I have a Yamaha RXV-371 receiver> I like it a lot but it does not have room calibration equipment. I don't want to get another receiver yet just to get this feature. What calibration equipment would you suggest?
You can download the free software Room EQ Wizard and use it with a calibrated UMIK-1 USB mic from Cross Spectrum, which costs only $105.
However, this will only allow you to take room measurements. Calibration includes equalization, so any manual calibration you do will depend on the EQ capabilities of your receiver. That typically requires fairly flexible parametric equalization with at least 5-6 available filters for each channel.