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. 

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.
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.

Hello Bill,

     I believe your issue is being caused by a bass room mode being present either at, or in the vicinity of, your listening seat.  Depending on the details, bass room modes are perceived as a bass peak(bass overemphasis), a bass dip(bass attenuation) or a bass null(bass absence due to cancellation).
     Your local hi-fi shop that mentioned a node cancellation are partially correct but the technical term is named a "bass room mode cancellation" and informally referred to as a "bass null".  Unfortunately, effective solutions for obtaining very good bass performance in a room are not as simple as adding room treatments.  I'm going to attempt to give you a thorough explanation of why it's difficult to get the bass sounding good in a room, in non-scientific terms, but be forewarned it'll probably get a bit lengthy.  However, I will tell you of effective solutions at the end of this explanation:  
      Your Wilson speakers are very high quality, expensive and have a rated bass output extension down to the audible lower limit of 20 Hz. However, it's highly unlikely that you're experiencing and enjoying bass response this deep at your listening position because the woofers, that are responsible for launching these very low frequency sound waves into your room are permanently affixed in their cabinet. This rarely discussed design flaw is true for any speaker, no matter its design type, that has a rated bass extension deeper than about 80 Hz.
     This permanent affixation of bass transducers in a speaker means they're not capable of being independently positioned in your room, and in relation to your listening position (LP), which is required to optimize the perceived bass response at your LP from 20 Hz up to about 80 Hz. The truth is that, even if the bass transducers in a pair of speakers are launching pristeen deep bass sound waves into the room, it's highly unlikely these sound waves will reach the LP in the same pristeen condition.
      The explanations for this reality are detailed and best understood via physics and how humans perceive sound, especially below about 80 Hz. The deeper a sound's frequency, the longer its corresponding full cycle sound wave and the higher a sound's frequency, the shorter its corresponding full cycle sound wave. Think of sounds, and their corresponding sound waves, as a continuum from long and deep to short and high. For example a 20 Hz full cycle sound wave is about 56' long and a 20,000 Hz full cycle sound wave is a fraction of an inch long.
     It's important to know that the longer bass frequency sound waves have omnidirectional radiation patterns and the much shorter midrange and treble frequency sound waves have highly directional radiation patterns. It's also important to realize that the longer, omnidirectional sound waves/tones, typically below about 80 Hz, are not localizable (individuals are unable to determine their specific position in space) by humans and that the much shorter, highly directional sound waves/tones, typically from about 80 Hz up to 20,000 Hz, are highly localizable by humans, and progressively more easily as the frequency increases.
     In addition, there are some peculiarities in how we humans perceive sound and sound waves:

- We don't even perceive a sound as existing at all until our ears detect a full cycle sound wave at a specific frequency, our brains process the input from the ears and the brain creates the perception of the sound at that frequency. Anything less than a full cycle sound wave being detected, results in no sound being perceived.
      This fact becomes especially important with bass perceptions in a finite room, since some full cycle deep bass sound waves may exceed the dimensions of the room. This requires the sound wave to bounce or reflect at least once off of a room boundary (floor, ceiling or wall) before the full cycle bass sound wave exists in the room, is detected by our ears, processed by our brains and the perception of a bass tone at a specific frequency is created.

- Since we generally can't localize bass frequency sounds below about 80 Hz, we perceive all bass below about 80 Hz as mono, which means no true-stereo deep bass exists below about 80 Hz.
     I stated no "true-stereo deep bass" because we are capable of perceiving a form of stereo deep bass thanks to our amazing brains. Our brains are able to perceive a fundamental deep bass tone below 80Hz, often reproduced by a sub and unlocalizable, as mono and perceive the fundamental deep bass tone's natural overtones or harmonics, which often extend beyond 80 Hz, are often reproduced by the main speakers and are localizable, in stereo.
     Our amazing brains are then capable of associating the mono fundamental tone with the stereo overtones or harmonics and localize the deep bass tone. The result is a form of stereo deep bass that I believe needs to be distinguished as something other than "true-stereo deep bass". For you, this means you can incorporate a sub or subs in your system and you still perceive a stereo sound stage illusion that is equal to, or more likely better than, your current one.

     The next facet of acoustic sound physics it's useful to understand is that all sound waves, at all frequencies, launched into your room by either speaker or sub drivers will travel outward and continue to bounce or reflect off of room boundaries (floor, ceiling and floor) until they are absorbed or diffused/scattered by acoustic room treatments, run out of energy and naturally decay or they collide with another sound wave.  
     Whenever these sound waves collide with each other, it creates what's called a "room mode" at the specific room location of the collision. These room modes/collisions happen all the time with midrange and treble frequency sound waves and, in an untreated room, are normally perceived as 'airiness' or 'liveness' qualities, which many individuals perceive as enjoyable.
     However, these midrange and treble room modes/collisions also negatively affect tonal accuracy, stereo details and stereo imaging. But these midrange and treble room modes affects can be reduced, mitigated and controlled to an extent through strategic deployment of sound wave absorbing and diffusing acoustic room panels/treatments.
      These room modes/collisions happen often with bass frequency sound waves, too. In an untreated room, however, bass room modes are normally perceived as bass overemphasis (a bass peak), bass underemphasis (a bass dip) or even a bass cancellation (a bass null).
      But these bass room modes effects are much more difficult to reduce, mitigate and control than midrange and treble room modes. The required bass trap room treatments are larger, more expensive and can't always be aesthetically placed at the specific room position they're services are needed.
     Okay, the preliminary topics have been covered on this tome, and it's finally time for me to tie this whole thesis together and get to my recommendations for your specific circumstances.
     Yes, I could have saved a lot of my time and yours by just stating I recommend you utilize the Audio Kinesis Swarm 4-sub distributed bass array (DBA) system as an ideal solution but I thought it was more valuable with you having a good understanding for my reasoning for my suggestion. Here's an Absolute Sound review of the AK Swarm system that gives a very good description of what to expect:

     I use the very similar AK Debra 4-sub DBA in my system/room and can state with certainty, if you have the available room space for four relatively small (1'x1'x2') subs in your room, that you'll be amazed by the near state of the art bass performance of this relatively affordable ($3,200) complete kit bass system. It's attractive in your choice of woods, the subs would be positioned around the perimeter of your room and are easily concealable and the bass integrates seamlessly with virtually any pair of main speakers.
     I also believe your very high quality main speakers deserve an equally high quality 4-sub DBA system. I think you could probably come close to the Swarm's performance by utilizing a pair, of properly positioned and configured, high quality subs. However, the very good bass would be restricted to a single designated listening position rather than throughout your entire room with the Swarm and the Swarm will likely cost a few thousand dollars less as well as being easier to set up and configure.

Best wishes,
Also you may want to contact Wilson for some insight and / or helpful info ... you already have insight into what why and how to best correct.
Don't know from bass room modes.
Nodes can be overcome by
1 Bass traps up the wazoo with one or 2 well places subs. Use REW for that.
2 Moving speakers and or seat until balanced at listening position
3 Abandon all hope of using the room for anything besides A/V. Get out your wallet and hire a home decorator to find a place for 4 subwoofers. Probably in lieu of seating.,
Honestly, it hardly matters which sub you use. I have three different types in my room. They all work together perfectly, and blend seamlessly with the mains.

The problem with EQ is you can only get it flat by putting more bass into the room. Bass energy takes time to dissipate in the room. Putting more bass into the room with EQ always results in slower muddier bass. So then you have to remove the extra bass with bass traps. When instead you could use multiple subs. Because there are more each one can put out less bass. It all adds up to the correct amount of bass. Its smooth because they're in different locations, greatly reducing the amplitude of the modes. Its just a way more elegant and effective solution all the way around.
+1 millercarbon

     It's also very important to realize that equalizers and automatic room correction programs and gear are not nearly as effective as multiple subs are at improving bass performance in a given room.
     Room correction (mics to measure room bass frequency response,  parametric equalization to adjust the bass  and amps to adjust bass output) is very effective at reducing the bass level of bass peaks in the room, since these bass level reductions at specific bass frequencies result in reduced overall bass amplifier power demands, but room correction is much less effective at increasing the bass level of bass dips in the room, since these bass level increases result in increased overall bass amplifier power demands, and bass amplifier power is limited.   
     In other words, automatic room correction has the unlimited ability to correct bass peaks and a limited ability to correct bass dips and nulls. It's also important to note that automatic room correction is going to optimize the bass at a single position, usually at the listening seat where the mic is placed to measure frequency response, which actually causes the bass response to be worse at other spots in the room and uneven in the room overall.  
     The beauty and elegance of utilizing multiple subs as a bass solution, is that it is based on the scientifically proven and reliable principles of how humans actually perceive bass sounds and tones in normal, smaller, domestic-sized rooms containing room boundaries (floor, ceiling and walls).  For example,utilizing the following scientifically proven and reliable principles or facts:

1.  Humans generally cannot localize bass sound tones at frequencies below about 80 Hz.  This means we're unable to determine where a bass sound tone is specifically originating from if its frequency is below about 80 Hz and we perceive all of these bass sound tones as mono, and we're unable to perceive bass tones in stereo below this 80 Hz frequency threshold.
2.  Humans don't even perceive sound at all until our ears detect a full-cycle sound wave, the brain processes it and then creates a perception of a sound tone at the detected amplitude,frequency, tone and pitch.
3.  Full cycle bass sound waves are omnidirectional and extremely long (a very deep 20 Hz sound wave is 56' long), full cycle treble sound waves are highly directional and quite short (a 20,000 Hz very high 20,000 Hz sound wave is a fraction of an inch long).  The length of full cycle sound waves are proportional to their frequencies; the lower the sound tone frequency the longer the full cycle sound wave and the higher the sound tone frequency the shorter the full cycle sound wave. 
4.  All sound waves radiate outward, the long bass soundwaves in an omnidirectional pattern and the much shorter midrange and treble sound waves in a highly directional pattern, and continue on their outward path until they are absorbed or diffused by acoustic treatments, run out of energy and decay, encounter a room boundary (floor, ceiling and walls) and are reflected and redirected in a new direction or collide with another sound wave travelling within the room.
5.  Since the main speakers and subs are continuously launching new soundwaves into the room, and all these soundwaves are constantly being reflected off of room boundaries (floor, ceiling and walls), sound waves inevitably collide or crash into each other. Whenever these soundwaves collide with each other, what's termed a "room mode" is created in the room at the specific spot in the room that the collision occurred.
6.  When the shorter and highly directional midrange and treble sound waves collide with another soundwave, depending on the angles of the collisions, the room modes created are typically perceived as a midrange or treble 'peak' (overemphasis), a midrange or treble 'dip' (attenuation) or a 'null' (midrange or treble cancellation or absence).  If these midrange and treble room modes are left uncontrolled by acoustic room treatments/panels, they are typically perceived as an 'airy' or spacious' quality.  However, these midrange and treble sound waves are also more easily controlled with strategically placed absorbing and diffusing acoustic room treatments/panels that reduce midrange and treble room modes at the designated listening position.
7,  When the longer and omnidirectional bass sound waves collide with another sound wave, depending on the angles of the collisions, the room modes created are typically perceived as a bass peak, a bass dip or a bass null/cancellation/absence.  However, these bass sound waves are much more difficult to control with strategically placed absorbing room treatment acoustic panels and traps, which often results in bass room modes at the designated listening position and elsewhere in the room.
      Finally,  I've reached the point, in this essay of a post, where it's appropriate to explain why and how utilizing multiple subs as a bass solution is such a beautiful and elegant solution:
     I've already detailed why bass acoustic room treatments and bass room correction software and gear are insufficient and poor bass solutions.  The beauty of multiple subs as a bass solution stems from the fact that it doesn't try to reduce the number of bass modes in the room, but rather and counterintuitively, its goal is to increase the number of bass room modes in the room.  The solution relies on the facts that bass is cumulative in a room  and, when multiple bass room modes exist in a room, our brains react and process this sonic chaos by summing and averaging the bass by frequency and creating a perception that the bass is powerful, solid, fast, smooth, detailed, dynamic and natural. 
     These multisub benefits begin to be realized, at a single designated listening position, with as few as a pair of properly positioned and configured subs.  
    Utilizing 3-4 subs, positioned in an asymmetrical distributed bass array (DBA) manner and optimally configured, results in even further enhancements to these multisub benefits along with extending them throughout the entire room, not just at a single designated listening position, and even better blending of its near state of the art bass performance with virtually any brand, model and type of main speakers.
     I believe this qualifies the 3-4 sub DBA concept as a beautiful and elegant bass system solution.  I can also personally and definitively state that the 4-sub DBA system works like a charm in my room and combo 2-ch music and 5.4 HT surround sound system. 

Your #6, when my room was brand new and empty, literally just one chair and the stereo on the floor, no room treatment at all, the bare walls created obvious modes at every frequency. There was a test CD with tones and some frequencies you could hear the dips and peaks dramatically come and go as you move around, sometimes in a foot or less. We don't notice this because most rooms are nowhere near so empty, and everything in a room either absorbs or reflects and scatters. So usually we only notice the modes with bass. But they're everywhere.
Hello millercarbon,

     Yes, exactly!  The negative sound quality effects of the combination, of highly directional midrange and treble sound waves constantly being  reflected off of hard and untreated room boundaries (floor, ceiling and walls) in an empty room,  are definitely numerous and obvious but it's also an excellent teaching tool.  
    As I think you're aware, until about 6 months ago I had zero room treatments in my room.  The odd part was I didn't notice any obvious negative sq effects in any part of the audible sound frequency spectrum without them.  The bass was near state of the art in my room with my 4-sub Audio Kinesis Debra DBA system without any bass traps or panels of any type.  The only semblance of bass room treatments in my room were fairly thick wall to wall carpeting and some well cushioned leather chairs and a sofa. 
      I even considered the midrange, treble and stereo imaging sq to be very good at my listening seat using a pair of large, 6'x2', 3-way  Magnepan 2.7QR dipole speakers with no absorbing or diffusing acoustic panels in the room at all.  I believe having my panels positioned over 4' away from the front wall, 2' away from the side walls, along with their being dipole speakers with a figure-8 radiation pattern, were probably responsible for them performing so well in my room sans room treatments.
     But I knew from online reading/research and audio forums, as well as having my room analyzed by GIK Acoustics, that adding the $3,500 worth of various room treatments that GIK recommended would likely be a very good investment.  I was most concerned that the suggested stacked bass traps in all 4 room corners, and the numerous other bass trap panels in the room, might negatively effecting the extremely good bass performance in my room.  But GIK and Duke convinced me that these bass room treatments would do no harm and probably only serve to improve bass performance. 
     So about 6 months ago, I bought the full $3,500 complement of GIK recommended room treatments and had them installed in my room. 
     What were my overall impressions of the sq effects of having all of these fairly extensive room treatments installed in my room?
     Well, the bass still sounds spectacularly good in my room but I don't think it's actually been improved with the added bass room panels and traps.  Sometimes I perceive the bass as sounding especially detailed, 3 dimensional, effortless or just plain amazingly natural and realistic on music or even tv programs and commercials.  But then I recall numerous times, prior to having any bass room treatments installed, that I noticed very similar bass perceptions.  I can definitely state with certainty, however, that Duke and GIK were correct and I don't believe the additional bass room treatments caused any negative effects to the bass sq in my room.
     On the other hand, the approximately 20 added absorption and diffusion panels in my room have had a profound positive effect on the midrange, treble and stereo imaging performance performance in my room at my designated listening position/seat. 
      I believe for the first time that my entire system has been optimized over the entire audible spectrum, from top to bottom while prior I perceived the bass performance only as being optimized and superior to the performance of the rest of the audio spectrum.  Overall, everything sounds very well balanced and a few degrees higher in sound quality.

That's why I'm looking forward to checking out Mike Lavigne's place this weekend. Some audiophiles are coming up from Portland. First stop my place, then on to Mike's. Kind of like a pub crawl. Heh.  

My room for sure has problems. Had a friend over a very long time ago, Holly Cole hits this one note and its just crazy overload loud. Told my friend sorry its the room I'm working on it. He says no way she just overloaded the mic. But I knew better. The corner tunes you can see in my system pics virtually eliminated this resonance. Cleaned up some other stuff as well.  

That like I said was a very long time ago. Like at least 20 years. My system is a whole lot better now. Room problems that back then blended in with other problems now stand out as room problems. To me anyway. Everyone so far thinks the room sounds great. Better than average sure. But not great. Mike Lavigne though, now THAT'S a ROOM!  

Bet your bottom dollar my eyes will be peeled every bit as much as my ears will be taking it all in especially looking for ideas to improve the sound in my room.
Problem is your room dimensions are conducive to suck out at a lot of low frequencies. Best short term benefit is listening position location. Which needs to be between two nodes one about 25Hz and another just over 40hz. I estimate you will want to be 16 feet from the front wall for best response.

Look up AMROC on the web and work it out exactly.

Lots of good suggestions for optimization in the thread.
Thanks for the reply's. 
I am not adding any subs. I got enough money spent on equipment, $45K.
I could spend money on having the Wilson Tech come set speaker placement. 
I have my seating position at 16 ft away from the front now. I could move it back a few more feet if needed.
I did shift the center of my speaker center to the right about 3 ft. That helped. I have a brain fart with the initial speaker placement.

I also added (2) 2 x 4ft sound absorption panels on the back wall and (2) 2 x 2 ft panels behind the speakers.  

Time to let my ears do the judging.  At this level of HiFi.... It is all in the room now. 
I had great luck using Vicoustic Extreme Bass corner stacks. These won't overdamp, just sound better the more you add. See my systems page.
@bill_peloquin, The 'Wilson' setup is demonstrated (somewhat) in a video by Wilson.
The process described begins with finding a 'neutral zone' and this can be best demonstrated with an assistant vocalizing a sentence / tone (an octave or  two). First against the wall and then moving into the room five inches at a time (or less). Until voicing (literally) sounds normal (like outdoors).
One note: Vocals is only one third of the audio spectrum.
Highs and lows also need to be addressed separately.
Also finding the correct distance between L/R (mains) is significant.
I would suggest that the distance should be one that gives the best perceived power for a given volume (same).
Set up the Mains first without the Center Channel.
Integrating the Center Channel afterword should be easy especially if you are able to adjust in the time domain.
Also notice that there is no 'room treatment' shown in the video!
The Wilson line would be a baffle less type design (generally) with a more uniform radiation pattern.
Once a zone (for placement) is located fine adjustments (inches / cm) can be made. Toe in as well (a further discussion).

" Thanks for the replies.
I am not adding any subs. I got enough money spent on equipment, $45K.
I could spend money on having the Wilson Tech come set speaker placement.
I have my seating position at 16 ft away from the front now. I could move it back a few more feet if needed.
I did shift the center of my speaker center to the right about 3 ft. That helped. I have a brain fart with the initial speaker placement."

Hello Bill,

     I think you need to reread my first posted reply on your thread. Apparently, you don't believe that bass sound waves behave very differently than midrange and treble sound waves do in any given room.  Or, you don't believe that all floorstanding speakers have the same inherent problem that they can be positioned in the room, and in relation to the listening position, to either optimize the midrange, treble and stereo imaging performance or they can be positioned to optimize the bass performance, but it's virtually impossible to optimize both at the listening position.  
    Unfortunately, the physics and acoustics related principles causing this issue remain true regardless of the price or quality level of the pair of floorstanding speakers utilized. The most expensive and highest quality floorstanders share this exact same problem with the least expensive and lowest quality floorstanders. The basic reason for this shared problem is that the bass drivers (woofers) are not independently able to be positioned in the room, and in relation to the listening position, to optimize the bass performance.  They're permanently affixed in place within the cabinet.
     But you've stated "you don't want to add subs because you've already spent $45K on your pair of floorstanders". You also stated, however, that " I could spend money on having the Wilson Tech come set speaker placement." Are you actually implying that Wilson professional techs know more about the physics and room acoustics of obtaining very good in-room bass performance than I do? Really?
     Well okay, I have to admit that's a very good assumption and definitely true. If this is the case, however, then they'd also know that everything I stated in my first post is true and they'd realize that there is no speaker placement that will optimize the midrange, treble, stereo imaging AND bass performance at your designated listening position.
      Perhaps this is the reason the Wilson Audio loudspeaker lineup also includes very expensive independently positioned subs? I suspect they'll recommend at least a pair of their budget bargain beauties for your room.  Of course, another option would be just buying this complete 4-sub DBA kit:

Best wishes,