Suckout at 40 hertz...less pricey solutions?

Glai points out that using DRC to address a null can be difficult, but it can be done. For example, several manufacturers produce a 12" sub with 1000 WPC. A pair of such subs (especially those with largeish cabinets) will provide 2 kW of amplifier power (more on peak) into a reasonably sensitive driver/box mechanical system, which will go a long way toward fixing the most stubborn null. This is a blunt force approach, maybe inelegant to some, but it works. As Glai notes, it may also prove expensive.

Good Luck

Marty

PS - When I note that your 40hz null will be mostly inaudible, I assume that it's deep and narrow @ 40hz. A broader null (particularly one extending higher in frequency) might certainly pose a more audible problem.

Hi you may want to try to use this program to help you with placement of your speakers. http://www.hunecke.de/en/calculators/loudspeakers.html
Cut and paste it to your browser.

I too have a similar problem to yours. My room is 13 x 14 feet with a 14 foot ceiling. The first thing I found was that the speakers have to be on the shortest end of the room. Or the end furthest from the door that enters that room and shortest in width. I tried my speakers on the long wall and I did not have good success. I also found that a room that small is not very good for bass when using some full range speakers that go below 35Hz and that can vary. I spent over 3 years looking for speakers that sound good in my Box Of a Room and I ended up with Spica TC60's and 2-Dali Suite 1.2 Acoustic Suspension Subs. The Spicas are rear ported but you can compensate for that in several ways. The subs were the hardest to place. I first had them between the speakers and the outcome was not consistent. Sometimes boomy, sometimes not much bass and sometimes just right.
Mr. Bau told me to move the subs closer to my listening position. This improved things. That helped but I needed them to be even closer. Because I didn't have any wall sockets nearby I could not move the subs closer to me from the front so I moved the subs behind the loveseat. I was instructed to put the phase to "0" and turn the subs half way of what they were when I had them in the opposite end of the room. This amounted to be about a 1/4 turn and my crossover was set to the lowest setting about 40 or 50Hz. I don't know what happened but my system was transformed. The bass tightened up tremendously and even though the subs were behind the loveseat I didn't notice they were there.
I used this as a guidline to place my subs: Mr. Bau shared this with me:
For inverting subs - place them near the speakers.
For non-inverting subs - place them near the listener.

With the phase set to Zero this worked out beautifully.
The other thing you can do to control bass is have some filters made to control the bass on your main speakers. The filters makes your speakers roll off where you want them too and then the subs take over and to their thing.
Vandersteen sells filters for it's speakers. I also don't know if you can do this for a solid state amp. I have all tube gear and it does work. I had Alon I MKII, VonSchweikert VR3, Living Voices, Athena 2's, Wharfedale, and may other speakers and I could not control the bass or it overwhelmed my room. The Spica TC60 or T50 with The Dali Suite Acoustic suspension 12" Subs worked.
This may be more difficult to do if you have an integrated amp. I have tried every trick to control the bass and this worked best for me so far. I also used the speaker placement guide included at the beginning to place my Spica TC 60's which helped allot. If you don't find your speakers on the list try to find a speaker with similar characteristics as your. If you have a floor speaker choose a floor speaker, etc. Place them according to the directions and see if you hear a differnce. Next, I will do the wall treatments. I'm very satisfied with my outcome but remember your small room cannot support a speakers going down low in the bass region. You have to tame it and control it as best you can.
I hope this helped you some.

I had a 50Hz suckout (-10dB) I resolved with a pair of bass traps (GIK 244). I have two powered subwoofs and just for the heck of it I took one bass trap off of the wall behind my head and I had one extra just sitting in the closet. I stood them up near each of the two subs in various configurations. After numerous iterations I (luckily) found that by placing them next to one another (for a 4'x4' trap), 6" from one side of one of my subs the null disappeard (mostly, only -3dB now). Bingo! -3dB for a narrow null ain't bad. Problem solved!
p.s. During the juggling process I tried one behind the other for a double thick trap and one on top of the other for a tall trap, but standing on the floor side-x-side worked best for me. Try it!

How wide is the notch? (in octaves or freq)

Google 'room mode calculator and enter your base dimensions. This could give you an idea of the resonant modes of the l/w of your room. The vaulted ceiling is tougher to figure.

I had a few nasty nulls at low frequencies. Between adding GIK Monster traps and 6 244's, thing improved, but I still had one narrow but deep null at 60hz. Speaker repositioning was the only thing that fixed it. I pulled the speakers a little further into the room, which also added more depth to my soundstage.