Up until a few years ago, I cautioned the average hobbyist against trusting their own acoustic measurements. Using a test record and a hand-held SPL meter offers limited benefit. The data is coarse and tolerance is high. Built-in displays on graphic equalizers and the like aren't usually much better. Readings with instruments such as those are really too ambiguous to be useful.

But these days, there are some pretty good options. Measurement systems aren't really cost prohibitive anymore. They use a PC and digital I/O, often times the built-in sound card. So this makes measurement systems pretty affordable.

Check out products like Smaart, Praxis, Clio, and LMS. Some programs are even free or nearly free and they do a pretty good job too, provided you spend some time to study them and learn how to set them up and use them properly. That's the biggest challenge, that and dealing with the environment. Check out LSPCad and Speaker Workshop.