John Sayers' Recording Studio Design Forum Archive

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I cut the plasterboard layers with the same diameter of the finishing air nozzleand tested that it was fitting ok then 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 plasterboard Then I placed the rockwool above the plasterboard and all around the duct and 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

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

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 … I'm not arguing your guidance.. I just want to understand better

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

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

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

Hi Simo,

Well, I did get some strange looks from the ladies at 'JoAnns Fabrics'

Apparently, the 'batten' material is used in a variety of applications. I think my material was the 4oz variety [need to check]. It is very lightweight [can tear easily], but it is both 'airy' AND it provided a type of 'primer' base that helped give an opaqued look for the fabric [made the panel covers and traps less transparent VISUALLY.

I debated whether to add the plastic sheets to start. But with the design I ended up with on the 4 corner traps, my frames can be pulled out and I could then add a plastic sheet.

To be honest ... the room just does not seem to need it. [at this point].

Currently, I'm doing very minor things to the room. Mainly I've been tackling several audio projects, and testing how things transfer to the outside world.

The biggest obstacle is my old, huge CRT monitor. I still looking [and saving up pennies] to replace this beast. Looking flatscreen around 24"+, with the right screen rez for running DAW's [I don't watch video too often]. Once bought, I can finalize my design for my desk size [all the parts are in the other room].

The OTHER factor is ... after being out of the studio for several years, I'm enjoying working in this room. Everyone that's been in is nothing but positive.

This Studio design forum is a godsend. That's why I try to read the postings most everyday, and occasionally, stick my foot in the door if I see something that I can spur an idea, or relate my experience ... and also try to give some moral support.

I wish you much success with your build. I sure you look forward to completing so that you can do what it is you've built this room for It can seem a daunting, endless process ... would just say, take one issue at a time [while keeping the big picture]. Sounds easy ... but designing and building something like this can be quite a challenge. The margin for error seems minuscule AND expensive !!

Great people here! but should it ever come about where you need to ask me a question or relate something about my build, please, do not hesitate! I'm quite confidant that the 'staff' GURU's will keep us on proper course .... thank goodness!

edit:

I should proper add ... I don't mean to imply that my rooms acoustical response is 'perfect'. I've tried to build everything accordingly. Gullfo's design was closely implemented [with a minor
mod to accommodate the structure I was limited too]. I've done only preliminary REW shoots of the room, and am using different main monitors than when I first started.

I can say that the current design and treatment is better than some Pro studios that I've worked [after 30 years ... there's been quite a few]. I can move quite freely about the room with only a slight aberration in the audio [mostly in the far back corner of the room]. At the desk, the lateral/vertical movement is solid with no undulations or skew in the audio spectrum.

I am certain that Gullfo [or Soundman] would see exactly how to improve/correct it more once I post REW files. But for the moment, I need to play, study and get my chops back up, and have a chance to really test the translations. I'm hoping that I would then better understand what I'm hearing and how the treatments would be applied and their result ... and hopefully make a bit a of cash doing what I enjoy

Anyway ... enough with the disclaimer Just wanted to point out that a single build doesn't make me an expert .... just a student that now has some better sense of what this Science entails.

Hey ... look forward to your progress reports !!!!

RJHollins wrote:Well, I did get some strange looks from the ladies at 'JoAnns Fabrics'

RJHollins wrote:This Studio design forum is a godsend. That's why I try to read the postings most everyday

I couldn't agree more, and I try to read as much as I can myself.

RJHollins wrote:I wish you much success with your build. I sure you look forward to completing so that you can do what it is you've built this room for It can seem a daunting, endless process

The wishes are mutual ! Yes, it is a daunting process most of the times, especially when facing it all on your own (never even attempted anything of this scale before in my life), but on the other hand as soon as you pass an obstacle and look back at what you've just done it is quite rewarding.

RJHollins wrote:would just say, take one issue at a time [while keeping the big picture]. Sounds easy ... but designing and building something like this can be quite a challenge. The margin for error seems minuscule AND expensive !!

You're totally right, I discovered too that the secret IS tackling one issue at a time. It's just that sometime looking ahead and seeing how much still need to be done, can make it difficult to keep the focus. For sure, reading here about how other people in your same or similar boat are facing it and receive nice encouragements like yours does give you the much needed push !

RJHollins wrote:Great people here! but should it ever come about where you need to ask me a question or relate something about my build, please, do not hesitate! I'm quite confidant that the 'staff' GURU's will keep us on proper course .... thank goodness!

Thank you so much for the offer man (totally reciprocated - without being too conceited ).
Really looking forward to read about your progress too !


Ciao

Simo

Hi everyone,

I've been quiet for some time now, but I have always been following the forum religiously.

The building is going ahead very slowly, between work, kids…and I guess breaking my hand in two different places in december didn't really help that …After 2 weeks of total rest I decided to go out and try to do whatever I could … (covering the broken hand from the dust with the mighty sainsbury's orange plastic bag, thus finding an alternative use from its usual "poop bag" duty ) thanks to the ''even working at the speed of an ant is better than nothing'' approach…I was upgraded to a terminator-like cast - surely this would make me go faster and then was no looking back… well kind of, as it turned out to be quite a challenge to try to frame timber, cut and install rockwool with one hand alone


Anyway, now I'm finally recovered and back on track…so here are some pics of where I have managed to take my studio build:
First I placed the 100mm 50Kg/m3 rockwool slabs in all the cavity of the inside-out walls.

I started with the front right-hand corner, beside the right speaker soffit. After lining the cavity with insulation I managed to squeeze within it two full hight hangers. As the front baffle of the speaker soffit will kind of close them in, the opening under the baffle plate will be the entry point for sound to reach the hangers ("sharing" the same opening to reach the smaller hangers under the speaker plane)

I then moved to the Live room and did the 12 degrees angled wall at the left of the room entrance. I completely filled in the cavity with insulation (superchunk style) and placed the rockwool slabs in front of that (i.e. facing the room) Next I made the frame to hang the air con unit for the live room (which I will fill completely with insulation - superchunk again)



... end of part 1...

... part 2 ...


I then lined the cavity to house the hangers at the rear corners of the control room and in the live room As the narrow tip of the angled cavity was too small to put in hangers, I cut the insulation with that shape to fill in the gap and placed the rockwool to "close it" Then I made the hangers using Pinnacle pinboard panels as the core, and glued with contact adhesive and tied the 5cm rockwool on both side.
I cut a small piece of left over conduit to pass a polyethylene rope through the core for hanging them…perhaps a bit excessive, but after seeing the brittle texture of the fibreboard I thought that it wouldn't kill me to spend and extra minute to do it and make me a bit more at easy knowing that the hangers won't break because of their weight... Being the paranoid person that I am, I didn't trustee idea of using eye bolts / screws to hang up the acoustic hangers. I preferred to use leftover pieces of timber screwed to the frame, cutting a small channel to pass the rope through: … hangers hanged It was great to see what many here have described, i.e. the effect of moving one hanger and causing the other to move as well… cool !


In the meantime my electrician finally installed the electric panel…we got power !!! Next I cut a piece of leftover plywood (i DO LOVE recycling leftovers !!) to go on top of the electric panel.
I did that to have a plane, allowing me to sit the triangle shaped insulation within that space, which was otherwise too small to house a hanger (and did the same on the other side for the same reason)

...end of part 2 ...

... part 3 ...


Back sloped wall :

I filled the cavity with fluffy insulation, then covered that with the usual rockwool slab …same on the corners... and here it is finished (…well, insulated at least …):
Next thing I used a 25mm conduit to pass the speaker lead and clipped the power lead so they are not in the way of the hangers:

left speaker conduit: right speaker conduit: Cut the plane where the speaker will rest:

left: and right:
Then it was the time for the hangers below the speaker plane
... end of part 3 ...