Ohms indicate a subwoofer’s impedance, that is, coil resistance. The lower the impedance, the more power is consumed, so the sound is louder. However, that can negatively affect the quality of sound. Subs with 2-ohm coils reproduce a louder sound than 4-ohm subs, but the latter gives a cleaner, softer sound. With a high-quality amplifier that matches your sub’s RMS power handling, the sound difference might be minimal. For more info, check our 2-ohm vs 4-ohm subs comparison post.