The -ohm rating of a speaker refers to the speaker's impedance, or resistance to electrical current. A lower impedance rating means that the speaker is more sensitive and requires less power to produce sound, while a higher impedance rating means that the speaker is less sensitive and requires more power to produce sound. The -ohm rating is not related to the quality or performance of the speaker, but rather to its compatibility with the amplifier and other components in the audio system. So a 4-ohm speaker and an 8-ohm speaker are different in the sense that they have different impedance ratings, but this does not necessarily mean that one is better than the other. It is important to match the impedance of the speakers to the output of the amplifier to ensure proper operation and to avoid damaging the amplifier or the speakers.