Purelythemusic wrote:Source of the post I’m used to so much quicker on normal building projects.
Right! But studios are very different from normal building projects. Contractors, building material suppliers, architects, and tradesmen often assume that building a studio is the same as building a house, office, shop, school, or most other "normal" structures, and proceed accordingly, but studios are a bit different. First-time studio builders often run into problems with contractors who think they get it, but don't. I'm not sure if you are following Howie's build (
http://digistar.cl/Forum/viewtopic.php?t=54): he's already hit several such issues with his contractors and suppliers. But he's not alone! This is fairly common among studio builders. And is frustrating! The folks from the regualr building industry think we studio builders must be nuts, with all the "strange" stuff we want them to do: they just don't get it.... Because: "We've always done it our way before, and it always worked before!".... Sigh!
Good isolation and good acoustics are not in their field of comprehension, it seems. They want to do things the easy way, not the right way.
There's lots of stuff that needs to be done differently, with most of that being related to the issue of isolation. In your case, even more so, since your isolation goals are so high, but even for a more modest studio, it is still a different process from typical construction. I try to warn people about this all the time, and perhaps some people think I'm just being hard-assed and silly about it, but there's sound, solid, logical reasoning behind my hard-assed silliness!
For example: sealing up tiny gaps. A typical construction workmen wouldn't even bother checking for gaps under the sole plates of a wall or around the edges of a wall, and even if he did notice one he wouldn't care. But that gap could cost the entire isolation of the complete wall! Here's one of my favorite scary graphs:
- loss-through-tiny-cracks-and-reduction-effect-of-small-gaps-on-TL.jpg (28.71 KiB) Viewed 35975 times
- loss-through-tiny-cracks-and-reduction-effect-of-small-gaps-on-TL.jpg (28.71 KiB) Viewed 35975 times
It's not very clear (I do need to go find the original again, and scan it at higher resolution), but you can just make out the numbers. What that shows, is how much isolation you lose from having a tiny crack, gap, or hole in a wall. The X axis (across the page) shows the isolation that you expected if the wall has no gaps, and the Y axis (vertical) shows what you actually get. So the very top curve on there says that if you have a gap equivalent to just 0.01% of the entire wall surface area, and you were expecting 50 dB isolation for that wall, you actually only get 40 dB. To put that in real terms: If the wall is ten feet long and ten feet high, that's 100 square feet. 0.01% would therefore be 1/100th of a square foot, or 1.4 square inches. So if you had a tiny 1/32" gap under your wall (less than 1mm high), under only one third of the length if the entire wall (just three feet long, or about 1m), that would already trash your isolation completely. Dropping from 50 dB isolation to 40 dB means that the wall now blocks
TEN TIMES LESS sound, and on things would would be heard
TWICE as loud, subjectively. All from a tiny crack that a typical workman wouldn't even notice.
Or electricians: if your electrician comes along, and cuts one single hole in your isolation wall for a light switch, that would be about 10 square inches, which is roughly 0.1% of the wall area: the graph says that you are now down to 30 dB isolation, which means the wall is letting through ONE HUNDRED TIMES more sound than it would have at 50 dB isolation.
Your really expensive studio wall now isolates about the same as a typical ordinary house wall! Add in another light switch and three outlets, you are at 0.5% open area, and you are down to 21 dB isolation. About as good as a thick cardboard box....
To put this ore clearly in real-world terms: Consider that the typical gap around a door, between the door slab and the jamb, is more like 1/8" to 1/16" wide, and 20 feet long (7 feet up each side, 3 feet across top and bottom)...
... That's 1.5 to 2.5 square FEET of open area,... call it 2 square feet, to make the math simple. That's 2% open area of the entire wall surface, so a single unsealed door in that hypothetical wall would drop your 50 dB isolation down to 17 dB, according to that graph. About the same as a paper bag...
(OK, I exaggerate just a little, but not by much!)
That brings into perspective the reason why studio doors have triple full-perimeter rubber seals on them, for high isolation...
The effect of tiny gaps and cracks is just one example of how studio construction is rather different from typical construction. There's plenty more...
Once again, I'm not trying to beat up on you Tom! I know that you already know this stuff, very well! I'm just using your thread as an opportunity to mention these things, so others who are following your build can be aware of it. And I do know that your build is generating a lot of interest for a lot of people, because your thread has about 6,500 views so far! So it's a good place to talk about these things.... Sorry if I seem to be battering you, but that's not the case! You already know far more about the pitfalls of construction than most first-time builders. I'm just using your thread as a platform to stand up and yell about some of my pet peeves ...
Purelythemusic wrote:Source of the post I didn’t actually know that there were two different products from green glue! It became apparent trying to use it as a sealant though!
Right! You should try to clean that stuff out from where you attempted to use it as sealant, since it won't ever dry fully: it remains tacky and gooey forever. The surface dries, sort of like with a skin over it, and that skin thickens a bit over time, but it never hardens. So wipe it out with a cloth as well as you can. According to Green Glue, you should: "Take care to remove the Green Glue from unwanted surfaces before it dries. Use 70% Isopropyl Alcohol to clean up Green Glue." It might be too late for that, as it the surface has probably already dried too much: You might need to use a knife to cut it out. After you get it off, then seal those joints and gaps again with the Sikaflex. That Sikaflex F11 stuff is excellent for most acoustic sealing purposes, and quite flexible, but still too hard for sealing around the silencer box sleeves. Sikaflex hardness is listed as 45 durometer Shore A, which is around 80 durometer Shore 00. That's not soft enough. For that specific application, I recommend Dow Corning 790, which is 15 duro Shore A: around 58 duro Shore 00, which is almost exactly the same as the Sorbothane pads. If you can't find the Dow 790, then next best (if you ca find it!) is "Soudaseal FR", rated at 20 duro Shore A (aprox 60 duro Shore 00: identical to Sorbothane 60), then after that any of "Ardex Flex Caulk", "3M 525 Polyurethane Construction Sealant", "Soudal Multibond SMX25", or "Sascho Lexel" are pretty good: all four of them are rated at 25 duro Shore A (aprox 62 duro Shore 00: very similar to Sorbothane 60). Next best is "Sascho Mor-Flexx" at 29 duro Shore A (about 67 Shore 00), then "Sascho Big Stretch" at 32 shore A (around 69 Shore 00). Beyond that, it's getting too hard.
Hopefully, you can find one of those for sealing around the sleeves of the silencer boxes.
Thank you for the explanation of the sleeve fitting like a glove into the cement boarding... the same way you build the sleeves into the silencer boxes themselves. So the sleeves become part of the outer leaf...so is the silencer for the outer leaf! Same with the inner ...Makes perfect sense now!
Right! So it needs some fairly accurate positioning of the silencer box, such that the outer sleeve ends in the right place. That's why I didn't put a dimension on that outer sleeve, as you'll need to measure carefully to the front face of the studs, then add half the thickness of the fiber-cement board: that's how long the outer sleeve needs to be.
What thickness fiber-cement board are you using? I'm guessing it is 8mm?
Yes I truly realise the implications of shooting for such a high goal. But really I want to spend my days with my family and my nights making music and if I couldn’t play drums at night then it wouldn’t be ideal.
I have high confidence that we'll achieve that! Your attention to detail so far bodes well for getting there. The weak points will be the two spots where the fresh air intake duct and the stale air exhaust duct go through the outer wall. Worst case, we might need to add some small silencer boxes for those, but hopefully that won't be necessary.
It is a true luxury to be able to contemplate a build like this. The cost testifies to the challenge of the goal!
It's a high goal, to be sure, but it is achievable.... just! It's pretty much at the limit of what a home-studio build can hope for. To go significantly higher, you'd need to completely float the inner room, on large springs... (Which would make it REALLY expensive...)
After a couple of weeks it will slow down but I think that may be good in a way because the acoustic treatment and room tuning seems like a stop design stop build process!
Right again! You've done construction before, so you know that getting the shell of a building in place is relative fast, and what takes time is the finishing off... Even more so with acoustics. So taking your time to do the interior is a really smart thing. You might not have noticed Andre's tag-line signature: He is so right about that! In fact, I think he might be a bit of an optimist with just 90%...
I can get my PA in there for an isolation test as the monitors I have available won’t be able to produce low end like the PA I don’t think... Mackie srm450 active pa or Mackie Hr828 monitors
Ahh! So you are a Mackie fan, just like me!
The SRM450's have the power for the job, but you are right; they don't really go low enough to do justice to a 5-string bass, or the low end of roaring keyboards. I have a pair of their "little brothers", the SRM350's, which I often use for small live events... but along with subs, to fill in the low end. The HR828s are quite a bit better: they go down to 35 Hz, which is fine for the initial testing. Mackie also claims that a pair of them can put out 120 dB SPL, which might be a little optimistic, but they should be able to get to 110 dB just fine, and probably 115 too. So you could use those for the tests (I'm assuming you have the 828 mk-II version, not the original "mk-I"?).
- Stuart -
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