When you connect two loudspeakers to the output of a stereo amplifier, you should not have be sure about the lead-in wires to be equal in length to avoid a time lag between speakers because only the speed of energy matters here.
It is not necessary to make the lead-in wires to your speakers exactly the same length because energy in cables moves at close to the speed of light and the difference in time between signals arriving at separate speakers will be too small for your ears to hear (making sure the resistance of your speaker wires is correct is much more important).
As a result, one should not be certain about the lead-in wires' length in order to prevent temporal lag.
