Tiny All-In-One room

#16

Minor Sunday update: finished the absorptive door with 20cm of Knauf Ultracoustic insulation (≥5000 kPa.s/m²) and now (keeping in mind that the door does not isolate perfectly) the back wall is considered as an acoustic "black hole" .

mdat:
https://mega.nz/file/Rk1UXJqT#9vP9Q4Vwy ... mQIZ0utRSY

Screenshots:
As expected there are only minor changes, mostly visible in the reflections diagram (ir).

: Hangers+door Waterfall

: Hangers+door Spectrogram

: Hangers+door RT

: Hangers+door IR

: Hangers+door FR

Here is the comparison between the previous situation (hangers only) and the added door insulation. Some strange behaviour in the mids I believe is from the various stuff that is still in the room and should be ignored:

: Hangers vs hangers+door RT comparison

: Hangers vs hangers+door IR comparison

Not big differences but certainly listenable. Music is more "focused" and clean now, details have appeared even in very low volumes, and high volumes are now tolerable..

And now two questions:
1) Planning the final layout many different configurations have passed though my sketchup and I ended up that the safest one for my limited space is with absorbent reflection points (30cm insulation) and full absorbent ceiling (30cm insulation), see previous post. I keep reading that insulation alone will not suppress the early reflections enough end the proper way is to redirect them, something that I am unsure if I can accomplish in this room. Will I gain anything noticeable if I embed hard reflective surfaces inside the insulation on the reflection points?

2) Seeking a way to tame the 42hz standing wave I am planning on using slot resonators in the above and below soffit sections. An also ideal place for a low tuned resonator seems to be the outer part of the soffit:

will the resonator be effective being so close to the side wall insulation? How big the gap has to be? Are there other options?

Thanks,
Dio

#17

Time has passed and things have moved forward a bit. The man with the drill came and made three really beautifull holes on the wall, where the hvac ducts, cabling etc passed through.

: The carrot man

: Nice!..

Then, I made the "on-wall" silencer and connected the fan. Being aware of the Murphy's laws I made the silencer internals visitable. Playing loud music (~95dbC) inside the room corresponds to about 56-57dbC at 1m from the silencer. I wouldn't call it bad performance for a start.

: Silencer gut view

: Anti-Murphy device

After done with that it was time to begin the soffit construction. Being tight in space and incorporating bass traps the soffits have a little strange shape but being bolted on the stonewall are rigid enough

: Tight space??

And finally time to fit the speakers in! It is allready a really tight fit, but I am thinking of additionally screwing them in the frame to turn it into one mass. Testing with loud tones didn't reveal any rattling or resonances from the (still unfinished) construction, which is good, of course.

: Test fit became permanent

Coming up next: side soffit slot aborbers!

: Waiting..

Thanks for viewing,
Dio

#18

It's Sunday and it's time for another update! The part the fun begins! Having finished the soffit frame and put the speakers in,I removed the office desk and took a measurement:

: Soffit frame - no desk

: Soffit frame - no desk RT60

: Soffit frame - no desk Spectrogram

: Soffit frame - no desk Waterfall

: Soffit frame - no desk FR

Mdat: https://mega.nz/file/I4tgSDLB#aiWCNF-eg ... wikcX7_efs

It seems that this office desk was a big problem for this small room, good I got rid of it... but what are these peaks? Something resonating? Been in a hurry to continue working I decided to investigate later. So I proceeded with stuffing the soffits and took another measurement.

: Soffits stuffed

: Soffits stuffed RT60

: Soffits stuffed Spectrogram

: Soffits stuffed Waterfall

: Soffits stuffed FR

Mdat: https://mega.nz/file/cp0wFbhK#ruX93jDiw ... NVHtJ_nCPE

Now things are slowly becoming nicer, but these 100 and 200hz things still exist... let's move on and build the side slot resonators and we will find out later.

: Soffit Side slot resonators

: Soffit Side slot resonators RT60

: Soffit Side slot resonators Spectrogram

: Soffit Side slot resonators Waterfall

: Soffit Side slot resonators FR

Mdat: https://mega.nz/file/okkwyZbI#X9H2R8rOT ... 9Bb-TPlpmE

Now, these resonators are tuned to 80-110hz, so they are doing their job on damping that 97hz resonance but that 200+ thing is still standing there proud... so with the old and tried method of playing the resonating tone and with the help of our friend "the mute button" the culprit revealed: it is the heater radiator! To verify I took another measurement. The results on the following post.

Dio

#19

So, the next two screenshots are with me in the room holding (and damping) that radiator, the images are self-explanatory, the 200hz resonance is gone!

: Side soffit slot resonators, me damping radiator RT60

: Side soffit slot resonators, me damping radiator Spectrogram

After finished with this it's time for the lower soffit slot resonators, the ones I had big expectations with.

: Lower soffit slot resonators

: Lower soffit slot resonators RT60

: Lower soffit slot resonators Spectrogram

: Lower soffit slot resonators Waterfall

: Lower soffit slot resonators FR

: Lower soffit slot resonators calculation

Mdat: https://mega.nz/file/BgdyUBDI#cCm2pWXh4 ... qTw6bTP8sM

To be honest in the beginning I was expecting a little more from them in the 42hz issue since the calculator gives o 0,7 coefficient in this region. Then I realised that only two out of ten slots have the cavity depth to absorb this frequency so I sat back and admired the rest of the performance.
First and most impressive is the total disappearance of the 200hz radiator resonance!! Unbelievable. Then the rest of the spectrum <300hz has also been tamed very well at around 200ms, not bad. That bump in the 600-900 hz in the RT I don't know where it came from, could be something from the stuff the still exist in the room.
Anyway, now it's time to finish the soffits with a 30mm thick MDF baffle.

: Speakers Baffle

: Speakers Baffle RT60

: Speakers Baffle Spectrogram

: Speakers Baffle Waterfall

: Speakers Baffle FR

Mdat: https://mega.nz/file/0kNCSDDb#NA9u9S4yL ... fsWQDJFafI

We see the lows have gained a few decibels from the baffle, we also see that the 42hz mode has shifted to 43hz since the room is now a little smaller. The rt60 is a little smoother also, but the cancelations in the 100-130hz region have been increased.
Next move is to built the upper soffit slot resonators, and I haven't yet decide if I should make a copy of the lower ones or if I should try to tune them as low in frequency as I can to hunt the lowest mode. What would you do?
The nicer of all is that the listening experience in the room has dramatically changed. Every tiny detail is revealed and the technical aspects in recordings are easily observed.I defenetely feel that I am moving to the right direction,

Thanks, Dio

#20

This is superb, and excellent progress in a small room.

The way you have presented the results is incredibly useful, thank you.

I'm contemplating acoustic hangers for the rear of my room, it was nice to see the difference they make in the very low frequencies. Do you know of any comparisons between acoustic hangers and only absorption in the same space?

Cheers!
Jennifer

#21

Great work! Really good outcome so far too.

Could you please share a link to the slot resonator calculator you’ve used? I suspect I might find it handy.

Thanks
Gareth

#22

Jennifer, Gareth than you for your kind words!
As far as I know there are not direct comparisons between hangers and plain absorption, at least not published. It’s really hard to know their true performances in every space with all these variables (room materials, insulation gfr’s, hangers construction). I chose hangers because I have faith in the designers (Hidley, Sayers, Newell, Stuart etc) work and of course because I like the challenge of building something more “exotic”, if you like...
The calculator I used for the slot resonators is this:
http://www.acousticmodelling.com/multi.php

Thanks!
Dio

#23

Thank you Dio. I have no doubt they work, just trying to figure out if they'll work in my place

I found this document that measures some aspects of them, attached to this post.

Cheers,
Jennifer

#24

This is the only known (to me at least..) study about the "why and how" of the hangers and it explains a lot. In practice see this built:
http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21927
This room has almost identical dimensions to mine, but if you look at it's baseline measurement it is clear that its character is directly opposite. While mine has strong modes reaching 1,3 secs RT and a mild behaviour in the upper range ( 500ms), this has just above 500ms in the lows but as high as 1,5 sec in the midrange! But in both cases hangers worked fine and did their duty. Could just plain insulation had the same result? Who knows...
There IS a build with insulation only back wall :
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=15
but it is already a little treated when the insulation is placed, so you cannot really tell..

Dio

#25

Excellent links there, thank you

Cheers,
Jennifer

#26

Hi Dio,

Congratulations! It's going very well!

I'm not being able to download your .mdats from MEGA links. It asks for some kind of key. How could I do?

Cheers,

Eric

#27

Thanks Eric,
It seems there was some malfunction when I pasted the links from Mega and I didn't noticed it at the moment.. Unfortunately I cannot edit the post, So I repost the mdats here:

Soffitframe:
https://mega.nz/file/I4tgSDLB#aiWCNF-eg ... wikcX7_efs

Soffit Stuffed:
https://mega.nz/file/cp0wFbhK#ruX93jDiw ... NVHtJ_nCPE

Soffit Side slots:
https://mega.nz/file/okkwyZbI#X9H2R8rOT ... 9Bb-TPlpmE

Soffit low slots:
https://mega.nz/file/BgdyUBDI#cCm2pWXh4 ... qTw6bTP8sM

Speaker Baffle:
https://mega.nz/file/0kNCSDDb#NA9u9S4yL ... fsWQDJFafI

Now they should be working.

Dio

#28

It's working now!

Thanks Dio.

Cheers,
Eric

#29

Hello people,
A few days have passed and there are things to share with you. As you may remember I was about to build my upper soffit slot resonators, and that's what I did:

: upper soffit slot resonators

And this is what I got after a loooot of effort:

: upper soffit slot resonators RT60

: upper soffit slot resonators Waterfall

: upper soffit slot resonators Spectrogram

: upper soffit slot resonators FR

No matter how I tried to tune, retune or detune them, the results were not satisfactory at all...
There was a huge hole in the lower midrange reverberation time while in the lows there was a weird rise of about 100ms (!!) with no real improvement anywhere.
The evidence:https://mega.nz/file/IhVQTZwA#KJtyaK5uWxpe1v25--4giQAILzx-lR4xtD6MWOx0QOU

The only logical conclusion I can reach to is that sound coming from inside the soffit where interfering with the resonator. It seems my soffit construction is not massive enough to support this kind of treatment built into it. That's why almost nobody does these things, failure accepted and lesson learned.

So it is time for plan B, and plan B was to turn the resonators to big insulation chunks:

: Upper soffit insulation chunks

: Upper soffit insulation chunks RT60

: Upper soffit insulation chunks waterfall

: Upper soffit insulation chunks spectrogram

: Upper soffit insulation chunks FR

At least that 150hz dirt has disappeared.. but strangely the very lows RT is still high and the rest is bumpy...

I am tempted to convert the side lots to insulation too.
Later, as I was making the frame for the absorptive ceiling I thought it was a good idea to screw some slats (50mm slats/20mm gap) over the upper insulation chunks:

And there is was.

: Upper soffit chunk slats

: Upper soffit chunk slats RT60

: Upper soffit chunk slats Waterfall

: Upper soffit chunk slats Spectrogram

: Upper soffit chunk slats FR

Evidence: https://mega.nz/file/sxME0bRS#7I2VGIiKM ... _r53mdc-3s

Minor changes, most of the RT is back to normal except this annoying low section...
It also seems that I have reach a point that in such a small space every thing in every place affects the measurements in various ways. Anyway let's move on!

Cheers
Dio

#30

Dio,

I am not certain so I am hesitant to comment but it looks as though you do not yet have a ceiling trap. My studio's designer says the ceiling trap is the most important. How much sound will be getting into the area above your soffits must surely be less than that which bounces off the ceiling. I wonder whether, if you did the ceiling before the above soffit areas you might see your measurements come out quite differently.

Regarding RT measurements, Soundman2020 maintais that decay time is more important than RT60 in a small room, Bert Stoltenberg says you cannot measure RT60 under the Schroeder frequency and Bjorn Omholt says RT measurements are not valid in small room since there is no real diffuse field. Bjorn recommeds looking at ETC measurements. This is an area I have no experience in but from what I have read I am not sure you are helping yourself by concentrating on the results of your RT measurements.

What do other people think?

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