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Power Level Effects On Port Tuning
As vent air velocity increases to some percentage of the speed of sound, noise,
distortion and other non-linear effects will become noticeable. Quite often,
these effects can be measured using the Woofer Tester Pro by examining the
impedance and phase at various power levels. In general, the rule of thumb
is that vent air velocity should not exceed 10% of the speed of sound, but with
the WT-Pro many of these effects can be measured first hand.
The WT-Pro screenshot below shows the effect that power has on a 12" woofer using
a 4" port. A clear progression of lower Fbox tuning with increasing power
and lower impedance peaks is shown for 10Vrms 1Vrms and 3mA drive levels.
Note: This overlay was constructed using a prototype WT-Pro and early
software version that did not have separate colors for each buffer.
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