According to this interesting-looking article here http://www.theregister.co.uk/2014/07/02/feature_the_future_loudspeaker_design/ http://www.theregister.co.uk/2

According to this interesting-looking article here http://www.theregister.co.uk/2014/07/02/feature_the_future_loudspeaker_design/ http://www.theregister.co.uk/2014/07/02/feature_the_future_l... the problem isn't frequency response but things like time delay, and it's not due simply to the very end but also to systems leading up to and around it like inaccurate crossovers and speaker cabinets that introduce time delay.