Mark K's Speaker Pages
...when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science...Lord Kelvin
Vifa XG18
Vifa XG18 driver evaluation-Note I called this the "XT18" and the "XG16" in a number of places. That's not correct. It's the fiberglass version, XG18. I'm not fixing all the graphs for this!
Nearfield frequency response-at 0.2"
At 0.25m
Impedance
Nonlinear distortion
This first series is just 3 toneburst testing in the usual manner.
Conclusion
The Vifa XG is an otherwise very nice driver, hampered by a limited xmax. So much so, that it is a poor performer below 100 Hz and still hasn't quite caught up to the Peerless or RS even by 400 Hz. Why the discrepancy between my numbers and John's over at www.zaphaudio.com? In general, the results of single tone harmonic distortion and multiple tone intermodulation distortion parallel each other. The difference is due to a "carryover" of poor xmax higher up in the spectrum. This type of three tone test tends to accentuate this, and so a driver like the XG tends to look worse. The XG has a very smooth, extended frequency response, and would work well in a lower order crossover. It's probably best used as a midrange driver in a three way or sub/sat system for optimum performance.