Just brilliant! 
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Hi Thomas, dare I say we are now heading back to the discussion of potential over damping …
As you say reflected sound becomes more and more directional, as we move up through the midrange into the tweeter territory. However I do wonder if the term ‘ reflected’ is viable to use for frequencies below Hz 100. Sub 100 Hz bass frequencies are mainly situated along the boundaries of our rooms as an excessive build up, and can be viewed as simply an area of higher air pressure concentration/ velocity. This pressure emphasis is clearly higher in the end of the room, where the speakers are situated.
An example: my PMCs are front ported just above floor level, and being sat about 3 metres away from them clearly demonstrates the power of a reproduced bass thump, as I can feel the effect it is having through the sofa as a resonant vibration. ( less now after filling it in btw.
).
I feel the primary area to attack the sub 100Hz bass lift are the immediate corners/ back wall behind the speakers. However great care is to be taken moving absorbers inside the inside edge of the speakers ie on the front wall, as I like you have also found, that this starts to strip the mids/highs of life. This is where your wooden 2D diffusers ( the white ones in the centre) are well placed.
Through my own experiments I have found, that once excess bass is managed in the corners and first reflection subdued on side and back wall ( but not fully eradicated= keeping it live) , the front wall actually has very little deleterious effect overall, this in my case even untreated ( and glass even 
).
An observation on the GIK website , which puzzles me when you look at their videos, is that one of their starter- packs is showing double stacked TriTrap corner traps in each of the room’s 4 corners. TriTraps are NOT bass absorbers , but their effect is to smoothen out frequencies above Hz 200 and beyond. Even in my case using them to control corner reflections behind me in this frequency range, had to be undertaken with great care to avoid conflicting with my own personal ‘ live’ parameters in my room. This could be an area well worth experimenting with for others, as no 2 rooms or ear lobes for that matter are the same.
I would agree entirely with you, that flattening the room response under Hz 100 takes some often large absorption, where sheer volume is the order of the day. I used Hofa bass trapsx4 and a monster GIK bass absorber placed on the floor specifically for this task, and this is probably where most people may loose their will to live- but volume it is, if you want to really wave ( no pun intended) the bass boom off- I cannot in fact say, that I have listened to music in many rooms, which sadly don’t suffer it!
In addition to above I also treated the sidewalls beside the speakers and found it to me to be important , however to give the speakers some lateral breathing space. This is something PMCs are renowned to thrive from, but I would image this working for most speaker designs per se.
So when people want to manage the sub 100Hz problem area, do make sure to check the efficiency in this particular frequency band in the specifications available from the manufacturer of said product.
All above is just a few experiences accrued from my own play with my room and my experience only!
Shall be looking forward to hearing how you get on with your membrane/ range limited absorbers Thomas 
ATB Peter
…and see I only mentioned my sofa once 
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Hi Thomas.
I don’t think immediate distance is too much of a problem behind your listening position, but for QRD diffusers the minimum distance is 5-6 feet.
ATB Peter
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Diffusion - Confusion - Definition
What is diffusion really is ?
Why bookshelves or CD racks can’t diffuse sound.
Not the most accurate explanation but worth the 6 minutes
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Hi Thomas.
Where exactly did you place your Vicoustic absorbers on the ceiling in relation to speaker baffles and listening position?
Also did you glue them onto the bare ceiling please?
ATB Peter
Can anyone tell me what these specs are showing. I used an iPad app to record frequencies in 3 different places.
First, behind my siting place:
In the corner left:
In the corner right
:
The pictures were not clear:
Behind my siting place:
The corner left:
The corner right:
The corner more on the left has an acoustic panel which helped:
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I treated my ceiling with 16 Vicoustic Cinema Round Premium panels.
They start being effective around 300Hz up 5kHz (and probably above).
I glued them directly to the ceiling (concrete with some plaster and painting).
I chose to use 16 panels because my listening position varies.
My daughter likes to play on the rug, so I push the chair backwards.
I also wanted it be nice.
So I placed the panels right in the middle of the ceiling with the spots surrounding them.
The benefit was quite stunning (much better stereo image and overall clarity).
Those panels are made out of foam, but are quite efficient at absorbing mids and highs.
16 panels could have been too much, but as the listening position is pretty close to the speakers. So it did the trick.
That panel has probably a core made out of foam, which means it absorbs mids and highs. It doesn’t absorb low frequencies, at all.
Placing that panel where you placed it, the effect is probably marginal (if no effect at all).
A measurement could confirm it.
Spending some time with Denis Folley or Jesco could be of some help 
I placed several information sources in the thread.
Learning is key.
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It helps Thomas, the bass is cleaner and there’s not little distortion of the bass like without it.
I don’t know, just can say that the sound is better with it. Like the cd tower on the right corner ( around 1,4 high) which helps too. I know, you will say that it’s useless, cds can’t absorb…but the angle is broken with this cds tower and it really ameliorated the sound.
As the heavy carpets, and isolation under speakers.
I am very satisfied with the results today. Just make 3% of my albums give some ( a bit) distorted bass that I will try to remove with probably some bass traps as trip traps in these corners.
But FR, if you are happy with the sound you are getting from the system, why not chill and leave as is! ATB Peter
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This is certainly the best advice to follow!
Because on some tracks I feel the bass is a bit distorted. Maybe 3 or 4 % of my library but it indicates me that something can still be ameliorated.
There is no rush but i want to try the GIK bass corner trip traps. Perhaps the sound will still improve.
Some months ago my dealer advised me to break the corner on the right, with per example an angle furniture. I put then the cds angle tower which really improved a bass distorsion I had on some tracks. But something more effective can perhaps replace this cd tower furniture.
Is it a kind way to invite me to leave that thread Peter?
I’m a little confused here by how your are using the word ‘destructive’. IWHT that reflections can be destructive or constructive - in the sense that the reflections can either be in phase or out of phase with the direct sound, and to varying degrees. If in phase, are they not constructive (in terms of interference)? Or am I using the wrong words here?
I understand the confusion.
Recording context :
Reflections are part of the fun.
Imagine a violin in nice concert hall. It’s nice.
Imagine the same violin in a very damped little room. Not cool…
Reverberation is part of the violinist performance.
These reflexions are constructive.
Nice to have. Nice to record.
Replaying environment:
In short (but really short, it is slightly more complex) :
- When exactly in phase reflections cause pics of pressure (more volume)
- When exactly out of phase reflections cause nulls of pressure (part of the signal is lost)
- When delayed reflections cause distortion.
You can easily experience that with low frequencies. Choose a boom-boom track, or pink noise (low frequencies), and move through the room.
It’s a funny thing to do. Sometimes you get an over-boom, sometimes nearly no-boom. Pics and nulls.
So yes, in the context of music replaying, our context, the room is always a problem.
There are only 4 solutions:
- Room treatment
- “I know but don’t care”
- Denial : “My system sounds perfect! My room has no problems!”
- Head Phones
But… The brain has great filter capabilities 
Even if reflections are indeed destructive, the brain handles that nicely.
At least to a certain point. In short : the smaller the room, the bigger the problems, the harder the brain needs to compensate.
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Or 5): my system sounds very good in that room and no need to treatment. Without being a denial but just reality.
However in most cases room treatment is necessary, or at minimum a little treatment.
Here is the experience of Dark Bear.
frenchrooster:
Have you tried bass traps on the corners ?
No - for the reasons you say. I’ve heard if well-implemented in difficult rooms they can rescue the performance and have an overall good effect, but if not done with care they can spoil things - for me, as it is probably somewhat a personal choice of preference.
A bit like some people prefer near-field listening and some far-field - I’m somewhere between in that I like a wide field for my speakers apart and find that can work well if you can get the side-walls away enough, a meter of more helps.
I’m not bothered too much about overall response - it is a room and will impart a character - but when the music is playing you should be drawn to the music and forget the room - if you can’t then the room needs attending to.
In effect I have ‘traps’ in my room in the form of voids behind side-curtains in evening when I draw them I prefer the effect - and the rear room and how much the door is opened into it makes a big effect on the bass performance - but that is if you are producing a lot of deep bass that is interacting with the room which the S800 do.
I’ve no hard-line on all this but feel in general that there is an Art or ‘Enough’ that many do not conceptualize as needed to get to where you need to be. More than enough is not always better if it takes something else away - when you do enough to get balance then you have your solution. A bit like filters - you have over-damped, under-damped and critical damped and generally you want somewhere close to critical and a bit toward under-damped to get good results.
DB.
Darkebear
The room is important - I in part chose my house because it had several good rooms for HiFi use! 
Large odd-shaped rooms with high ceilings and good structural walls also helps. I’d have also preferred a good solid floor but in the end I found treating the floor with substantial reinforcing under the speaker area (three times thicker there now) and also under-floor cross-brace with steel girder running diagonally across the room worked well (I have a cellar under my room) - and allows me to hide all speaker cables and also not have them in large contact with the floor, which also sounds better to my criteria of a lively sound.
But with smaller more modern room I’d opt for somewhat smaller speakers.
But I love the textures and immersive qualities of seamless deep bass that getting a good room is more important than diverting money into HiFi IMO.