Well, THAT's Not Gonna Fucking Work!

Re: Well, THAT's Not Gonna Fucking Work!

Mark DeArman said:
Well I reproduced the phase response in the HF now. The error comes from a one sample difference of the t0 to the impulse response of the HF LP filter type response of a DSP. I'll produce the results here in the forum later on. This is what I was wondering about originally. The t0 choice can dramatically effect results with SMAART or when other measurements which determine the frequency response from the FFT of the derived impulse response. I would like to also point out that I will make available all algorithms and programs which I used to make my measurements if requested. I can't pass out the swept sine programs but the algorithms I will give away for free. In fact they are on www.cascadeacoustic.com in the tutorial section. The Lock-In Amp program from Feldman I will pass on if anyone wants.

P.S. I'm not trying to sell any product to the sound reinforcement industry. I don't want anyone to think my website plug is against SMAART or SysTune. Course I'll bet on the SysTune measurements all day above others.

I'm still trying to get a SMAART system down here... duh this is taking like a week... too long. We have five licenses.
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Yes, the phase response will be affected by the choice of the t0 time relative to the true arrival of the IR. More specifically, properly choosing t0 can remove the excess delay (propagation time. latency, etc.) from the measurement an leave only the inherent phase response of the device under test. Deviations from the proper section of t0 will result in the signal (IR) arriving too early or too late which will cause changes to the phase response.

For a more detailed explanation see http://www.excelsior-audio.com/Publications/Phase_Response_&_Receive_Delay.pdf.
 
Re: Well, THAT's Not Gonna Fucking Work!

Charlie Hughes said:
No, it most definitely is not. Phase is frequency dependent, polarity is not.
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You’re correct of course Charlie … sorry bad choice of words/explanation… we started with the polarity inversion talk and I just continued... I should have said the output will need to be inverted etc...etc.
It’s explained better here http://www.midasprosound.com/cms/cmsfiles/pdf/ClassicCrossoverNotes.pdf in particular Fig 4


Peter
 
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