Macro 6 ?

[dsnyder]

Before I go changing everything in the room, I remembered that I have sweep recordings from previous sessions that could be instructive. Here's an unwrapped phase plot of the Valorem PRIMUM monitors on different stands but in the same room. I recorded these sweeps about six months ago:



Rewinding the clock a bit further, here's the DALI Oberon 7 towers in the same room from May of 2020:



And, the oldest sweep recording that I have is from January of 2016, almost six years ago. This time with Legacy Audio FOCUS SE towers in the same room but with completely different electronics and somewhat different placement:



And, the unwrapped phase:



Clearly this phase anomaly in the right channel is entirely due to the room, not the loudspeakers, equipment, precise placement, or measurement protocol. Could it be that my brain is so completely acclimated to this out-of-phase behavior from 52 to 72 Hz from years of listening that the system sounds wrong to me when it is corrected? Or is there something deeper going on with the science of digital room correction vs reality in real-world asymmetrical listening rooms like mine? Recall that half of the back left wall is open to the floor below.



I feel like I have more questions than answers. The saga continues…

[UliBru]

David,

1. yes, your room is causing the observed effects
2. the pictures are equivalent. REW shows the phase in degrees whereas Acourate shows radians.
3. be aware that the magnitude and phase charts show a steady state. This means you see the phase differences with a long signal. But music is not steady state. So also the transition can be important.
So you can e.g. create a sinewave of frequency 53.467 Hz (arbitrarily selected a frequency bin from the phase picture) and convolve it with the pulse responses. The zoomed-in result shows:

Sine.png (44.33 KiB) Viewed 950 times

Now a sinewave is ok for steady-state discussions. But what about a chirp? Create a chirp and apply also a convolution. The result is

Chirp.png (33.16 KiB) Viewed 950 times

So for a short tone the picture is not as bad as for the sinewave.
We have to recognize that the result also depends on the music content.
4. a FIR filter can influence the magnitude and the gain. From the pictures above you can see that e.g. a single phase shift cannot heal all. You can reach a matching steady-state but then the transition area will get weaker. You can e.g. boost the magnitude of the (black) steady-state sinewave but then the peak at the beginning will be much higher. So we can only find compromises or we need to improve the room itself.
5. If you are used to listen to the phase differences indeed ICPA may sound phasey to you. If you cannot get used to the ICPA result then you simply have to leave the correction without ICPA. In many cases ICPA improves the result. But I do not postulate that it can heal everything.

[dsnyder]

Fascinating stuff. Thanks so much, Uli.

Merry Christmas, and Happy New Year!