Start from one consistent driver data set
Fs, Qts and Vas describe a small-signal driver model. Use values from the same manufacturer data set or measurement session. This tool does not mix parameters from a database or infer missing values from the driver diameter. The comparison changes only the net box air volume.
A smaller air volume adds stiffness. In this ideal model both the system resonance Fc and total Qtc rise by the factor sqrt(1 + Vas/Vb). A larger volume reduces that factor toward one. This is a mathematical comparison, not an automatic recommendation for the driver.
Read the response against its stated reference
The chart shows amplitude relative to the ideal high-frequency asymptote. It does not predict a sound-pressure level at a microphone or the response in a room. The frequency grid is logarithmic from 5 to 1000 Hz; the downloadable CSV includes every displayed sample.
F3 is the low-frequency half-power crossing of the modeled response. Fc is the system resonance, and the two differ when Qtc differs from the Butterworth value. A peaked response can have a half-power point below its resonance while still emphasizing a different frequency region.
Keep the model separate from the finished loudspeaker
Inductance, box leakage, fill, diffraction, room gain, driver excursion and thermal compression are not included. The tool therefore cannot tell whether a design can play a particular signal at a particular level. It provides a reproducible first comparison to inspect alongside measurements.
Save the driver values and both box volumes with the project. If you edit the result, prepare a fresh export before sharing. The numerical report records the exact values so a second calculation can reproduce the comparison.