Studio build in Wales, UK...again!

[Paulus87]

Hi guys,

While waiting for your collective wisdom pertaining to my questions in my post above, I have a more pressing question.

To update you on my roof situation; I have now ripped out all of the insulation from every rafter bay, and taken down all of the hangers. The ceiling is now naked. To make things even more heart breaking (temporarily) I have cut in two 1'x1' gable vents on each gable, so a total of 4 vents.

I have also found a way to install soffit vents by installing them below the wall top plates; as there are large corner traps exactly where these soffit vents are located, for each vent I will need to make an air pathway through the insulation in the traps, up to the empty rafter bays above.

Now I am considering whether or not to install a ridge vent as well.

Here are the ventilation guidelines for the UK:

https://www.wienerberger.co.uk/content/ ... nt_001.pdf

According to those guidelines, I fit in to the very first example: my building is less than 10 meters wide, with a roof pitch of 22.5 degrees, and I have a non permeable membrane on the top of the roof deck (not an underlay, but still non permeable). That means I technically only need soffit vents and no ridge vent.

However, if I were to put insulation on the ceiling which follows the rafter line (so behind my hangers) then I would assume I would fit into the example further down "Warm roof with impermeable (HR) underlay". Which means I would need a ridge vent, and the soffit vents would need to be increased to 25mm continuous air gap instead of only 10mm.

So now I need to make the decision; do I install the insulation up there now so that it's done, and put in a ridge vent? then all I need to do in the future is block up all the vents and build my outer leaf, but in the mean time the internal room can be completely finished.

Or do I go for option 1 and not install a ridge vent, then install the insulation up there in the future once the outer leaf is already constructed, and just live with the lack of treatment behind my hangers for now?


If I was to install a ridge vent and put the insulation up in the ceiling then of course I would need to leave a 50mm gap behind the insulation, which is fine, but I am wondering if all these vents are going to make the place super cold and draughty in the winter... I am wondering if I should install a ceiling of homasote on the bottom of the rafters, which goes from ridge to eaves, leaving the necessary ventilation behind it, but keeping out some of the cold and draught. Then I can install the insulation on the face of the Homasote.

So, after that long winded explanation, here is an actual question for you: If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption?

Thanks for taking the time to read and I appreciate any answers you can give me,
Paul

[Paulus87]

I guess everyone is clueless as me when it comes to my questions then

I think I'll go with a soffit vents with an equivalent of a continuous 10mm free flow air path, keep the gable vents and install the rafter line insulation once the outer leaf is built, it's probably the cheapest and easiest option right now.

I am still interested for the sake of future reference whether one would regard homasote (or other soft fibre board) as insulation or a mass when it comes to a MAM assembly. Perhaps it's both?

Paul

[Gregwor]

Now, what are the effects of introducing openings in the baffle, such as those often seen in Newell designs where the amps are racked in openings below/to the side of the speakers themselves?

In other words, how do these openings compromise the huge massive baffle wall? Do the openings do away with the whole point of building a massive continuous baffle in the first place?

Since the openings are very small, it shouldn't affect the infinite baffle concept. Only major changes in sheathing angles would mess it up.

My thoughts are that the baffle wall will act in a similar way to a speaker cabinet, if completely sealed it will be like an infinite baffle design where no low end can get behind the speakers themselves. If there are openings, then it will act like a ported speaker cabinet.

There is probably enough damping in the wall cavity to not worry about it acting like a ported cabinet. If the cavity wasn't fully filled then that would be a different story.

If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption?

Could you maybe just put up vapour barrier to tame the drafts? Your condensation shouldn't be an issue if there is good ventilation above the barrier, no?

Thanks for taking the time to read and I appreciate any answers you can give me

Sorry I haven't been around here too much lately. I've been busy as heck but you're the roof master these days anyway! Care to share some nightmare pics of your room with everything torn out? Keep your head up. It's going to be awesome when it's done!

Greg

[Paulus87]

Now, what are the effects of introducing openings in the baffle, such as those often seen in Newell designs where the amps are racked in openings below/to the side of the speakers themselves?

In other words, how do these openings compromise the huge massive baffle wall? Do the openings do away with the whole point of building a massive continuous baffle in the first place?

Since the openings are very small, it shouldn't affect the infinite baffle concept. Only major changes in sheathing angles would mess it up.

My thoughts are that the baffle wall will act in a similar way to a speaker cabinet, if completely sealed it will be like an infinite baffle design where no low end can get behind the speakers themselves. If there are openings, then it will act like a ported speaker cabinet.

There is probably enough damping in the wall cavity to not worry about it acting like a ported cabinet. If the cavity wasn't fully filled then that would be a different story.

If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption?

Could you maybe just put up vapour barrier to tame the drafts? Your condensation shouldn't be an issue if there is good ventilation above the barrier, no?

Thanks for taking the time to read and I appreciate any answers you can give me

Sorry I haven't been around here too much lately. I've been busy as heck but you're the roof master these days anyway! Care to share some nightmare pics of your room with everything torn out? Keep your head up. It's going to be awesome when it's done!

Greg

Thanks for the reply Greg, I do have some nightmare pics haha I’ll upload them soon for your entertainment.

I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers).

Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity.

What do you think?

Paul

[Waka]

I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers).

Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity.

What do you think?

It doesn't look like there's an easy to do this without having to take it down again Paul. If I were you I would staple it to the bottom of the rafters (not the rafter ties, so above the hangers) to avoid troublesome HF reflections whilst you're using the temporary room.

How long are you planning on waiting before building the new outer leaf? Are you expecting another winter. If not I might not worry about the draught. But if you are it would probably be worth the trouble and expense to just put up some temporary vapour barrier above the hangers and then when you build the outer leaf, snip the cable ties on some of your hangers and then pull down the vapour barrier. You're kind of in uncharted territory with your inner as a temporary outer leaf, then build around it later studio build.

Dan

[Paulus87]

I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers).

Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity.

What do you think?

It doesn't look like there's an easy to do this without having to take it down again Paul. If I were you I would staple it to the bottom of the rafters (not the rafter ties, so above the hangers) to avoid troublesome HF reflections whilst you're using the temporary room.

How long are you planning on waiting before building the new outer leaf? Are you expecting another winter. If not I might not worry about the draught. But if you are it would probably be worth the trouble and expense to just put up some temporary vapour barrier above the hangers and then when you build the outer leaf, snip the cable ties on some of your hangers and then pull down the vapour barrier. You're kind of in uncharted territory with your inner as a temporary outer leaf, then build around it later studio build.

Dan

Good ideas Dan, yes it is totally uncharted territory, I think I may even be the only person who has chosen to do it like this on the forum, I only know one other studio that was done like this which was a WSDG project.

I thought of the hf reflection problem and was thinking I could combat that by just putting some more treatment below the vapour barrier... my thinking is, in a normal residential build the vapour barrier would be installed on the bottom of the rafter ties with the ventilated loft space above it, then the plasterboard ceiling in front of the barrier (facing the internal room below). I need to add removable ceiling panels there anyway, which will be wooden frames with stretch fabric and insulation.

Then when it comes to removing the barrier I just take the panels down, pull the barrier off and then put the panels back up.

Makes sense or no?

Paul

[Waka]

I need to add removable ceiling panels there anyway, which will be wooden frames with stretch fabric and insulation.

Then when it comes to removing the barrier I just take the panels down, pull the barrier off and then put the panels back up.

That makes sense. I'm sure as a temporary measure it doesn't matter too much where you place it. Assuming you're not leaving it 5 years before you change it. Just go with wherever seems to be the easiest to remove it afterwards.

Dan

[Paulus87]

Just to clarify I've drawn a diagram of the proposed plan.

In reality, the soffit and gable vents would all act like inlet/outlet vents depending on the wind etc.

The vapour barrier would be installed on the underside of the rafter ties then go down under my horizontal corner traps and then sealed to the walls.

The soffit vents are actually installed under the wall top plates, and behind the horizontal corner traps; therefore I need to make sure there is an unobstructed path between the vents and the roof deck, I'll use some chicken wire or something just to keep the insulation out of the way.

According to the roof ventilation guidelines in the UK a roof with an impermeable membrane (roofing felt) does not require a ridge vent or gable vents if:

- there is the equivalent of a continuous 10mm air gap all the way along the eaves on both sides
- the building is less than 10m wide
- the roof pitch is less than 35 degrees
- insulation does not follow the rafter line

However, high level ventilation can be installed as an extra precautionary measure.

I think due to the fact that the studio will not be subject to excessive moisture (such as in the case of a bathroom or kitchen), the combination of a vapour barrier, soffit vents and gable vents should be more than enough to keep the studio in good condition until I build the outer leaf.

One pertinent thought I have though is if the vapour barrier is preventing the vapour from getting into my 'attic space' then where will that moisture go? It has to go somewhere. Therefore am I better off not installing a vapour barrier so that it can escape out of the vents? or am I better off letting it escape out of the wall ventilation system attached to the silencer boxes that will be installed?

Thanks for all your help guys, it really helps me to keep going!
Paul

[Paulus87]

What do you guys think of angling windows vertically instead of horizontally at first reflection points?

For me, it could save a lot of floor space, since then I wouldn't need "soffit wings". The idea is to deflect the rays away from mixing area, and I am aiming for the entire width of the console (11'). The majority of rays would go up into the ceiling hangers/trap.

My side walls would be about 1' thick with angled waveguide absorbers, so the angle of the windows can be sufficient to make this work, I think.

What do you guys think?

Paul

[Waka]

What do you guys think of angling windows vertically instead of horizontally at first reflection points?

For me, it could save a lot of floor space, since then I wouldn't need "soffit wings"

That's an interesting idea. It could work but only if you have the ceiling height and absorption. Will you get a 20ms+ travel time on the waves before they return? Also what about below the angled bits? Have you ray traced whether a ray heading off axis down and reflecting just below the angled bits and then off the floor and back up towards the mix position.

Dan

[Paulus87]

What do you guys think of angling windows vertically instead of horizontally at first reflection points?

For me, it could save a lot of floor space, since then I wouldn't need "soffit wings"

That's an interesting idea. It could work but only if you have the ceiling height and absorption. Will you get a 20ms+ travel time on the waves before they return? Also what about below the angled bits? Have you ray traced whether a ray heading off axis down and reflecting just below the angled bits and then off the floor and back up towards the mix position.

Dan

Thanks, Dan.

So if I did it like this, yes I would have to completely rely on absorption in order to trap certain reflections and stop them from getting to the listening position, even those reflections that would otherwise arrive sooner than 20ms. However, I am yet to decide exactly how all encompassing this needs to be...the typical recommendations are for any reflections of 500hz and up to be attenuated at least 20db and arriving at the listener's ears no sooner than 20ms after the direct sound. With lots of thick broadband trapping up in the ceiling, below the proposed windows and on the sidewalls/rear walls I don't think any energy above 500hz would even survive once it hits the treatment.

What do you think?

I am battling between 2 main designs right now, one with soffit wings and one without.

The design with soffit wings takes up a hell of a lot more space since I am aiming for a massively wide sweet spot of over 11' and 5' deep. Which means the speakers themselves need to protrude further into the room and the wings take up considerable space in order to connect them at the correct angle to the side walls to produce this console wide sweet spot.

The design without soffit wings gains me an extra 5 square meters! But, I have the issue of either getting rid of the windows on the side walls altogether or making them work but without sacrificing floor space to do it.

Getting rid of the windows would solve a lot of issues for me and here's my thoughts on why:

As we know in an ideal world it would be nice to have a full spectrum RFZ at all frequencies, but even with the perfect geometry deflecting the waves this is not possible once you get down to where the energy stops behaving like rays and becomes more omni. The other thing I do not like about a geometric RFZ is outside the zone the response is screwed again, which makes me think that relying purely on absorption is a better way to go. It is possible to absorb all reflections coming off of the side walls with the correct treatment especially since the angle of incidence means that the energy is passing through the absorption diagonally, thus increasing the thickness of absorption that the waves "see". This is especially true if both broadband and membrane traps are used for example, resulting in a room wide reflection free zone. This is the concept of non environment rooms.

But, having the windows would make it a much nicer and more practical place to work. I'd have natural light coming in through the window on the right with a nice view out to the natural world, and a view into the iso booth on the left.

Perhaps, I cannot have it all, but I still want to try.

Any advice greatly appreciated as always!

Paul

[Waka]

The design with soffit wings takes up a hell of a lot more space since I am aiming for a massively wide sweet spot of over 11' and 5' deep. Which means the speakers themselves need to protrude further into the room and the wings take up considerable space in order to connect them at the correct angle to the side walls to produce this console wide sweet spot.

You might be trying to get a reflection free zone this wide, but do your monitors even support the same fidelity at such an wide angle? You might avoid destructive interference but the sound stage will be screwed 6' off axis anyway. If you go full non-environment room like you said, you cut off almost all reverberation, are you comfortable with that? RFZ seeks to improve comfort of the listener by maintaining sound energy in the room in a non destructive way.

As we know in an ideal world it would be nice to have a full spectrum RFZ at all frequencies, but even with the perfect geometry deflecting the waves this is not possible once you get down to where the energy stops behaving like rays and becomes more omni. The other thing I do not like about a geometric RFZ is outside the zone the response is screwed again, which makes me think that relying purely on absorption is a better way to go. It is possible to absorb all reflections coming off of the side walls with the correct treatment especially since the angle of incidence means that the energy is passing through the absorption diagonally, thus increasing the thickness of absorption that the waves "see". This is especially true if both broadband and membrane traps are used for example, resulting in a room wide reflection free zone. This is the concept of non environment rooms.

You're right very low frequencies don't behave much like rays, but mid-lows do to a degree still send most of their energy "directionally". You say you can absorb all reflections off side walls. I'm pretty certain Newell has 1m thick wall treatments to achieve this. Are you doing this? Because that sounds like a lot of floor space is lost there. Does it really save space over RFZ?

How are you planning on using membrane traps? You can't use them at first reflection points if you're using absorption there. I haven't got the research to hand at the moment, but I believe membrane trap effectiveness will be reduced if behind absorption.

Dan

[Paulus87]

The design with soffit wings takes up a hell of a lot more space since I am aiming for a massively wide sweet spot of over 11' and 5' deep. Which means the speakers themselves need to protrude further into the room and the wings take up considerable space in order to connect them at the correct angle to the side walls to produce this console wide sweet spot.

You might be trying to get a reflection free zone this wide, but do your monitors even support the same fidelity at such an wide angle? You might avoid destructive interference but the sound stage will be screwed 6' off axis anyway. If you go full non-environment room like you said, you cut off almost all reverberation, are you comfortable with that? RFZ seeks to improve comfort of the listener by maintaining sound energy in the room in a non destructive way.

As we know in an ideal world it would be nice to have a full spectrum RFZ at all frequencies, but even with the perfect geometry deflecting the waves this is not possible once you get down to where the energy stops behaving like rays and becomes more omni. The other thing I do not like about a geometric RFZ is outside the zone the response is screwed again, which makes me think that relying purely on absorption is a better way to go. It is possible to absorb all reflections coming off of the side walls with the correct treatment especially since the angle of incidence means that the energy is passing through the absorption diagonally, thus increasing the thickness of absorption that the waves "see". This is especially true if both broadband and membrane traps are used for example, resulting in a room wide reflection free zone. This is the concept of non environment rooms.

You're right very low frequencies don't behave much like rays, but mid-lows do to a degree still send most of their energy "directionally". You say you can absorb all reflections off side walls. I'm pretty certain Newell has 1m thick wall treatments to achieve this. Are you doing this? Because that sounds like a lot of floor space is lost there. Does it really save space over RFZ?

How are you planning on using membrane traps? You can't use them at first reflection points if you're using absorption there. I haven't got the research to hand at the moment, but I believe membrane trap effectiveness will be reduced if behind absorption.

Dan

Dan, I'm enjoying this discussion, hopefully it is helping both of us to increase our knowledge of the subject, so here's a few more of my thoughts.

My quested mains have extremely wide dispersion, its something stupid like 80 degrees per side, and Roger Quested recommends that the listener be 80-100cm in from the point of the triangle where the axis cross. Of course, I do not expect it to be full range dispersion all the way out to 80 degrees, but soft some drivers are very flat and very wide and I would expect pretty flat up to about 30 degrees per side. In my design without soffit wings I am angling my speakers at 25 degrees instead of 30, which helps with this requirement as well as producing a much wider image the width of the console as well as at the couch.

Yes good points about treatment taking up a lot of space, but the two designs I am contemplating have the same side wall treatment so it will not eat up more space by not doing soffit wings. Newell’s designs often have relatively shallow side walls as well since adopting more modern methods of absorption than the traditional hangers. But I am not going to go full NE style for the reason you mentioned, but I want to include some aspects of the concept into my design as well as aspects from other designs. I would be more inclined to go with a balanced non environment ala John Brandt but with a few twists. My basic concept is alternating broadband absorption and bass trapping (via membranes) everywhere except areas that do not direct reflections back to the listening position which will have reflective surfaces and/or diffusion, those areas are for the listeners self noise cues to put the listener at ease.

Really the only difference between my two designs is the front wall in each. One is further forward with soffit wings with windows and the other does not have the wings and relies purely on absorption instead of deflection at first reflection points, the rest of the treatments would be the same.

Regarding membrane traps, yes I remember you bringing up this point of absorption in front of membranes effects the membranes themselves and there is a recommended distance that should be maintained between them. https://www.gearslutz.com/board/studio- ... -mass.html this is an interesting read, it seems that high Q membrane would ideally be tuned in place IF your intention is to hit a room mode, but my interest in using them is to absorb LF reflections not necessarily absorb modal ringing (more on this later) It’s also done by newell, Hidley, Thomas northward, Wes lachot they all use membranes with absorption in front. According to the book architectural acoustics absorption can even be applied in front of helmholtz resonators since the insulation in front does not effect the air going into the device. Of course, you need to take into account what frequencies are going to be attenuated (and by how much) before they then reach the device behind, and then you must tune the device to that range.

I have come up with a membrane design which has a 550mm cavity with good absorption between 30-50hz, the center frequency being 40hz with a fairly wide Q for a membrane. Broadband absorption can be applied over this to stop the membrane reflecting mids and highs. I’ve also come up with a diffuser/helmholtz/absorber a bit like the resonators you’ve built under your speakers, but using a fractal design which has high - mid frequency diffusion and then low frequency absorption (between 60-70) thanks to the slots and the waveguides inside the cavity. Well, it works in theory but will it work in practice? It’ll be fun finding out. So, I am aiming to achieve broadband absorption and low frequency control with minimum depth. I will also achieve this by not having really heavy inner walls but allowing a lot of low energy to escape through into the adjoining rooms (apart from the live room) such as the hallway, entrance and machine room. I do not need total isolation in those areas so I am using them as giant membrane cavities with the thinner inner walls acting as the membrane, this should help reduce the modal ringing I mentioned earlier.

Sorry for the long reply, I need to just upload my designs so that you guys can get a clearer image of what I’m going on about! So I’ll do that ASAP.

Feel free to share what you think of my ideas and again I appreciate all the advice I’ve been given so far.
Paul

[Paulus87]

I am really intrigued by the idea of using Homasote as part of a membrane absorber.

The material itself is strange since it's classed as a structural panel but also an insulation board. It is porous, not massively dense (I believe it's between 5-6kg/m2 for 1/2"?) and flexes. It has self dampening but not particularly great at decoupling other structures. It is light weight and would not make a good isolation product by itself. It is in between limp and rigid...all of this makes me wonder how it would act as a membrane.

I have absolutely loads of the stuff left and may do some experiments where I make some large 4'x8' membrane traps with it, perhaps 2 on the rear wall to see what effect (if any) it has.

I even wonder if it would be good as part of a sandwich in a full wall treatment - thick fluffy insulation behind it with a 2-4" layer of Rockwool in front. A sort of modex plate but without the steel plate. I read a thread in which John used panels of homesote (or equivalent) with insulation on the face and then wrapped in fabric on a rear wall of one of his builds.

My gut instinct thinks it will increase absorption around 100 - 200hz as it has an okay absorption co-efficient around 125hz IIRC. I see the main advantage of this is in an inside out wall where it could act as a constraint layer in the absorber, resistance to flow, improving absorption behind it in the stud cavity, decreasing overall required depth for low frequency absorption, while also providing a more solid and durable surface than a fabric covered light fluffy panel.

It would also be easy to tear down if it made things worse/didn't achieve anything.

What do you guys think? Anyone else tried it?

Paul

[Paulus87]

My last couple of posts haven't sparked much interest or discussion, and I doubt this update will be overly exciting either, especially since this really isn't that relevant to studio building since it's about making large holes in what's supposed to be an isolated structure. however, for the sake of completeness I present to you the story of my newly installed soffit vents:

I was trying to avoid adding these soffit vents as much as I could since it seemed 1. a shame as it'll make holes in my studio and 2. it's a lot of work for a temporary solution. But, the more I researched interstitial condensation the less risk I wanted to take, so I bit the bullet and just got on with it.

It was a challenge for many reasons; the first was I had actually blocked up the area above the top plates where the walls meet the roof with 4x2s and OSB, so there was no longer a gap there. It was too thick to drill through with a hole saw easily, especially without risking going through the actual top plates... and to top it off, I had built large corner traps over the exact area I needed to get to.

There was no way I was ripping all that out, so after a lot of mental problem solving, I just decided to put some holes lower down, below the top plates. Since the holes are opening out into the corner traps it means I can just make a pathway through the insulation for air to get in and under the roof deck, and they won't be seen from the inside. When it comes to blocking them up it will be super easy since I'll just lay a long strip of OSB over the whole lot and seal round the perimeter before putting a layer of extra mass on the rest of the walls.

Initially I was planning to just drill one hole for every rafter bay and stick a round plastic vent in. This is what I did first of all and then after re-reading the roof venting recommendations again I realised I should have a 70mm round vent every 160mm O.C. I had no where near enough vents... no problem I thought, I can just drill extra holes all the way along until I have enough... the problem is the framing gets in the way so I cannot achieve the required 1 vent every 160mm. The other problem is each 70mm vent only provides 1600mm of ventilation, not 3848mm (total area of the 70mm circle) because the closed portion of the vent takes up over half of the total area!

So, I need 1600mm vented area every 160mm in order to provide me with a continuous 10mm gap for the entire length of the studio.

What I worked out was if I put 3 holes without vents per rafter bay that would provide me with 138,528mm2 worth of openings, which is more than enough since I only need 73,000mm2. Surprisingly, if I was to put a vent in each one of those holes then I would only end up with 57,600mm2.... not enough....and I couldn't really squeeze more holes for vents up there since the framing is in the way.

So I decided to leave 3 open holes in the walls, and box them I'm with proper soffits around them with vents every 160mm.

I have to say, it seems like a hell of a lot of vents...

It was a fairly straight forward thing to build, the only thing I regret doing is drilling all the holes before test fitting the panels. This is because I marked the hole positions perfectly straight and cut them out exactly to the line, however, because the wall is slightly off square it means that the vents look like they're not going in a completely straight line due to the wall pushing the panels out slightly in the middle. It's subtle, but could have been avoided if I screwed the panels up first, then ran a string line to mark the line for cutting out the vents. Not the end of the world, this is only temporary anyway. Still, handy to know for the future.

I've only done one side at the moment, but when I do the other side I'm hoping it'll be faster. Then I can get on with doing more of the exciting stuff and hopefully my condensation woes will be behind me.

Paul