Control Room Problem

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I have started to work on my new control room. The room have this dimentions: 6 meter (18 ft.) X 5 meter (15 ft.) x 2.6 meter (7.8 ft).
As you see, the ceiling high is too low. I will treat the ceeling with 2" Rockwool, and it is timberlogs every 3 ft. in the ceiling. The Rockwool will be installed between them.

I only use nearfield monitoring (Genelec 1031 and NS-10)

I will install variable Helmholtz, 3 ft. high from floor, on the sides.

Bass traps on the rear corners, and membran absorbers on the rear wall.

Whats the ideal RT60 in a control room with this dimentions ??

Thanks

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