SIMO Studio - Construction Phase

Sorry, me again :oops: ...just quickly: Is there a minimum width I shouldn't go under on the vent at the top / bottom of the speaker box? I was thinking an opening 30mm x 220mm. Would that be ok to allow enough air circulation for my speakers? Thanks ! Simo

What speakers? :) Personally, I'd take a look at the heat sink on the back of your speaker, and make it quite a bit wider and deeper than that. If there is no heat sink, then I'd go for at least 2/3 the width of the speaker and 3 or 4 cm deep. When the speaker is sitting on a stand, there's plenty of space for air to circulate, but when it's in the soffit there's no space at all, so be generous with vent dimensions. - Stuart -

They are Genelec 1031A. The speaker dimensions are: 393mm (H) x 251mm (W) x 291mm (D). I was proposing a 220mm x 30mm vent, so it can't be much wider than that. But I guess I could make it slightly deeper, say 4-5 cm? (unfortunately I can't make it deeper than 4cm - 5cm max, otherwise the box will end touching the wall on the back :( ) Simo

Hello, I've made the speaker boxes (pics to come). I haven't placed the sorbothane lining inside yet (I'm going to glue it with some strong glue / contact cement). Since that the sorbothane isn't very hard, I'm worried that if I have to pull the speakers out and push them back in their box the sorbothane layer would tear off. So here my question: Does the speaker case need to be screwed to the plane is resting on? Because if not, I could have the "pulling straps" around the case (instead than around the speakers) and be able to pull out the box + the speakers as a joined thing? I would of course restrict the movement (sideways and back to front) of the speaker case with a frame around it which will be screwed to the resting plane. Would that work? Thanks ciao Simo

…slight bump perhaps?… :oops: Any idea if the approach with the strap around the box (which won't be screwed to the plane underneath) will not compromise the effectiveness ? Sorry for being insistent :oops: . It's just that I've got a some free time before a busy patch at work, and would love to get as much done as possible before that. Many thanks ciao Simo

I'm not so sure that would work. If the box is not screwed, nailed, or bolted down, I suspect it will vibrate, shake, move and do other unpleasant things. I wonder if you could put something like a sheet of paper between the rubber and the speaker, so that it slides in and out more easily? I think part of the problem is that the rubber "sticks" or "grabs" the sides of the speaker cabinet, but if you put something in between, then it should go in and out a lot easier. Maybe? - Stuart -

yeah that could work, yes… perhaps the only concern would be the heat from the cabinet after hours of operation (?)… but the idea is good, I'll definitively play with it. Grazie Stuart :thu:

Hi all, I'm about to finish the ceiling for the control room (pics to come soon).. I know I know... I'm soooo   s  l  o  w, but work is keeping me busy (without which this project wouldn't go much further anyway) and two little girls need quite a bit of time - most of you know what I mean I'm sure ! :-) So, looking ahead: I wanted to build something to break the reflections between the floor and the ceiling - with them both being  flat, i.e parallel to each other. The options I'm considering are: 1) A cloud hard-backed with a layer of 18mm plywood angled downwards on the front of the CR, hung on heavy duty chains and hooks, with a gap of 30cm circa from the walls. This will start from behind the sitting position (highest point) and descend with a 12 degree angle to the front of the CR (lowest point). The only concern here is its weight and how I can trust the strength of the hooks and chains... 2) A modification of the previous point: Basically all the same as described above apart from having the highest point (behind the sitting position) attached to the existing CR ceiling frame. I was thinking of doing it this way in order to save same room height, which is not much already :-) (Note):  Would it be a problem not having the cloud completely "free standing"? just guessing here, as I'm not sure if that is a requirement for the cloud to work properly or that doesn't really matter? 3) Build a sloped false ceiling (just the frame, not hard-backed with plywood), directly connected to the walls all around, with the cavity between this and the flat ceiling filled with insulation and then acoustic hangers at the front of the room (space permitting - otherwise all insulation). (Note):  This obviously won't break the reflections between floor and ceiling as the two will still be parallel, but has the advantage of having a greater quantity of absorption material (soft insulation in the cavity and rockwool slabs between the framing). I guess I could add a plywood layer at the top of the frame (and then insulation between the beams), but wouldn't that create a 3-leaf structure? sorry - getting confused here :-( Which one would you recommend? Really hope you can point me in the right direction. Many Thanks in anticipation ! Ciao Simo

I don't see how "option B" can be hard-backed, since the backing would be interfering with the ceiling joists. Sure, you could cut slots out of the backing, but that kind of defeats the purpose of the backing! And if you happen to need to change the angle, you'd need to cut deeper slots or fill them in again... I think I'd go with "option A". My $0.02... - Stuart -

Thanks Stuart, yes I think I'll go with option A… easier to build, adjust, remove (if needed). I read somewhere that a 18mm plywood layer and a 18mm MDF layer screwed and glue together should be used for the back of the cloud (the MDF adds mass and the ply adds stability)… but I'm a bit worried about its final weight as I will spend quite a bit of time sitting under it :-) (I was planning of using 100mm x 20mm timber for the framing just to minimize that) What type of hooks should I use ? Thanks Simo

I read somewhere that a 18mm plywood layer and a 18mm MDF layer screwed and glue together should be used for the back of the cloud (the MDF adds mass and the ply adds stability)…

I don't think it needs to be that massive. The density of plywood and MDF are pretty similar, while MDF is slightly more dense, so that "wisdom" you read seems to be a bit off. I'd go with just a single layer of plywood.

What type of hooks should I use ?

Heavy duty ones! Good enough that each one can take the entire weight of the cloud, if possible. You do NOT want that thing coming down on your head, so make sure you have plenty of safety margin in your hooks and chains, such that no single or double point of failure can cause it to fall. - Stuart -

Just to mention ... 'Gullfo' did the design for my hard backed clouds, and recommended the combination of MDF and plywood. It worked out very nicely, as the MDF provided mass, and the plywood [with its mass] also allowed for attaching my aluminum frames AND the ability to staple the fabric cover to the top side of the plywood. MDF alone is not as easy to work with. Here's a link to my section on the cloud construction and mounting design: viewtopic.php?f=1&t=14794&start=390 just additional info :)

Thanks Stuart and RJ for your advice. Much appreciated ! I'll calculate what will be the weight of the cloud (as it's quite big) and then decide… I might divide the front cloud in two instead of a big one... Also, I was planning to have three smaller clouds at the rear of the room. So, clarified that a hard-backed cloud is the way to go at the front of the room (being my ceiling flat), I was wondering if I'll need to have these three smaller ones at the back hard-backed as well? By the way - Fantastic build RJ !! Ciao SImo

Hello hope all is well. It's been a while since my last post. It seems I'm going to have a quiet time in front of me now so I'm hoping to get a lot done. I thought it was time for a little update: I built a plate/structure to attach the AC wall mount indoor unit…this required some "particular" cutsRemoved the plasterboard layers between two studs to pass pipes/cables throughOuter-leaf penetrations drilled at the bottom, inner-leaf penetrations drilled at the top. This gave me an offset between the two penetrations of 1.8m. I made the holes few mm larger than the pipes, then I filled that gap with insulation, backer rod and caulked. The space between outer and inner walls was filled with soft insulation, and I placed 5cm rockwool slabs between the studs. Finally I re-attached the usual two layer of plasterboard from inside the room. CR:Having that single stud bay NON inside-out (unlike everywhere else in the construction) shouldn't be a problem because the top part will be the backing of the angle superchunk (so it will have insulation in front of it again), whereas the bottom part will have a sofa in front of it. LR:Then, Inner ceiling construction: - 50x150cm rafters resting on walls top plates- 25x45 mm timber ledgers screwed to ceiling rafters and caulked CR:LR:- to close each bay I used two plasterboard "plugs" (1x 15mm fireline, 1x 15mm sounbloc) screwed to ledgers from below and caulked CR:LR:- view from above- wire penetrations were filled with insulation, backer rod and caulked from above and below....to be continued....

..... - 5cm rockwool placed above the plasterboard "plugs" between the ledgersand then completely filled the rest of the void (which varies from 5cm at the rear of the room to 30cm at the front) with soft insulation Fresh air system: This consists of two paths per room: A. the INCOMING FRESH AIR PATH with fan (at a rate of 60 l/sec, allowing 10 l/sec per person)with inline silencer(note: in this pic you'll notice that the circular connection - to connect the silencer to the duct - is in the wrong place… I temporarily put it there just to take a photo without realizing it :oops: , but then it was fixed correctly at the end of the internal bent - top left) The fans will be connected to a weather proof 20 amp 1-phase isolators (not done yet, I hope next week), so I can switch them off either from there or from the main electrical panel. B. the OUTGOING STALE AIR PATH with silencer. As the void between outer and inner ceiling was way to small to install the silencers on the inside, I decided to have them on the outside of the building (like "realdoyle" did on his build: viewtopic.php?f=2&t=13828&start=30):(I will build some sort of weather cover for these) I did used the small void between ceilings though to run the 80mm flexible insulated ducts(with as many bents as I could to minimize noise turbulence) to connect the fans and silencers to the inside vents.This is one of the entrance from silencer to duct (again the gap around the connection was filled with insulation, backer rod and then caulked):.......

....... I cut the plasterboard layers with the same diameter of the finishing air nozzleand tested that it was fitting okthen I used a 70-90mm jubilee clip to firmly attach the insulated flex duct to the air nozzlesealed all around and used the duct tape to fix the insulated cover of the duct to the top of the plasterboardThen I placed the rockwool above the plasterboard and all around the ductand here's the finished vent And this is how it looks like now: front:rear:right hand side:ciao Simo

Great work! Keep the pics coming. Charlie

Thanks Charlie ! After the latest update, it's question time :lol: I'm starting doing the bass traps with acoustic hangers, and I have one question: Does the side facing the room need to have insulation all the way from top to bottom or do I need to leave a port with no insulation to allow the sound to get into the trap? Mr. Alton Everest in his Master Handbook of Acoustics states: "At the bottom of the cavity the sound pressure is at its maximum, and the air particles velocity at its minimum. On the other hand, at the opening of the trap the sound pressure is at its minimum whilst the air particles velocity is at its maximum. This low pressure at the opening generates a vacuum that sucks the surrounding sound energy inside the trap, creating a "hoover" effect. Also placing a glass fiber slab to close the opening determines a great friction to fast vibrating air particles, resulting in maximum absorption" So, according to his statement the answer would seem NO, as the path for the sound entering the trap and reaching the hangers should be only through the acoustic obstacle represented by the fibreglass / rockwool slab, right? What confuse me though is the approach used for the port at the bottom of the speaker soffit, often used as a bass trap with hangers. I always thought that part left without insulation was just to allow air to circulate and get to the speaker box vents… but I read (I can't remember where) that the part is there to create a clear passage to the hangers instead... …. so which one is right? I mean, if that was the case, shouldn't I leave a similar port on the side facing the room of every bass trap with hangers, like for instance the ones at the rear of the control room? Hope is not too confusing :oops: ciao Simo

Does the side facing the room need to have insulation all the way from top to bottom or do I need to leave a port with no insulation to allow the sound to get into the trap?

None of the above! :) You seem to be confusing a bass trap with a speaker soffit. The front face of your entire bass trap should just be cloth, nothing else. The purpose of the port at the bottom of John's speaker soffit design is simply to allow sound in, so that it can be trapped among the hangers. The rest of the front face has to be solid, as it is part of the infinite baffle design. In your case there is no soffit: the entire things is hangers, so you want the entire thing to provide free passage for sound. So just plain cloth is all that you need.

Mr. Alton Everest in his Master Handbook of Acoustics states:

What page are you referring to? I don't recall that Everest discussed hanger-based bass traps in MHoA. Maybe you were reading about some other type of trap? - Stuart -

Thanks for your response Stuart In the 5th edition, it's on pag.208-209 (Absorption chapter). Here's a preview (credits are there, but let me know if it's a problem posting it here and I will remove it straight away)… it really looks like he's talking about hangers there, especially when he mentions the "famous Hidley bass trap design" on the last sentence :?: (Also, of less importance of course, if a cloth is the only covering for that (not small) section of the room, it will be a fragile point, as if someone would lean on it, he/she would easily damage it or even worst risk to fall inside it :oops: :twisted: :?: … I'm not arguing your guidance.. I just want to understand better :oops:

That's a different type of trap entirely, working on a different principle. It is a tuned cavity, a resonant device, that is designed to treat a specific range of frequencies. It is basically a "box" protruding into the wall, and the dimensions of the cavity are chosen to treat certain frequencies. The absorption is there to damp the resonance, and also just to absorb. Those are not hangers, since there is no central board to which the absorption is attached. Tom Hidley used several different devices in his rooms, not just hangers. It isn't clear which one Everest is referring to here. But whichever way you look at it, what Everest is describing on that page is not what you are talking about! You have a hanger trap the bulges outwards, into the room, and has no resonant cavity. Everest is talking about a device that goes into the walls, starting flush at the surface, and is resonant.

it will be a fragile point, as if someone would lean on it, he/she would easily damage it or even worst risk to fall inside it

A very valid point. That's why some people put simple wood slats across the front, widely spaced so that they do not become Helmholtz resonators themselves. There are some examples of that in threads here on the forum. I don't have any links off hand, but you should be able to find some with the "search" feature. - Stuart -

next to the cloth, it is wise top add a low pass filter. like a sheet of plastic or even a thin layer of wood. else the absorber will be broadband, sucking too much hi frq out the room. leaving it tumbalanced....

Gotcha, thanks for clarifying that Stuart ! I will do (more) search to find some of those threads :thu: Thanks Ro, much appreciated ! Yes, I'll definitely follow your advice and put some thin sheet of plastic under the covering cloth. I guess that doing that, apart from giving some hi frequencies back to the room should also provide some sort of protection from breathing insulation particles... simo

simo wrote:

Gotcha, thanks for clarifying that Stuart ! I will do (more) search to find some of those threads :thu: Thanks Ro, much appreciated ! Yes, I'll definitely follow your advice and put some thin sheet of plastic under the covering cloth. I guess that doing that, apart from giving some hi frequencies back to the room should also provide some sort of protection from breathing insulation particles... simo

Just to mention. When it came time to building my 'chunky corner traps', I used a material called 'batten' for the first layer, and then covered with a nice breathable fabric. This was done, also, for all the broadband absorbers and for all the ceiling clouds. I did not use any thin plastic sheet, although I was aware of the technique and had no pre-knowledge what the room response was going to be. This is for my control room. I have a good amount of treatment [may look to add more in strategic corners], but the room does NOT sound dead at all .... very controlled ... yes. I did record an acoustic guitar and voice in the control room and the recording sounded clear, full, articulate, and natural. As to the 'batten' material ... absolutely no traces of insulation dust or irritations at all. I think the clouds benefited the most. Hey ... I'm watching and learning from your build, and it's looking great ! :)

Thanks for your input RJ. I've been studying your build very closely too ! (I particularly like your clouds construction using aluminum plaster corner beadings - very clever idea indeed !!) ….it's great how - thanks to this fantastic website - we can all learn from each other experience! Thanks for the batten idea….I've never seen it before, but from your pics it seems like a thin soft fabric, doesn't it? I'm sure it's great to keep insulation dust at bay but is there any reason why you preferred over a thin plastic sheet? I know you said your room does not sound dead, but wouldn't a thin sheet of plastic reflect high frequencies more effectively, after being partially absorbed by basically every treatment in the room? …just curious :) … ciao simo