The Subwoofer DIY Page
Bluetooth Speakers - the Mifa Wildbox
07 August 2022
Apart from a hump in the low bass response, and some boosted highs, the frequency response is quite flat and the distortion level is pretty low, especially considering the size of the bass drivers involved (75 mm). Response drops like a rock below 50 Hz, but this is only to be expected from a speaker that size. While the boosted highs can make the Wildbox sound a bit sharp on-axis, off-axis the treble response drops off a bit and in any case it's fairly easy to address with the built-in EQ in my Android phone.
Pictured below is the distortion curves for the Mifa Wildbox at the SPL level that I performed the frequency response measurements. The measurement was taken with the mike located very close to the speaker, centered between the two bass drivers. As such, the response shown is primarily that of the bass drivers.
As can be seen from the graph, apart from a small "blip" just under 500 Hz, measured distortion remained very low until the bass region, where the additional excursion requirements start taking their tool, with the THD peaking at just above 10% between 60 Hz and 70 Hz. While 10% sounds like a lot, most people have enough trouble noticing this level of distortion in pure tones at bass frequencies, and definitely won't notice it with music. Unfortunately most of the distortion seems to be odd-order distortion, suggesting that the driver's linear excursion limits were starting to be exceeded (and odd-order distortion is a lot more objectionable than even-order distortion). Nevertheless, it was possible to turn up the Wildbox's volume by an additional 6dB before the distortion started to be really noticeable at bass frequencies with the same sine sweep test. However, that it was allowed to reach objectionable levels was a curiousity to me, as I thought that Mifa would've used DSP to roll the bass back a bit at higher volume levels to prevent this from happening.
A bit of EQ applied at the source can help to make the Wildbox's response even better. Pictured is the EQ that I use on my Android phone. Dropping the bass a little (1 or 2 dB at 60 Hz), but leaving the BASS mode on allows the Wildbox to continue to produce great bass down to 50 Hz, but reduces noticeable distortion at higher playback levels, and trimming the treble response a bit IMO makes it more enjoyable to listen to for long periods.