That one might interest you :
→ Bass Traps: Can They Take Away Too Much Bass? - AcousticsInsider.com - YouTube
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Hi Thomas, I would very much agree. If you look at my photo underneath my skinny carpet from the red line up to the speakers, there is no wool underlay ie 1st floor reflections are damped only very lightly. From the red line and back and underneath my listening chair I have added 10 mm wool underlay. This to me produced the best open and lively sound without the feel of a 1st reflection disturbance as such. Mad old World really 
Best Peter
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That is essentially the way many studios are treated at the opposite end to the speakers - - sadly very few of us have anywhere near the amount of space needed to contemplate that approach!
Active traps like the PSI you mentioned few posts ago would be the most space-effective at the bass end, albeit at a cost. I’m a bit unclear what you plan to do with the PSI given the above, but I’m looking forward to your experience because active traps have intrigued me since I first heard of them a few years ago - it may be the only way to go in my room, but some building work before I know what’s needed.
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Hi Thomas… thank you for your wonderful reply.
I’m getting the drift, certainly of your message with bass containment.
Interesting feedback from your experience.
I like the V’acoustics Extreme Bass Traps. Well-built and deep enough.
Saw the RPG equivalents … hmmmmmmmmm.
I’ve been following the man too! Thanks! 
ok! Much appreciated … when I’m struggling, I’ll let you know…
It’s such a fine balance to get right - mere mortals like me will need some serious help with measuring mics - but it will all be worth it, with patience.
It’s generally true. So important addressing first reflections. I had placed some RPG Bad panels on my side wall first reflections for the SBLs at that time… it absorbed some but also brightened up the highs with a more metallic sound due to its hard plate diffusor surface - and after some serious listening just didn’t do it for me in the overall scheme of things after the outlay. So I had them removed somewhere else. The SBLs seemed to relish very careful room treatment to really bring them to deeper song, as their tailored sonics were already well-controlled when paired with the 52-monos and the CDS2. I had to remove the BAD foam panels in my smallish room to hear the SBLs sound at their most natural. I guess in hindsight from that experience, I have learnt it’s patience from trial and error to find something that will work complementarily with our speakers and room. No one thing fits all and the type of panel we place on first reflection points doesn’t automatically guarantee it will be for the overall better - gotta try different types to find that sweet spot balance where the speakers just disappear and the music just flows unhindered - where everything sounds right to our ears.
So important as well. Happy to read this in your journey, Thomas! Without adequate juice, the system can’t sing to its fullest potential. 30A dedicated lines minimally for me and corresponding thick gauge wire. Depends on the amplifier used. Sometimes, Thomas, I am thinking whether these “hi-end” electrical cable types which cost more, really do bring that much more to the table. It’s a fallacy to pay more for the sake of things, when I suspect simple, good quality electrician wire will suffice. I could well be so wrong and am happy to hear feedback.
How do we conclusively tell one brand of electrical wire is really better than another since there is no way to do A-Bs? Just because it is expensive? I’m happily exploring.
Cheers and keep your posts coming. 
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I am still wondering which acoustic treatment project I will opt for.
The original and “radical” project would be optimal. It will guarantee me a superb, almost perfect, frequency response of the listening room.
But this option is expensive and will require 2 months of installation.
The high cost of this option is due to the price of the chosen absorbing material: Caruso IsoBond.
This material costs, on average 5 times more than rock wool. I will use ~15m3 !
I chose this material because it has the same acoustic properties as glass wool but is not harmful to health.
The second option is faster and much cheaper. It is an addition to what I already have.
I’ll get a technician to come this weekend.
We’ll discuss the feasibility of the project and its cost.
Here is a very interesting article on the different materials available for acoustic treatment, their properties and the cost per cubic metre.
→ Rock wool, glass wool, hemp - which material is best suited for absorbers? — Jochen Schulz
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Hi Thomas I started my room with 6 vicoustic multifuser 64 on back wall and front wall I am putting the multifuser 34 it hard to explain but room sounds smooth and bigger .
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I have made some changes to the acoustic treatment project: I will increase the thickness of the “absorbing walls” by 10cm.
I will therefore have a volume of 17.6 cubic meters of absorbing material all around the listening area!!!
The front wall will be the same as before: a large diffuser of 3.25 square metres and membrane absorbers.
The 50 cm thick absorbers will allow the control of frequencies up to 45 Hz!
But I am still hesitating between 50 cm and 40 cm thickness. Such a thickness of absorbers takes up a lot of space in the room…
Increasing the thickness of the absorbers by 10 cm allows to gain ~10Hz and control frequencies down to ~43Hz !!!
Dilemma: space versus control…
Obviously, the space available for walking around will be reduced. But from an acoustic point of view the room will still be 38 square meters. 
Would it over-dampen the room, Thomas… once fixtures are done, tougher to adjust or change if at all. Wish you a successful project and a lovely listening room for all sorts of sorties.
Why is that?
I have roughly 60% absorption down to ~43Hz. That’s not bad, is it? 
But, more importantly, I have a very homogeneous absorption down to 70Hz !!!
In short, all this will allow a well balanced decay time down to ~40-50Hz. We are far from over-damping, aren’t we?
I wouldn’t know the technicalities. If you are certain what you’re doing, by all means!
Fixtures are always a gamble for me.
I don’t wish to hinder your progress or plans - so it is calculated “trial and error”. Just sharing considerations. Cheers
Thank you for your thoughtfulness, and you’re right to warn me. Once you’ve installed it, there’s no going back.
I’ve already had my share of trial and error 
What is often called “over-damping” is simply an imbalance.
It is that imbalance that gives the impression of a muffled sound, which has lost all life.
Technically the lower end of the spectrum takes over and dominates the rest. Hence the impression of a dull sound that has lost its life.
If we absorb in a, more or less, homogeneous way, and include some diffusion, then the whole thing remains balanced, and we achieve our goal: more speakers and less room.
I had quite a few people in my living room. No one thought my room was over-damped. In fact, they were pretty astonished by the quality of the low end! Especially some double-bass lines.
What surprised me was that they thought my room’s low end was good. Because under 85 Hz the measurements are not that great… 
Who knows what they are used to… 
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I just ordered ~15 cubic meters of sound absorber for the new acoustic treatment of my listening room.
It’s not rock wool or fibreglass; it’s Caruso IsoBond.
All the acoustic advantages of rock-wool,or fibreglass, without the health hazards.
It is a lot more expensive, but health is priceless.
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You must be spending some money on your new system hope it all works out for you.
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Yes, I believe the system will sound really good.
I tried not to do things by halves.
The room treatment alone is worth more than a NAP 500 DR.
The thought of someone steering room acoustics mania at many levels further is welcome … I respect it. Keep it carefully up, Thomas!
Every penny’s worth once the system sings and grooves, and comfortably supports shattering crescendos with equal aplomb.
Wish you and your quest the very best, Sir, and may your arm hair tingle and stand on ceremony with goosebump floods in perpetuity.
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In my system the power source had a fairly significant impact on the sound.
Adding a transformer (made by a highly respected consultant in the hi-fi world - and you should see HIS system 
) transformed the sound of my 500 series - my dealer’s comment was «well, now you have Statement level sound 
»
No turning back after I heard it, and beauty is that the sound can also be (subtly) tweaked with different phases.
One of best investments I made, sound for pound, and for less than the price of a naim power supply.
Massively tightened up the bass, whilst adding what I can only describe as enabling the system to breathe…
The sound just became more open, bigger, dynamic… ALIVE! And it made inroads into arresting some of the nasty room resonances I was experiencing. Maybe worth considering for you guys on that room treatment journey…
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Great shot the transformer looks the size of a substation!
Hi Charlie,
Are you building a new house?