There are several key specifications that you should consider when purchasing components for your DIY speakers. These include:

1. Frequency response: This is the range of frequencies that the speaker is designed to reproduce. You'll want to choose a speaker with a wide frequency response to ensure that it can reproduce the full range of sounds in music and movies.
2. Sensitivity: This is a measure of how loud the speaker will be when driven by a certain amount of power. A speaker with a higher sensitivity rating will be louder than one with a lower rating, given the same amount of power.
3. Impedance: This is the electrical resistance of the speaker. You'll want to make sure that the amplifier you use is compatible with the impedance of the speaker you choose.
4. Power handling: This is the maximum amount of power that the speaker can handle without being damaged. Make sure to choose a speaker that can handle the power output of your amplifier.
5. Size and shape: You'll want to choose speakers that are a good size and shape for your intended application. For example, if you are building floor standing speakers, you'll want to choose drivers that are large enough to produce good bass response.
6. Brand reputation: It's always a good idea to choose components from reputable brands that have a track record of producing high-quality products. This can help ensure that you get the best possible performance from your DIY speakers.