When buying a home theater subwoofer, it's important to consider the following factors:

-Size and design: Make sure the subwoofer will fit in your room and match your decor.

-Power and frequency response: Look for a subwoofer with enough power to handle the demands of your room and speakers, and a frequency response that extends down to at least 20Hz, the lower limit of human hearing.

-Type of subwoofer: There are two main types of subwoofers: sealed and ported. Sealed subwoofers are more precise and accurate, while ported subwoofers are more efficient and produce more bass.

-Placement: The placement of the subwoofer in your room can have a big impact on its performance, so make sure you have a good spot for it.

-Brand reputation and customer reviews: Research brands and read customer reviews to get an idea of the subwoofer's performance and reliability.

-Price and warranty: consider the price and warranty of the subwoofer.

-Connectivity: check that the subwoofer has the right connection options that match your AV receiver or amplifier.

It's a good idea to listen to different subwoofers before making a purchase to ensure you're getting the one that best suits your needs and budget.