post #3916 of 3916

Talking about phases and how to rectify them


Can you tell me If I understand correctly, this is how it works:


Lets say we only have 2 different drivers, 1 bass  and 1 mid/highs the crossoverpoint is at 1500hz, 1st order High Pass crossover shifts the phase of the mid/highs driver by 45 deg.


Now the mid/high drivers leads by 0.0833ms


Phase angle (deg) φ = time delay Δ t × frequency f × 360


 time delay Δ t = 45/(1500*360)

                         =0.0833 ms   

which means that sound at 1500hz arrive at the eardrum faster buy 0.0000833 sec. So in order to get both drivers in sync I need to make the mid/highs driver sound travelling a longer distance.


Assuming the speed of sound at 20 deg Celsius is 343.2 m/s  (though at body temperature it's closer to 353 m/s) the difference in tubing length should be 343.2*0.0000833= 2.85 cm (1.125 inches).


So the tube length for the mid/highs driver should be 2.85 cm longer than the tube for the bass driver.


what about the rest of the higher frequencies 1501hz-20khz? they have less time delay than the 1500 hz but now they will have to travel along the tubelength appropriate for the 1500hz delay...?


also is this right?: 1st order filter shifts the phase forward by 45 deg

                           2nd order filter shifts the phase forward by 90 deg

                           3rd order filter shifts the phase forward by 135 deg

                           4th order filter shifts the phase forward by 180 deg 

Edited by ForceMajeure - Today at 4:04 pm