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Friday, May 26, 2017
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 Calculate the effect of additional mass on the Thiele-Small Parameters




The calculation is based on the relative growth of Massa-moving mass (mms) of the driver.
The Equivalent Volume and the Transducer constant BI, however, remain unchanged.
The efficiency decreases due to the extra mass by 20 * log (M).


A suitable driver should have:
  • Low Fs
  • Low Qts
  • High Mms

Please do not exaggerate the additional mass, there are physics limits!

Woofer Parameters
fs: Hz
Qms:
Qes:
Qts:
Mms:
SPL: db (1 W/1 m)
 
Added mass: grams
 
Calculated new Parameters
Mass-Factor:
SPL loss: dB (1 W/1 m)
 
new fs: Hz
new Qms:
new Qes:
new Qts:
new SPL: dB (1 W/1 m)




 Example ( SEAS Prestige CA26RE4X (H1316) 10" Paper Cone Woofer )


Original TSP + 50 grams + 100 grams + 150 grams  
Re 6.1 6.1 6.1 6.1 ohms
Le 3.08 3.08 3.08 3.08 mH
Fs 25 16.5 13.2 11.3 Hz
Qms 3.99 6.05 7.57 8.83 -
Qes 0.30 0.45 0.57 0.66 -
Qts 0.28 0.42 0.53 0.62 -
Mms 38.5 88.5 138.5 188.5 grams
Sensitifity 91 83.8 79.9 77.2 dB