John Sayers' Recording Studio Design Forum

For what purpose? Just for sealing? Or for decoupling? You can only decouple a wall with neoprene underneath it if you also use some form of isolation on the bolts that hold the wall in place, and if you do your calculations correctly and only tighten the bolts so that they do not over-compress the neoprene. Compress it too much, and it flanks, so you gained nothing. The neoprene has to be compressed to the optimum range when the room is finished: if not, then you waste a lot of time, money and effort for no purpose at all, if your objective is decoupling the walls.

But if you just want to seal them, then you don't need isolated bolts, and you can tighten them any way you want.


So assuming you are just planning to use neoprene for sealing, not for decoupling:

The bass trap frames do not need sealing if you are going to do superchunks or some other form of pure absorptive treatment, but if you are going to do a tuned treatment (like slot walls or some such) then they do need sealing.

But what concerns me is that angled wall thing on the right, highlighted in red: What is that? Is that going to be a slot wall or something? You cannot put drywall on that, since it would create a third leaf, so I'm assuming it will be a slot wall? If so, then yes, it does need sealing. If not, then what are your plans for that?

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart,

Thanks for your response and advise !

The reason why I put rubber strips under the walls is because the concrete floor is quite uneven in certain areas, so it is just for sealing (Not for Decoupling).

Yes, the angled wall (highlighted in red) IS a slot wall. You can see the plan on the 1st page (towards the bottom) of this tread.


Ciao

Simo

"You cannot put drywall on that, since it would create a third leaf,"

To be fair, it is already a modified mass/air/mass (a new term I learned) applied directly to an existing residential wall sheathed on both sides with a decoupled interior mass. The existing wall/structure has an exterior/studs/interior panels. This get's called a two leaf (a double sided single frame assembly) so the additional insideout walls create the multiple air spaces we all try to avoid.

Certainly we try to avoid if possible, but everything matters so it may not have been possible to avoid.

Just an observation,

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Brien Holcombe
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Sound: You can't stop it, you can only try to contain it.

Thankyou very much for your observation Brien !

…just a quick note tough: in my case the existing wall/stucture has not an "exterior/stud/interior panels" but it's made of concrete blocks with concrete render both on the inside and on the outside…. so I hope in my case the additional insideout walls will not create the multiple air spaces you describe on your observation ??!!?

Simo

Exactly. That's why it would have been a third leaf if you would have put drywall on that angled frame. But since it will be a slot wall, then you don't have a problem.

Correct: You only have two leaves and one air gap. Adding the slot wall does not really create a third leaf, so you'll be fine like that: But you do need to ensure that the cavity behind the slats is sealed. In order to work correctly, the slot wall must be sealed.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi there,

Hope you are all well !


I'm building the splayed wall on the right hand side of the CR, which will be a slot wall.
My question is about the area at the right of the speaker soffit ….

A) shall I close and seal the cavity where the soffit frame and the splayed wall meet and put some hangers in there ?

….or….
B) shall I leave the entire cavity as it is (empty), essentially just making a deeper slot resonators ?

Thanks a lot in anticipation


Have a great Easter !!

Ciao
Simo

Hi simo,

B is my choice.

Referring to one of John Sayers SKP's for soffit mounting and this page, http://johnlsayers.com/Recmanual/Titles/Acoustics2.htm on the HELMHOLTZ RESONATOR, it looks like it should be a sealed cavity.

-charlie

Hi Charlie,

Thanks for your reply!

Perhaps I didn't managed to explain myself clearly sorry…
I was definitely planning to seal the frame directly behind the right speaker soffit (as kindly posted by you)…. my design though differentiates from your attached pic in that I've got a "reinforcing frame" going from the straight inner wall to the splayed slat wall (let's call it "Z").
If I place a gyprock sheet just there, I would in fact be left with 2 cavities ("A" and "B").


Thus, I was wondering if it would be worth to have hangers in the sealed cavity "A" (in order to have a bit more low frequency absorption in the room) and have a smaller sealed cavity "B" (being the slot resonator's cavity)

…or…

not having the gyprock sheet at all attached to the "reinforcing frame Z", thus having a "bigger" slot resonators (as per your attached pic).

Hope I made myself a little bit more clear

Thanks again !


Ciao
Simo

Simo,

I am no expert, just an avid reader of this forum trying to refer you to some of the documentation I have found relating to your situation.

I would wait until one of the known experts on the subject chime in.

Will be interested in seeing what they say....


good luck
-charlie

Hey Charlie,

thanks a lot for your documentation man, much appreciated !….I'm not expert either

Let'sjust wait and see if one of the expert finds the time to have a look at this.

All the Best !

Simo

cavity A should be open to the back of the speaker soffits and yes, putting hangers there would be good. the B cavity behind the slats needs to be sealed.

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Glenn

Glenn,

Great, thanks so much for your explanation!

…just to make sure before I proceed building it…is this what you mean ? :

and then place hangers in there


Sorry to be a pain , but I need to clear my head and ask one more question:
Having hangers beside just the right speakers (as I haven't the same space on the left hand speaker soffit)

won't this produce an "unbalanced sound field" (being the right side of the room more absorbent at low frequencies)?
… or … giving that low frequencies are non-directional by nature will mean that it does not matter where the low freq absorbers are positioned within the room (so in practice I'll be fine )?

Ciao
Simo

yes it's somewhat unbalanced but if i'm correct - this is what you have to work with and it shouldn't be problematic. so yes, go ahead with the additional absorption with the hangers (the new construct looks right) and make sure the two soffits have equal absorption.

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Glenn

Great,

Thanks so much for your help Glenn, really kind of you !!

All the Best

Ciao
Simo

Hi there!

Hope you are all well !!


First of all:
Glenn, you said "make sure the two soffits have equal absorption"… sorry but this makes me a bit confused… If the area named "A" on previous pic (which I was planning to fill with hangers) will then be part of the right soffit (being it open to its rear), won't this make the right soffit MORE absorbent than the left one (which has NO hungers behind it)? Really sorry for not getting it (and keep annoying you) ! …but …. Help!!
It's not that I don't trust you (actually it's completely the opposite)…it's just that I would like to understand things and not just execute them !


Also, about Hangers….. Since that I can't find homasote here in UK (for the core of my hangers), when I was looking for other soft fibreboard sheets the only alternative was the fibreboard laminate flooring underlay (which it's just 5mm).
It doesn't give specification about the Kg/m3… what I can say is that It's very soft, so that you can actually tear it with your hands! What do you think?
here is the link: http://www.wickes.co.uk/fibreboard-unde ... vt/201508/

Do you know what else I can use as an alternative for the core of my hangers?
Perhaps thin (4mm or 6mm) MDF? thin (9.5mm) Plasterbord sheet?


Many Thanks
Simo