Mixing room build in Whaley Bridge, UK

[TheMillPS]

Hey everyone!

First of all a disclaimer to say we’re not very technically minded when it comes to acoustics and are self taught on Google SketchUp, so please bare with us if we’re totally wrong on some stuff - we’ve made an effort to research what we can in bits of free time we have!

Our company is coming up to it’s first year of trading and we’re looking to upgrade and build our first studio space. Come January 2016 we’re going to be building a mixing room, which will also double up as a space to be used for tracking solo instruments when necessary. We’ve been following the forum for a while, and actually used advice on this forum to treat our previous room, but this project is a little more complicated!

What We Do

We’re a production company, offering both filming and recording primarily to musicians. We work on all sorts of projects from classical to more contemporary music. Most of our work comes from the classical & acoustic styles though.

This Project

To give you some context, we’re building our mixing room in a warehouse located in an industrial site in Whaley Bridge, UK. We’re sharing the space with a carpenter who is planning on having his workshop in the same space. He occasionally uses large tools which produce quite a bit of noise! His loudest tool goes up to 93dB but he would only use this for maximum 20 minutes per day. We’re not too worried about his noise levels as he doesn’t use his big tools a lot and isn’t in the building every day, but would be good to isolate our room as much as possible. Some larger tools may cause vibrations - are we right in thinking the concrete floor should absorb this?

Attached are 3 Google SketchUp drawings of the proposed room, as well as a mobile phone photo of the warehouse exterior. In the warehouse next door are Steel Workers and we’re just divided by a thick breeze block wall. Our mixing room will be built alongside this wall (see SketchUp plan). We can’t get access to see inside the warehouse until December at the earliest unfortunately, but we’ll be able to give more precise details of the warehouse as soon as we get access.

One thread we came across that has been of great help was Allen’s mixing room build, found here: http://johnlsayers.com/phpBB2/viewtopic ... lit=soffit. We’ve read through this thread and based a lot of our ideas on this room as we think there are many similarities!

What we’re trying to achieve

We’re looking to make our room 5.4m long, 4m wide, 2.8m height. We based those dimensions on our very vague understanding of room modes, and this seemed to be pretty reasonable from looking at the Bob Golds room modes calculator - correct us if we’re wrong! We do have a degree of flexibility with the dimensions, however we can’t really go over 5.5m x 5m x 3m. The warehouse has a concrete floor and is 12.5m long by 10m wide and roughly 5m high at it’s lowest point (the roof is an open gable roof, so it’s highest point is roughly 8m). After everything is complete, we probably hope to achieve around 50-60db of isolation. Luckily we’re not very near residential properties, so can mix into the night without worrying about disturbing people.

As we mentioned, this will be primarily a mixing room, but we do want to have the ability to track drums, guitars & vocals etc. for lower budget projects.

Our build will have to take place in stages, rather than all at once due to the need for the room soon, and the fact we won’t have the budget to finish everything perfectly in one go. Our budget for the first stage is £2300 ($3400) and we hope to have the rest of the money (perhaps another £1500/$2200) for room tweaks/upgrades later on in 2016. Below is an outline of the 2 stages.

Stage 1: Building the initial ‘shell’ of the room.

This will include building 1 layer of wall, ceiling, fitting floors, acoustic treatment and electrics. We want this initial stage to include tuning the room, and even if it’s not 100% ideal isolation at this point, we want it to at least sound and look really good.

Stage 2: ‘2nd leaf’ wall & ventilation

Build a ‘2nd leaf’ around the walls that will be open to the rest of the warehouse. This will obviously include a 2nd layer to the ceiling as well, with a double door going into the studio. We hope this will complete the isolation we’ll need. Stage 2 will also include building a nice cloud (if needed - we’ll talk more about this at a later stage).

So ideally we’d like to build the walls & ceilings, speaker soffits, ventilation, electrical facilities and acoustic treatment within these two stages. I know that may seem totally crazy, but this is what we can afford for 2016. It’s worth knowing that the carpenter we’re sharing the warehouse with is helping us build the room for no charge, and he’ll be purchasing all of the materials at his traders discount.

We have also already made 15 acoustic panels from advice previously given in this forum. Below is a picture of those panels which we can re-use in the new room. We’ve already costed this up and we’re just about in budget so far. We’ll be in this place for a minimum of 5 years, hopefully longer, so we want to do as good of a job as we can!

Where we’re up to

So far nothing has been done apart from research, trying to learn how to use SketchUp to throw some plans together, and writing this post. We didn’t want to order any materials or finalise plans until we had some input from people who really knew what they were doing before we spend precious budget on mistakes!


Questions

1) Something we’re clueless on is ventilation. We’ve read about the HVAC systems in this forum, but have no experience or knowledge of what’s best for our situation. There are no existing ventilation systems in the warehouse. We probably won’t be able to afford an actual unit in January, but obviously we want to build the room in a way which will accommodate an air conditioning unit in the future, and in the meantime allow for fresh air to circulate. What are you thoughts on this?

2) If we’re building the 2nd leaf wall at a later stage, should we keep the outside of the ‘shell’ wall with open rock wool, or would it be ok to cover it temporarily with a cheap board until we build the 2nd leaf wall?

3) Are the angles of the splay walls & speaker soffit walls suitable? Are there any formulas or software we should be using to work this out in relation to our room dimensions?

4) We’ve seen a lot speaker soffit designs for upright speakers but not many for our Adam A77x type. Do you know of any soffit designs we can work off for wider speakers? In these drawings the height of the speakers are at ear level, which we assume is correct. Should there be a formula to follow for this, or is it a case of what ever is ergonomically best for the engineer?

5) Ideally we’d like the cables at the desk to be as hidden as much as possible. We thought that maybe we could insert plug sockets into the floor by where the desk will be. Our flooring will just be laminate on the concrete slab. Has anyone got any recommendations/experience with this?

Many thanks to everyone who has already posted valuable information on this forum! Looking forward to hearing people’s thoughts and getting some input.

Dave

Warehouse.PNG

Initial Design.PNG

Birds Eye Angles.PNG

warehouse.jpg

panels.jpg

[Soundman2020]

Hi Dave, and Welcome!!

Just clarifying: this ONLY going to be a control room? No associate live room in the same warehouse? That's what it sounded like, from what you said. Is that correct?

He occasionally uses large tools which produce quite a bit of noise! His loudest tool goes up to 93dB

What type of "loud tools" are we talking about? When you say 93 dB, how did you measure that? dBA or dBC?

Some larger tools may cause vibrations

Do you mean floor-mounted tools, rather than hand tools? Something like drill press, table saw, thicknesser, lathe, or something along those lines? Something that is directly bolted onto the concrete slab floor?

are we right in thinking the concrete floor should absorb this?

Perhaps not... If that machinery is producing vibration that gets directly into the slab through a mechanical connection, then that is the same as impact noise, and will probably be audible in your control room, since it will be transmitted directly through the concrete. An easy way to tell is to use a stethoscope: if you have a doctor friend or nurse friend, then borrow one and listen to the floor at the place where you plan to build the CR, while the carpenter is using each piece of his machinery. If you hear the noise in the stethoscope, then you have a problem. Make sure the carpenter is actually using the machinery to cut wood: not just that it is turned on and running. Most of the vibration and noise comes from the cutting action, not so much from just the motor rotating.

If this turns out to be an issue, then you have two possible solutions. Isolate your floor (big money, complicated), or offer the carpenter free isolation pads for his gear! It would very likely be cheaper for you to buy suitable isolation mounts for whatever it is that causes the slab vibrations, and have it installed properly, rather than to try to float your floor. It is ALWAYS better to eliminate this type of problem at the source, as well, rather than trying to deal with it at the destination...

In the warehouse next door are Steel Workers

Do they also make a lot of noise, and is your slab connected to their slab?

We’re looking to make our room 5.4m long, 4m wide, 2.8m height.

That's a decent size for a small control room, yes. But are you SURE you checked that with Bob Gold's calculator? Because I just did, and found this in the section on the three critical BBC tests:

- 1.1w / h < l / h < ((4.5w / h) - 4): Pass
- l < 3h & w < 3h: Pass
- no integer multiple within 5%: Fail (ratio3 = ratio1 * 2)



It's not too much of a big deal though. If you did want to twiddle and tweak, you could fix that by making it more like 5.30 x 4.15 x 2.90. That also gives you more floor area and more volume, which is always good.

However! You are proposing to use an RFZ design, with splayed walls, which implies that the room is no longer rectangular, with 6 sides: It is now trapezoid, with 8 sides, so simple room mode calculators, such as Bob Golds, are no longer accurate, and don't really tell you what the modal response will be.

But I'd say that you are probably good with that size.

Below is an outline of the 2 stages.
Stage 1: Building the initial ‘shell’ of the room.
Stage 2: ‘2nd leaf’ wall & ventilation

That's a rather "upside down and back to front" way of going about it! You could do it like that if you wanted, but I do hope you realize that you won't have any isolation at all to start with, and the room will sound pretty lousy. It won't work properly until "stage 2" is complete. Are you aware of that, and OK with that? You mention other people ("we"), so it would be very important to warn the others that after spending all that time and money for stage 1, it won't sound good inside, and it also won't isolate! It will also be uncomfortable to work in (no HVAC)...

even if it’s not 100% ideal isolation at this point, we want it to at least sound and look really good.

It can look good after stage 2, but it won't be sounding too good, for several reasons that are rather complex.

Stage 2 will also include building a nice cloud

That's one of the reasons it won't sound good, and won't be accurate acoustically. Until the cloud is in, you'll have major modal problems in the vertical plane, and major reflection issues, which implies a lousy sound-stage, inaccurate tonal balance, and a few other things too.

I know that may seem totally crazy,

Yup. Crazy, but doable, and it is a workable plan as long as you don't need to do any critical work in there before stage 2 is complete.

Where we’re up to
So far nothing has been done apart from research, trying to learn how to use SketchUp to throw some plans together, and writing this post. We didn’t want to order any materials or finalise plans until we had some input from people who really knew what they were doing before we spend precious budget on mistakes!

Very, very smart move! Way too often we have new members join the forum after they have already started, and they usually aren't too please to learn about all the things they did wrong, and need to take apart and re-build.... You guys are doing it right: first plan it through completely, and only then start building...

1) Something we’re clueless on is ventilation.

HVAC is a big and rather important part of studio building, and often overlooked until it is too late. You need to do quite a bit of math here, to design your HVAC right. That's the starting point.

There are no existing ventilation systems in the warehouse.

No problem: even if there was one, it probably would not have been much use to you. You would have needed to do yours independently anyway.

we want to build the room in a way which will accommodate an air conditioning unit in the future, and in the meantime allow for fresh air to circulate. What are you thoughts on this?

As long as you don't mind working in uncomfortable conditions, and as long as your ventilation is good, then you could do that. But do be aware that you won't have any control of humidity in the room until the HVAC unit is in place...

2) If we’re building the 2nd leaf wall at a later stage, should we keep the outside of the ‘shell’ wall with open rock wool, or would it be ok to cover it temporarily with a cheap board until we build the 2nd leaf wall?

I woulkd just cover it in thick plastic for now, then that that off just before you build stage 2. That is mostly just to keep the insulation in place, and to protect it from being damaged by people walking around. Apply it as broad strips with small gaps between, to make sure that it does not act like a second vapor barrier.

3) Are the angles of the splay walls & speaker soffit walls suitable?

No.

Are there any formulas or software we should be using to work this out in relation to our room dimensions?

Yes.



Not so much formula and software, as rules of thumb, trial and error, and slogging away with SketchUp to get it right.

4) We’ve seen a lot speaker soffit designs for upright speakers but not many for our Adam A77x type. Do you know of any soffit designs we can work off for wider speakers?

You don't have to mount them horizontally: A77's can also be mounted vertically. Like this:

A77X-vertical-mount.png

That was a conceptual design I did for one of my customers recently. In the end, he opted for other speakers (which are similar to the A77's, and will also be mounted vertically), so this wasn't actually built, but it would have worked just fine. You could do something similar.

In these drawings the height of the speakers are at ear level, which we assume is correct. Should there be a formula to follow for this, or is it a case of what ever is ergonomically best for the engineer?

Speakers should be set up such that the ACOUSTIC AXIS is located 1.2m above the floor, which not surprisingly is the height of your ears when seated. Get a tape measure and check... How did I know that? Because that's roughly the height for most people when seated. Maybe 1 or 2 cm higher or lower... the majority of people will be around there.

But do note that I said "acoustic axis", not "top of speaker" or "bottom of speaker" or "center of speaker". The acoustic axis is the point on the front panel of the speaker where all of the sound appears to come from. The manufacturer should be able to tell you that. If not, there are ways of estimating it...

So set up your speakers such that the acoustic axis is 1.2m above the floor, or maybe a bit higher for big speakers like these when mounted vertically.

There are also other similar rules of thumb regarding where your speakers should be positioned in the soffit baffle, the distance from the side walls, the angles (not 40°!), and the position of the engineer's head in the room, which defines the location of the desk, console, etc.

We thought that maybe we could insert plug sockets into the floor by where the desk will be. Our flooring will just be laminate on the concrete slab.

Then you'd have to chase channels in the concrete floor, if you wanted plugs in the floor... Laminate flooring is only a few mm thick...

You could do that if you want, but if you are only renting the space, you might find that the owner will not allow that.

Another option (less attractive) is to use rubber "cable trays" on top of the floor, running from the front wall to the desk, to organize your cables, and have your outlets and patch panels built into the desk itself. Something like this:

floor_cable_protector1.jpg

floor_cable_protector4.jpg

- Stuart -

[TheMillPS]

Hi Stuart,

First of all, thanks so much for the welcome and the quick, in-depth answer - really gave us a lot of things to think about!

We've spent the last 5 days doing more research and getting literal headaches trying to work out some of these things, but have made little steps in progress and are very gradually piecing together things we've learnt.

Just clarifying: this ONLY going to be a control room?

That's correct - there will be no live room, at least in the near future! However, we will be tracking solo instruments in the control room from time to time.

What type of "loud tools" are we talking about? When you say 93 dB, how did you measure that? dBA or dBC?

That was measured 93dBA. It wasn't actually measured by us, but by the guy we're going to share with. Here is a list he gave us of his bigger tools:

- Bandsaw
- Dust extractor
- Panel saw

In terms of little power tools he also has a compressor.

Do you mean floor-mounted tools, rather than hand tools?

Yes the bigger tools are floor-mounted.

If this turns out to be an issue, then you have two possible solutions. Isolate your floor (big money, complicated), or offer the carpenter free isolation pads for his gear!

That's great - thanks for these suggestions! We won't be able to find out whether this is an issue until we move in in January as we start the build, but because funds are limited we'd go for the isolation pad solution anyway so can presumably sort that out then.

Do they also make a lot of noise, and is your slab connected to their slab?

They are relatively noisy, but not as loud as the louder tools that will be in the workshop. Unfortunately won't be able to get an accurate reading on this until move-in day. Get the keys on 28th December, but won't order any materials until 2nd week of Jan just in case anything needs changing last minute (which I'm hoping not!!). I think that their slab is connected to ours as well, yes.

Because I just did, and found this in the section on the three critical BBC tests:

Totally didn't see that, thanks for pointing it out - on the amended plan I've gone with the new dimensions you suggested.

It won't work properly until "stage 2" is complete. Are you aware of that, and OK with that? You mention other people ("we"), so it would be very important to warn the others that after spending all that time and money for stage 1, it won't sound good inside, and it also won't isolate!

We understand it won't be great until we can get stage 2 complete, but there are only 2 of us and we're both aware of the implications. 1 of us will actually be working in a video editing room which we'll be building next door - i've done a sketch of what stage 2 will consist of with the other room in place as well. Will this other room cause any issues? He won't be very loud, the kind of video editing he does mostly involves promotional videos (interviews basically).

We were wondering about whether there is any point at all trying to tune the room after stage 1? I guess not from what you said. If not shall we just put up our current sound panels on first reflections to help a bit until we can get the 2nd leaf built and cloud and other treatment build?

It will also be uncomfortable to work in (no HVAC)...

The good thing is that we will be in winter UK and will be COLD! We won't need air con to cool the place down, especially seeing as most of the time there will be only 1 of us working in there. The main thing is making sure there is some sort of fresh air getting in. We're hoping to build the rest of it by summer so when it starts to get (slightly) warmer, we should have something in place to control humidity and temperature. Researching air con systems and everything has given me the biggest headache I think. So much information to try and take in - very overwhelming! I wish there was just a simple '10 step guide' to designing it on a budget.

Yup. Crazy, but doable, and it is a workable plan as long as you don't need to do any critical work in there before stage 2 is complete.

Well that's definitely reassuring! We can work around a few months of a slightly lousy sounding room as it is better than the alternative - trying to mix in a complete un-soundproofed bedroom at home. Don't think I'd be very popular.

Not so much formula and software, as rules of thumb, trial and error, and slogging away with SketchUp to get it right.

OK, so in the 2nd picture below is a new diagram I drew, this time in 2D to try and get it right before building a nicer looking one. Here the soffits are at 30 degrees, and the splay walls are at 19 degrees. The '38%' line where the listening position currently is is 38% down the full length of the room, not taking into account the splay walls creating different lengths in the room. Is this still suitable and if not what's the best way of working out the best listening position now the room is not rectangular?

I've also tried to do some ray tracing (sorry it's a little messy - did it in SketchUp!). Let me know what you think about the new layout and whether it's an improvement. The one thing that I was worried about is the splay wall starts a little behind the listening position, but couldn't get it to work any closer unless the splay walls were at quite a bit of a bigger angle.

You don't have to mount them horizontally: A77's can also be mounted vertically. Like this:

Thanks for that - looks great! I think we'll probably do something like this, as we also have Yamaha HS50M speakers which we'll have on our desk and having the A77x mounted vertically will make these easier to position and not being in the way!

But do note that I said "acoustic axis", not "top of speaker" or "bottom of speaker" or "center of speaker". The acoustic axis is the point on the front panel of the speaker where all of the sound appears to come from. The manufacturer should be able to tell you that. If not, there are ways of estimating it...

Had no luck finding this out from manufacturer but will look around to find out the "ways of estimating it.."

Another option (less attractive) is to use rubber "cable trays" on top of the floor, running from the front wall to the desk, to organize your cables, and have your outlets and patch panels built into the desk itself.

I like this idea of having them build into the desk! Thanks for suggesting that - I think we'll go for something like that and work out the positioning of the rest of them around the room

Another couple of question for now

1. Can we achieve the RFZ without an angled ceiling using the cloud we'll construct, or does the ceiling need to technically be angled?
2. Is there a specific type of wood recommended for the front panel of the top part of the soffits? We'd like the look of a walnut wood.

Thanks again for all your help! Much appreciated

Dave

Stage 2.JPG

Ray Trace 2.JPG

[Soundman2020]

We've spent the last 5 days doing more research and getting literal headaches trying to work out some of these things

Only headaches? So you didn't get the blithering heebie-jeebies yet? You can still walk a straight line and talk coherently? Then clearly you aren't trying hard enough!

Seriously, studio design can drive you nuts, as there are just so many variable to juggle, all at once.

That was measured 93dBA.

For loud sound sources you should measure using "C" weighting. "A" is a good approximation of how we perceive quite sounds, but "C" is a better approximation of how we perceive loud sounds.

Yes the bigger tools are floor-mounted.

So vibration in the slab might be a real possibility?

but because funds are limited we'd go for the isolation pad solution anyway so can presumably sort that out then.

It won't be cheap to isolate floor-mounted carpentry tools, but it will be an awful lot cheaper than floating your floor!

I think that their slab is connected to ours as well, yes.

I hope that isn't the case...

sketch of what stage 2 will consist of with the other room in place as well. Will this other room cause any issues?

Nope! That would actually be a good thing, and will improve isolation since you will now have a proper 2-leaf MSM isolation system for the Control Room. If you did want to isolate his room as well, it wold not be difficult to do.

We were wondering about whether there is any point at all trying to tune the room after stage 1

You'll be able to do some things, yes, but it will likely change once the second stage is in place. I would at least do the basic treatment in there, which you will need regardless, then fine-tune once stage-2 is up.

The main thing is making sure there is some sort of fresh air getting in.

Yep! That is, indeed, rather necessary...

Researching air con systems and everything has given me the biggest headache I think. So much information to try and take in - very overwhelming!

Absolutely! It's a much, much bigger deal than most people realize...

OK, so in the 2nd picture below is a new diagram I drew, this time in 2D to try and get it right before building a nicer looking one. Here the soffits are at 30 degrees, and the splay walls are at 19 degrees. The '38%' line where the listening position currently is is 38% down the full length of the room, not taking into account the splay walls creating different lengths in the room. Is this still suitable and if not what's the best way of working out the best listening position now the room is not rectangular?

That's a good start, yes, and much better than the original. However, you have the acoustic axes of the speakers intersecting inside your head, which would be fine if your ears where were your eyeballs are... but since your ears stick out to the sides of your head, your speakers need to be angled a little less to take that into account, and the acoustic axes need to intersect about 12" to 18" behind your head.

You can also bring the straight section of the side walls a but more forwards in the room, to roughly where your head is, or even a bit more still, then angle the front-side wall parts a little more, which will help with your RFZ.

Also, each speaker should not be centered left-right on the soffit front baffle: it should be offset somewhat, to reducing the "lobing" or focusing effect. if you can get it about 2/5 ths of the distance across, that's a reasonable compromise.

The one thing that I was worried about is the splay wall starts a little behind the listening position, but couldn't get it to work any closer unless the splay walls were at quite a bit of a bigger angle.

Yup! Nothing wrong with having them at a bigger angle: that helps your RFZ to be wider...

also have Yamaha HS50M speakers which we'll have on our desk

Not a good idea! Having speakers on your desk, or above the desk, or on the console meter bridge, or anywhere in that area, creates a whole series of nasty artifacts and reflections. Try to avoid that like the plague! Put your speakers on stands just behind the desk, never on it or over it. (Yeah, I know you see that all the time in sound magazines, but just because you see it does not make it right! I often see picture of politicians lying through their teeth, but that doesn't make what they are saying true or correct! )

1. Can we achieve the RFZ without an angled ceiling using the cloud we'll construct,

You can, yes, provided that the cloud is "hard-backed" (massively so), large enough, and angled correctly.

2. Is there a specific type of wood recommended for the front panel of the top part of the soffits? We'd like the look of a walnut wood

The type of wood does not matter. What does matter is that the panel has to be massively heavy, and rigid. So you could build it up from a couple of layers of thick MDF, plywood, OSB, drywall, lead sheet, MLV, or anything else that is dense enough, then glue a walnut veneer or walnut panel to the front, purely for aesthetics.

- Stuart -

[TheMillPS]

Hey again!

Sorry for disappearing for a couple of months - the end of last year got a bit crazy busy leading up until Christmas, and only just getting some free time after moving everything into storage in the new place to carry on with the planning. The space is now ready for us to build in, and we have more accurate measurements which is good. The only downside is we've had to make our room a little smaller as we initially mis-judged the space we had!

So we've re-drawn the design with the new dimensions, but also taking into account the advice from your last message, having the splay wall start at around the sitting position, and the acoustic axis intersecting behind our head so we can listen with our ears rather than eyeballs . The new dimensions are 4.8m x 3.7m x 2.9m. This seemed to look good on the Bob Golds calculator - correct me if I missed something like last time!

New drawing:

Room Close.JPG

For context in larger space:

Room in Warehouse.JPG

How do these new drawings look? Our idea is to attach studs to the outside walls (top and left of drawing), and stuff with rockwool to put extra insulation and to make the 2nd leaf on those sides more soundproof. The right and bottom walls will obviously just be built by us like normal. The only issue here is the door which we'll be covering, which is a metal exterior door. What do you think would be the best way to deal with that? We can't actually remove it as we can't structurally change the building.

We're also thinking to try and build the 2 leafs in stage 1, and actually get in there and start working, but leaving the decorating until we have the money for that as we feel sound is more important than aesthetics short term! It should only be about a month working in a slightly ugly room before we get the laminate and paint sorted.

We also won't be able to build a new cloud for a while, but we currently have 8 100mm home made rockwool panels and 7 50mm thick ones. We were thinking of hanging 3 of these from the ceiling until we can afford to build a slightly nicer larger one. Would you recommend using the 100mm ones over the 50mm ones for this?

Now it comes to ventilation! We've come up with an idea based on a drum room build we saw, where they managed to get really good isolation and fresh air using this cheaper option:

Ventilation.jpg

Using two ECO DMEV HT fans, we will have one on the external wall, and one on the internal wall. Both fans will feed through ducting that is fed in-between the studs in the wall, feeding to a vent (here's a link http://www.envirovent.com/trade/product ... /eco-dmev/). The question is what your opinion is of this, and also how to get the ducting through the 2nd leaf? Do we go straight through the 2nd wall, or use a similar snaking method for the outside leaf as well?

Another little question we had was about painting - is it OK to plaster the inside walls of the room?

Thanks so much!

Dave

[Soundman2020]

The new dimensions are 4.8m x 3.7m x 2.9m. This seemed to look good on the Bob Golds calculator - correct me if I missed something like last time!

That looks fine, yes. But do be aware that the prediction won't be accurate, as your room is not rectangular: It will be close, but the angled soffit walls still do have an effect on there, so the actual response won't be exactly what the calculator predicts.

taking into account the advice from your last message, having the splay wall start at around the sitting position,

Are you sure they are angled enough to create the RFZ? Did you ray-trace to check that? To me it looks like there might be an issue there....

How do these new drawings look:

Looks good. You could probably move the axis intercept a bit further back in the room. You should also get your speakers off-center from the soffit baffles, to reducing the lobing and focusing effects.

Our idea is to attach studs to the outside walls (top and left of drawing),

Why? That doesn't make a lot of sense...

and stuff with rockwool to put extra insulation and to make the 2nd leaf on those sides more soundproof.

The mineral wool does not increase soundproffing. It provides damping on the internal resonances going on inside the cavity, and it is a necessary part of the MSM system. Without that, you'd lose a lot of isolation. So it isn't something that you do to get a bit more isolation: it is something that you absolutely MUST do if you want any isolation at all! Not because the mineral wool isolates by itself (it doesn't), but rather because it provides the damping that is critical for the MSM system to work well.

But why do you want to put studs in there? Why can't you just put the insulation in there on impaling spikes, in the normal manner?

The only issue here is the door which we'll be covering, which is a metal exterior door. What do you think would be the best way to deal with that? We can't actually remove it as we can't structurally change the building.

Build a "plug" for that door, in the same way as you would for an external window. But first, do check your local building codes and regulations: of that door is an egress path for emergencies (fire, for example), then you might not be allowed to close it off.

We're also thinking to try and build the 2 leafs in stage 1, and actually get in there and start working, but leaving the decorating until we have the money for that

OK, but you'll still need to do the acoustic treatment in order to have a usable room, and the treatment is often built with aesthetics in mind, along with acoustics. Decoration and acoustics don't have to be two different things.... They can be combined....

as we feel sound is more important than aesthetics short term!

Agreed!

We also won't be able to build a new cloud for a while,

... then you won't be able to have good acoustics for a while!!

but we currently have 8 100mm home made rockwool panels and 7 50mm thick ones.

I would use those for the basic treatment of the room: the thicker ones would probably make good bass traps in the corners, and the thinner ones could serve as absorption on the side walls and rear wall.

We were thinking of hanging 3 of these from the ceiling until we can afford to build a slightly nicer larger one.

That would work reasonably well.

Now it comes to ventilation! We've come up with an idea based on a drum room build we saw, where they managed to get really good isolation and fresh air using this cheaper option:

The concept is fine, the implementation is not. Silencer boxes rely on several acoustic tricks at once to greatly reduce sound transmission. It isn't just about baffles and changes in direction, although that's a part of it. There is also the sudden changes in cross-sectional area which create large impedance mismatches at the transition points, plus the sudden reduction in air flow velocity, and the all-important acoustic duct lining. Your design does not consider any of these critical points of silencer design, so it would not work very well.

Here's how to build real silencers that do work:

http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
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http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16

You need to do some math here, to figure out the dimensions that you will need for your silencer boxes. You can't guess! You need to ensure that the internal cross section is large enough (after considering the thickness of the duct liner) in order to get the air flowing slowly enough (flow velocity) but with the correct volume (flow rate), while creating those impedance mismatches at the transitions, and several sudden direction changes, plus massive baffles, and thick enough walls...

Using two ECO DMEV HT fans, we will have one on the external wall, and one on the internal wall.

Why two? Balancing the flow rates between them would be a nightmare in such a small room... And having one fan INSIDE the room would be kind of silly, considering that you want to keep all noise OUT of the room!

The room will be doubly sealed, twice-over perfectly hermetic. If you have one fan sucking air out of the exhaust duct, then the pressure drop will automatically draw air in through the supply duct. Assuming that you use the correct fan for your flow rate, flow speed and static pressure, of course...

here's a link

I have to say that I get really, really concerned when I see those "one size fits all" claims in advertising hype! That's a major red flag for me, and I just turn and run when I see that. Did you check the actual air handling capacity of that fan at all? How many cubic feet per minute of air can it move? At what speed does it move that air (feet per minute)? What static pressure can it handle, and how does that affect the flow rate and speed? How does that compare to what YOU need for YOUR room?

Red flags! Big ones! Lots of them! Waving madly!

The question is what your opinion is of this,

I would have to say: "lousy".

and also how to get the ducting through the 2nd leaf?

... in the same way you get it through the first leaf.... If you want high levels of isolation, you need a silencer box on EACH leaf, on EACH duct....

Another little question we had was about painting - is it OK to plaster the inside walls of the room?

That depends on your basic design concepts, and how you plan to treat the room... If you build using the "inside-out" technique, then it would be rather hard to plaster the walls... If you build conventionally, then that would be fine.


- Stuart -

[TheMillPS]

Thanks again for all your help! Much appreciated, and we feel we're gradually getting more clear on a lot of things!

Are you sure they are angled enough to create the RFZ? Did you ray-trace to check that? To me it looks like there might be an issue there....

I just did a ray trace, and it seems to me to be OK, but let me know! I've moved the speakers off-centre from the soffit baffles and they now intercept slightly further back in the room as well.

Ray Trace New.JPG

Why? That doesn't make a lot of sense...

I actually have no idea, a ridiculous idea haha. Impaling spikes make a huge amount more sense - thanks for pointing towards those! We're currently working on meeting with the landlord to suss out whether we can block that door off. If not, then we'll just have to move the room a meter or so forward in the warehouse and build the 2nd leaf of that side wall like the others.

OK, but you'll still need to do the acoustic treatment in order to have a usable room, and the treatment is often built with aesthetics in mind, along with acoustics. Decoration and acoustics don't have to be two different things.... They can be combined....

Agreed! We're going to try and treat it as best we can with our panels we have, which will do an OK initial treatment, then once we've tested the room properly and saved more we'll make some more permanent treatment which also looks nicer!

The concept is fine, the implementation is not.

I would have to say: "lousy".

We’ve done some further research into air conditioning and as you kindly pointed out to us - we got it very wrong! We basically copied an air con design from a studio build YouTube video, but it’s become clear that they didn’t quite think it through properly. Hopefully the following is an improvement…

We’re now looking at a CAB-160 unit from this company http://www.justfans.co.uk/cab-acoustic-fans-p-236.html to fix to the outside vent of the 2nd leaf. At full power, this will provide us an hourly air change of 7.6 (max of 390 m3/h) , which using the correct formulas seems to be suitable for our room. Are we on the right lines here? You can find the specs for the CAB-160 on this PDF: http://justfans.co.uk/catalogues/CAB.pdf. We’re also now clued up on silencer boxes and their purpose, so we’ll get on that!

Just wanted to ask about the open supply duct. Because we’re essentially putting a 4 inch hole in the wall, how well do you think the silencer boxes and weaved ducting will be at soundproofing? We won’t be running long lengths of ducting - I imagine it’ll be around 3m in total - but with the silencer boxes on both ends, do you think this will be good enough to not let much sound pass through? I'm presuming this will just be open at each end as there won't be a 2nd fan pushing air into the room?

Thanks for all your generous help - we're probably going to start ordering things next week to get work on the shell as soon as we've made sure the door situation is OK!

Dave