First measurement in REW

[vlk44]

Hello,

I'm new to REW. I have a set of active speakers and a subwoofer (B&W Formation Duo). I have a living room without any acoustic treatment. I suffer from low frequencies in the room and would like to improve it. I made my first measurement- see below.
I wonder why the sound level in the RTA is only around 40 dB. Before the measurement I made a calibration of the volume level to 75 dB using an SPL meter. I'm not sure if I have the settings wrong. And I'm not sure if such a measurement could be used for further optimization?

 

[John Mulcahy]

The SPL meter figure is showing you the total energy across all frequencies in the sound being picked up. The RTA is showing how much of that total occurs at different frequencies. The RTA appearance settings have an "Adjust RTA levels" option that will shift the RTA plot upwards to make it look more like the result of a sweep measurement at the same level, but it's an artificial adjustment to help with interpretation, the unadjusted plot shows the actual frequency distribution of the sound energy.

Use the Limits button above the graph to set a sensible SPL range, your graph currently spans about 240 dB, a 60 dB span is typically more useful.

 

[vlk44]

Thank you for the explanation!