It is interesting to study the audibility of phase distortion. I have listened to a square wave through a loudspeaker and can barely tell the difference caused by a level of phase distortion which makes the wave visibly unrecognisable as a square wave on an oscilloscope. One's eyes are much more phase sensitive than ones ears! In order to do this one must find a phase coherent loudspeaker and listen in the nearfield, before the room interactions have had their effect. Very few speakers on the market are phase coherent. If phase accuracy was extremely important multi miked recordings mixed using a conventional desk would sound even worse than they do! An electrostatic is fairly phase coherent in the first 3 to 4 feet in front of the speaker. By the time the back reflection is heard (and the extra stereo "depth" thus created enjoyed) there is no phase coherence whatever. A friend of mine designs dipole speakers which sound great. I have some of his prototype units at home just now. The biggest benefit is the cost savings associated with the box. Producing an effective closed box speaker where a considerable proportion of the sound being heard is not cabinet vibrations is spectacularly expensive, and rarely achieved. Creating an effective baffle to effectively separate front and rear waves needs a good understanding of the physics but then can be done relatively inexpensively. They have to be positioned very precisely within the room to achieve bass evenness and extension. The Celestion 6000 system was AFAIK the first to exploit this acoustic characteristic, the bass module was positioned and orientated correctly then the main speaker put on top. The position of the bass units was calculated for each customer by Celestion using the listening room plan. They are spectacularly effective when thus positioned, but probably had a tiny market because, as you so rightly write, most people have to put their speakers where they go! Frank On 16 Feb, 2005, at 06:23, A. Lal wrote: > The ear's sensitivty to group delay (or waveform integrity as you put > it) is well beyond what most xovers produce.