150Hz dip - what is the likely cause?

[sting004]

Hi all - to preface this, I have an 18' x 20' untreated room. Listening position is probably 8' from the speakers (Revel F36s) which are toed in to the MLP.

I've run Audyssey MultiEQ (yep, just the basic) and this is what I seem to get consistently. I have Dynamic EQ on. Crossover at 80hz. I'd imagine the towers are roughly 2 feet from the wall, with the left one being situated in a corner. I can't really pull them out any further from the wall.

There's a large rug in between the speakers and the couch.

Any idea what could be causing this dip?

I've also noticed that on some bass heavy songs, the cabinet of the speaker almost vibrates. I've never had this happen on any other speaker and am hoping there's a way to smooth it out a bit more.

I don't have access to any other room EQ or measurement software.

 

[Eneko]

I am far from been an expert but, by chance, I just saw this video and since the frequency is not so different it may give you a first clue…

 

[abdo123]

How far is your Speaker from the back wall? how high is it off the ground? what's the height of the room?

 

[dougi]

It is mostly likely the reflection from the wall behind. There are various calculators as a starting point.

Experiment moving them. The calculator will give you an idea which way the null/peaks will shift. You could try to absorb at the wall but difficult to do at those frequencies, and consistently across a wide range. Others may have a different view.

 

[pozz]

SBIR. Likely wall behind, as @dougi said.

 

[JG2020]

How to Fix Speaker Boundary Interference (SBIR) Issues​