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Huge hole in upper bass response - Suggestions?

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That doesn't seem to be a practical suggestion to me, given the room.
Diffuser panels might help but you really need to pull out at least a little. Doesn't cost you to try. Fire up the REW simulator, enter room dimensions (as square) and move a head.
Edit: him not you, sorry about that. Enable back refractions graph while keeping the head close to the back wall in REW simulator.
 
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After more than 40 posts it might be time for more radical measures ;-)
I do not know how important sound quality is for you and I doubt that this is what you are looking for, but moving the speakers a bit here or there and adding a panel or two will not change the situation significantly. You are probably already close to the best available option.
A radical approach would try to get rid of SBIR, asymmetry as much as possible, very early wall reflections, ....
If you are handy, a bunch of 2x4 and some drywall could produce this:
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You would have to EQ of course as the baffle step compensation built into the Elacs will be completely off.
And additional treatment might still be a good idea.
 
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You know that tweeter height is relative to woofer height, yes?
Woofer height, not tweeter height. As I posted earlier, this is a classic case of the Allison effect.

Example: f=120 Hz. wavelength =1120/120 =9.3 feet, d=9.3/4=2.3 feet = 2.3 x12 = 28 inches. (Approx)

To the OP: which boundary approximately corresponds to this distance from the woofer? I suspect it is the floor- woofer distance.
 
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Sane people use tweeter height as a vertical reference point for 2-way speakers.
I don’t understand what you mean. The dip is in the bass frequencies where the woofer is operating , so we really need woofer to boundary distance.
 
I don’t understand what you mean. The dip is in the bass frequencies where the woofer is operating , so we really need woofer to boundary distance.
Yes, but you don't want to mismatch the tweeter level with your ear level. Everyone uses tweeter height to position the speakers vertically unless tilted down. I have my DBR-62's tweeter set up this way, at 1.18m, 33 cm higher than the OP. Yes, the problem is the woofer-to-floor distance and I simmulated it in REW before giving any suggestions.
 
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Fundamental comes with it's harmonics and fixing it fixes (narrows) the following two.
The fundamental is ~50. Taming that helps with the ~100 and ~200 Hz humps. (But note, he hasn't said he dislikes the bass emphasis.) How does it tame the ~120 Hz 'hole'?

You first do that and then even pick up mic and do the measurements you want to work on. He really needs to pull out of the wall behind him.
Yes.
 
The fundamental is ~50. Taming that helps with the ~100 and ~200 Hz humps. (But note, he hasn't said he dislikes the bass emphasis.) How does it tame the ~120 Hz 'hole'?


Yes.
No that's just for room mode and he won't if he doesn't move out.
This is 30 cm from back wall, and second is 88 cm, pink is back wall refractions .
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It might not be to cm in practice but won't be far either.
 
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Looks like a text-book example of the Allison effect.

Inspecting the graphs, the dips in the region between 100 to 200 Hz indicate that the room boundaries are approximately 1.5 to to 2.5 feet from the woofers. Even if you move the speakers farther away from the walls, the floor bounce will remain because of the height of the speaker stands. This is why Allison speakers. had woofers near the floor.

I would suggest getting two woofers or subwoofers one for each channel, NOT mono, preferably corner placed and use a high crossover frequency around 200 Hz to the satellites. SVS and HSU woofers would likely workup to this frequently . You will need some type of DSP to do the crossovers, set time delays and DRC.

Off the top of my head, I can’t think of an alternative solution. Other than redoing the room or using massive amount of treatment..

Edit: FYI - To first order, for one boundary, Wavelength of null = 4 *d (approx) where d is distance to boundary. Frequency of null = speed of sound/wavelength
I'm facing a slightly similar problem to OP. I would just like to thank you for this reply, I found it helpful in my case as a potential avenue forward .

Today I have my speakers stacked right on top of my subs (the subs then sitting on a small riser/table). A humpty dumpty floorstanding 3-way speaker, sort of. Genelec 8030C + SVS SB-1000 and a $10 Ikea end table. Probably the greatest performance/price ratio for a high performance full range "floorstander".

Because of the stacking, I have zero issues with phase, imaging at high crossover and such, but I then also get the issues of having just the pair of speakers. As of last attempt, a giant gorge between 230 and 290 Hz is driving me nuts. Going to try and see if your suggestions might do the trick. Thanks again!
 
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