Please, opinions about my new 2ch room

joaovieira · May 5, 2013

Gentlemen,

I will build maybe this year a new 2ch room in my house. It will have 35 sqm, more than the 14 sqm I have now. The dimensions are 5m x 7m x 2.75m.

Due to construction rules and land ocupation in my Condo, I will have to build it underground. In fact, as you can see in the architecture pictures I will post, from the total high of 2.75m, 0.60 m will be out of the ground level.

The idea is to build a set of reinfirced concrete screwpiles around the perimeter of the room. Each screwpile will have about 4m and they all togheter will allow the escavation of the room. As the screwpiles are concrete reinforced, the idea is to work inside to level the wall and use it as the room wall.

I am not really worry about the engeineering process, this I can handle as I am civil engineer.

My concerns are about electrical instalation and room acoustics.

I will have an acoustic engineer helping me with a first acoustic treatment. But I know that it will be modified after the room is ready.

Please, advices! Thank you.

joaovieira · May 5, 2013

The design:

amirm · May 5, 2013

OK, I am not a civil engineer so don't know what a screwpile is

. I do know that having concrete walls is bad for bass response. So if that is what it means, you should build another room inside it with more flexible material. You will lose some space of course that you could put to decent use for insulation.

joaovieira · May 5, 2013

Amirn, thanks for your answer. If so, I will have to think about an alternative. I could use wood. If it was all wood would it be ok? Or make brick walls inside.

Keith_W · May 5, 2013

Amir, the reason why concrete walls are bad is because they reflect sound waves. Wood is better because it lets long wavelengths through - but that is provided what is beyond the wood isn't going to reflect sound. Given that he is building his listening room underground, his room will be surrounded on five sides by material which is less dense than concrete - it might absorb some sound, but it will probably reflect some as well. He might also need the concrete for structural purposes. It may be better to advise him on bass absorbent material instead.

Nyal Mellor · May 5, 2013

Aim to build another room made of wood and sheetrock inside the concrete walls. You might need to make the room wider / longer and deeper than you currently plan to. If you are DIYing this then do yourself a favor and read the 3rd edition of Philip Newell's studio design book which has some good examples of room within a room construction. As Amir says concrete walls (and brick too) are bad for bass.

As for electrical that is reasonably simple. Everything audio should be on one circuit where the hot, neutral and ground all runs directly back to your main panel (not a sub panel). Essentially a spur circuit. No lights, air conditioning, etc should be on this circuit. If you work out your components power draw and it is greater than what can be supported by a standard residential circuit then just upsize the gauge of the wiring and use a bigger breaker in the panel. Finally make sure you use an isolation transformer, unless your power is really bad in which case a dual conversion UPS might be better. See our power guide and linked articles for more.

joaovieira · May 6, 2013

Nyal,

Thank you. I'll search for the book. I hope there is an electronic edition.

About the electrical, in my small room things are more or less like you described. I have an independent circuit, and this brings to the room 2 hot and one neutral in a very nice cable, and the groung in a separated and more simple cable. Each mono amp is connected to a separated hot.
I was thinking in using this same design, but then you mentioned an isolator transformer. What is that for? Sorry for my ignorance. My power supply is very good and stable.

JackD201 · May 6, 2013

Greetings joao,

I built my music room in the basement as well and I too did a semi (walls and ceiling) room within a room. As a civil engineer I'm certain you will be fully aware of the water proofing requirements but I am mentioning it because I don't see it in your plans. In my case I did sealing on floors and walls prior to the RWAR construction and also laid perforated pipes below feeding a redundant pump system with generator back-up and a cistern. You can see what I did in page one of this thread

http://www.whatsbestforum.com/showthread.php?1740-JackD201-Almost-Done

Ethan Winer · May 6, 2013

joaovieira said:
I will have to build it underground.

The other posts are correct that concrete walls reflect bass frequencies the most, but I'm not convinced building a room within a room is your best solution. Yes, the added sheet rock walls can absorb some bass frequencies a little. But it seems to me that a better solution is to build bass traps that target the specific problem frequencies you actually have, and with much higher efficiency.

You can predict problem frequencies using my Graphical Mode Calculator program. Normally such calculators are not precise enough for predicting which mode frequencies to trap because normal "flexible" walls change the frequencies. But since your walls are massive cement, and backed by yet more mass (the dirt), the frequencies calculated should be very accurate. So I'd build bass traps similar to the ones in this article, but tuned to your room's specific problem frequencies:

Build a Better Bass Trap

--Ethan

joaovieira · May 6, 2013

JackD201 said:
Greetings joao,

I built my music room in the basement as well and I too did a semi (walls and ceiling) room within a room. As a civil engineer I'm certain you will be fully aware of the water proofing requirements but I am mentioning it because I don't see it in your plans. In my case I did sealing on floors and walls prior to the RWAR construction and also laid perforated pipes below feeding a redundant pump system with generator back-up and a cistern. You can see what I did in page one of this thread

http://www.whatsbestforum.com/showthread.php?1740-JackD201-Almost-Done

Hi Jack,

Yes, everyone that sees my design asks about the drainage issue. It is already addressed in another set of draws, but I can tell you one good thing about it is that the water level is deeper than the room position, as measured in many days along the year and observed during the 4 years I live in that home. Before construction it was 4.5 m deep. So the protection will take care of the raining water infiltration.

By the way, congratulations for you very nice room. And thanks for the link and for your kind answer.

Jack, did you hired someone to design the acoustic treatment of your room? I've been searching for someone to do that, and all I found was an acoustic engineer that will charge me (if I hire him) $5k to design it after the room is done. If so, what is the advantage of building a brand new room if I can't address the acoustic problem by the selection of materials and shape of the room? Go figure..

joaovieira · May 6, 2013

Ethan Winer said:
The other posts are correct that concrete walls reflect bass frequencies the most, but I'm not convinced building a room within a room is your best solution. Yes, the added sheet rock walls can absorb some bass frequencies a little. But it seems to me that a better solution is to build bass traps that target the specific problem frequencies you actually have, and with much higher efficiency.

You can predict problem frequencies using my Graphical Mode Calculator program. Normally such calculators are not precise enough for predicting which mode frequencies to trap because normal "flexible" walls change the frequencies. But since your walls are massive cement, and backed by yet more mass (the dirt), the frequencies calculated should be very accurate. So I'd build bass traps similar to the ones in this article, but tuned to your room's specific problem frequencies:

Build a Better Bass Trap

--Ethan

Ethan, very nice calculator. I will certainly use it. And the bass trap construction will help me a lot.

microstrip · May 6, 2013

joaovieira said:
(...) Jack, did you hired someone to design the acoustic treatment of your room? I've been searching for someone to do that, and all I found was an acoustic engineer that will charge me (if I hire him) $5k to design it after the room is done. If so, what is the advantage of building a brand new room if I can't address the acoustic problem by the selection of materials and shape of the room? Go figure..

I would happily pay the $5k if I could find some one I can trust to design my sound room. One risks spending a lot more and specially spending a long time using the try and correct later approach.

Unfortunately part of the "trust an expert" means for me listening to his portfolio, something it is not possible. My non-expert advice for you would be contacting Art Noxon of ASC.He is one of the people who, as Amir, strongly warns about bass problems in concrete rooms - he must be able to help solving them using ASC the Isowall based systems.

joaovieira · May 6, 2013

microstrip said:
I would happily pay the $5k if I could find some one I can trust to design my sound room. One risks spending a lot more and specially spending a long time using the try and correct later approach.

Unfortunately part of the "trust an expert" means for me listening to his portfolio, something it is not possible. My non-expert advice for you would be contacting Art Noxon of ASC.He is one of the people who, as Amir, strongly warns about bass problems in concrete rooms - he must be able to help solving them using ASC the Isowall based systems.

That's my dilema, microstrip. We don't really have experts with much experience on that. I was expecting someone to help me before I build the room, but what I found was help on the correction of the room problems. I wanted to make something on the selection of materials and shape to spend less in bass traps and stuff.

JackD201 · May 6, 2013

joaovieira said:
Hi Jack,

Yes, everyone that sees my design asks about the drainage issue. It is already addressed in another set of draws, but I can tell you one good thing about it is that the water level is deeper than the room position, as measured in many days along the year and observed during the 4 years I live in that home. Before construction it was 4.5 m deep. So the protection will take care of the raining water infiltration.

By the way, congratulations for you very nice room. And thanks for the link and for your kind answer.

Jack, did you hired someone to design the acoustic treatment of your room? I've been searching for someone to do that, and all I found was an acoustic engineer that will charge me (if I hire him) $5k to design it after the room is done. If so, what is the advantage of building a brand new room if I can't address the acoustic problem by the selection of materials and shape of the room? Go figure..

Hi Joao,

Yes I contracted the acoustics firm that built one of our sound stages and all of our new studios and editing suites.

If I'm not mistaken Walters-Storyk Design Group has an office in Rio. I've worked many hours in spaces they've designed in the past.

The advantage is that part of the contract includes predetermined performance targets and it is the responsibility of the designer/contractor to meet those targets. They have to keep going until they do without you having to pay a cent more. Add an interior design component to the package and you get both performance with aesthetics to match. Looks are subjective of course and many don't mind having a listening room that looks industrial. It doesn't have to be that way though.

Ethan Winer · May 7, 2013

joaovieira said:
Ethan, very nice calculator. I will certainly use it. And the bass trap construction will help me a lot.

I should have mentioned that for your specific room, I'd line all the walls with wood panel bass traps, then apply rigid fiberglass absorption at key places in front of the wood traps. As opposed to the system of alternating traps described in the article. Again, you'll build the traps to the target specific mode frequencies of your room. When you're ready, post here and I can help with the specifics.

--Ethan

joaovieira · May 7, 2013

Ethan, this is great! Thank you so much, I will certainly post to get your kindly help.

João.

Aoyama · Jun 5, 2013

Hello João,

I really like the idea, box on a box, sure with glass or rock wool inside.

Can you change the height to 3m? Cause 5x7x2,75m make modes to close in my opinion, 24Hz, 34Hz and 62Hz cause the second width harmonic is 68Hz and to close to 62Hz.

Keep in mind if the room born right, the system go right.

I'm just finishing my dedicated listen room, with dimensions of 4x5x2,6m, but i made a huge bass trap on the ceiling, with good absorption in 2 modes, but in the length mode only a little.

Try call Tomas from Nemesis audio diffusers he can help you too.

[]s

zztop7 · Jun 5, 2013

***hydrostatic pressure !!!

Concrete & Drainage:
Rain Water may not be the issue here, but hydrostatic pressure may come back to haunt you [even with pumping from beneath a slab].
You & your equipment will not like a damp or Wet room.
I realize that you are a Civil Engineer, but I have researched structural concrete & hydrostatic pressure problems extensively.

If you would like more comments on this, I can follow up later today.

By the way, please define your Condominium: ?high rise [I doubt] / low rise / maybe a connected series of town houses/row houses? What walls or floors adjoin other residences.

Respectfully,
zz

joaovieira · Jun 5, 2013

Aoyama said:
Hello João,

I really like the idea, box on a box, sure with glass or rock wool inside.

Can you change the height to 3m? Cause 5x7x2,75m make modes to close in my opinion, 24Hz, 34Hz and 62Hz cause the second width harmonic is 68Hz and to close to 62Hz.

Keep in mind if the room born right, the system go right.

I'm just finishing my dedicated listen room, with dimensions of 4x5x2,6m, but i made a huge bass trap on the ceiling, with good absorption in 2 modes, but in the length mode only a little.

View attachment 10098

Try call Tomas from Nemesis audio diffusers he can help you too.

[]s

Thank you Aoyama. You confirmed what I was feeling, I was thinking on using 3m. Now I am certain to do that.

Tomas is the one I contacted and he is probably going to help me on acoustics. He was very recommended.

zztop7 said:
Concrete & Drainage:
Rain Water may not be the issue here, but hydrostatic pressure may come back to haunt you [even with pumping from beneath a slab].
You & your equipment will not like a damp or Wet room.
I realize that you are a Civil Engineer, but I have researched structural concrete & hydrostatic pressure problems extensively.

If you would like more comments on this, I can follow up later today.

By the way, please define your Condominium: ?high rise [I doubt] / low rise / maybe a connected series of town houses/row houses? What walls or floors adjoin other residences.

Respectfully,
zz

Hi zz, thank you for helping on this.

My condo is very big, it will be around 400 homes when everyone builds their homes. We buy just the land, it is gated place.

The houses have to be built at least 2m from the wall that separates them. The maximum high is 10m for each house.

I have been here since the design of the infra estructure - my company made the design for earthwork, pavimentation, drainage, water supply and sewage. During construction we kept tracks of water level, and since I am living here the water level from underground has never reached the bottom level of my future room.
In my house I made an earthwork adding 2.0 in average to the natural terrain level. Now I will excavate 2.6m.

My home backyard faces to a conservation area where nothing can be built. The level of the terrain of that area is about the same level of the bottom of my future room, so in more than 7 years of tracking this region was always dry. So I expect that the water level will not reach my room.

For rainning water I will make an extensive waterproof painting of the walls in my room.

Please tell me your thoughts about. It would be very helpfull.

zztop7 · Jun 5, 2013

Brazilian Screwpile

Hi Joaovieira,
I am trying to get my head around the structural plan before making too many comments. I did get your Brazilian definition of condominium so far [very different from USA].
Please define a Brazilian screwpile [you did say concrete reinforced]. In USA it is a steel structural piece [piling] screwed in the earth for structural reasons, but maybe in Brazil it is the hole excavated by a screw & filled with a rebar cage and concrete.
Are these screwpiles going to be inside the perimeter of the structural walls of the house, or are they outside the perimeter? Are the screwpiles going to reinforce the existing structure of the house also? How deep will the screwpiles be below the finished audio room floor?
Most important - were any studies done to determine whether there were any layers or other distribution of expansive clay in your soil?
How far down to bedrock?
Is the existing area the crawl space under the main floor?
This may seem detailed, BUT once you build a concrete room you cannot fix it properly if there is a problem, you can only rip it out & start again.
Best to you,
zz

Please, opinions about my new 2ch room

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