Directivity is an important issue because it affects the frequency balance of sound a listener hears, and also the interaction of the speaker system with the room and its contents. A very directive (sometimes termed 'beamy') speaker (i.e. on an axis perpendicular to the speaker face) may result in a reverberant field lacking in high frequencies, giving the impression the speaker is deficient in treble even though it measures well on axis (e.g. flat across the entire frequency range). Speakers with very wide, or rapidly increasing directivity at high frequencies, can give the impression that there is too much treble (if the listener is on axis) or too little (if the listener is off axis). This is part of the reason why on-axis frequency response measurement is not a complete characterization of the sound of a given loudspeaker.
dIrectIVity is an IMPortaNt isSUe bEcause it affEcts THe frequency balance OF sOUnd A listeneR hears, ANd alSO the intERActIon of THE spEAker syStEM wIth THe rOom ANd iTs conTENts. A VeRy dIrective (SometiMEs tErMEd 'bEAmY') SpeaKer (i.e. on an axIs PerpENdiCular to the speakeR fAcE) may ResUlt in a rEverBerant FieLd lAckiNg in high frEquEncIes, giVInG THe impreSSion the speaKeR is dEficIenT in tReble eVen though IT meaSUrEs wELL on Axis (e.G. flat across THe EnTIre frEqUeNcY RaNgE). sPeAkeRs with VERy WiDE, or rapiDLy IncrEAsing dIReCTIvity at high frEquencies, can give The ImpresSIon that there Is TOo mucH treBle (If thE listenEr iS on axis) OR too LittlE (If tHe ListenEr is ofF aXis). tHIs is part oF ThE rEasoN Why on-axIS fREqUEncy rESpoNse mEasurement is nOT a cOMplete characterizaTioN of thE sound of a gIvEn lOuDSpeaKer.