EXPERIMENTS! EEEERIIIIK, PLeaz DEESAAAART, pag 7 and 8

[timogiodeson]

A closer look of the measurements all together, up to about 1K
P.S. All these new measurements begin on page 7 , post #8 counting down from the top of the page) info's etc...

[timogiodeson]

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[timogiodeson]

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[timogiodeson]

Timo,
Stupid question.
Since you did the calibration, which is good:
Can you add a measurement of your empty room?

Not problem Eric,
All the new measurements including the empty room start from page 7 , (post #8 counting down from the top of the page)with all the info etc...

Due to the small differences I have the feeling that you have more or less absorption already (which could be very possible with your construction).

It calls for time but it should be possible to reverse calculate the absorption you have in your room.

How? I guess this is important...
Eric, your feelings are very important! !
Every time I listen to the empty room, I don't now why... I like it!
It is just a little too bright and comb, but the bass it's not too heavy, and overall sound like if It breathes again...

It feel heavier when I introduce absorption ..

I'm worry that at the end , if we over absorb some important frequencies...the aluminum or plastic foil in front of the panels will not bring back enough life for the acoustic instruments...
What about if is not only the very high frequencies?... Maybe too much mid or mid low absorption or peaky absorption combined with the room absorption can sound bad too you know...

Your feelings....
The way I built the room...
I only glue up with liquid nail the last two layers toward the room, ! And in some areas I did a bad job, there is some airspace between the layers, in this areas the wall sound almost like a drum if I play on it...
maybe the all things act like a giant membrane panel trap of some weird kind...?

(Also last month I built some kind of panel trap directly on the door , it's made with 1/4" plywood spaced with 1x2 furring strips just 1" from the door , I filled up the 1" airspace with 1/2" ceiling tiles screwed to the door to avoid contact with the 1/4" plywood and then I sealed all.)

One of the main thing we experienced by comparing Chunks and panels in the corner is the explicit peak at around 100 Hz for the panel.

I noticed this peak behavior too, kind of unpredictable with 8 pounds.. it's interesting to see for example that the small Lenrds do not peak at 100hz...
They absorb uniformly just very little of the low end without peaks or shifts..
Instead the larger panels have this peak behavior,
I noticed also in my experiments that a large 4x8 panels across the corner peak at about 40hz instead 100hz..

Do you think this peak behavior on the corners is a positive things?
It's not better to absorb uniformly with flat absorption on the walls?

Looks like corner absorption shift peaks and nulls to different frequencies too.. see for example the 8 pounds with Lenrds behind where a new big null at 75Hz appear just by adding Lenrds behind the 8 pounds!

I'll wait for the reverse calculation things before proceeding...
I don't know how to do that....

[BIG8]

Do you think this peak behavior on the corners is a positive things?
It's not better to absorb uniformly with flat absorption on the walls?

Timo,

I think that you are confusing the notion of Peak absorption behaviour of some treatment objects with Peaks and Nulls response of a room.

If not, do tell what you mean, because it feels like you are stumbling over something else.


Cheers,
Jean

[timogiodeson]

OK Jean, look on top of this page, the measurement 20hz to 140hz for example...or below.
look what happens to 78hz just by adding Lenrds behind the 8 pound panels... that's is the cyan color line...
the null at 108 Hz disappeared but there is a new one and wider at 78hz
combine that with the 45hz null ..and all the rest of similar things happening to the rest of frequencies and then .. who know what your ears will tell you at the end? Very unpredictable...
Also go back to page 4 where I measured all the corner absorption behind the drums..
The only measurement that shows considerable improvements in the 40hz is the ones of the 4x8x4" large panel floor to ceiling...but as you see a new deeper null appear at 98hz.... etc etc..


*grey line, empty room (not really empty but without acoustic treatment )

*olive line, 16 Lenrds, 4 in each vertical corner floor to ceiling

*violet line, 8 pound 4" mineral wool floor to ceiling in all 4 vertical corners

* cyan line, combination 8 pounds with Lenrds behind, floor to ceiling in all 4 vertical corner
* blue line, 8 pound 4" floor to ceiling in all 4 vertical corners plus 16 Lenrds in the horizontal ceiling wall corners

[BIG8]

OK Timo,



'Treatment' objects like tuned Helmolz resonators and panel traps are said to 'peak' because they have a narrow bandwidth of efficiency, meaning the frequency range at which their 'treatment' efficiency is the highest is very narrow. eg: they can be tuned to something like 100Hz and they will have high efficiency at dealing with 100Hz. That efficiency will drop dramatically as soon as you move away from 100Hz.
The 'peak' in this case refers to their efficiency per frequency behaviour, not at the room response.

Broad band treatment objects or absorbers, like the stuff you are experimenting with, will have a much wider bandwidth of treatment efficiency, meaning they will be efficient over a wider frequency range.
They may not be as efficient as narrow band objects at dealing with specific trouble frequencies.


Both these types of treatment objects will not themselves cause your room to peak or dip.

What may happen, though, is that you have a series of modes very close to each other frequency wise, and the effect of each cancel out to appear normal, as if there were no peaks or nulls. Due to some treatment which you add, you end up dealing with one of the modes, removing its cancelling effect on the other modes near to it, causing the other modes' influence on your room's frequency response to appear (peaks or nulls).

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It is becoming difficult to follow the results of each tests you make.

May I suggest that you use a vertical axis with unit separation of 3-5dB, and the whole 20-20,000Hz range for the horizontal axis, and/or just the 20-400Hz range to focus on the low frequencies, there is no benefit in showing the fine details of each segments from 400 to 20,000Hz
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the total surface areas of your room (floor + walls + ceiling) is 1008 sq.ft (from what I got from your drawing). I understood Eric suggested that you went for 30-35% treatment coverage of that with broadband + other details, to reduce the SPL.

How are you planning to proceed with that?


Cheers,
Jean

[timogiodeson]

OK Timo....
What may happen, though, is that you have a series of modes very close to each other frequency wise, and the effect of each cancel out to appear normal, as if there were no peaks or nulls. Due to some treatment which you add, you end up dealing with one of the modes, removing its cancelling effect on the other modes near to it, causing the other modes' influence on your room's frequency response to appear (peaks or nulls).

Cheers,
Jean

Thanks Jean,
It's not better to leave them cancel out and appear Normal and forget about them?
hey...maybe I'm just lucky... that's explain why I like the the empty room...why not?

How are you planning to proceed with that?

Yes I'm ready to proceed with 30 35% broadband, painting the ceiling as suggested etc... between foam and mineral wool I have enough material already for the experiment....But I guess I know already how it will sound ..I had the material inside the room many times...the only difference will be painting the ceiling tile...and a small broadband cloud over the drums....
I 'm waiting for Eric, the inverse calculation things... I guess he was feeling something!!!.. probably very important.

Due to the small differences I have the feeling that you have more or less absorption already (which could be very possible with your construction).
It calls for time but it should be possible to reverse calculate the absorption you have in your room.

Also Arthur said

The problem with EQing the sound you are making is that you tend to want to correct for the deficiencies in what you are hearing. So if you use foam to EQ sound above 1k, then your drum kit will feel too heavy in the mids and bass and you will lighten up on the power you are delivering to the bass and toms.
It’s just like recording engineers. If they work in a room that is bass light (as in acoustic tile ceiling) then they will bring more bass into the mix and end up with a bass heavy record.
Arthur Noxon
Acoustical Engineer
http://www.tubetrap.com

Not matter what it is..mode that cancel out and appear normal, absorption built in in my construction, or the acoustic tile ceiling, what I ear it's more important than anything else.....
When I seat at the drums or piano and I play I right away know something wrong or better or worst ... it's just difficult to explain...
At the end some how the empty room with only acoustic tile ceiling doesn't sound too bad compared to what I experimented until now... . ...

P.S. All the measurements (page 7 -from post N.8 until here) are just different views of the same initial 5 measurements , EMPTY ROOM DETAILS are in page 7

MY LAST IMPORTANT QUESTION
What I need to understand is:

Please take a look of the measurements below..
In my empty room without acoustic treatment the difference in the range of level between the two extreme (43hz/68db and 520hz/84db) it is 16db's in one third octave smoothing , and about 27db's in regular view
I don't have any reference this is the only room I ever measured,
so I don't know, but I guess the measurements doesn't look really bad in the low end.. axially looks worst from 300hz and up i guess..
What do you think?
The measurement of a room with the same dimension but built regularly and without acoustic tiles and also without the cabinets, drums and grand piano inside... will look the same as far of bass frequencies?
Acoustic treatment in this room don't make a huge difference I guess, especially in one third octave smoothing..
Can be that axially this room it's OK already (has already enough absorption built in) and I just need to avoid some bright cymbals and snare rim shots reflections from the adjacent walls and floor??

[timogiodeson]

With acoustic treatment in all 4 corners floor to ceiling

[timogiodeson]

Eric , where are you

[Soundman2020]

I only just noticed this thread while I was looking for something else. Astounding what happened here. So much intention, persistence, and effort, yet so much misunderstanding, disorganization and confusion. In all of the hundreds of posted graphs, there is not one single graph of what really matters: time-domain response. They are all just frequency response, with a few scattered RT-60 graphs, which are basically meaningless for a small room anyway. Not one single decay graph. Not a single waterfall plot. No spectrogram. And no real systematic plan for determining what the room is doing all by itself, and what each type of treatment is doing. So much effort, basically wasted. It seems like the basic goals were set arbitrarily and unrealistically, without ever understanding the realities of acoustics in small rooms. It seems this was a search for a magical material that would warp time and space in order to achieve the impossible. And therefore, sadly, it failed. If the goals would have been more realistic, and the implementation more systematic, and the advice of all the acoustic experts who weighed in on the thread with real, solid, sound advice had been headed, then the room could have actually ended up quite decent. The entire thread reminds me so much of a small dog chasing his own tail, round and round round in the same circle, not realizing that he can never get there, simply because the goal is impossible.

Sad.


- Stuart -

[dufo]

This thread is totally bizaar! It should be stickied for an first rate example of exactly what NOT to do. I wonder if the OP is still around and how his room ended up in the end.

I still cant figure out with all the advice here, AND two fo the most important books in his possesion ( Build it like the Pro's, and I think the Master handbook of acoustics), he still persisted down the dead end of RT60 rubbish and no time domain testing as Stuart mentioned.

Never seen a more chaotic and disorgansied attempt at doing a room.

[tingliu]

Both these types of treatment objects will not themselves cause your room to peak or dip.


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