The frequency range of sound box basically is by sound box box and loudspeaker unit organic union decides, it's loudspeaker unit decision not just.For example, loudspeaker certain, the size of box, have without opening, how is the structure inside, can affect the frequency range of whole sound box to a large extent, basically be to point to the effect of low frequency end of course.
Of course, in theory, the active speaker (speaker) is a power amplifier frequency range will be affected by the power amplifier, but the audio power amplifier to do 20 ~ 20 KHZ range do flat response, compared with the passive speakers (with no power amplifier), would be easier, so we can generally ignore the influence of the frequency response of the whole system power amplifier.