A Question About Time Alignment

The problem only occurs with reproduction. It does not apply to live music. All frequencies travel at exactly the same speed depending on the barometric pressure (air density). The problem is cause by crossover design, when certain frequencies are shifted in phase. It can also be caused when drivers are placed in disparate locations such as frequently occurs with subwoofers. Definition and imaging improve when a system is "time aligned." This can be easily demonstrated with digital crossovers that have control over delays. The problem that occurs when adjusting time alignment with driver location is that perfect alignment can only occur along the centerline between the speakers, but then that is where you only get a proper image anyway. The best solution to the problem is a single driver and no crossover except maybe to a subwoofer with digital time alignment. 

The time it takes for the low notes to arrive at your ears is slower than the highs no t because they are inherently long but because the voice coil of the woofer is mounted behind the baffle whereas for the tweeter it is mounted almost about the same level as the baffle hence the tweeter is closer to yours ears than the woofer.

Maybe instead of “slower”, do you mean “delayed”?

The former is speed/velocity, and later seems more like time/distance.

in colloquial speech fast or slow refers to time. For example fast food refers to food that is prepared quickly. There is no mention of distance in that.

There is so many partial truths and misinformation in this thread about time and phase aligned speakers. I strongly suggest digging through past threads here on AudioGon on the subject. 

I have read through this thread over the past few days and have purposely stayed out.  There are some reasonable explanations in this thread and others that don't show a real understanding of time & phase..... I will try to provide an accurate and very simple explanation.   

Over all time alignment is addressed.  All frequencies travel at the same speed,  Just because one frequencies wave length is longer, does not mean that the frontal wave of one frequency will reach you at a different time as another.  

On speaker design what we align is the portion of each driver where the sound is emitted, which is normally, aligning the front of each voice coil.  This allows all drivers sound to reach the ear at the same time. .... drivers can be staggered or sloped.   

Phasing.... fairly simple actually.... If it were possible to have a PERFECTLY phased speaker, which does not exist, 2 way, 3 way 4 way does not matter.  In each of these speakers, perfect phasing means all speakers cone movement would operate in unison.  This really cannot happen, so perfect phase cannot happen.  What we normally do is to get phase alignment at the crossover frequency.  When each driver is in phase at the crossover frequency, you normally get a quite good sound stage.  Each crossover type will cause some sort of phase shift, normally 60 to 180 degrees out of phase.  With alot of work, I have seen some drivers as close as 15 degrees of absolute phase with another, but normally achieving near phase alignment at the crossover point works very well. If you think about it in frequency, its fairly easy to understand why you cannot achieve absolute phase alignment. a tweeter may produce 3000 hz and up, well its obvious that the tweeter is moving at 3000 cycles per second, so a woofer moving at 60 cycles, obviously cannot produce sound waves in perfect unison.  Each driver does its job and we do the best that we can to produce time and phase alignment.  The better that alignment the better soundstage and imaging are produced.   If you think about it in the deepest sense,  Phase really is time, if drivers are out of phase with each other, frequencies are leaving the drivers at different times, thus effecting time alignment.  I hope this all makes sense and helps in some way.  Tim