Need help with room and speaker setup, big dip from 250-80hz


I have a very small and odd room.  The room itself is 9' wide by 10' long with 9' ceilings.  The wall directly behind my head is only 3' tall, above that it opens up to my family room and kitchen.  I have the speakers firing down the 10' length.  The speakers (Sonus Faber Guaneri Evolution monitors) are toed in directly at my head, 3' from the front wall, and 1.5" from the sidewalls.  I have bass traps in the corners, absorption at the 1st reflection points and ceiling, and a mix of absorption and diffusion on the front wall.  My listening chair is right up against the short back wall.

I just did a quick measurement of my room using a cheap RS SPL meter and some test tones.  It seems I am -6db at 630hz and 250-80hz.  Any advice what I can do to help alleviate these dips?  As you can tell by my room dimensions I do not have a lot of flexibility.  Thank you.
Convert?fit=crop&h=128&rotate=exif&w=128tboooe
I should also note that my biggest dips are at 80 and 160hz.  Not sure if that helps or not. 
Have you tried less toe in and maybe try 2ft from the side walls (a little closer together)? When I went for a demo many years ago with SF Cremora auditor M's the dealer had them toed in pointing to my shoulders.
Your missing bass maybe on the ceiling..measure up there. There are ways to redirect the pressure not negate pressure as with the traps. Tom 
This may not true any more depending on the vintage of your RS meter, but they used to be known to need a well documented adjustment to results to adjust for variations in its ability to measure at differing frequencies. Search online and you'll find a table that tells you to add or subtract from each result (e.g. "at 80hz +3db"). I think the adjustment is based on limitations of the built in microphone. 
Squarish rooms are tough, although with a 3' tall half wall, higher frequencies might act as if you are in the "bigger room" ignoring the half wall. Many speakers manufs. suggest a diagonal setup in squarish rooms. Could be worth a try if everything else mentioned doesn't work out to your satisfaction. Cheers,
Spencer
The port on these speakers appears very small, and could be causing a reflection off of the wall/corner that effectively cancels out the frequencies you mention.

First - remove the bass traps - temporarily

Try different distances from the wall with the speaker toe-in at around 5 degrees. Keep the speakers about 7 feet apart to start with.
 
Once you have reasonably good bass performance try varying the space between the speakers and then adjust toe-in for a final adjustment

Once you get a pleasing sound re-install the bass traps to see if they are over compensating on certain frequencies

You may then need some minor adjustments for best sound once the traps are installed
 
I have a pair of studio monitors that suffers from a similar problem - they required over 1 meter of space behind the rear of the speaker, but since I did not have that much room, I ended up installing a cowling over the port which redirected the airflow downwards. This seemed to resolve most of the issue - the rest was remedied with correct speaker placement/toe-in.

I can now place the speaker much closer to the wall - i.e. down to 8 inches

My speakers originally came with a foam plug for the port that helped a little - it did not stop the airflow, just slowed it down a little

Personally - I do not use meters for two channel systems - I let my ears be the judge.

I do find a meter helps greatly with Surround Sound systems

Regards...
First of all, thank you all for the input. I spent a few hours moving my speakers around my music room, trying to move the speakers closer to the front wall, closer together, adjusting the toe, etc. I was able to get varying degrees of success but I still had massive nulls throughout the frequency range 80-250hz. I finally tried moving the speakers further out into the room. My reasoning was that I had good bass response below 80hz so I could lose a bit but hopefully still be within 3db of flat. I also moved my speakers further apart so that I was listening in an equilateral configuration. The results were better than expected. From 20-1000hz, I was within 3db of 70db. My only small null was at 800hz where the response was -6db down.
Sir

You have not taken the floor or the ceiling position out of the equation when you moved the speakers. You moved the speakers relative to the walls not to what is above or below. All speakers have a speaker floor bounce cancellation relative to the distance of the bass driver. You can have much the same cancellation from that same driver to the ceiling though at a different distance and frequency. If your monitors can be placed on the floor or on  shorter or taller stands or supports for testing this will give you more insight into a placement to reinforce the frequencys you are in search of. Tom
tboooe - have you tried putting the speakers against the 3ft wall?

If yes - did you still get dips in freq response?

What is on the floor? if it's hardwood - try a rug in front of the listening position.

Regards...
The rug will act as a comb filter and could add some benefit, a natural wool rug will be best..but will not help at 80hz. Tom
Deqx? that ought to clear up all your troubles.
I bought 2 SVS subs and solved my room problem which sucked out the deep bass at the listening position. Lots of info on the web about this topic. 

My my speaker positioning and listening position have created stunning imaging and soundstage.  The compromise was the deep bass and it drove me crazy.  The bass was perfect before I rearranged the room setup (in an irregular shaped room) and it was good to find this solution.  The subs are barely making any sound, but it fills out the missing frequencies at the listening position perfectly!
First, get a calibrated microphone. They’re $25 to $100. Dayton imm6 or UMIK-1

That your dips are happening at multiples of each other testify to having a standing wave due to wall surfaces around 7 to 8’ apart.

Room EQ Wizard has a bass decay chart which will help you see the problems with more clarity. REQW is free, but I use OmniMic.

When you plug the speakers, you are reducing bass and reducing the chance of exciting the room modes. What’s happening is that the room is ringing, like a bell. If you play no bass, you won’t hear it, so it sounds better, but, bassless.

Make sure your bass traps are adequate. GIK Soffit traps are among the best and least expensive below 200 Hz. If after placing you still have those nodes, then increase bass traps first. The better your bass traps the more chance of lifting the lows, clipping the highs AND getting a better response regardless of listening location. They are the enabling tech. for room equalization. If you can’t EQ, it’s because your room treatment isn’t enough.

After assessing that, add a miniDSP unit or equivalent. Don’t try for flat, I usually use about 1 to 1.5 db downward slope above 70 Hz. Works best for music and movies.

If you don’t haver enough traps you wont’ be able to lift the dips, but you should be able to clip the peaks. What you’ll see in addition to the 80 and 160 Hz dips are some massive peaks, like +20 dB. By lowering them you’ll get a more full bass experience. Again, the better the room treatment, the easier and better your EQ results.


Best,


Erik
I should also say adding subwoofers and placing them correctly is a great solution. :)  But since you mentioned you don't have a lot of freedom in your room I did not pursue that. The same advice applies though, except with a sub finding the place that excites the room modes most evenly is paramount.