Need Help: KH120A + Dual KH750DSP Nulls in untreated room

[staticV3]

Furthermore, set RTA->Cogwheel->Max overlap to 93.75% for slightly faster data acquisition.

And I'd also disable "Stop at: 45". Personally, I usually do 100-150 AVGes, even 300 at times though that's decidedly overkill.

Regarding the dip in bass response, try replicating your room and speaker placement in the REW Room sim.
If that shows the same dip with both subs active, then that's a solid indicator that the tool is reliable.

Next, try to find sub placements in the Room sim that have no strong dips.
Peaks are ok, those you can cut with PEQ. Dips OTOH you can only fight with room treatment, placement, or fancy DSP like Dirac ART.

 

[levimax]

I realized if I use the Psychoacoustic Smoothing, it's almost a perfect system (but not really xD)
View attachment 488017

Your system really will sound almost perfect the way it is. Chasing dips can be frustrating and counterproductive and while placement and room treatments usually don't have any negative effects they sometimes can. I have tried sub placement that results in smoother response but preferred another position for sound quality. I find symmetrically placed sub(s) close to the mains to generally be preferable which is what you have. I would spend some time listening (and enjoying) and then make changes one at a time to see what if any difference you can hear and what you prefer. There is no rush because you are over 95% there anyway. Changing more than one thing at a time is a recipe for confusion and anxiety. Good luck and have fun.

 

[ENEN]

As a fix, try enabling the "Uncorrelated" check box in the Generator window (requires REW Beta version here).
That's designed specifically for measuring stereo systems and may circumvent weird phasing issues that may happen otherwise.

Edit:
Oh also, in the RTA Window->Cogwheel->Appearance, turn off "Use Bars on RTA". That makes the measurements easier on the eyes.

Furthermore, set RTA->Cogwheel->Max overlap to 93.75% for slightly faster data acquisition.

And I'd also disable "Stop at: 45". Personally, I usually do 100-150 AVGes, even 300 at times though that's decidedly overkill.

Very detailed instructions! : D Today I tried the MMM using the REW Beta version with the "Uncorrelated" option enabled / 93.75% Max Overlap / Stop at: 150. The results this time seem different from yesterday's: a null value appeared near 27Hz, which wasn't there before (I wonder if it's because this measurement is more accurate that it stands out)

Spoiler: MMM RTA 1/48 - No Smoothing - Left + Right

Big Nulls at: 27Hz / 33.7Hz / 77.8Hz / 109Hz

Spoiler: MMM RTA 1/48 - No Smoothing - Left

Big Nulls at: 80.1Hz / 111.8 - 117.3Hz / (From here I'm not sure if they are meaningful but just listing them) 512Hz / 604Hz / 827Hz / 883Hz
Big Peak at: 237Hz

Spoiler: MMM RTA 1/48 - No Smoothing - Right

Big Nulls at: 82.2Hz / 105.9Hz / 320Hz

Your system really will sound almost perfect the way it is. Chasing dips can be frustrating and counterproductive and while placement and room treatments usually don't have any negative effects they sometimes can. I have tried sub placement that results in smoother response but preferred another position for sound quality. I find symmetrically placed sub(s) close to the mains to generally be preferable which is what you have. I would spend some time listening (and enjoying) and then make changes one at a time to see what if any difference you can hear and what you prefer. There is no rush because you are over 95% there anyway. Changing more than one thing at a time is a recipe for confusion and anxiety. Good luck and have fun.

I agree with your suggestion, I tend to adjust too many things each time without controlling the variables, which sometimes backfires.

The ripple in the high frequencies is caused by the comb filter effect from the reflections on the desk. You can try placing the monitor at ear level on the desk. Increasing the distance from the desk will reduce the effect somewhat. You can put a thick blanket on the desk and take a REW measurement. You should see a difference above 1khz. You can check for early reflections on the REW impulse graph.

The DIP at the 106hz on the right monitor can be caused by the right wall. You can try to increase the distance to the right and then the null should shift and decrease. An absorber at the reflection point on the right wall should decrease it as well.

I have similar system with 2xKH80 and 2xKH750. I posted some measurements in the past (2xKH80 and 1xKH750) here: https://www.audiosciencereview.com/...ll-us-how-your-bass-sounds.22567/post-1806762

And wow, your system's low-frequency response makes me drool!



* Edit: Replied to wrong user

 

[staticV3]

Very detailed instructions! : D Today I tried the MMM using the REW Beta version with the "Uncorrelated" option enabled / 93.75% Max Overlap / Stop at: 150. The results this time seem different from yesterday's: a null value

Nice to see that now, treble response is identical between one side playing and both!

 

[ENEN]

A minor update on November 06: I wanted to share today's experience with you guys.

I imported my newly created room model into the previously recommended Eigenmodes Simulator, and I found that even without adding precise furniture model, the standing waves observed in the previous REW Measurements perfectly matched the frequency nodes calculated by the simulator! It's incredibly useful, and I highly recommend it!

I think the next step can only be acoustic treatment! I want to go a step further.

* Edit: The niche behind my speakers is causing a lot of trouble!!