Yes, sweeps are an alternative, but you need to do several and average them out to get an accurate reading. RTA and moving mic will automatically do averaging, and its much faster.
Sweeps have the advantage of collecting phase information though, so if you want to work with phase (or let someone else do it, like Thierry at homeaudiofidelity) then you have to do sweeps. But for an easy and newbie-friendly guide like I tried to in this thread, I felt RTA/movinc mic was best.
Magnus,
I agree to that. Dirac uses sweeps but forces you to do them many times at suggested mic positions.
I tried REW on three systems by now. On two of them I found a slightly defective theater or midtweater and changed them. That can be best seen by doing a nearfield frequency sweep measurement around 5-10cm in front of each membrane. That is a nice application for sweeps and a good start.
I’ve tried rew using this guide before and am revisiting it after several months.
Question: how come my measured graphs are so low in overall dB, way below 75dB, around 30dB lower than expected.
I calibrated to 75dB using a umik1 mic as per first few steps in the guide.
I can’t get my head around it. Managed to do it before, without this issue.
Yeah it can be confusing. The problem I believe you are having is Overall SPL (OSPL) relation to SPL plotted across frequency. Both are a measurement of pressure - OSPL is the measurement of pressure with out regard of frequency content. SPL plotted against frequency is the pressure in each frequency bandwidth (frequency resolution of graph). To get the OSPL of a SPL graph the individual filter SPLs need to be converted to pressured square - summed and the take the square root (RootSumSquared) - yielding a overall pressure. From that a OSPL can be computed by:
OSPL=20*Log(overall pressure/reference pressure)
In your graph the filter bandwidth is variable - but let’s assure 1000 filters and the average SPL is 46dB. This yields a pressure per bandwidth of .004 pa.
The pressure squared is 1.5924e-5. That pressure squared time 1000 filters is 0.159 pa. Taking the squared root yields a overall pressure of 0.1262 pa.
OSPL = 20*Log(0.1262/20e-6) = 76dB
There is an “Adjust RTA Levels” checkbox in RTA window - controls - Appearance, try changing that and see if that helps:
The graph reflects a Overall Sound Pressure Level of ~ 76dB. Which is ~ your calibration level. No need to adjust RTA levels. The graph is correct.
Thanks for the input! I tried both suggestions ie leaving it as it is, and “adjust rta levels”, and both turned out pretty similar in the end (sound wise and volume knob level wise).
Much appreciated for the help!
Hello gentlemen,
This is my second measureme
nt since I changed the sub (I now have a Rel T / i7). Looking at the graph I see that there is a drop after 5khz. How that came about was not the case with the old sub. Thank you for your helpAdd images
I don’t know how a sub could produce that. Try measuring without the sub connected perhaps and see if its still there. But it looks like it almost becomes quiet after 8kHz which should be clearly audible for cymbals etc.
Also, the dB scale is to wide, set 30dB to 100dB as scale (the Limits button up to the right).
You really should change the vertical access along the lines that @magnus suggested. You can’t draw any conclusions with these as they are currently laid out.
Better still, save a measurement file and attach.
It can then be loaded and analysed by helpful souls.
Ps the camera icon with the ‘capture’ title enables the capture of the viewed screen. Much better than a photo. 
Thanks Alan, I will remember that.
I can not upload measurement (Sorry, the file you are trying to upload is not authorized (authorized extensions: jpg, jpeg, png, gif, heic, heif).
There certainly is a way
Something seems wrong with that measurement, maybe faulty mic or wrong calibration file. If that measurement was correct you would have a very dull and lifeless sound.
Yes that is right. I will try to repeat the measurement tonight (maybe the mic calibration file is not appropriate). Attached is a measurement from 7 days ago.
That looks much better. If you actually had the sound the new measurements indicate you would hear it, the difference would not be subtle. You can even try adding a low-pass filter in Roon at 10 khz and if that makes an audible difference you know the new measurements are wrong.
Magnus, I repeated the measurement several times (left, right speaker and both) and no changes. I have noticed this happening since I downloaded a newer version of rew beta V5.20
(I also got a new sub at the same time).
Not sure how to fix that, maybe try on REW forums or email the developer directly at feedback@roomeqwizard.com
Did you drop your microphone on the floor, maybe?
Did you also check your microphone calibration file?
Marin, I checked the calibration file and it is ok and my microphone did not fall to the floor. Maybe it’s a problem because I don’t use the hdmi connection (from Mac to amplifier), because on Naim unit Nova I can only use the airplay connection from my macbook air. (sorry English is not my native language)
