It's worth pushing through the pain barrier with this, honestly!

The SPL meter is just a sound level meter. It doesn't connect to anything in your system, you just use it to measure and adjust the level of each channel when you put the processor in to calibration mode.

The idea is to set every channel so that the level of sound which reaches your seated listening position is the same across L/C/R/RR/RL and each sub. The Radio Shack models are fine, I use the digital display version. Cheap to buy, and does the job.

Did you get the firmware through ok?

Cheers,
George