiting!


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PostPosted: January 30th, 2018, 9:41 pm 
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The HX300-12OB servo amps are here and warming up to room temp before unpacking. Cold soaked at 28 degrees for awhile before finding it.

Tomorrow for connection and testing!


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PostPosted: January 30th, 2018, 10:46 pm 
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The Rythmik Audio HX300-12OB servo amps arrived today and now installed with the subs.

Tomorrow will be testing with the digital crossover and see what happens.


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PostPosted: January 31st, 2018, 9:03 am 
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The servo amps are up and running with subs and the digital crossover. Pink noise sounds very smooth and goes low. No room boom, just bass.


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