Help interpreting measurements Duntech Pcl 500, null in the 7k range

[Ludovico Dal Ponte]

Hello,

i'm asking help to intrepet the measurements i took yesterday in my room with a calibrated UMIK 1 mic.
It's a well treated room, measuring 3.9m width, 5m lenght e 2,2m height. The Ceiling is made of a light layer of wood (so i guess very bass frequencies travel above that) and the room is at the first floor of an old house.
My listening area sits at 38% circa of the lenght of the room, speakers are placed in equilateral triangle near the front wall, just after the acoustic panels

I'm getting cancelations at 122Hz 480Hz 1000Hz 1900Hz which i think could be caused by a room mode, but not shure.
What i'm not understanding is the massive null that occurs in the 7,6 / 8 kHz range, which doesn't show in the single speakers measurements.
I add screenshots of SPL and expecially Phase measurements wich I can't interpret practically.
I add a measurement of the LR after the correction with Ik Multimedia Arc Usb, tuned to my preferred listening target curve.
I last add a photo of the studio. In the measurements the bass traps are right behind the speakers, and there was absorbent material (Isolmix) in the reflections points of the desk and under the desk

Thank You Really much

Ludovico

 

[sm52]

7 kHz. It could still be a reflection. At the point where the microphone stood. Take measurements at adjacent points 2 cm from yours. Or play both speakers with pink noise from the REW generator. Turn on the RTA window for measurement. Slowly move the microphone about your measuring point. Watch how the graph changes.

 

[Alkaloid]

I wonder if it is the absorbtion points? Some highs always get absorbed more than lows. Rarefraction gets rid of the reflection but keeps the energy equal. Doesn't "equalize" out the highs but disperses the reflection throughout the room.

 

[jeppekristoffer]

As you can see you dont have any problems when each speaker is measured independently. Only when measured together. Its because the phase aproaches 180 degrees out of phase, starting at 2000 kHz and reaching 180 degrees out of phase at 7-8 kHz. Is the distance between the speakers and the microphone IDENTICAL? A 7 kHz wavelength is only 5 cm which means that if the distance from one speaker to the microphone and from the other speaker to the microphone differs +-2.5 cm then you will get the phase cancelation you see in the L+R measurement. In my opinion you have no problem. Or at least only a couple of centimeters of problem. Put the microphone equidistant from both speakers. Measure with something. Not just the eyes. And measure again.

 

[Ludovico Dal Ponte]

Thank you all for the kind responses. I'm pretty sure the speakers are equidistant but maybe microphone placement wasn't. I'll check again and let you know.