Wow! Let's start by saying that the volume level of this speaker is LOUD! Indeed it have 4 active drivers, 2 for bass/mid and 2 for high's L+R of the device's face, and a pair of "passive drivers" that helps with the bass in the middle of the unit in front and on back.
It can go really high on volume without too much distortion.
It depends what kind of music you are trying to play.
It can produce (for it's size) VERY well heavy bass for pop/RnB/DrumNbase and like minded style of music but within a "logical" volume level. i could say near 50 to max 60-65% of unit's max volume capability.
In that point if you stream through an app/device that have Equaliser.. you can lower/tweak a little bit the "bass bandwidth" and then you can squeeze a little more volume output without so noticeable distortion in bass..
You DIDN'T bought a 18" EV P.A Sub :P
After that point you can feel/ that the "bass/mid drivers" are starting to show their "size limit".. and the quality of the sound starts distorting as you go higher.. This is something very logical for that size of drivers.. but after all the quality and the maximum volume they can reach is still amazing for their driver size/device size !