Whether or not a 15-inch subwoofer is too big depends on a few factors, including the size of the room, the type of music you listen to, and your personal preferences.
In general, a 15-inch subwoofer is larger than a 12-inch subwoofer. This means that it will require more space to accommodate it. If you have a small room, a 15-inch subwoofer may be too big and could overwhelm the space.
In terms of sound quality, a 15-inch subwoofer can produce deeper bass than a 12-inch subwoofer. This is because it has a larger diaphragm, which can move more air. If you listen to a lot of music with deep bass, such as hip hop or electronic music, a 15-inch subwoofer may be a good option.
However, it is important to note that not everyone prefers deep bass. Some people find it to be too boomy or overpowering. If you are not sure whether or not you want a 15-inch subwoofer, it is best to listen to one in person to see how you like it.
Ultimately, the decision of whether or not to get a 15-inch subwoofer is up to you. Consider the size of your room, the type of music you listen to, and your personal preferences to decide what is best for you.
Here are some additional things to keep in mind when choosing a subwoofer:
- Power: The subwoofer needs to have enough power to produce the desired bass level.
- Frequency response: The subwoofer should have a frequency response that extends down to at least 20 Hz.
- Enclosure: The subwoofer should be enclosed in a cabinet that is properly vented.
- Placement: The subwoofer should be placed in a location where it can produce the desired bass level without causing any problems.

