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Updates for "Loudspeaker Measurement Technique?"
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natandmark
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Updates for "Loudspeaker Measurement Technique?"
The "library" article titled "Loudspeaker measurement technique" describes a potentially very useful technique for evaluating loudspeaker frequency response, but need a bit of updating. The article was written for the ADC-216, which was as noted in the article is replaced by the PicoScope 4262. The parameters for the ACD-216 are not the idential as those for the newer 4262, making approach described in this article somewhat difficult to implement. For example, the technique requires accurate control over the signal aquisition time to effectively eliminate reflected sound, but its not at all clear how to do this with the 4262. Is the scan time referred to in the article the same as time gate for the 4262? Is there some way to control the aquisition time window for FT analyses for the newer device, for example, to limit aquisition time to a specific number? What is the equivalent of the trigger delay referred to in this article -- there is no possibility of a negative value for this parameter in the more recent device, so what to do?! At any rate, if anyone could update this approach for the 4262 I would greatly appreciate it!
Re: Updates for "Loudspeaker Measurement Technique?"
Hi natandmark
The issue is more to do with the the difference between the the older version of PicoScope software used in the experiment (PicoScope 5) and the current release of PicoScope software (PicoScope 6) and the fact that the ADC-216 can only use PicoScope 5, while the PicoScope 4262 requires PicoScope 6.
To be able to refer to the parameters as they are defined in our latest version of software, you will need to turn on the Properties Pane so that you can see all of the relevant parameters at a glance. To do this go to Views->View Properties. Then, in spectrum view, the properties that will apply to the ones mentioned in the Library Experiment are as follows:
PicoSocpe 5-------------------PicoScope 6
Number of Data Ponts--------Number of Bins
Scan Time---------------------Time Gate
Trigger Delay-----------------Time Delay (and Pe-Trigger)
The parameters that affect the size of the Time Gate value are the Spectrum Range (to the right of the Home icon), and the Number of Bins (Spectrum Bins in the FFT Options). Decreasing the Spectrum Range, and/or increasing the number of bins increases the Time Gate. Larger Time Gate values will obviously decrease the responsiveness of the FFT plot, reducing it's ability to track the reverberation decay.
Although the Trigger Delay has been replaced by Time Delay, you can't use negative values, so if you want to create a negative Trigger Delay you will have to reduce the percentage of Pre-Trigger to effectively push reflections off of the end of the trace.
To open a Spectrum view that is related to the Scope view, you need to, from a Scope View, go to Views->Add view->Spectrum
Bear in mind that this is a very simple experiment to get an understanding of the dynamic behaviour of sound emanating from a speaker in a room. For more practical data (to more accurately characterize the speaker behaviour) you would need to consider either, using the largest room that you have access to, and/or adding sound treatment equipment to make the room more anechoic, or finding a quiet spot outside and just laying the speaker on its back (see here: https://en.wikipedia.org/wiki/Loudspeaker_measurement).
Regards,
Gerry
The issue is more to do with the the difference between the the older version of PicoScope software used in the experiment (PicoScope 5) and the current release of PicoScope software (PicoScope 6) and the fact that the ADC-216 can only use PicoScope 5, while the PicoScope 4262 requires PicoScope 6.
To be able to refer to the parameters as they are defined in our latest version of software, you will need to turn on the Properties Pane so that you can see all of the relevant parameters at a glance. To do this go to Views->View Properties. Then, in spectrum view, the properties that will apply to the ones mentioned in the Library Experiment are as follows:
PicoSocpe 5-------------------PicoScope 6
Number of Data Ponts--------Number of Bins
Scan Time---------------------Time Gate
Trigger Delay-----------------Time Delay (and Pe-Trigger)
The parameters that affect the size of the Time Gate value are the Spectrum Range (to the right of the Home icon), and the Number of Bins (Spectrum Bins in the FFT Options). Decreasing the Spectrum Range, and/or increasing the number of bins increases the Time Gate. Larger Time Gate values will obviously decrease the responsiveness of the FFT plot, reducing it's ability to track the reverberation decay.
Although the Trigger Delay has been replaced by Time Delay, you can't use negative values, so if you want to create a negative Trigger Delay you will have to reduce the percentage of Pre-Trigger to effectively push reflections off of the end of the trace.
To open a Spectrum view that is related to the Scope view, you need to, from a Scope View, go to Views->Add view->Spectrum
Bear in mind that this is a very simple experiment to get an understanding of the dynamic behaviour of sound emanating from a speaker in a room. For more practical data (to more accurately characterize the speaker behaviour) you would need to consider either, using the largest room that you have access to, and/or adding sound treatment equipment to make the room more anechoic, or finding a quiet spot outside and just laying the speaker on its back (see here: https://en.wikipedia.org/wiki/Loudspeaker_measurement).
Regards,
Gerry
Gerry
Technical Specialist
Technical Specialist