The number of watts you need for a 12-inch sub depends on a number of factors, including the subwoofer’s power handling rating, the desired sound pressure level (SPL), and the type of music you listen to.
Power handling rating
The power handling rating of a subwoofer is the maximum amount of power that it can handle without being damaged. Subwoofers with higher power handling ratings can produce higher SPLs.
Sound pressure level
The sound pressure level (SPL) is the loudness of the sound. SPL is measured in decibels (dB). A higher SPL means a louder sound.
Type of music
Different types of music have different bass frequencies. For example, hip hop and rap music have a lot of low-frequency bass, while classical music has less. If you listen to a lot of bass-heavy music, you will need a subwoofer with a higher power handling rating in order to achieve the desired SPL.
General rule of thumb
As a general rule of thumb, you should choose a subwoofer with a power handling rating that is at least equal to the power output of your amplifier. This will ensure that the subwoofer is not being overdriven.
However, if you want to achieve very high SPLs, you may need to choose a subwoofer with a higher power handling rating than the power output of your amplifier. This is because subwoofers are typically less efficient than other types of speakers, and they require more power to produce the same SPL.
Example
For example, if you have a 12-inch subwoofer with a power handling rating of 500 watts RMS, you should choose an amplifier with a power output of at least 500 watts RMS. However, if you want to achieve very high SPLs, you may need to choose an amplifier with a power output of 600-700 watts RMS.
Other factors
In addition to the power handling rating, the type of enclosure and the placement of the subwoofer can also affect the SPL. For example, a subwoofer in a ported enclosure will produce louder bass than a subwoofer in a sealed enclosure. And placing the subwoofer in a corner of the room will also increase the SPL.
The number of watts you need for a 12-inch sub depends on a number of factors. However, as a general rule of thumb, you should choose a subwoofer with a power handling rating that is at least equal to the power output of your amplifier. If you want to achieve very high SPLs, you may need to choose a subwoofer with a higher power handling rating than the power output of your amplifier.