Fuzz, you don't need to have super equipment to measure your speakers accurately. Here's a couple of good products to start with:
Dayton Audio EMM-6 Electret Measurement Microphone Allows For Accurate Acoustic Measurements At A Fraction Of The Price 390-801 and
Dayton Audio DATS Dayton Audio Test System 390-806 and
Untitled
You are most likely measuring a speaker whose drivers are all oriented vertically, TM, MTM, TMM, etc.
First thing I can tell you is that your speaker has a full baffle step, unless of course you're measuring a system with a subwoofer. There's no loss of output below (approximately) 500Hz due to 2pi to 4pi transition.
Second, the measurements with a dip in the frequency if assuming to have been taken off axis horizontally (just assuming to describe a what if scenario), would indicate a bad speaker indeed. With a bad power response. The dip occurs at the crossover frequency, approximately 2.3kHz in your case.
This happens when the speaker has been engineered poorly. The crossover point was chosen incorrectly, too high. If the woofer is 7" or greater, it will beam at those frequencies. Now this was maybe due to the fact that the tweeter is too small, it has no clean lower frequency output, or poor power handling, forcing a higher crossover point. In that case, better drivers should have been chosen. Or a smaller mid-woofer. Or even a 3-way should have been considered.
Please tell me what speaker this is and how it was measured and I will tell you more about how it performs.
