Originally Posted by indus1
Is this better?
Anyway, the REW room sim suggests that the sub is in the optimal position. In addition my sub is huge (by UK standards), it's a XTZ 3x12 sub and so placement is limited anyway.
A note about the presentation of your waterfall. It is important that the lower limit of the waterfall be set properly. As a convention in this thread, we normally set the lower limit of the graph to be 40dB from the peak measurement level. A simple way to determine the correct lower limit value is to generate the Spectrogram. On the right side of the spectrogram is a bar that shows the peak measurement level:
Subtract the peak level, and use the resulting value to set the lower limit for the waterfall. An, as Alan has pointed out, ALL REW measurements should use the log scale for the horizontal axis, not the linear scale. To change scales, click the "Freq. Axis" tool at the top of the screen:
Here is a waterfall with linear scale:
Here is the same waterfall with a log scale:
Note how much easier it is to analyze the 15-100Hz range when the graph is using the log scale.
As for the measurement level, you should follow the REW guideline to assess the noise floor in your room. A typical listening room will have a noise floor in the 45-50dB range. Once you know the noise floor, follow the Guide instructions on how to set your measurement output level (page 65, step1 1). The level should be typically 40dB above the noise floor, or 85-90dB.
And finally, to assess whether you are seeing bass ringing or not, look at the first 20dB from the top, down to 75dB in this example. Look at the shape of the "ridges" in the waterfall. It is desirable that the ridges be a uniform distance apart, starting at the top of the graph, and extending down through the -20dB level. In the example above, the area 45-300Hz shows good ridge uniformity, signifying low bass resonance. However, at 35Hz, there is an area of tightly-spaced ridges extending from the top all the way to the bottom of the graph. This is an area that demonstrates bass ringing, and should be the focus of attention if bass resonance reduction is the objective. Below 35Hz, the ringing is once again under control.
Now back to the measurements you posted. The waterfall, as posted, is useless to assess bass ringing. Please consider posting it correctly. The sub only measurement is not good at all. A -40dB dip at 58Hz must be audible, and is at a frequency that is quite important. We understand you have a really nice monster sub that can't be moved around, but if that is the case, then learn to live with bass response that is far from optimal. As someone mentioned, in hindsight several smaller, less expensive subs probably would have achieved a better response. And finally, you don't comment on whether the graphs were produced with or without room correction. Automated EQ may provide some relief.