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Hi,

I posted a different thread in which I posted a couple of graphs and received feedback that my graphs reflected that I clearly made a mistake in measurements. I followed the advice offered and I think I discovered a calibration error which led to some strange graphs. Now I believe I have a couple of graphs from a measurement I took which I would like your help interpreting. Though I have read all the posts and info on REW, including the tutorial from RealTraps, I still am having trouble understanding what I am reading. First, please tell me if my graphs still reveal an inaccurate measurement.

To provide background on the measurement underlying these graphs, they were taken in my studio control room which is about 15' x15' between the parallel walls I face and have my back to and my side walls are roughly 12' apart, though the walls are not parallel as one wall is built at about a 20 degree angle in relation to the other so that at the end I am facing, there is a distance of 12 feet between the two walls in that corner, while as the wall fans out a bit, the two walls are about 14' apart at the junction behind me. The room is treated with a lot of Auralex 2" foam to absorb high end, some other foam that absorbs more mids and then bass traps from floor to ceiling on three of the four corners of the room (the last corner of the room has doors so I can't put bass traps there). I have NS-10s and JBL4410s both as near-field monitors and the measurement underlying these graphs were taken with the JBL4410s (JBL's published Freq. Range is 33hz-30,000). I have no subwoofer. The measurements were taken with an EMM-6 with a Frequency Sweep lasting 1m/23.8s from 15hz to 22,000 with the mic at zero degrees placed where my right ear is when I am mixing/listening, with cross-spectrum cal file narrow response loaded. Both speakers were playing the same signal from the right channel.

Assuming my measurement is accurate, can someone help me understand the two graphs above. The "All SPL" graph concerns me because I seem to have very little sound pressure starting at 40hz, clearly after my speakers are supposed to generate full sound pressure and then it only slowly rises until it reaches 200hz and only then does it seem to reach a fairly level sound pressure. (By the way I used 1/6 octave smoothing to make the data readable). Is this telling me I have too many bass traps or that my speakers are just not providing enough sound pressure until 200hz? What measurement/graph should I take/use to evaluate the speaker's ability (which I guess would tell me whether I need a subwoofer).

Then, regarding the waterfall graph, which I limited to reflect the low end from 15hz to 500hz, how do these results relate to the SPL graph, since on this I am getting virtually no bass between 30hz and 50hz. How should I interpret the rest of the spectrum shown on this graph?

Any help in understanding how these graphs reflect the behavior of sound in my room would be greatly appreciated.

Thanks to all!
WM
 

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I'm no expert, but....

Looking at the waterfall plot, you've controlled the ringing with your bass traps so my guess is that deep null from 30-40Hz is a function of your speakers, not the room.

The lower volume at the low end is probably also a function of your speaker's ability to generate sound at those lower frequencies. If you need those lower frequencies then I suggest a subwoofer to fill in there.
 
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