John Sayers' Recording Studio Design Forum Archive

I think I've got most of my studio design thought out now.

I've opted for these key features:

Interior dimensions:

H x W x L:
2.75m x 3.6m x 5.3m - With a flat interior ceiling instead of sloped

Walls:
External: 100mm studs, 100mm Rockwool Insulation, 9 OSB sheathing x 2 layers
25mm Cavity
Internal: 100mm studs, 100mm Rockwool Insulation, 9mm OSB sheathing, 15mm Plasterboard x 2 layers

Ceiling:
170mm x 47mm joists supported by internal walls, 100mm Rockwool Insulation, 9.5mm Plasterboard, 15mm Plasterboard x 2 layers

Roof:
195mm x 47mm joists supported by external walls, 100mm Rockwool Insulation - suspended against roof sheathing, leaving large air cavity of min 70mm increasing as roof slopes up 1:20 pitch.
9mm OSB sheathing x 2. 100mm Square vents every 400mm along soffits of each long edge of flat roof.

Box Silencer along each outside soffit of roof the whole length. Inside sectioned to provide a lined baffle for each vent. This should provide adequate airflow to meet building regulations requirements for vented flat roofs.

A/C:
http://www.arredatutto.com/en/olimpia-s ... 62622.html
With silencer box for inlet and outlet on exterior wall.

Ventilation:
http://www.fansandspares.co.uk/shop/pro ... -axial-fan
With Silencer box on each side of wall around fan.

Inlet for fresh air on opposite side of the room with silencer box on each wall skin.

Silencer boxes all made with mass to match mass on the wall it attaches to.

Windows:
Designed following instructions in Rod Gervais' book.

Door:
Single Sand-Filled door as designed by Jhbrandt. Roughly 100kg. In a frame with seals as outlined in Rod's book. (I have a supplier near me for the Zero branded seals if anyone is interested, roughly £160 for the drop seal and threshold inc. VAT) I'm not installing magnetic weather stripping as I will be installing a lock and latch to my door as it is an exterior door (As described in jhbrandt's instructions for his sand door), and this holds the door tight against the seals.

I'm going to be starting a thread in the Studio Construction sub-forum soon to track the progress and get specific advice.

Let me know if there's anything you've noticed could need adjusting.

Regards,
Daniel

I was interested in mini split systems like those but opted against them

... I'm just wondering how you plan to get the humidity under control. HRV's do nothing for humidity... You live in the UK where high humidity is an issue year round, yet you need to keep it at a constant 40%RH for your instruments, equipment, and mics, as well as to control mold. How are you going to do that with nothing that has that ability to dehumidify?

the outside unit is loud (52db for that one you linked).

The get a quite one! There are many systems available on the market that put out only a tenth of that.

it's also not really possible to isolate the unit due to overheating.

Sorry, but I don't agree! Reducing the level of an outdoor mini-split compressor to be pracically inaudible is not hard to do. And it will not cause overheating.

The system I linked is actually an all-in-one system. It requires no outdoor system at all,

In other words, it does not dehumidify....

In my situation I require the system to have low inside dB AND outside dB ha! I'm trying to have as little impact on my surroundings as possible

Not a problem. Both can be done, without too much hassle.

How do I know? I have TWO mini-split compressors at my house, one is about 2m from the property line to one of my neighbors, the other is around 4m from the sidewalk. I have never had any complaint about either, after ten years, and in reality you cannot hear either of them. My neighbor on the other side has one on her roof, and I have never heard that one either. A couple of years ago we installed four very large units on a local church, and even when all four of them are running full bore, the neighbors can't hear a thing.

You seem to be imagining farr too much about these units, and rejecting them outright from fear, not from knowledge, even though they are an absolute necessity for a studio. You do need some form of HVAC, even though you think you don't. An HRV does not replace an HVAC system: it compliments it.

- Stuart -

Soundman2020 wrote:

I was interested in mini split systems like those but opted against them

... I'm just wondering how you plan to get the humidity under control. HRV's do nothing for humidity... You live in the UK where high humidity is an issue year round, yet you need to keep it at a constant 40%RH for your instruments, equipment, and mics, as well as to control mold. How are you going to do that with nothing that has that ability to dehumidify?

It wasn't actually myself who mentioned about buying a HRV system I haven't got any plans to install one at present. The AC I linked actually claims to provide 0.6l per hour of dehumidification. Do you think this is insufficient?

The get a quite one! There are many systems available on the market that put out only a tenth of that.

it's also not really possible to isolate the unit due to overheating.

Sorry, but I don't agree! Reducing the level of an outdoor mini-split compressor to be pracically inaudible is not hard to do. And it will not cause overheating.

Thats good news! I couldn't find any information my searches, but I did find lots of advice not to block or store the condensor anywhere but in open air. Can you link to a quiet system any chance? Or give me an idea how to isolate the noise of one?

It's true I've not installed one before, but I've been going on the info online. The dB listed was compared to traffic noise. Traffic noise is uncommon in my area and that was my reasoning for looking to alternatives like I linked.

Kind regards,
Daniel

Good news! I have officially got planning permission with the dimensions and garden location to build the studio.

So I'd like a little help with the layout if possible. I like the window placement as they are at the moment, but if necessary I can change them before my construction begins.

This is what I have for the flush mounted monitors: How does it look?
Are there any alterations you would make?

The speaker baffles will be made out of thick MDF on a timber frame and cavity filled with insulation. The speaker will be housed in an MDF box with an open back and chicken wire used to maintain a free flow of air from the back of the speaker box to the bottom and top air ports.

Thanks,
Dan

Hi Dan

I'm sure others can give more accurate advice, but I am thinking you will want to bring your speakers away from the corners of the room a bit. Your diagram shows them being almost in the corners. I remember reading Stuart's comments on one thread that said the speakers should be at 28% of the room width, but this might be when they are stand mounted rather than soffit.

Regarding the windows, I'm guessing you can't have them opposite each other (for improved symmetry in the room) because of what they'll look out on/location of the building in the garden?

Good luck!

Gareth

garethmetcalf wrote:Hi Dan

I'm sure others can give more accurate advice, but I am thinking you will want to bring your speakers away from the corners of the room a bit. Your diagram shows them being almost in the corners. I remember reading Stuart's comments on one thread that said the speakers should be at 28% of the room width, but this might be when they are stand mounted rather than soffit.

Regarding the windows, I'm guessing you can't have them opposite each other (for improved symmetry in the room) because of what they'll look out on/location of the building in the garden?

Good luck!

Gareth

Hi thanks for your response Gareth. I had read something about the corners being non ideal, but hadn't myself found any info on whether flush mounting lessens the problems associated with this. I chose to use the corners as this reduces lost floor space. I have actually moved the baffles into the room a little more in my most recent design to feed a duct behind it for ventilation. I'll upload that design soon.

Hopefully Stuart can give some more info on the speaker positioning.

The Windows ideally would be placed on that wall yes. The opposite wall is possible but at lot less desirable functionally. I had read that windows perform similarly to walls acoustically ( aside from the obvious fact you can't place treatment over them and them still do the job of adding light to the space! ) so I might need to check after designing treatments.

Dan

I had read something about the corners being non ideal, but hadn't myself found any info on whether flush mounting lessens the problems associated with this.

Wellll... sort of, yes, no, maybe, sometimes, never, always, definitely and certainly not! Yes, speakers in the corners without soffits are a big no-no. Always. Avoid. Yes flush mounting in vertical soffits is a huge improvement, highly recommended, always (as Gareth can tell you, and he's not even finished with his place!). Yes soffit-mouting does eliminate several major artifacts that are a a huge problem otherwise. And yes, it can reduce the effects of having a speaker in the corner... sort of .. because it eliminates the corner... sort of... but not really.

I wish I could be more specific, but there's lot of factors in play, and I always recommend keeping speakers out of the corner, even when soffit mounted. Technically, soffit mounting eliminates some "virtual images" of the speaker, but it can also add more if not done carefully, and it wont eliminate the virtual images of a speaker that is still on a line into the corner, if the front and side walls are still prominent.

But anyway, the general rule is to keep them out of the corner.

I remember reading Stuart's comments on one thread that said the speakers should be at 28% of the room width, but this might be when they are stand mounted rather than soffit.

Right! But like all such exact, perfect numeric "rules", it's not really a rule at all! It's just a guideline, a good starting point, and the actual position can certainly be changed as needed, within reason. The same applies to the famous "38% rule", which I find isn't the best spot in most rooms. But it's a good starting point...

Are there any alterations you would make?

I would set your speaker aim point ("axis intersection"), the point where the acoustic axes from both speakers cross over each other, a distance behind your head. Maybe 12" to 18" or so. That forces your ears to be on-axis to the speakers. With your current layout, you sort of have that, but the angles are too large. Try to get your speaker toe-in angle to around 30°, give or take 5° or so.

Also, try to get your head (ears) to about 38% of the room length (38% away from the front wall), give or take about 8%.

Stay away from 25% for both your speaker location and also your head location (50% as well).

The speaker baffles will be made out of thick MDF on a timber frame

VERY thick MDF! I normally use at least two layers of 3/4" MDF, and sometimes other layers of magical secret stuff... You want a LOT of mass on your baffles. Also, your frame needs to be very solid, rigid, tough. I often use 2x6 framing for most of it, with a bit of 2x4 in some places.

I chose to use the corners as this reduces lost floor space.

Designing soffits is not about saving space in the room: it is about getting the geometry and acoustics right! The design of the soffits must create a true reflection free zone around the listening position, and that will require that the soffit faces must be at certain locations, and angled in certain ways, regardless of how much room space that uses up. If the soffits are not designed correctly so that they fully perform all of their functions, then there's not much point in having them...

So, first of all get the general layout and geometry right, with enough space for framing, ventilation, treatment inside the soffit, etc. Then ray-trace that to see if you have a reflection free zone or not. If not, then either adjust the angles or add extra surfaces until you do get that. Then add treatment to the room, based on the position you ended up with. Once you have that, then try fiddling with the positions and angles a bit, to see if there might be a better solution, even one that saves you some floor space. But don't save floor space at the expense of getting your soffits right.

- Stuart -

Soundman2020 wrote:Wellll... sort of, yes, no, maybe, sometimes, never, always, definitely and certainly not! Yes, speakers in the corners without soffits are a big no-no. Always. Avoid. Yes flush mounting in vertical soffits is a huge improvement, highly recommended, always (as Gareth can tell you, and he's not even finished with his place!). Yes soffit-mouting does eliminate several major artifacts that are a a huge problem otherwise. And yes, it can reduce the effects of having a speaker in the corner... sort of .. because it eliminates the corner... sort of... but not really.

I wish I could be more specific, but there's lot of factors in play, and I always recommend keeping speakers out of the corner, even when soffit mounted. Technically, soffit mounting eliminates some "virtual images" of the speaker, but it can also add more if not done carefully, and it wont eliminate the virtual images of a speaker that is still on a line into the corner, if the front and side walls are still prominent.

But anyway, the general rule is to keep them out of the corner.

I would set your speaker aim point ("axis intersection"), the point where the acoustic axes from both speakers cross over each other, a distance behind your head. Maybe 12" to 18" or so. That forces your ears to be on-axis to the speakers. With your current layout, you sort of have that, but the angles are too large. Try to get your speaker toe-in angle to around 30°, give or take 5° or so.

Also, try to get your head (ears) to about 38% of the room length (38% away from the front wall), give or take about 8%.

Stay away from 25% for both your speaker location and also your head location (50% as well).

Cool so I've updated my design and I've done some ray tracing to find a reasonable RFZ.
Head is at 38% from front wall. The purple spot on the floor is the point that the speakers "aim" diverge.
My best RFZ has been using 35° angled speakers (Still in the corners though, but hopefully I'll be able to overcome obstacles this may present.)

I've been able to deflect troublesome reflections using some angled panels in front of my soffits. What would these be made of? I was thinking 2 x 2 framing and a layer of plaster board, filled with some insulation. This reflective surface doesn't need a lot of mass though right? As the reflections I'm most concerned about are higher frequencies that act more like a ray and can be deflected more reliably. Low frequencies disperse more randomly and can't easily be tamed in this way correct?

With this design I'm going to have to move at least 1 window. I may instead place 1 larger window more centrally on the wall.

You'll see I've added absorption to the rear wall and corners (including a panel on the door) and I've added some absorption against the speaker soffits to catch some lower reflections from 50° - 60° off axis rays.

What do you think?

Daniel

I've finished ray tracing vertically. I've used an angled panel attached to the ceiling to reflect the more off axis ceiling reflections further down the room away from the listening position. I'm not sure whether I can do anything much for floor reflections. Between 52° and 60° off axis are the only ones entering the mix position.

To quote Stuart on another thread:

You can also do a bit of "devil's advocate" prioritizing, by seeing which ray it actually is, and deciding if you will allow it to live or not... If it is a ray that started out with an angle of 10° or 20° from the speaker, then you really cannot allow it, since that is practically on-axis for most studio monitors. If it started out as 60°, on the other hand, then it's probably not too much of a problem, since that is pretty far off-axis, so it is going to be a mostly lower frequencies on that path, which are probably not too directional anyway.

So I'm thinking these may not be too much of a problem (also considering the likelihood that parts of the desk will reflect some of these rays away from the listener).

There is also a parallel ceiling cloud hung above the most of the room. 50mm from ceiling with 50mm insulation.

My speaker origin is set at 1.3m from the floor.

What do you think?

Dan

Cool so I've updated my design and I've done some ray tracing to find a reasonable RFZ.

Great! It's looking reasonably good.

(Still in the corners though, but hopefully I'll be able to overcome obstacles this may present.)

Slide your entire soffit out into the room a bit, slide the speaker over towards the middle of the room a bit, and reduce the angle a bit. The speaker should NOT be centered on the baffle... I used to think that was a good idea, but then I did the math and discovered that it's not so good...

I've been able to deflect troublesome reflections using some angled panels in front of my soffits.

Right, but instead of making them in that "sawtooth" form, just make then as a flat panel that transitions from the soffit to the side wall. I call those "soffit wings".

What would these be made of? I was thinking 2 x 2 framing and a layer of plaster board, filled with some insulation.

You could do that, but I prefer something a bit more substantial, such as thick MDF.

This reflective surface doesn't need a lot of mass though right?

Nope... Wrong...

As the reflections I'm most concerned about are higher frequencies that act more like a ray and can be deflected more reliably. Low frequencies disperse more randomly and can't easily be tamed in this way correct?

Wrong... Take a look at the dispersion diagram for your speakers. Those panels are at fairly high angles off-axis (maybe 35° to 60° or so), thus they will see mostly mids and lows, almost no highs.

I've finished ray tracing vertically. I've used an angled panel attached to the ceiling to reflect the more off axis ceiling reflections further down the room away from the listening position

Right! Make that into a "cloud", with absorption below and above, and the thick, solid, hard surface in the middle. The "meat in the sandwich" so to speak. Very effective.

I'm not sure whether I can do anything much for floor reflections. Between 52° and 60° off axis are the only ones entering the mix position.

Right! It's hard to deal with floor-bounce and yes it will cause a dip in your frequency response, likely somewhere in the region of 110 Hz, give or take a couple of dozen. That's very typical of home studios. It might be possible to deal with that with some thick carpet "throw rugs" in front of / under the desk, and also with the desk design itself, as well as counter-absorption on the lower front area of the soffit, to deal with the reflections that come back from the desk towards the soffit. But even so, this is pretty much always a problem in small studios.

What do you think?

You are certainly on the right track, and clearly you are doing your homework, taking things serioulsy, and discovering many of the issues that less careful people totally miss, ... then wonder why their studios sound not-so-good! So congrats on that, and your advances bode very well for your studio to be smooth and even, well balanced, and a great place to mix in!


- Stuart -

Hi Stuart,

Thanks for the advice and words of encouragement!

Slide your entire soffit out into the room a bit, slide the speaker over towards the middle of the room a bit, and reduce the angle a bit. The speaker should NOT be centered on the baffle... I used to think that was a good idea, but then I did the math and discovered that it's not so good...

...instead of making them in that "sawtooth" form, just make then as a flat panel that transitions from the soffit to the side wall. I call those "soffit wings".

Ok, so I've taken on board the speaker positioning advice and pushed them in as far as I can without having to lose any room length (the baffles literally meet in the middle).
I've made two RFZ ray traces with "wings".
The first is the simplest, it works, but needs a significant angle to reflect the further off-axis rays, also it doesn't have as large a RFZ. Also the wing's angle terminates very close to the speaker and I imagine this is not ideal as it limits the size of the parallel flush baffle surface.
My second wing design seems to be a big improvement. By chopping a corner off the wing where it meets the baffle I can get away with a far less extreme angle. This reflects troublesome off axis rays in-front of the RFZ zone towards the opposite wing where it is reflected towards the back wall. This design allows the wing to finish further from the speaker along the baffle, as well as increasing the size of the RFZ.

I understand the second design is similar to my "sawtooth" form before, but there is a difference: The "cut-off" bit of the wing is parallel to the side walls. This means that reflections are still sent away from the speakers and not back towards the front wall as in my previous design, they also don't create an acute angled corner between the baffle and wing.
I'm leaning towards the second wing design at the moment. They happen to have the bonus of using up less floor space and reducing room volume less too.

Can you see any obvious problems with the new design(s)?

Thanks!
Dan

Ok, so I've been steadily building the studio and I'm coming up to the point where I will be installing my outer skin silencer box. So I'd like some feedback on my design if possible. I have a three skin roof as I need ventilation below my roof deck. So the outer leaf silencer box will be screwed and sealed to the boards on the underside of the roof joists. The fan will be an inline fan and flexible ducting residing in the roof void. The inner leaf silencer box will be screwed and sealed to the top of the inner leaf ceiling boards. The ceiling is an inside-out design. Flexible duct will run between the silencers.

I've calculated I need 180 CFM, the fan I'm looking at provides 211 CFM flow rate, so it seems ok: http://www.fansandspares.co.uk/shop/pro ... -125mm-dia.

I'm looking at a 4 way ceiling diffuser on the inlet large enough to reduce the air velocity to 100-300 FPM.

Let me know of any mistakes you can see in the design below, if possible. Thanks.

- It looks like you double your cross sectional area for the first little section of your outer leaf silencer box, but then as soon as it hits the end of the first baffle, it gets really small again. You need to maintain that large cross sectional area all the way to your register. So, your boxes need to be twice as big as they are right now. The point at which changes occur create noise. Having a tiny inner leaf silencer path that opens up huge right at the outlet will create turbulent noise and defeat your efforts to get quiet air movement. That's why you do it all right at the inlet of your first silencer.
- How are you physically going to install your inner leaf silencer and connect it via flex duct (which isn't very rugged)? I suppose if you do it in modules, you could make it happen, but just something to think about.
- Have you figured out what LVL studs will hold the weight of your ceiling with that super heavy silencer box? You need an engineers stamp to pass inspection, and in some cases even buy the wood.

I want to see pictures of your build so far!!!

Greg

Hi Gregwor thanks for the advice.

That makes sense about the turbulence. I'll extend the box design. I was under the impression that I needed multiple changes in flow area throughout the box though in order to cancel out some noise. Are you saying this should happen in relation to the doubled volume though and not the original air volume? ... If you follow my thought process.

Yes, I'm building the inner ceiling in modules, so I'll lift it between the joists and straddle 2-3 joists. My trada table gives me the max static load for joist sizes, so I'll double check it.

You can see the build diary here:
http://www.johnlsayers.com/phpBB2/viewt ... 10&t=21269

Thanks

Are you saying this should happen in relation to the doubled volume though and not the original air volume?

If I understand what you're saying, then yes.

Inlet of outer leaf supply silencer = supply duct size. As soon as the air hits the inside of your box, it should double in cross sectional area and remain that way, period.
Return should be exactly opposite.

I've attached a picture of my control room return silencers. The one on the right is the inner leaf and the one on the left is the outer leaf. Unfortunately, my situation isn't perfect. I don't have the space (due to my wooden sleeves running between joists) to maintain the cross sectional area. So, my inner leaf box is big and the outer leaf is small. I've obviously removed the tops of the boxes so you can see it better.

Greg