A Question About Time Alignment

Related is the issue of keeping your speaker wires the same length. The lengths we use are very small relative to signal speed, but, I still follow the rule. Makes a big difference using expensive cable.

I am pretty sure that the speed of sound is relatively constant at a given temp.

The speed of light is also a constant, and the speed of electricity is usually a bit slower than the speed of light for most cables.

The main reason to keep the cables the same length is more for resistance and the other electrical parameters like inductance and capacitance.
It has nothing to do with the shorter cable getting the sound to the speaker faster, slower or at an equal speed as the longer cable.

You also have to take the room  size , and  room treatment or lack of 

for 1st reflections ,bounce reflections  and hard surfaces ,as well of bass nulls n the room ,setup and damping ever more so effecting the sum ,Everything counts !!

Time alignment has nothing to do with instruments placement in an orchestra, that will (or sould) show up in the recording of said orchestra.

Remember, we are reproducing the recording of the orchestra and that recording includes cues as to where the sound of each instrument originated at the time of the recording.

Also, the speed of sound doesn’t change with frequency --

As mentioned above, time alignment in speakers has to do with the sounds coming out of different drive units. Take a guitar for example and a two-way speaker. Assuming that some of the notes of that guitar are reproduced by the tweeter and some by the woofer, you realise that a delay in the sound emanating from the woofer will sound odd --

As mentioned above, Wilson (and others) tries to minimise delays by aligning the drive units vertically - for example, the back of a tweeter with the back of a woofer, meaning the woofer cone will seem to be well in front of the tweeter.

The rest of the delay compansation has to be done in the xover -- a very difficult task and AFAIK very few speaker manufacturers attempt it.

Supposing that you use a sub, try it moved forward and then backward during a listening session. Beside having the effect of the wall, you should be able to tell that time alignment does have an effect on the sound.  [Adjustments on a Wilson will be less dramatic].

I am glad I am a speaker designer and Not a Physicist like some here. Sound is altered not only by distance. Especially when yo consider that the speed of sound is relatively SLOW. Sound is altered and affected by Temperature, Humidity, Barometric pressure... So once again, when it comes to speaker design, I am so glad I don't know anything about sound propagation. One of the first things I worked with 40+ years ago was where I placed my drivers, front to rear. In an effort to find the best placement and the least sound cancelation. If this placement wasn't a factor then room treatments would also be meaningless.

I mentioned just a couple of days ago how I was tweaking the Cant/Tilt to my speakers experimenting on how it changes the WHOLE soundstage. Just by a few degrees. and what it the main thing that is being modified, the forward position of the individual cones by just a few centimeters at a time. This is a simple inexpensive experiment that ANYONE can do on their own at home. You must also realize though that if you are using something like Diraclive this will change how your system is tuned by Dl.

Also, though Diraclive does wonders on manipulating reflective signals and how they interact with each other, it is minimal AT BEST when looking at Frequency.