Q of closed enclosures

[Michael Gaedtke]

Hello, I have come across another task for which I have not yet found a solution in REW: You can measure the Thiele-Small parameters. This requires two impedance measurements - either in two different enclosures or with an additional mass on the diaphragm. This also works very well. For some projects, however, it is necessary to evaluate the resonance point of a loudspeaker in the enclosure - for example, if the loudspeaker has been installed in a closed enclosure and you want to check whether the desired resonance Q of the design has been achieved. Such an evaluation of a single resonance point for resonance frequency and overall Q is apparently not currently possible with REW - at least I have not found a solution for this. It would be very helpful if there were a tool for this in the future.

 

[John Mulcahy]

If you just select a single impedance measurement as the Free air measurement and click Calculate parameters you will get resonant frequency and Q results.

 

[sm52]

I tried this. If Voice Coil DC Resistance is zero (when the TS parameter calculation window first opens, this parameter is zero), the calculate button is inactive. Why doesn't REW take this parameter from the measurement data?

 

[John Mulcahy]

Why doesn't REW take this parameter from the measurement data?

The coil DC R cannot be reliably estimated from the measurement.

 

[Michael Gaedtke]

Ah, that works. Unfortunately I overlooked this feature and always tried to select a second impedance response. With this tip my problem is solved. Many thanks for your quick help and best wishes from Germany (quite rainy these days).

 

[sm52]

The coil DC R cannot be reliably estimated from the measurement.

Thanks for the info. Previously, I measured this resistance with a multimeter, but REW wrote a message that it was too small or too large (I don’t remember), and I began to indicate the resistance at the lowest frequency. Are there many parameters that depend on the exact value of this resistance?

 

[John Mulcahy]

Are there many parameters that depend on the exact value of this resistance?

No, but it might affect the model fit for some drivers.