the sub itself will sound the same given at either ohm load it is being powered with the same wattage. however if your wondering if you run you sub at 2 or 8 on one particular amp?, then yes it will sound different. ohms can easily be thought of as a damm, as the ohm (resistence) goes down, the more water will flow through the dam. same as if the ohm load goes up pretend the dam is closing up some and less water (wattage) will flow. usually a halving in impedence(ohm) is a halving in wattage. 1000 @ 1ohm 500 @ 2ohm 250 @ 4ohm 125 @ 8ohm in other words, the lower the ohm(resistence) is on to your amp the more power is allowed to flow from it
(but to be technical the lower the impedence presented to an amp, the higher the harmonic distortion level becomes and its damping factor is decreased, well thats a different topic)