SIMO Studio - Construction Phase

[simo]

me again

...while trying to sort out this 'conduit break point', I'd like to start covering all this horrible rockwool as I'm really tired to breathing it.

I assume I need to use the thinner plastic layer I can find.

So the question are:
1) Can I place this plastic layer underneath the black cloth under the slat resonators as well?
Or perhaps is not recommendable to use the "reflective" plastic layer as the slats will already be reflective themselves and instead just use this plastic layer to cover the rest of the rockwool in the room?
Perhaps it's better to use something less reflective under the slats (something like the 'batten' used by RJHollins in his build)?

2) Also, can I use the 'weed control matting' (perhaps with fire retardant treatment sprayed onto it) for the "black" cloth under the slats?


Thanks as always !


ciao
Simo

[Soundman2020]

I thought that the priority here was to de-couple them.

That's the main priority, yes, but you still want a continuous seal, and some mass, and some structural integrity. I would be concerned that if you tried to pull any new cables through there, that thin packing foam would rip. Also, if it is the type of foam that I'm thinking of, it is "breathable", not air-tight.

Also, I felt that since the points where the conduit enters both walls are sealed - around and inside it - on the front (from inside the room) and on the back of the plasterboard - it would make it quite difficult for the sound to escape from there and eventually leak in the gap between the walls from the conduit break point.

You will probably be OK, as long as the ends of the conduit are vary carefully sealed. Right now, you have an open pipe into your air-gap, through the conduit! So you need to take extra care to seal that: Stuff in as much insulation as you can, around the cables, forcing it down the pipe as far as you can get it, then apply liberal amounts of acoustic caulk over that, to completely seal the end of the conduit. You might even want to put a "putty pad" over that seal too (after the caulk is cured), to make sure that you have enough mass there.

And even if a portion of it does leak, then it would encounter the same "resistance" to get out the conduit on the other wall…

I'm assuming that the thin foam is not air tight, and certainly is not rigid enough to resist the resonances inside the wall cavity, so basically it isn't there, acoustically. sound inside the cavity has a free and open path to both sides of the wall, through the conduit. That's why it is very important that you seal the ends of the conduit on both sides very, very well.

To understand the difference, hold a piece of that think foam over your ear, and see how much sound it blocks. Now hold a piece of the sorbothane over your ear, and see how much that blocks...


- Stuart -

[Soundman2020]

1) Can I place this plastic layer underneath the black cloth under the slat resonators as well?

I would not use plastic on a Helmholtz device (such as a slot wall), since they are based on the movement of air inside the "neck" and on either side of the neck. Putting plastic in there would probably interfere with that mechanism

The cloth itself should help to keep the fibers under control.

2) Also, can I use the 'weed control matting' (perhaps with fire retardant treatment sprayed onto it) for the "black" cloth under the slats?

You probably could, but that would probably defeat the purpose! The real purpose of the black cloth is aesthetic: it is there to hide the interior of the resonant cavity, so you can't see the ugly insulation. If you use something that has a wide weave like matting, then you'll still be able to see inside! Use black cloth that is "breathable", meaning that if you hold a piece over your mouth and nose, then you can easily breathe through it, without noticing any resistance to air.

- Stuart -

[simo]

Thanks for the clear explanation Stuart !

You will probably be OK, as long as the ends of the conduit are vary carefully sealed. Right now, you have an open pipe into your air-gap, through the conduit! So you need to take extra care to seal that: Stuff in as much insulation as you can, around the cables, forcing it down the pipe as far as you can get it, then apply liberal amounts of acoustic caulk over that, to completely seal the end of the conduit.

Honestly, I think I did just that, as you can see on the pic (third from the bottom) on my post in the previous page, which shows the steps of the sealing process you describe here (all in one pic)… 1-open tube, 2-insulation (lots!) inside the conduit all around the cables, 3- foam (just to have a bed for the caulk), 4-caulk (Lots!!!)
I might add the putty pad there, as you suggest..…why not?!

Anyway, regardless of all of that, I think I'm going to follow your advice and swap that light foam with rubber…just to be safe


Ok, NO plastic and NO weed matting on the Helmholtz !


Grazie Stu !!


Simo

[Ro]

Simo, that boxing-in-the-vents is a super smooth plan. And you did a great job, nice skills. It makes the "view" much more pleasant this way, more "one" with the exterior walls. thumbs up.

Keep up the good work, and keep the pix comming ofcourse

[simo]

Thanks Ro,

much appreciated !

I'm trying to make up for all the time lost between work and injuries, so I'm working on more than one thing at the time…. today I'm tackling the CR clouds framing, then it will be doors time, and then …. …. I'm aiming at finish it by the summer…. time will tell !

[xSpace]

2) Also, can I use the 'weed control matting' (perhaps with fire retardant treatment sprayed onto it) for the "black" cloth under the slats?

I have used weed control matting for projects, and it can work since it has no weave to speak of, but is more designed to smother the plant. The issue I had with it was getting the right weed control cloth that would take the fire retardant spray and not deteriorate the weed control cloth.

[simo]

Thanks for the advice and for sharing your experience Brien !

The reason why I asked in the first place was because I have a big roll of weed control matting lying around and wondered if I could recycle it

Since that I've got a bit of time before tackling the slats construction, in the meantime I might try to spray fire retardant onto a sample of it and see what happens…



Simo

[Soundman2020]

2) Also, can I use the 'weed control matting' ... for the "black" cloth under the slats?

I'll repeat what I said before, because I don't think I explained it too well.

I would not use the weed control matting instead of black cloth behind the slats, for two major reasons:

1) It is basically plastic sheeting with tiny holes in it, and will therefore interfere with the operation of the slots. A slot wall is a Helmholtz resonator. It works because the "slug" of air trapped in the "neck" of the device, which is the slot itself (the gap between two adjacent slats) vibrates, moving in and out of the slot for a certain distance either side. That's why you see the "neck correction" or "effective depth correction" terms in slot resonator calculations: the slug moves in and out, BEYOND THE LIMITS OF THE SLAT, into the open air in front of and behind the slats. This area extends roughly 20% of the thickness of the slat. So, for example, if the slat is 30mm thick, then the neck effect extends for another 6mm, or 3mm each way. So the slug needs to move 3mm into the cavity, and it needs to find insulation there, to damp it! If you put "plastic sheeting with holes in it" in the way, then you are BLOCKING the movement of the slug, PREVENTING it from properly moving into the insulation. In other words, you prevent the resonator from resonating... Plastic sheeting is NOT like cloth in this aspect: cloth is open-cell and fibrous, similar to insulation, and therefore does not interfere with the movement of the air slug.

2) The entire purpose of the black cloth is aesthetic. It is there to hide the ugly insulation that is pressed up right against the slats. It is supposed to be matte black to block light from getting through. Maybe yours is different, but the weed matting that I have seen is rather shiny and reflective: It would not do what the black cloth is there for. You would be able to see it, as it reflects light.

So personally, I would NOT use that behind the slats, which is what your question asked originally. Where I WOULD use it, is BEHIND the black cloth on superchunks, some parts of ceiling clouds, and other absorbers. Since those are purely absorptive devices, not resonant, it doesn't matter if the matting blocks air movement partially, and that matting certainly would help to prevent the insulation fibers from filtering through the cloth, and also reflect some highs back into the room. In other words, for your superchunks, put some of that matting between black cloth and the insulation. But you still need the black cloth, since that matting stuff is shiny plastic.


- Stuart -

[Ro]

Yes, you will not use a *filter* on any *tuned* absorber, like Helmholz.
A (low-pass) filter is functional on broad-band absorbers; you can "tune" them a bit by reflecting mids/highs back into the room. Remember, you can never have enough low-end absorption but you *can* have to much mid/high absorption. It's because mids/highs are much more easy to absorb. If you're not carefull you'll un-balance the room.

Tuned absorbers, tho, are to absorb exactly *that* frq-range you tuned them for. Adding any filter will undo your precise tuning.

[simo]

Right

I totally got it now ! NO MATTING OR ANY OTHER "FILTERING MATERIAL" UNDER THE HELMOLTZ RESONATORS !!

and now, after such explanation that ugly matting goes in the ground - where it belongs - "controlling" the weed !

No seriously, Thanks SO much Stuart and Ro for stopping me compromising lots of hard work just for saving few pennies

(I won't ask this thing ever again - promised !)

GRAZIE !

Simo

[xSpace]

"1) It is basically plastic sheeting with tiny holes in it,"

Which is why I said what I did. Commercial grade weed control material is not plastic. It is listed as Spunbond Polyester.

But, in my defense, I had some and I tend to use what I have on hand if it meets the criteria for the application.

[simo]

Hi all

I'm in the process of building the clouds for my studio.
They have hard backing (I'm planning a single layer of 18mm plywood), apart from the channel for the lights (with no insulation and not backing for ventilation obviously).

Here's a sketch of one of them, just to see it better:

cloud 1.jpg

cloud 2.jpg

cloud 3.jpg

The question is:

Do I need FIRE-RATED down lights?

My electrician said that in the UK is not a requirement, especially in cases like mine where you have lots of air around them. It IS a requirement when spot lights are placed between floors (for instance on the ceiling of the ground floor…).

What do you think?
Can I get away with normal (non fire-rated) down lights for my clouds?


Many Thanks as usual


Ciao
SImo

[xSpace]

As long as there is no insulation or material touching the can that can catch fire, no you do not need a fire rated light can.

[simo]

Thanks for your explanation Brien !

I know all topics related to safety are (amongst other) specialties of yours, so your reply makes me feel better.... and - not last - save a bit of £££ (as the fire-rated ones are more than three times more expensive!)

Yes, there will be NO insulation touching the light can at all !