| Delay measurment method - understanding question |
 Posted: Tue Jun 26, 2012 2:27 am |
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| AFMG Pedro Lima |
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| Joined: 05 Jun 2010 |
| Posts: 269 |
| Location: Germany |
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| Dear Nicola,
I have received the measurement files. Thank you for your time.
Please notice that in order to use the Delay Analisys plug-in one needs to acquire the Transfer Function for each system under test (in your case, each driver).
From the Overlays you have sent and from the doc file, you can see for instance that in the Impulse Response tab (IR) there is nothing but noise for the Medium drive. That is reflected in the Transfer Function Magnitude tab, where you can clearly see that the frequency response displayed does not correspond to the driver response.
For the Tweeter overlay, there is some information but still that is not good. You can notice that from the very low values of Coherene in the TF Mag tab and also from the low signal-to-noise ratio in the ETC tab (notice that the peak is only about 18dB higher than the measurement noise floor).
That said, please allow me to advise you to refer to the section about Dual Channel FFT measurements in Systune user's guide. It can be found from the page 63 on.
Feel free to return the contact in case of further doubts after referring to the document.
Best Regards,
Pedro Lima
PS: Thank you for your valuable feedback with respect the procedure on the memory issue.  |
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| Posted: Thu Jun 28, 2012 7:22 pm |
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| AFMG Pedro Lima |
| Forum Moderator |
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| Joined: 05 Jun 2010 |
| Posts: 269 |
| Location: Germany |
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| Hi Doug,
Sure, good idea. Thanks.
The first picture below shows very bad Impulse Response data. Notice that there is almost only noise in the measurement. One cannot even see the impulse. There is also no meaningfull data in the Transfer Function Magnitude (frequency response) tab.
The Impulse Response below is a bit better. But still, there is too much noise in the measurement. Notice also the low Coherence values for the Transfer Function Magnitude.
Next, a very good measurement. In fact, the Coherence values are very high. In practice they are usually lower for a high number of Averages. See the Impulse Response. There is only a rather thin line other than the Impulse. In the TF Mag tab one can see the high Coherence values. Note that for the lower frequencies the values are low, and the data is masked. That is expected since the measured system did not produce enough low frequency contents.
The measurement quality can be evaluated from the ETC tab. Note the signal-to-noise ratio.
Hope this helps.
Best Regards,
Pedro Lima |
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| Posted: Fri Jun 29, 2012 5:10 pm |
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| ¡Pedro! That was absolutely beautiful. :) |
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_________________
God bless you and your precious family - Langston |
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