In order to perform FFT based transfer function measurements, you need a few tools to put together as a system to perform your measurements.
Any FFT based measurement rig based on the Mac or PC platform will include the following components, These are minimums:
It is only logical to choose a measurement software application that works with a computer / computers you already own & use. Many of the measurement software applications are PC only. In order to run them on a Mac requires a virtualization app like Parallels or VMware. Unless you plan on doing bench measurements in the same location, a laptop of some sort is almost mandatory. With that said, having access to a larger screen can make the measurement process go faster.
FFT audio measurement software (Smaart 7, Smaart 7 DI, Spectra Foo Complete, Systune). Verify that the application you want to use works with your computer OS. All of the software I am aware of allows for a time restricted demo. It would be wise to download the demo of more than one application & use it during the trial period. Then decide which one best fits your needs. There is a page under the SOFTWARE link where you can download the demos.
A (2) channel audio interface with at least (1) line input & (1) mic input that can provide P48 phantom power & (1) line level output. Having more inputs & outputs allows for more measurement options at the same time.
An omni measurement mic. Preferably that includes a IFRC (individual frequency response curve) & is known to have a known flat response.
A variety of short, medium & long XLR male to XLR female, XLR female to TRS male, XLR male to TRS male, TRS male to TRS male, XLR Y cables (single female to dual male)
In order to allow for more configuration options, it is helpful to have a mixing board for routing signals. The mixing board could be a small portable mixer or it could be the console you are using for a large event.
Unless you already have a basic understanding of how to interpret the results of your measurements, you’ll need to begin the journey of studying about sound system design & optimization. Fortunately Bob McCarthy has done all the ground work for us & put it into a text book that is readily available.