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Post by pandamonk on Jan 10, 2018 17:33:15 GMT
Hi everyone, I should've joined this board years ago but I'm glad I finally have. I am planning a new studio build in a 30'x10' garage and have a few quick questions before I begin. I plan to build John Sayers style inside out walls to save on space and on the inside I'd like to create membrane bass traps, that Ethan recommends here, everywhere except the first reflection points and rear wall. - Firstly, is this a good idea?
- Secondly, do I calculate room ratios from the drywall or from the plywood membrane? (I'm planning on 1.00 x 1.14 x 1.39)
- Thirdly, I understand the rockwool shouldn't touch the membrane to allow it to vibrate but can it touch the rear wall (Ethan had wood spacers in the image)?
- And finally, would this type of trap create an unwanted triple leaf?
Thank you in advance, Lee
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Post by rock on Jan 10, 2018 22:52:36 GMT
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Post by pandamonk on Jan 11, 2018 1:41:58 GMT
Thanks very much. It's a great read. I plan to have various types of traps throughout the room including membrane traps (with insulation to widen the Q), 4" broadband traps in the first reflection points, broadband traps in the rear corners, a curved wood panel diffuser floor-ceiling in the centre of the rear wall with insulation behind to (hopefully) trap bass and finally a sofa (it'll absorb something). I also expect the actual stud walls themselves to absorb some of the bass. The room size will be around 7' x 8' x 9'9" (not ideal I know, but all I've got to work with) so space is tight and I'll need as much bass trapping as possible. Also, from my understanding (and correct me if I'm wrong), a membrane trap like the one recommended by Ethan (below), isn't tuned as such. Yes the panel dimensions will have a resonant frequency, but the plywood will also have a resonant frequency based on how tight it is tuned (think drum head) and also resonates at a higher frequency at the edges (also like a drum head). When you add insulation, it widens the Q making it less effective at the tuned frequency but more broad in the bass frequencies it absorbs.
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Post by rock on Jan 11, 2018 14:40:28 GMT
I don't know what you mean by "isn't tuned as such". As I understand, it's tuning is determined, as you point out, by the materials and construction but I am not aware of a "tuning adjustment". If you know of a way to adjust the resonant frequency after construction, that would certainly solve one drawback of using them but it still would only target a narrow band. Most small rooms will benefit from wide band absorption but if all you need/want is narrow band, go for it.
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Post by Hexspa on Jan 11, 2018 17:39:07 GMT
hi panda, welcome.
Ethan does not recommend tuned absorbers, in general. He is a broadband absorption advocate, primarily. He reasons it thus: you have limited space and in that space there are a multitude of problems. Therefore, use broadband exclusively - especially in a small space.
Regarding room ratios, there are a number of ways to determine ideal ratios. You can search this forum for a few posts I've made on the topic. However, your room is smaller than the recommended minimum. For that reason, I would be content that the room isn't square or near multiples. Although, your "shell" of 10x30' is a multiple. Exactly how that pans out, I can't say. Besides ratios, you should know there are also guidelines limiting the multiplier from which the rear wall distance is derived. In other words, having your rear wall 3x your width could also be detrimental.
Not to ruin your parade. It looks like you're excited.
Hope that helps,
Thanks.
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Post by pandamonk on Jan 13, 2018 14:08:45 GMT
I don't know what you mean by "isn't tuned as such". As I understand, it's tuning is determined, as you point out, by the materials and construction but I am not aware of a "tuning adjustment". If you know of a way to adjust the resonant frequency after construction, that would certainly solve one drawback of using them but it still would only target a narrow band. Most small rooms will benefit from wide band absorption but if all you need/want is narrow band, go for it. Sorry, let me clarify. Yes it has it's resonant frequencies, based on a number of factors, but it isn't tuned to only target those narrow frequencies, like a Helmholtz. This is because the edges resonate at higher frequencies (like a drum) and the insulation dampens the membrane, therefore lowering the fundamental and widening the Q. From wikipedia "Resonating absorbers often incorporate porous absorption internally to simultaneously lower the resonant frequency and broaden the spectrum of absorption."
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Post by pandamonk on Jan 13, 2018 15:14:22 GMT
I just read that "A typical panel-type trap is effective for frequencies around one octave either side of the centre frequency, which at least has the advantage that you don't have to be absolutely accurate to get results."
The centre frequency that I have calculated for an 8' x 2' x 4" trap with 3/8" ply is 72Hz (the mode for room width), so these traps should be effective from 36-144Hz. I also plan to make some 7' x 2', 4' x 2' and 3' x 2', extending the range up above 230Hz. I will also use porous absorbers in around 1/3 of the room - at the first reflection points and the rear wall.
Remember I'm planning on using inside-out walls, so the studs and rockwool will face inwards. If I just go porous, it'll be too dead, so I might as well add some plywood, create some reflections and trap some bass.
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Post by rock on Jan 13, 2018 15:24:42 GMT
Thanks for the clarity. The Wiki entry also says "Such devices can be enormously effective over their tuned range, but can take up a great deal of space, especially when installed in arrays, and thus are sometimes not a practical solution." Sorry that I don't have and practical experience with this type of absorber, at least in part because Ethan has unrecommended them in favor of wideband porous types. Having said that, there is nothing stopping you from building the resonant types so if you do, please take lots of photos, and before, during and after acoustic measurements and share your progress with us. I know it will be a learning experience for me and probably many other members here. One more note about porous absorbers: You still should consider using them for RFZ on side walls and ceiling and they can also be used on walls for flutter echoes but I think that is your intention. Hexspa's comment re dims can be addressed by shortening your room a bit. Here's a room mode calc if you don't have one. amcoustics.com/tools/amroc?l=28&w=10&h=8&ft=true&r60=0.6Cheers, Rock
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Post by rock on Jan 13, 2018 15:39:28 GMT
Do you need isolation for your studio? Rod Gervais' book covers what you need to know. Basically has to do with enough drywall in only 2 layers with one space between. I mention this because I would imagine you'll want to beef up the existing walls first since you can't get to them after you build your inside walls.
In your first post you mention "Triple leaf", is the above 2 layer concept what you meant? If so, I think the main point of using only 2 layers or M-A-M (mass -air-mass) is that more than 2 layers is wasted materials and money. If you build a panel absorber in front of a 2 layer wall system, it is not meant to provide isolation so even though you have 3 layers in some places, I can't see how it would negate the isolation you already have with 2 layers.
As far as "too dead", IMHO a small room can't be too dead, especially for recording. Just add reverb.
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Post by Hexspa on Jan 13, 2018 15:50:14 GMT
I just read that "A typical panel-type trap is effective for frequencies around one octave either side of the centre frequency, which at least has the advantage that you don't have to be absolutely accurate to get results." The centre frequency that I have calculated for an 8' x 2' x 4" trap with 3/8" ply is 72Hz (the mode for room width), so these traps should be effective from 36-144Hz. I also plan to make some 7' x 2', 4' x 2' and 3' x 2', extending the range up above 230Hz. I will also use porous absorbers in around 1/3 of the room - at the first reflection points and the rear wall. Remember I'm planning on using inside-out walls, so the studs and rockwool will face inwards. If I just go porous, it'll be too dead, so I might as well add some plywood, create some reflections and trap some bass. Panda, your real problem isn't going to be liveness it's going to be volume. Every boundary will be too close to make use of it's reflectiveness. The only exception would be if you could direct the specular reflections in such a way that they'd arrive at your listening position after around 14ms. Given that would be pretty challenging, I assume you won't do that. Indeed, even if you were to use diffusion to enhance the ambience, they would have to be no more than 4" deep to work properly so close; and that's just for a single sweet spot. And unless you use an abfussive product (one that diffuses and absorbs), you will be left with less surface area which could've otherwise been used to combat modal problems via absorbers. While many things in this world are possible, some are more straightforward than others. So, unless you plan on undertaking a larger-than-necessary course of action, just stick with thick and plentiful absorption. Thanks. EDIT: I see from your earlier posts that you already are sold on the need for absorption. While I have no experience with these quasi-resonant absorbers described above, I can all but guarantee that broadband with and without FRK will take you farther faster.
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Post by pandamonk on Jan 13, 2018 16:49:04 GMT
Perhaps I should explain my entire build.
Currently I have a 18' x 10' x 1'6" concrete base from a garage which the previous owners of my house dismantled. I have a 12' x 10' space behind this which I plan to pour concrete up to the original base giving me 30' x 10' x 8' to play with (the maximum size you can build in the UK without requiring planning permission).
I've got a lot of PA and lighting equipment which requires at least 8' x 6' of storage within this structure, leaving me 24' x 10' for the studio and I'd prefer 2 rooms.
Having built a standard MAM wooden framed studio before with absorption panels within the rooms, this time I plan to build the main structure from 6" or 8" dense concrete blocks with John Sayers style inside-out walls inside so the studs and rockwool face inwards so the walls ARE the absorption panels rather than building normal walls and then having to hang panels. I'll then need to add some reflections (it'll be too dead) which is why I thought about installing some 3/8" ply and creating membrane traps.
The inner rooms will be floating and untied from the outer structure. Between the inner and outer walls I'll have a thin layer of insulation. For the ceilings and roof it'll be MAM with double layers of plywood with green glue between sheets. The floor will be double plywood, with green glue between, all floating on rubber sheet direct on the concrete base. I'll be using double fire doors throughout.
Hopefully this all makes sense. I'll post plans when I finish them.
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Post by Deleted on Jan 13, 2018 19:35:08 GMT
I'll be commenting about that floating floor idea. I'd say just forget it. You have already a perfect concrete slab, think about it. You have the whole planet earth pressing against that concrete slab and keep it from resonating. (I assume its build directly on the ground) If you build two rooms in same concrete slab there might be some impact noises that can be heard through that floor, but other noises shouldn't be coming in or going out. To avoid those two room impact noises, it's just easier to build drum risers and little risers for amps. In many cases floating the floor makes things just worse. If you don't like how that concrete floor looks you can just coat it normally using whatever you like. Perhaps I should explain my entire build. Currently I have a 18' x 10' x 1'6" concrete base from a garage which the previous owners of my house dismantled. I have a 12' x 10' space behind this which I plan to pour concrete up to the original base giving me 30' x 10' x 8' to play with (the maximum size you can build in the UK without requiring planning permission). I've got a lot of PA and lighting equipment which requires at least 8' x 6' of storage within this structure, leaving me 24' x 10' for the studio and I'd prefer 2 rooms. Having built a standard MAM wooden framed studio before with absorption panels within the rooms, this time I plan to build the main structure from 6" or 8" dense concrete blocks with John Sayers style inside-out walls inside so the studs and rockwool face inwards so the walls ARE the absorption panels rather than building normal walls and then having to hang panels. I'll then need to add some reflections (it'll be too dead) which is why I thought about installing some 3/8" ply and creating membrane traps. The inner rooms will be floating and untied from the outer structure. Between the inner and outer walls I'll have a thin layer of insulation. For the ceilings and roof it'll be MAM with double layers of plywood with green glue between sheets. The floor will be double plywood, with green glue between, all floating on rubber sheet direct on the concrete base. I'll be using double fire doors throughout. Hopefully this all makes sense. I'll post plans when I finish them.
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Post by rock on Jan 14, 2018 0:16:22 GMT
For isolation of the concrete floor from room to room, you might consider cutting the concrete. Rod Gervais shows using compressed mineral wool to isolate the floor plate 2x4 from the floor.
You have built a studio before so you know what kind of sound you like/want so hey, it's your room, go for it.
As far as your inside frame goes, you know the thicker your frame and insulation is, the lower the frequency your open walls will be effective.
It'll be great to see your final plans.
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Post by Hexspa on Jan 14, 2018 2:25:12 GMT
There's a well-known engineer who is famous for reamping. He has two separate structures with a separated concrete foundation, as rock alludes to, and he is happy with it.
You know in your heart what is right for you. But, in the spirit of controversy, Sylvia Massey is a proponent of an "open air" facility where the control and live room are one. The larger your room, the more flexibility you get in terms of ambience vs. absorption; not to mention potential connection with the artist and easy of physical maneuverability.
Given that you have space constraints, I'd consider some of the mentioned proposals.
Thanks.
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Post by pandamonk on Jan 15, 2018 16:06:05 GMT
I'll be commenting about that floating floor idea. I'd say just forget it. You have already a perfect concrete slab, think about it. You have the whole planet earth pressing against that concrete slab and keep it from resonating. (I assume its build directly on the ground) If you build two rooms in same concrete slab there might be some impact noises that can be heard through that floor, but other noises shouldn't be coming in or going out. To avoid those two room impact noises, it's just easier to build drum risers and little risers for amps. In many cases floating the floor makes things just worse. If you don't like how that concrete floor looks you can just coat it normally using whatever you like. Perhaps I should explain my entire build. Currently I have a 18' x 10' x 1'6" concrete base from a garage which the previous owners of my house dismantled. I have a 12' x 10' space behind this which I plan to pour concrete up to the original base giving me 30' x 10' x 8' to play with (the maximum size you can build in the UK without requiring planning permission). I've got a lot of PA and lighting equipment which requires at least 8' x 6' of storage within this structure, leaving me 24' x 10' for the studio and I'd prefer 2 rooms. Having built a standard MAM wooden framed studio before with absorption panels within the rooms, this time I plan to build the main structure from 6" or 8" dense concrete blocks with John Sayers style inside-out walls inside so the studs and rockwool face inwards so the walls ARE the absorption panels rather than building normal walls and then having to hang panels. I'll then need to add some reflections (it'll be too dead) which is why I thought about installing some 3/8" ply and creating membrane traps. The inner rooms will be floating and untied from the outer structure. Between the inner and outer walls I'll have a thin layer of insulation. For the ceilings and roof it'll be MAM with double layers of plywood with green glue between sheets. The floor will be double plywood, with green glue between, all floating on rubber sheet direct on the concrete base. I'll be using double fire doors throughout. Hopefully this all makes sense. I'll post plans when I finish them. That's fantastic. It'll save me a fair whack on the dozen or so sheets of ply, green glue and rubber sheet.
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