Hi
today I was using the QA403 (SW release 1.222) and the QA461 transducer driver to measure the Thiele Small Parameters of an Audax HM210G6 woofer chassis (new chassis, no burn-in). I was using the SPKR Impedance automated test.
According to the datasheet (see https://www.audax-speaker.de) the Vas value of the chassis is 85 liters. With the SPKR Impedance automated test (added mass method), I measured the Vas at 10.279 liters. Although TSP measurements of loudspeaker chassis usually show quite some deviations from the datasheet, this result seems wrong. I have used a spreadsheet to verify the Vas calculation.
Formulas used are:
| Cms = (fs^2 – fsm^2) / (4 * Pi^2 * fs^2 * fsm^2 * m) |
|---|
| Vas = Rho * c^2 * Sd^2 *Cms |
|---|
(fs and fsm: resonance frequency w/o and with added mass, Sd: effective area of cone, c: speed of sound, Rho: density of air)
The result of my Vas calculation is 97.08 liters. This seems within the typical error range of such measurements. I re-verfied the Vas calculation using the ls_param spreadsheet from the Elliott Sound Products website ( Measuring Loudspeaker Driver Parameters ) - Vas calculated as 98.09 liters.
It seems that the SPKR Impedance automated test has a bug in the Vas calculation. Does anyone else have experience with this automated test?
Best regards
Andy