Air gap behind absorption only needed for modal resonances?

[Jens Eklund]

Regardless, added depth (be it wool or air gap) increases low frequency performance of a velocity based absorber:

Porous Absorber Calculator V1.59

[syncussion]

Originally Posted by Jens Eklund

Regardless, added depth (be it wool or air gap) increases low frequency performance of a velocity based absorber:

Porous Absorber Calculator V1.59

Hmm.. That means I am getting something very fundamental very wrong.
Can you please explain where my logic fails?

This is how I was thinking:
Sound, say the high pressure part of the wave, goes at 340 km/s against the wall, bounces off it and the frequency will determine how far away from the wall it will meet the low pressure part of this same wave that's still traveling in the direction of the wall. Where they meet the velocity is 0 as at that specific point away from the wall for that specific frequency the + and - will cancel each other out making the air not move at that specific point.
The above story means that velocity based traps will work against a wall without airgap for low frequencies, as for low frequencies the "allways 0 pressure" point would be farther away from the wall for lower frequencies.
Hmmm as I'm writing this, I think I found the flaw in my logic for myself already.. let me guess, 0 pressure difference point does not translate to 0 air velocity? Ah indeed probably not as air flows according to pressure difference. And of course air doesn't flow well from a wall Which is why we need an air gap roughly speaking..

Ok got it, thanks!
And very good to know.. I'll make them with air gaps now (would've just put it against the wall in certain places before!)

[Tom Higgins]

Yes, because you're making velocity-based absorbers.

Originally Posted by syncussion

I'll make them with air gaps now

[syncussion]

Originally Posted by Jens Eklund

Regardless, added depth (be it wool or air gap) increases low frequency performance of a velocity based absorber:

Porous Absorber Calculator V1.59

Thanks for the link of the porous absorber calculator.
However.. I'm guessing it shouldn't be trusted too much?
As I see a clear difference between outcomes of the calculator to specified (and measured) values for actual rockwool products.

Before, based on measured values, I was planning on using 60kg/m3 rockwool panels. (see attachment) in a thickness of 2 plates, so 18cm total, on all walls.
If I look at actual measured values for products of this density and thickness I see good performance in the lows.
But the calculator gives pretty poor performance in the lows. Airflow resistance is somewhere between 16k and 50k rayls/m. It says most lows will reflect back (as it doesn't matter whether I make it 18cm thick or 180cm).

Which one to trust?
I'm thinking actual measurements.
However, are those product measurements perhaps made with noise on one side of the obsorption material and the mic measurement on the other side??
If so, then the product measurements can't be trusted as they will include reflected sound!!
And I'm not looking for isolation here to the outside world. I'm looking for absorption inside my room.

[syncussion]

I don't get it..

Take this information:
Air flow resistivity, absorption and density for isolation products in Norway

sound absorption values:

Frequency ---------------------------------- : 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000
Rockwool ProRox WM100 - 100mm - (new 2012) - : 0.90 0.92 0.85 0.74 0.84 0.910 0.94 1.02 0.95 1.010 1.040 1.050 1.030 1.0700 1.100 1.0600 1.070 1.070
Rockwool ProRox air flow resistivity: Equal to, or more than 50 kPa*s/m2

Now if I put this info into the porous absorption calculator, then I get nowhere near these values!
I mean, 0.90 absorption at 100Hz is stated for the prorox wm100 100mm example above.
If I put this in the calculator then I get about 0.20 absorption at 100Hz, big air gap or no air gap doesn't matter much, and this doesn't get any better if I change the thickness to for instance 1000mm.

Can someone tell me which one to trust?
I get a delivery of 165 plates tomorrow, but now I'm thinking I may have to cancel this?

[gigi]

you can't compare measurements done in reverberation rooms with results from PAC (only normal incidence) = two very different things

[syncussion]

ok but then which one to trust?
Are the 60kg/m3 9cm thick (would double them up to 18cm thick) rockwool plates with air flow resistance of somewhere between 16k and 50k I'm about to buy, good at absorbing the bass in my room or not?
PAC says no, measurements say yes.
And I have no idea which one to belief and I don't have the money to try out and fail.
Surely many here must know as it has been done so many times in practice before right?

[Jens Eklund]

Originally Posted by gigi

you can't compare measurements done in reverberation rooms with results from PAC (only normal incidence) = two very different things

+1

In studio acoustics, it´s the specific incidence absorption performance that usually is the most interesting since we seldom have big enough rooms that can support a completely diffuse (and thus random incident) sound field, but rather are concerned with early reflections of specific incidence.


EDIT:

Also, for those that still doubt the models, please remember that the Delany & Bazley's model used in the PAC is an empirical model.


EDIT 2:

But please do also remember to use the models in the right context. If using a rigid, high-density wool board (high flow resistivity), it will function more as a membrane absorber than a porous (velocity based) absorber and if so, you’re using the wrong tool to predict performance.

[syncussion]

Originally Posted by Jens Eklund

+1

In studio acoustics, it´s the specific incidence absorption performance that usually is the most interesting since we seldom have big enough rooms that can support a completely diffuse (and thus random incident) sound field, but rather are concerned with early reflections of specific incidence.


EDIT:

Also, for those that still doubt the models, please remember that the Delany & Bazley's model used in the PAC is an empirical model.


EDIT 2:

But please do also remember to use the models in the right context. If using a rigid, high-density wool board (high flow resistivity), it will function more as a membrane absorber than a porous (velocity based) absorber and if so, you’re using the wrong tool to predict performance.

Ok, so even though the PAC is based on empirical measurements, it uses these measurements to ONLY calculate the velocity based absorption.
And this does not translate in to practice for anything other than low density wool?
While the rockwool I've ordered isn't very rigid (it's not hard, one can push it in with a finger), most of it's low frequency performance comes not from velocity based absorption but because the low frequency sounds push against the wool making it vibrate which it then damps internally?

So.. I can assume that the boards I ordered in practice do actually perform well in the low frequencies? Only there is no calculator available to easily show me how well it will perform.

My plan is (/was, still in doubt now) to treat my ceiling and walls + windows completely (full cover, no empty spaces) with this 18cm 60kg/m3 rockwool (air flow resistance of lets say 25k rayls/m).
I wish to achieve a very dry sound including bass. My room is large, 70m2 with 4m high ceiling. I'm separating part of this space with a rockwool division so my actual workspace is smaller (about 30m2).
My walls and ceiling are all dry wall with 10cm of rockwool behind this, and one wall is completely double glazed windows (which would be covered as well by the rockwool).

Do I have a good chance that this will work? Or does this raise a red flag with anyone?

Many thanks for any additional insights!

[DanDan]

sync, acoustics when applied to the real world is complex.

A mode is only a single reflection reiterated.

So a gap should place the fibre in a region of higher particle velocity.

If the surface area of your trap is small compared to the boundary then other losses start to kick in. The Bass Wave just passes by the relatively tiny trap.
In that case, might be better back at the wall, who knows.

Yes, Max Pressure, Zero velocity at the boundary.

Here's another calculator which includes Random Incidence.
Porous Absorber Calculator

Do remember that fibre traps behave in a very amplified manner in corners.

DD

[syncussion]

Hi DanDan,

Thanks for your reply and the calculator link!
I like the Komatsu model's results better already
(and it says that the Delany & Bazley model is not accurate below 200hz)

Still it does not agree with measured results?
A 100mm thick 50,000+ Pa.s/m2 gives less than 0.7 absorption at 100hz in best case scenario, yet measured result states 0.9
But it comes much closer already I'm happy to see.
Also what I'm seeing in measured results is that dense rockwool seems to outperform glasswool and the calculator? Could this be true in reality?

Well in any case I'm rethinking my order.. will probably cancel it.
Playing around with the calculator makes me see that I'd be better off going for less dense rockwool or glasswool and make it thicker.

Thanks again for the help!
I'll go plan things better now.

[DanDan]

For some reason that I temporarily forget I use Miki. Empirical again I think.
The angle of incidence depends on the mode or single reflection path and locations. e.g. A corner panel is at 45 degrees to incoming axials.
Try that in the Calculator. Try different GFR figures, thicknesses and airgaps.
I like to try 75 degrees and such to get an 'optimistic' perspective now and again.
Common Gas Flow Resistivity numbers.

Be aware though that corners change everything. Much like placing a speaker in a corner there is a serious multiplication of LF absorption there.

DD

[syncussion]

Thanks again!

The Miki model makes it even more clear that 25k GFR isn't very good. 8k GFR does much better.
Just canceled my order.

The link you sent is great as well!
I'm going to find me some good stuff now..
I'm going to aim for the deadest room around haha

[syncussion]

Ah something keeps bothering me.

Taken from this post:
Air flow resistivity, absorption coefficients for isolation products in Germany

"
Rockwool ProRox
Air Flow Resistivity: Equal to, or more than 50 kPa*s/m2
(I got this number from Rockwool tech support.)

Frequency ---------------------------------- : 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000
Rockwool ProRox WM70 - 50mm ------------------ : 0.17 0.29 0.46 0.57 0.80 0.890 1.01 1.10 1.08 1.060 1.090 1.050 1.060 1.0900 1.070 1.0500 1.080 1.050
Rockwool ProRox WM80 - 50mm ------------------ : 0.16 0.38 0.59 0.66 0.85 0.890 1.04 1.05 1.00 1.040 1.070 1.010 1.030 1.0600 1.060 1.0700 1.050 1.040
Rockwool ProRox WM100 - 50mm ----------------- : 0.16 0.37 0.60 0.64 0.86 0.910 1.01 1.07 1.03 1.020 1.050 1.000 1.010 1.0800 1.070 1.0900 1.070 1.050
Rockwool ProRox WM70 - 100mm ----------------- : 0.70 0.94 0.96 0.81 0.94 0.980 1.02 1.07 1.01 1.000 1.020 1.050 1.050 1.0800 1.070 1.0900 1.070 1.060
Rockwool ProRox WM80 - 100mm ----------------- : 0.77 0.90 0.88 0.77 0.89 0.920 0.95 1.00 0.97 1.000 1.050 1.030 1.050 1.0600 1.070 1.0500 1.040 1.050
Rockwool ProRox WM100 - 100mm ---------------- : 0.90 0.92 0.85 0.74 0.84 0.910 0.94 1.02 0.95 1.010 1.040 1.050 1.030 1.0700 1.100 1.0600 1.070 1.070
"

Here is the measurement report:
http://www.gearslutz.com/board/attac...absorption.pdf

This measurement report looks very reliable.
It describes well how the measurements were made (including pictures), and I can't find a fault in it.
And it is extremely similar to how I plan to apply the absorption in my studio (fill whole walls with it)

I lean towards trusting such a report more than I trust the calculators.
And the 2 are certainly not in agreement.
The calculators give low absorption values for in the low frequencies for this setup, much lower than the actual measurements.

What to do here?
Can someone tell me why I should trust the calculators over such a reliable and clear measurement report?
Because this report makes me think: simply get the prorox wm100 10cm thick, don't even worry about an air-gap, and be done with it.

[localhost127]

Originally Posted by syncussion

Here is the measurement report:
http://www.gearslutz.com/board/attac...absorption.pdf

This measurement report looks very reliable.
It describes well how the measurements were made (including pictures), and I can't find a fault in it.

Air gap behind absorption only needed for modal resonances?

[Jens Eklund]

Before bashing models of porous absorbers:
Q 4 Avare

As long as one compares apples to apples, simulations (at least empirical …) will line up with real data from measurements. If you compare apples and oranges (impedance tube data and reverberation chamber data) it won´t, but it won´t in real life either so what’s the point in comparing apples and oranges?

[syncussion]

Originally Posted by syncussion

I lean towards trusting such a report more than I trust the calculators.
And the 2 are certainly not in agreement.
The calculators give low absorption values for in the low frequencies for this setup, much lower than the actual measurements.

Well, actually.. I take that back.
The Komatsu model does mimic the measurements pretty good!
If I select 80000 Pa.s/m2 or so (which seems likely for the WM100).
And I see the absorption coefficients in the report are not the same as those in the calculator, in the report they can go above 1.0. So we have to take the absorption coefficients in the report a bit lower to make 1.0 correspond to 100% absorption. Once this is done Komatsu agrees with the measurements.
That's good news

[syncussion]

As for apples and oranges. I don't see why they would say 2 different things. (and apparently they don't if you take the Komatsu model)
I'm interested in finding out how to make an as dry a room including bass as financially reasonably possible.
I'm simply trying to do this without making a mistake, like buying a lot of rockwool and then after listening and measuring finding out I did it all wrong and have to do it again.
But now I see calculator and measurement line up well enough to trust, so I have trust now I can do it right the first time
(edit: with air-gap )

one more edit:
What I also meant, is that if you take the calculator you can simulate closely the same situation as the measurements done in the report.
No air gap, random incidence. That's how the report measurement was done basically. an somewhat large empty concrete room with most of the floor surface covered with the absorption material, then speakers making sound in the room and mic measuring the difference in reverberation between empty room and one with absorption.
The only model which agrees with the measurements here is the Komatsu (2008) model.

[Jens Eklund]

Originally Posted by syncussion

As for apples and oranges. I don't see why they would say 2 different things.

Impedance tube measurements and reverberation chamber tests will show very different results, especially in the lows, close to the limit frequency range of accuracy of the reverberation chamber. Some results from reverberation chambers (if used slightly inappropriate) results in absorption coefficients of 3.0 ... ! This is naturally a result that reviles the inaccuracies of the test method at lower frequencies. Impedance tube measurements are more precise, especially (naturally) for normal incidence since they only measure that (and reverberation chambers don´t).

[syncussion]

Hmm ok..
Giving it some more thought I see now why a model like Mika is perhaps more accurate in describing absorption in a room where all walls are treated and not just one.
And surely DanDan knows these matters way better than I can grasp them so I should trust him on this

But this is what I was thinking: in the measurement room of the report we have many modal resonances making the reverb, and only one surface absorbing. Many of the modes don't have a direct reflection to that absorbing surface. But this is only for the higher frequencies which are very directional, when a bass reflects it reflects spherical, so if the absorption causes one wall (the floor in this case) to have less sound then the other modes will "bleed" to this absorptive wall, moreso for lower frequencies. This is why you'd see relatively more lows absorbed in this scenario. But if in a studio all walls are covered there is perhaps no such "bleeding" and the results would become perhaps like Miki model? Does that make sense?

[syncussion]

Originally Posted by Jens Eklund

Impedance tube measurements and reverberation chamber tests will show very different results, especially in the lows, close to the limit frequency range of accuracy of the reverberation chamber. Some results from reverberation chambers (if used slightly inappropriate) results in absorption coefficients of 3.0 ... ! This is naturally a result that reviles the inaccuracies of the test method at lower frequencies. Impedance tube measurements are more precise, especially (naturally) for normal incidence since they only measure that (and reverberation chambers don´t).

Ok thank you!
So Miki model it is
Which I don't like as it means lots of hard work to get the bass absorbed, but so be it.

[DanDan]

sync, the reverb room tests specifically keep the absorption away from as many bouncaries/ corners as possible. If you are targeting bass, you will be doing the opposite. The larger SuperChunks are quite effective, the smaller ones not so much. Full deep back wall treatments are extremely effective, if deep enough. However, if targeting bass I really think it would be remiss not to consider VPR's carefully. Given the repeated spectacular results we are seeing.

Taking a step or two back, have you analysed this room?
Measurements?
Dimensions?
Materials forming the boundaries, e.g. concrete, sheetrock on studs,....?
DD

[localhost127]

Originally Posted by syncussion

Hmm ok..
Giving it some more thought I see now why a model like Mika is perhaps more accurate in describing absorption in a room where all walls are treated and not just one.
And surely DanDan knows these matters way better than I can grasp them so I should trust him on this

But this is what I was thinking: in the measurement room of the report we have many modal resonances making the reverb, and only one surface absorbing. Many of the modes don't have a direct reflection to that absorbing surface. But this is only for the higher frequencies which are very directional, when a bass reflects it reflects spherical, so if the absorption causes one wall (the floor in this case) to have less sound then the other modes will "bleed" to this absorptive wall, moreso for lower frequencies. This is why you'd see relatively more lows absorbed in this scenario. But if in a studio all walls are covered there is perhaps no such "bleeding" and the results would become perhaps like Miki model? Does that make sense?

pay close attention to the type of source (speaker) used in the pdf document (reverberation chamber method) you linked to -

[syncussion]

Originally Posted by DanDan

sync, the reverb room tests specifically keep the absorption away from as many bouncaries/ corners as possible. If you are targeting bass, you will be doing the opposite. The larger SuperChunks are quite effective, the smaller ones not so much. Full deep back wall treatments are extremely effective, if deep enough. However, if targeting bass I really think it would be remiss not to consider VPR's carefully. Given the repeated spectacular results we are seeing.

Taking a step or two back, have you analysed this room?
Measurements?
Dimensions?
Materials forming the boundaries, e.g. concrete, sheetrock on studs,....?
DD

Hi DanDan,

What's a VPR?

I've attached a drawing of my room with the rough dimensions and materials.
(didn't draw it in but also plan to fully fill the ceiling with absorption where the studio is.
Btw the room is completely open, one space, so 2 absorption "walls" are only absorption nothing reflective.

I have not measured the room yet, will order the behringer mic later tonight.
The room is very reverberant now, almost no treatment, and is bass light. No obvious modes and only mild bass buildup close to walls and floor (due to size and materials I assume)

edit: Btw, I also plan on isolating the speakers from the stands and stands from the floor (best as I can), and put absorption on the floor close to the speaker. And try to fully absorb the reflection of speaker - floor - me, as I've found the O300 give a terrible dip in the mids in the reflection of the floor but become truly flat in the mids and the best speaker I've ever heard when I absorb this floor reflection. (almost sold the o300 before I found this out, and reading these forums I see more people have this problem. See the vertical radiation plot of the speaker on the K+H site to see what's the problem when you don't absorb this reflection)

[DanDan]

The VPR is an enhanced LF absorbing trap. Very easy to DIY and extremely effective.
My Experiment with a Metal Panel Absorber
I note your room is Bass light. I was anticipating something like that.
Probably a lot of light panelling/sheetrock.
This suggests that much less and cheaper HF treatment where needed may be the way to go.
But let's see those measurements. Best to Zip the .mdat REW file so we can play with it.
Do at least L, R, and L+R sweeps.

DD

[syncussion]

Originally Posted by DanDan

The VPR is an enhanced LF absorbing trap. Very easy to DIY and extremely effective.
My Experiment with a Metal Panel Absorber
I note your room is Bass light. I was anticipating something like that.
Probably a lot of light panelling/sheetrock.
This suggests that much less and cheaper HF treatment where needed may be the way to go.
But let's see those measurements. Best to Zip the .mdat REW file so we can play with it.
Do at least L, R, and L+R sweeps.

DD

I've just ordered the measurement mic.
Will post the measurements here within a week including zipped .mdat REW file. (found the thread on how to post measurements already)

Interesting that less and cheaper HF treatment may be an option, and thanks for the suggestion!
But right now I am still leaning towards very dry / near anechoic for sound reasons.
Up till now I've always found less reflections and reverb to be what I prefer.
I wish to truly look into the audio like with headphones.

Why not use headphones some may think But I don't like headphones!
They never truly convince me, I hear too many faults with their frequency response, dynamics, etc. And bass is too different in headphones, I need bass to be real. Also there something unnatural about closing in my ears and the driver so close, you're not getting "head related transfer function" (if I spelled that correctly) and sound gets beamed too directly into the ear canal. I've had good headphones, like Sennheiser HD800, and many others, Also AKG K1000 which were the best of the headphones in some ways but still nowhere near what my O300 speakers can do.

Now I've heard some great listening rooms (but no truly pro studio control rooms though). And those listening rooms were all somewhat live and some did fantastic things to the sound, but it's not what I'm looking for.
I want "headphone" with speakers. If a sound is completely dry, like a synthetic hi-hat for instance, I want to hear it completely dry and tight.
If I'm trying to create an artificial space in my mix I want to be transported into that space, not a combination of that space and the room I'm in.
If I'm not wrong, only a very dry space can give me this. Not the more standard studio design where only the first reflections are absorbed / deflected and a diffuse room sound comes later.
Having said that.. I've never actually heard such a dry room.
Maybe I'll regret it later, but I want to try it out anyhow

I actually moved to this apartment specifically to make such a room. I figured I have enough space, high ceiling, many windows letting out deep bass, no parallel brick walls close together to give strong modes (only perhaps floor/ceiling a little), etc. Seemed doable / treatable to me on instinct and what I had read about acoustics up till then.
And I also think that by covering whole walls + ceiling with absorption will actually save some costs. I found from experience that more than half the money for building normal traps goes to materials (wood, fabric) other than rockwool/glasswool. The way I would do it would be cheap with fabric only on one side and no wood only wires from ceiling to floor (or ceiling beam to wall for ceiling absorption), and perhaps some "wire maze", all very cheap. I figured I can do it for between €1000 and €1500 total where by far the majority goes to the actual absorption material.

As for the VPR, I read about it (but didn't pick up on the abbreviation) and it looks amazing indeed!
Should after normal treatment my room have problems in the bass I'll surely look into it!

[syncussion]

Received the measurement mic and my new absorption (huge amount of fluffy fiberglass)..
Started a new thread to continue the part about treating my room, as it's no longer about about the original topic in any way.
Treating my room log

[DanDan]

Big Headphones indeed. The 0300 should work well for you. I auditioned them here amongst others. Ultimately all the monitors sounded the same and I learned how important the room was.
When your room is treated and 'dry' I recommend you experiment with HF roll off. Many of us find flat response in a dry room way way too harsh and bright.
More importantly it leads to dull mixes.
The curve (or it's cousins) has worked well for many for decades
http://www.bksv.com/doc/17-197.pdf
Same at Understanding RTA at studiotips.com

DD

[syncussion]

Hi DanDan,

Thanks for your advice!
I've come across this paper before (from other posts you've made here), and have taken it into consideration.

However, right now I'm finding much reason behind a totally dry room, and I'm not afraid of a bright sound (I'm willing to adapt).

Up until now I've found a bright sound not acceptable due to 3 main reasons.
First reason was speakers, I've found older speakers with metal dome tweeters to have something wrong in the treble, some harshness which requires the room to correct it to my ears. Speakers with soft dome tweeters I found lacking in treble up till now btw, the opposite of metal dome tweeters. I know this is very much a generalization that doesn't hold for all speakers. But in any case, I found in the O300 a tweeter that satisfies me and I can stand its pure sound under dry conditions I estimate. (infact I'm hoping it will become slightly brighter in the high treble under dry conditions, it will be perfect then)

Second reason is speaker boundary interferences in the bass.
I can't stand when the fundamentals of sounds get eaten away by destructive interference which you get when you place speakers roughly more than 80cm away from the back wall, or by placing speakers high from the floor (as in above 120cm for the bass driver or something like that). To counteract the nasty dips in the bass this causes one would need a very warm room or speaker to not get a harsh sound.
(edit: the 120cm+ for near field listening, it depends as much on listening distance as well where the first interference dip occurs of course)

Third reason is reflections and reverb.
I find early reflections can alter / tilt timbre to become harsher. And reverb alters the balance between energy of transients and energy of sustained sounds, giving the transients much more energy than is actually on the recordings, this can easy give high mid harshness etc I find. I also prevents many high frequency info to be resolved as info I find and it can become a bit of a mid/high frequency "wash" which can be harsh too.

So I'm thinking that a dry room properly done will avoid all these problems (I will even absorb the first floor reflections and floor area around the speakers with 50cm thick fibreglass).
And will allow high frequency info to be fully resolved which will give a transparent view into the recording. I love bright when it resolves and sounds good. I'm not getting that enough right now, right now it's slightly too bright perhaps sometimes in an unresolved way, I'm hoping to get brighter in a resolved way. That would surely sound amazing and I'd love to work that way.
I want a sound that can truly hit hard in an extremely dynamic way also in the mids and highs. I want amazing "snap" that can take your head off etc
I think this is the only way I can realize this.

Btw, non environment rooms, and FTB rooms are all basically dry and flat rooms right?
At least from the point of the speakers, only with extra reflections from the point of the listening postition/user to make the human feel more like he's in a normal room.
Those rooms seems to be well loved, and users describe the most wonderful audio qualities.

I don't think I will be able to get a truly dry room into the deep bass, even with 50cm+ of fluffy fiberglass on all walls, ceiling and part of the floor. Maybe I'll still have +3 at 50hz, but if the calculators and my guesses of my room are somewhat correct I'll be able to get it with virtually no dips and peaks other than the +something at 50hz and below or so, which I could correct with minor eq on monitor out.
And I'm not having any compromises in audio like many non environment etc rooms, like floor reflections or some minor other reflections (even though diffuse) to make me more at easy in the room. Maybe I'll be uncomfortable but I think (hope) I'll be able to have world class sound

Ohyeah btw, one more reason for harsh sound can be the DAC.
I found a good DAC now, the Violectric V800. So no harshness from source side either.