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Discussion Starter #1
I have a soudblaster external MP3+ soundcard. I am looking at the measurement sweep in the Spectrum Anylizer using a loopback and checking distortion levels. I would like to know if the sweep looks good, particularly the areas I have arrows pointed to. I used full output of my soundcard with line level in max with a -12 sweep and no mic calc loaded. The settings looked like this.



When I first setup my card, I was able to set the levels the same but since something has occurred and it does not. I am not certain whether I need to re-install the driver for seperate USB inputs. I am not sure why it reads soundblaster 2. I don't know why the level is low.



Purple -

Distortion info

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 32.9Hz, -27.0dB FS
Based on 8 harmonics
THD 2.606%
THD+N 7.848%
2nd harmonic 2.538%
3rd harmonic 0.593%
4th harmonic 0.013%
5th harmonic 0.006%
6th harmonic 0.011%

Blue -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 123.0Hz, -27.0dB FS
Based on 8 harmonics
THD 1.182%
THD+N 7.359%
2nd harmonic 1.132%
3rd harmonic 0.340%
4th harmonic 0.009%
5th harmonic 0.008%
6th harmonic 0.002%

Green first -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 147.9Hz, -27.0dB FS
Based on 8 harmonics
THD 1.143%
THD+N 7.350%
2nd harmonic 1.105%
3rd harmonic 0.290%
4th harmonic 0.005%
5th harmonic 0.002%
6th harmonic 0.001%

Gold -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 339.1Hz, -29.1dB FS
Based on 8 harmonics
THD 1.008%
THD+N 62.197%
2nd harmonic 0.982%
3rd harmonic 0.229%
4th harmonic 0.003%
5th harmonic 0.004%
6th harmonic 0.006%

Green 2 -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 468.0Hz, -30.5dB FS
Based on 8 harmonics
THD 0.931%
THD+N 74.946%
2nd harmonic 0.896%
3rd harmonic 0.251%
4th harmonic 0.003%
5th harmonic 0.003%
6th harmonic 0.007%

Blue 2 -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.0dB FS
Distortion at 123.0Hz, -27.0dB FS
Based on 8 harmonics
THD 1.182%
THD+N 7.359%
2nd harmonic 1.132%
3rd harmonic 0.340%
4th harmonic 0.009%
5th harmonic 0.008%
6th harmonic 0.002%

Red 1 -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.6dB FS
Distortion at 3,025.6Hz, -46.0dB FS
Based on 6 harmonics
THD 0.073%
THD+N 99.263%
2nd harmonic 0.018%
3rd harmonic 0.017%
4th harmonic 0.023%
5th harmonic 0.035%
6th harmonic 0.041%

Red 2 -

65536-point spectrum using Flat-Top window and no averaging
Input RMS -61.4dB FS

If anything looks wrong please let me know.
 

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Discussion Starter #2 (Edited)
I will try a measurement of my room and see if I get similar results of using my laptop instead of my soundblaster.

Here is the settings of my laptop soundcard and calibration file. My laptop has a line-in option.





This is distortion of my laptop versus the soundblaster using my laptop battery.

Laptop distortion at 25Hz.



65536-point spectrum using Flat-Top window and no averaging
Input RMS -14.2dB FS
Distortion at 25.0Hz, -14.2dB FS
Based on 8 harmonics
THD 0.042%
THD+N 0.721%
2nd harmonic 0.028%
3rd harmonic 0.029%
4th harmonic 0.002%
5th harmonic 0.006%
6th harmonic 0.005%

Soundblaster distortion at 20Hz.



65536-point spectrum using Flat-Top window and no averaging
Input RMS -27.9dB FS
Distortion at 20.0Hz, -27.9dB FS
Based on 8 harmonics
THD 0.042%
THD+N 1.016%
2nd harmonic 0.023%
3rd harmonic 0.016%
4th harmonic 0.014%
5th harmonic 0.011%
6th harmonic 0.007%
 

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Discussion Starter #3 (Edited)
They look the same.

Laptop



Soundblaster



Soundblaster



Laptop



When I calibrate my RS digital meter to 75dB the target tracks near 78dB in REW. When I calibrate the mic to near 78dB it tracks 75dB. I think I calibrated the soundblaster graphs with 77dB or 78dB. If I am lowering the level on my DVD player so it uses 75dB, which one am I looking at in relationship to these graphs? When I use the RTA the subwoofer level looks hot. Am I listening to levels where the target tracks 78dB?
 

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Discussion Starter #5
Correct me if I am wrong but I think I may have this figured out. What I have here is tons of gain do to coupling, subwoofers that roll of very gradual at 35Hz is exagerating a distortion level caused by this effect that is being displayed on my waterfall measurements as the very large sine waves roll across this very large tuning area. What is correct is that the output level of frequency is determined by the RTA which is calibrated. The subwoofers should measure flat, and it so happens that I have treated my room with treatments so that this gain is somewhat at a flat level, but in truth I have gain caused by the coupling of my subs and them being co-located. The correct thing to do would be to measure the actual output of the subs, then to equalize this to the intended and total frequency output of the subwoofers for which they were intended, or close. The other option would be to make the room smaller, only which would be more room gain, and less of the subwoofers actual FR.
 

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Discussion Starter #7
It looks better on the RTA. It looks like I have the option to turn down my speakers subs and mains as low as a 72 target on this DVD player also. Center channel needs some work and the speakers might use some distance tweeking. I will give it a try and see how it is.

 
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