Attic Shaped Studio

#76

I forgot to mention that the knee walls will consist of 1 layer of OSB 3 facing the eaves, then green glue, then another layer of plasterboard facing the inside of the room. The OSB is good because the eaves are a potentially damp space, and it will also allow easy attachment of sockets, patch bays, cable duct and so on.

Cheers,
Jennifer

#77

Wow! I've just spent some time reading through all of your thread about the HVAC part, Jennifer, and going over the calculations, and it sure looks like you have done your homework here!

One caveat, which Starlight already brought up: using outside air to cool your room might not do all that you expect. I'm thinking specifically of humidity. This is something that even many studio owners and musicians don't take into account, but it is rather important! So I'll climb on my soapbox again, and vent one more pet peeve....

(Excuse me hijacking your thread again, Jennifer!)

So: Relative Humidity is the subject...

Relative humidity refers to the amount of moisture vapor present in the air. It ranges from 0% (very dry) to 100% (very moist). Here's a rather common HVAC chart that shows how humidity affects your health:

0% humidity is on the left edge, 100% on the right edge. Each red triangle shows the range where a specific health problem occurs: the wider the wedge, the greater the problem. As you can see, there's a zone in there, from about 35% to 55%, where health issues are minimal.... and not surprisingly, that's also the zone that people find to be the most comfortable, regardless of temperature. 50% in a hot climate feels nicer than 25% or 75%, and 50% in a cold climate also feels nicer than 25% or 75%.

So that's the first part: human health and comfort. But what about your gear and musical instruments? For equipment, if the humidity is too low (below about 40%) then there's a good chance of electrostatic discharge happening: often just called "static electricity" or simply "static": What happens when you walk on a wool carpet with synthetic shoes, then touch the doorknob... ZAP! Not good for gear, or people! On the other hand if the humidity is too high (above about 70%) then you can get corrosion of metallic surfaces (including rust), as well condensation, and muck accumulating on cooling fans and grills, rather than just dust. Somewhere around 50% seems to be the "sweet spot" for gear.

And instruments? Well, here's where it gets really interesting for studios. Many musical instruments are made of wood. Wood is a natural fiber that "breathes": it exchanges its own internal humidity with the atmosphere around it. In a damp atmosphere, it absorbs moisture and swells up. In a dry atmosphere it releases moisture and shrinks. Dry for too long? It cracks. Damp for too long? It warps. Joints loosen...

And of course, as the wood swells and shrinks with changes in atmospheric humidity, the tuning changes! Yup. And not by just a little bit. Taylor Guitars have a lot of data about this, and they say that the top panel of an acoustic guitar will change in width by about 1/8" (3mm) when the humidity changes by about 20%. Try turning the tuning pegs on a guitar to make a string 3mm longer or shorter, and you'll see just how much that is! And that's for an acoustic guitar: imagine what the change is like on a very much larger instrument, like a double bass, cello, kick drum shell, floor tom, ...or piano!

So, if you have a room where the humidity is swinging wildly, or even mildly, you'll find the need to re-tune your instruments all the time, to compensate. Either that, or put up with songs starting off in one key, but ending up in another... unintentionally!

So, getting back on track; it is important to keep the humidity in your room fairly constant at all times. So far, I showed that people are good with humidity in the range 35% to 55%, gear is good in the range 40% to 70%... and instruments? Fortunately, it runs out that wood is happiest at about 47%.... which is the exact humidity that Taylor has in their factories, throughout, in all locations.

Conclusion: keep your room at 47% relative humidity, and your instruments will sound great, won't need returning, your gear will be happy, and you will be comfortable and healthy.

Now for that "caveat": The outside humidity might or might not be 47%! Most likely not. The air you bring into the room directly from outdoors, might be a lot more humid than 47%, or a lot less humid. If it just rained out there, or if it is foggy, or if you live close to a large body of water (river, lack, ocean, loch...) then chances are the humidity is way up there, around 100%. If it hasn't rained in days, and it's been warm and sunny... or cold and sunny, chances are that the humidity is much lower: probably under 35%.

Sooooo... I'd suggest that you add in "something" to keep the humidity under control. Depending on your local climate, you might need to dehumidify the incoming air... or to humidify it. A mini-split system will always dehumidify when it is cooling the air, so that might be fine if the air is humid. Or you might need a humidifier. But something a little more sophisticated than this one:

(At least it is cheap to run: plugs into a USB port...).

The best solution here (but not cheap!) is an ERV: "Energy Recovery Ventilator". It is similar to an HRV ("Heat Recovery Ventilator") in that it transfers heat between the incoming and out going air, but the ERV also transfers humidity. So, assuming that you have 47% in your room, an ERV will help to keep that in the same range, because if the incoming air is drier then it will transfer humidity from the outgoing air to the incoming, and the reverse happens if the incoming ir is more moist... except that the difference between indoor and outdoor has to be rather large, to get good transfer. And there's also the issue that... " it transfers heat between the incoming and out going air"! Which is what Jennifer does NOT want! She wants to get the cool air in, and the warm air out, without transferring any heat....

Conundrum!

This is what Starlight was getting at, with his comment on humidity.

To find out how bad this issue is, I'd suggest that you get a good quality, calibrated hydrometer, and measure the indoor and outdoor humidity under various weather conditions, to see what the levels are like. Maybe you don't have a problem at all! And maybe you do....

Once you figure this out, then you can take a look at possible solutions, ... if any are needed. I'm hoping that your location has a mild climate, where humidity is almost always around 50%, naturally.

The other thing I noticed with your plan, Jennifer, is that you are bringing in and removing air from the same end of the room: the end where the glass is. I usually try to bring in air at the rear of the room, and take it out at the front, so the air can move through the entire room. It can be done your way, but ensuring that it circulates well is more problematic: the rear of the room might not get the cooling and "freshening" that you are looking for. I'm wondering if it is possible to run a duct from the inlet silencer to the rear of the room, inside the room, and have your register(s) back there to supply fresh air to the room. I had a case like this a few years back, where the only place to position the silencers was at the front... so this is what I did:

You can see the return registers in the ceiling itself, but there's also a strange wooden box running between the soffits, above the door... that carries one of the supply ducts... there's two of them, and one runs down each side of the room, up against the ceiling:

I had to split the flow into two paths to keep the flow velocity low and also reduce the static pressure drop. The ducts down both sides of the room end in large registers on top, directly behind the air intake for the mini-split.

I am concerned that having the bottom of the silencer in such close proximity to the ceiling below would lead to more sound getting into the room below. Does this fear have any foundation?

That should be fine. If you are worried about resonance in the boxes possibly getting into/out of the rooms through flanking, then put Sorbothane rubber "feet" under the box, to decouple it from the floor below.

This will be soon after phase 1 is finished and working properly. It's a simple method of getting better air circulation and distribution by extending the supply vent closer to the rear of the room. If ever a mini split is required, around this area would be a good place for it I think.

... and I just came across your "phase two"!!! Which takes care of what I was highlighting above, so no need to repeat that! You already thought of it..-

This part will eventually be integrated into the "as yet to be finished" soffit design that will be something like this;

I know that Genelec sells a "soffit mount" box that has the speaker poking half way out the wall, as you are showing in your model, but to be honest I've never really understood WHY they do that! My guess is to get decent air flow around the speaker, for cooling, but there are other ways of doing out. My concerns with it sticking out so far from the wall, include edge diffraction, SBIR, and other potential issues. It makes more sense to have it fully flush... which is hard to do, but I do have a design that I did for soffit-mouting the egg-shaped Genelecs! It was never built (as far as I know), and the guys I did it for never even paid me for it (!) :oops:

, so its untested.... but theory says it will work just fine.

Actually, I just remembered that they could NOT have built it as designed, since I left some key parts out of the version I sent them 8-)

, when they were supposed to pay... I had a feeling it was going to go south, so I left out those critical details until the payment came through... which it never did!.... Thus, if they tried to build it without that, it would not have worked... :shock:

But anyway, the design is there still, some place. I'll see if I can dig it out.

Total static pressure at 186 m3/h (6 changes per hour) is 147 Pa.

Sounds about right. That's roughly 0.5 inches H20.

All in all, it looks like you have all your ducks in a row, Jennifer!

With the above caveats about humidity.

- Stuart -

#78

Thank you very much for your thorough review Stuart, it is very reassuring indeed. I can now start this part of the project in earnest.

Your information on humidity is really helpful. Average relative humidity round here varies from 65 - 80%. Not ideal, so I'll keep an eye on that. There is always the mini split option further down the line. Since air from outside with no humidity control constitutes the vast majority of ventilation in domestic properties in Scotland, my hope is that it will be ok here too.

One thing for sure, it will be a vast improvement on the current situation. It's got up to 38°C (100°F) in that room on several days so far this summer. And it's not been a hot summer, I think outside was just a little over 20°C those days. The room is South facing and all that glass acts like a greenhouse. Not a great environment to work in.

Thanks for the information on soffit mounting the Genelecs, that's something to figure out in the future too. Eventually I have to decide whether to keep them and add a sub or replace them with deeper full range monitors (no sub). I like them a lot, and would prefer to keep them if possible. Once I have the room wall beefed up hopefully there will be enough isolation to have the sub work at mix volume without it leaking to the rest of the house.

Who knows, it might even be possible at the moment. Every now and then I'm tempted to buy a used Genelec 7050 and see what happens. I could sell it on at cost if it doesn't work out. I do worry about it injecting sound right into the structure of the house through the floor it is sitting on though. Maybe it could be floated on sorbothane to reduce this.

Thanks again,
Jennifer

#79

The room is South facing and all that glass acts like a greenhouse. Not a great environment to work in.

Have you looked into applying heat-reflective film to those windows? There are some good ones out there now. Not too expensive, when you consider the cost savings in cooling. One drawback, is that most of those also make the glass partially "one-way": you can see well from the darker side towards the brighter side, but not so well the other way. Thus, during the day you can see out through your windows, but somebody outside can't see in very well... but at night, that is reversed: you can't see out so well, while folks outside can see in. That might not be an issue for you at all, but in some cases it is. I think 3M now has a product that still allows good visibility out at night. Not sure. I seem to recall seeing that, some place.

Anyway, it might be worth looking into that, in addition to your HVAC system. Some of those films you can apply yourself, others need professional installation.

Eventually I have to decide whether to keep them and add a sub or replace them with deeper full range monitors (no sub).

In addition to extending the bass range of your speaker system, subs can also have a very, VERY useful acoustic treatment purpose. With careful positioning and tuning, they can eliminate some stubborn acoustic issues in your room: SBIR, floor-bounce, and some modal issues come to mind... Even with a single sub, well placed, you can get some quite good, and rather useful results, but with a pair of subs you can do something much more interesting: you can implement a "plan wave bass array" (also sometimes called a "double bass array", but this has nothing at all to do with the instrument of the same name). Basically, by careful location of the subs, and precise manipulation of the phase and timing, you can get the two subs to work together such that they cancel out acoustic issues. Think of it like this: one sub creates the wave with a positive phase, that wave moves across the room and exactly as it reaches the other sub, that second one is creating the "negative" (phase inverted) version of that wave.... so in effect, the second sub "sucks up" or "cancels out" the wave from the first sub. By locating the subs at the right spots in the room, you can get some nice things happening at the mix position...

So, if you like your Genelecs, you can maybe keep your Genelecs! Adding one (or two) good subs would give you the bass extension you are missing, and also deal with some of the issues in your room.

Every now and then I'm tempted to buy a used Genelec 7050 and see what happens.

I'm rather partial to the Neumann KH805 for this application. It goes down loooooow, is smooth and tight, and not excessively expensive. I've used it successfully in a couple of places, and in fact I'm working on one room right now with a pair of them, set up as a plan wave array. That one is getting close to completion, so I'll post some more about it when its ready. The owner wants to remain anonymous, but he doesn't mind me sharing photos and results. Right now, we are chasing down some final acoustic issues in the room, then we'll get into the tuning proper. You might want to follow that thread (when I start it!), so you an see if it is applicable to your case.

- Stuart -

#80

Jennifer! Beautiful studio. I don't know what has taken me so long to stop by your thread. I am tuned in and excited to see this soffit build! Such a nice space already and you clearly have a ton of knowledge on the subject. I've been learning a lot just reading through. Best of luck moving forward. I ended up going the soffit direction myself. Really stoked to take things to that next level.

Cheers
Trevor

#81

Thanks Trevor. Soffits a wee bit away in the future still, but absolutely will be done :-)

Thanks for the suggestion for heat reflective film for the windows Stuart. I already have the Velux heat reflective roller blinds fitted to the windows, all six panes. That hot peak of 38°C in the room was with them all completely shut. The weather was terrible today - cold with heavy rain - so for the first time in months I was able to open the blinds and have a view outside again. Luxury!

A small update: on this thread https://www.digistar.cl/Forum/viewtopic.php?t=742 I mentioned improving the frame of the studio door. I've now done this for the doors to room 1 and room 2. The path of sound is Room 1 <-> Landing <-> Room 2. The landing is about a metre wide.

Subjectively, I'd say it has improved the transmission loss for bass frequencies between rooms 1 and 2. In room 2, I used to notice a little bit of kick drum thud and snare from my reference track playing at ~85dB in room 1. Since improving the doors the kick drum thud has been reduced, the snare not so much. Fascinating, and I would tentatively say very encouraging as these mids and lower mids are presumably much easier to reduce with further improvements.

The sound isolation between the two rooms, while not amazing, is certainly useful. With a mix playing at 85dB in room 1, it is barely audible in room 2. For example, the bleed from same mix playing through a pair of headphones in room 2 is louder than the bleed from room 1.

Loud vocals in room 2 are barely audible in room 1. Percussion is the same, even percussion with a deep resonance like djembe. It's really nice being able to monitor recordings at quiet volumes and still know you are hearing "the truth" through the speakers.

More isolation improvements to come in the future, but as a step on the way these results are exceptionally satisfying, and not something I would have thought possible with standard house stud walls. My thanks again for all your help and encouragement.

Cheers,
Jennifer

#82

Thanks for the suggestion for heat reflective film for the windows Stuart. I already have the Velux heat reflective roller blinds fitted to the windows, all six panes.

The difference with the reflective film is that it is on the outside surface of the glass, and stops the heat from getting through. The blinds, on the other hand, are on the inside of the room, and can only reflect back heat that already made it through the glass.

38°C is pretty wild! Rather uncomfortable to play, track and mix in that heat! Wow. No wonder you are so keen on fixing this.

- Stuart -

#83

Soundman2020 wrote:The difference with the reflective film is that it is on the outside surface of the glass, and stops the heat from getting through. The blinds, on the other hand, are on the inside of the room, and can only reflect back heat that already made it through the glass.

Understood, thank you. Hopefully the ventilation will do the trick. If not that would be an option, and relatively easy to apply to the exterior pane from the balcony.

Cheers!
Jennifer

#84

First step on the path to fresh air today, the plumber was in and removed the small radiator at the front left of the room. The radiator was always in the way, and prevented the installation of a fully straddling absorber in that corner. One reason the bass response is far less even on the left than right.

Before, albeit a while ago;

After, with the resultant holes filled with putty pad scraps. Oh these wires! How does such chaos come about despite our best plans? Fortunately the plumber was able to remove the radiator without moving them. It would take considerable mental effort to remember where they all go :-)

And an almost fully straddling corner absorber can be installed at last. As the drywall on the area will be removed to fit the ventilation silencers and grilles it's just a temporary one sitting on top of an offcut of rockwool in a sack for the moment;

It is now a closer match to the absorbers on the right. Still not perfect due to the door preventing the diagonal straddler going full length. Soffit design will solve this in the future.

Happy days. The radiator is being relocated to a cold spot in our garage, really nice to have a good use for it.

Cheers!
Jennifer

#85

Greetings Jennifer,

Nice to see the progress. Also very nice to be able to reuse a radiator. Those are the sorts of things that often wind up in landfills.

Oh these wires!

That pic is the best argument ever for conduit, although in your case a culvert might be more in order!

All the best,

Paul

#86

That's good news, Jennifer! And with that radiator out of the way, building your soffits is going to be a bit easier.

Oh these wires! How does such chaos come about despite our best plans?

You do seem to have a problem there! Your studio seems to have been invaded by thick streams of black spaghetti that oozed out of some nasty B-grade horror movie! :ahh:

I do hope you can tame it, before it attacks you....

How does it sound in there, now that you have more even treatment? Is the difference noticeable?

- Stuart -

#87

endorka wrote:Source of the postHappy days.

Great progress, Jennifer. Well done!

#88

SoWhat wrote:Source of the postNice to see the progress. Also very nice to be able to reuse a radiator. Those are the sorts of things that often wind up in landfills.

Absolutely! Doubly good as the room above the garage tends to get colder than the others. Hopefully it will help a bit.

That pic is the best argument ever for conduit, although in your case a culvert might be more in order!

LOL! As Stuart says, it's absolute B grade horror movie stuff. The cables go to the landing and room 2. Audio cables / multicore to both, and computer cables to the landing. The real horror arrived the once or twice a cable went wonky and had to be replaced. Fortunately they are sealed into the wall with putty pads rather than caulk. Definitely some better planning for this is in order come soffit design time, I think several runs of conduit are in order.

How does it sound in there, now that you have more even treatment? Is the difference noticeable?

Here are the "before" measurements with speakers positioned as they are now, i.e. close into the corners, not in the window bay like the first picture. They show clearly the effect of far less absorption on the left side in the consequent huge boost in low end for the left speaker;

It's obvious in the overlaid waterfall plots too, the left speaker overpowers the right to a significant degree in the 50 - 80Hz region;

It's very noticeable to the ear too. Last week I was mixing some music with a djembe, and the low end wooommph with a peak at ~60Hz was ringing out of the left speaker like nobody's business. It sounded amazing, but of course wasn't actually there in the recording. Just the left hand side of this particular room :-)

I'm aware of the problem so make low frequency EQ and mix balance decisions in mono on the right speaker, with occasional checks on headphones. The mix gets there in the end but would get there faster if the room was accurately responding to both speakers.

So has the radiator removal and full straddler on the left improved things? I've not had time to measure yet. My ears tell me "a bit", but I am still aware of the louder and longer decay of the djembe at 60Hz. Next obvious culprit is of course the shorter diagonal straddler on the left side. 50 and 62Hz seem to correspond to the width and height modes of the room, so it seems likely.

I'm sure this can be solved too with a good soffit design. In the meantime, when I get a moment I'm going to stuff some light flully in the left diagonal straddler and see if it can soak up some of the slack :-)

Cheers!
Jennifer

#89

Your studio seems to have been invaded by thick streams of black spaghetti that oozed out of some nasty B-grade horror movie!

Ed Wood is smiling down you, Stuart!

#90

It's obvious in the overlaid waterfall plots too, the left speaker overpowers the right to a significant degree in the 50 - 80Hz region;

Yep. That's a pretty big difference, for sure! It would be informative to do some REW math operations on that, and get the difference between the left and right speakers, to see how bad it really is, in the frequency domain. Soffits will certainly help to iron that out!

- Stuart -

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