Room Treatment Question, lost the lowest bass notes.


This is what I have:
25 x 40 ft room 12 to 15 ft tall ceilings

The stereo is on the narrow wall on one end of the room. (I can move it 90 degrees if needed).
I have a pretty good system, Wilsons, Audio Research, VPI, I do not think I have to give what components are. They are considered high end.
Here is my problem.  My seating position is about 15 ft away from the speakers.  The lowest notes that I know that are on the recording are NOT being presented. For example: Lyle Lovett - She has already made up her mind.  There are a few super low notes on the song. I have heard them before when I had a lesser stereo.

I did find that when I stood near the open door at the far end of the room, I can hear them. But when I move towards the center of the room near the far wall, They go away. It is very easy to hear the drop off.

I spoke to a couple of HiFI shops in the LA area. One mentioned a Node Cancellation. I do not know what that is.
I added (2) 2 x 4 section of sound absorption material high on the back wall. The only conclusion I came up with is the low notes are being cancelled once they bounce off the back wall and head back to the front wall. Stop the bounce and the low note have a place to go.

I am thinking correctly here or am I just reaching for straws, and I am. 

I am no scientist. Please answer in non scientific terms.

Thank you. 
Bill 


128x128bill_peloquin
Do an internet search on audio room modes.  From your description you are listening in a null area for low frequencies.  As a quick fix move your seat forward or backward until the low notes reappear.
Perfectly normal. Happens everywhere. Very low bass waves are much longer than even a large room. So they reflect back and the same wave cancels itself at certain locations. That's why you stand somewhere and hear it, move somewhere else you don't. Also you will notice some frequencies are way too loud depending on where you stand. Where this happens depends on the frequency. With just two speakers all you can do is move them around, and all that will do is move the lumpy bass around. 

None of the stuff the shop is suggesting will do anything other than move the same lumpy bass around. The only real solution to smooth even powerful and DEEP bass is multiple subs. Preferably four. Search DBA, distributed bass array, or Swarm subwoofer system.
@OP,
Even if your components are high end, the real issue is how they work together
Be that as it may, I do think you are experiencing a room node dropout.
My first recommendation is to place the speakers closer to the middle of the room.
I, too, had such issues. I ended up placing my speakers near the middle of the room. I ended up getting a better soundstage, as well as more focused bass. In fact I got a bit of a bump near the corners of the room, but thankfully, I don't sit there.
Millercarbon's rec for the DBA is a good one, and relatively inexpensive.
My recommendation for subs would be the new Vandersteen Sub 3's. They have a built in graphic equalizer that can be adjusted to the individual room.

Bob