[Big Red Machine]

Neither condition exists here.

[JohnR]

Are you running a sub? If so, what crossover frequency?

[Big Red Machine]

No sub John.  Salk HT2 TL's only.  Quite the hump at the low end.  The speakers are rated down to 30 or 35 hz.  I think the room modes are taking over.

My Bob Gold response is

Freq % Wavelength, 1/2, 1/4 p,q,r Mode Group Weighting
28.7 hz 39'4", 19'8", 9'10" (1,0,0 Axial) Start iso, End iso
41.3 hz 30.5% 27'4", 13'8", 6'10" (0,1,0 Axial) Start iso, End iso
50.3 hz 17.8% 22'6", 11'3", 5'7" (1,1,0 Tangential) Start iso, End iso
57.4 hz 12.3% 19'8", 9'10", 4'11" (2,0,0 Axial) Start iso, End iso
70.6 hz 18.6% 16'0", 8'0", 4'0" (0,0,1 Axial)
70.8 hz 0.2% 15'12", 7'12", 3'12" (2,1,0 Tangential) Start iso, Near
76.2 hz 7% 14'10", 7'5", 3'8" (1,0,1 Tangential)
81.8 hz 6.8% 13'10", 6'11", 3'5" (0,1,1 Tangential)

[JohnR]

Can you try some different positions for the speakers? That would help see if there's an easy way to improve things. The room looks pretty well damped though - what does the RT60 graph look like?

[bpape]

The spacing of modes looks pretty good other than around 70Hz where they're only 0.2% apart. Target is 5% with 4% being acceptable.

On the decay time, in small room acoustics, T30 is more commonly used.  T60 is more for large room acoustics though you can certainly extrapolate down.  The spectrogram is also something to be used in addition to the waterfall and frequency response to look at intensity at a given time and frequency.

[JohnR]

In REW, the button to get to the plot is labeled "RT60" (It shows T20 and T30.)