Frequency Response

I’ve recently started measuring my in room response and it’s become an entirely new learning process.  I’ve become slightly obsessed with smoothing out the in room response as much as possible through speaker placement and room treatment placement.  
Anyhow, I’ve got a dip in the response from 330-400 hz at my listening position.  The dip is not there when I stand vs. sit in this spot.  I’ve tried moving the speakers all over and I’ve tried fixing it by moving my acoustic panels around but I still can’t get rid of this nasty dip...

Does anyone have any other ideas I can try?  Has anyone here had similar issues with your room cancelling out certain frequencies higher up than the bass region we are usually talking about and what did you do to overcome them?
@erik_squires , thought the same thing. I put a panel on the ceiling right above and forward of where my listening seat is, right where 350hz was loudest.  Didn’t do much.  Then I took 2 panels from the front wall and put them on the ground in front of the speakers... Nothin.

It may just be this crappy little room Im working with.

Surprisingly my bass response is good.  0db at 28hz and -3 at 24hz. 
My response is pretty crazy / peaks and dips.  Just shows how much work my room needs.  I am actually hearing strange reflections when the program is playing this clicking noise in order to locate distances.

Anyways, I may work on it some more today and see if I can figure it out.  Wish I had some 25 foot runs of speaker cable.  I’d just move my speakers around...

I think it could be a camber, caster issue to fix it. BUT the reason is probably the XO point.  I fixed quite a few by tipping them forward or backward. It is usually forward for a dip in the mids, and back if the tweeter is boiling my ears AND I want a little better Mid Bass response.  Start with 1/2" and then go all the way down to shems. The chair idea is a good one to tune it the rest of the way..

Just remember, a little mojo goes a long ways.. Flat has never made me happy. It's always been a very slight frown, looking after tuning it the way I like it,  I hear what I like.. Slight rise in the middle. When I measure (not to often) it's always the same.. a slight frown on the PEQ. 2 db rise is just about right..

Cup your ears and see if it's what you like (chair forward call or EQ it.)

Happy hunting..

How about the floor between/behind the speakers??
It is a vertical problem. It is difficult increase volume in one area. Easier to attenuate volume.
If you put acoustic tile on the ceiling you will attenuate everything over 250 Hz and probably wind up with the same problem. It is called a "null."
If you have carpeting on the floor removing it probably won't help either.
The easiest way to fix it is Room Control. Check out my system page and DEQX.
 I just difn’t know or think that they happened above 100hz or so.  Never thought abkut hugher up frequencies cancelling themselves out. 
Happens at every frequency. Every wave hits a flat surface reflects and all the reflections interact with direct waves to cancel or reinforce. Happens all over the place. Its just that usually there's so many things in a room the reflections are going every which way and its hard to notice.   

Way back when I was doing my room nobody in Seattle knew the first thing about any of this and I had to figure it all out myself. Fortunately this is one of many, MANY essential audio items explained in Robert Harley's The Compete Guide to High End Audio.    

Everyone today wants to go the easy techno route with microphones and stuff but you can do it all just the same with paper and pencil just fine. Diagram your room then start looking for modes using either math like I did or you can cheat with one of these  

Where if you plug in 350Hz you will find the wavelength is 38.6" which perfectly explains why you hear it sitting but then stand and its gone. How much ya wanna bet the diff between ears sitting and standing is about a half a wave, or 2 feet? Its all physics, see? 

In my room early on it was an empty rectangle, not a thing in it, and I could play test tones and some of the higher frequencies would be completely different one ear vs another. Because as everyone knows I have a big head, not quite 38.6" though, it was probably more like 13kHz.  

One way you can control that 350Hz peak is to break it up, which by now you can probably figure out is going to involve some panels that are around 3 feet square, which angled slightly will send those frequencies off in different directions breaking up the mode pattern you have now. Don't quote me this is off the top of my enormous head which has had so much stuff stuffed into it for so long now half has sloshed out but even so as you can see a few things still sloshing around in there. Get the book, or search around, you know its out there. It is after all basic wave physics.