Freq Resp +/-3dB (Hz): 34 Hz – 20 kHz : The spec shows the range of frequencies a speaker can produce measured from 20Hz to 20kHz. 20Hz to 20kHz is regarded as the range of human hearing. This spec is taken in a anechoic chamber which basically removes any room interaction. +/- 3dB is a tolerance window. So basically the amplitude relative to the frequency does not deviate more than 3db from the center of the graph taken.
Freq Resp +3dB- 9dB (Hz): 25 Hz – 20 kHz: This is the same thing however instead of taken in a anechoic chamber, this is a "in room" response of the speaker noted by the +3db-9db. The specification takes into account room interactions and room gain. Personally, I do not pay much attention to "in room" specs as every room is different so it is not a very accurate measurement. You can take this spec as a "best case scenario" for performance in your room.
Impedance (Ohms): 4 Ohms Impedance Graph: Impedance is the speakers resistance to power or impeding the flow of power. 4 ohms is the nominal rating for this speaker and is rated to be no greater than 1.25 times the minimum impedance within the pass band. The minimum impedance is 3.2 ohms. Whether this is a hard 4 ohm speaker or easy 4 ohm would be determined by the phase angle which is not shown.
X-Over 160 Hz & 2.3 kHz: These are the two crossover points which separate what frequencies the bass, midrange and tweeters play. This spec tells us nothing about the performance of the speaker.
