Optimum, Balanced Solution for Basement Ceiling?

[Furious G]

Hello all,

With the help of a contractor, I'm finishing a basement area (12 x 24 x 7) in our new house.



The studio area I'll be talking about is solely the tan rectangle area with the stairs. Addditionally, the long wall not impeded by the stairs measures 24 inches, not 21.

This is my first thread here, so forgive me if I make some newbie mistakes. I will try to be as forthcoming and detailed as possible about what I want to achieve with the ceiling and where I'm at so far. I'm going to address everything regarding the ceiling - the floor above/below, as well as the lighting/wiring. I have to pre-know a lot of this if as will save me time/money later because I'm working with a contractor who will 'just do it the standard way' unless I say otherwise.

Music is my living (performer/gigging, teaching, recording, producing) and this basement is going to be lesson studio by day, recording environment by night, as well as a backdrop to my YouTube channel for online lessons and videos. The video content will be everything from blogs to instructional to performance based. Succinctly, this is not a hobby, and I'm a 'once and done, do-it-right kinda guy. Important to mention here - I'm not a huge DIY guy (another reason for using a contractor).

The area above where i'm going to be placing the mixing desk (wall opposite the stairs) is the living room of the house. I have a 6 and 4 year old with heavy feet, and obviously very distracting when I'm teaching, even more so when recording. I want to be able to sing / belt some takes at 2:00 AM after a gig without worrying if it's going to wake the wife and kids up on the second floor. I know I cannot get TOTAL isolation given the limitations that I've presented myself (mentioned in detail below), but want to do what I can:

The solution for the ceiling I come up with has to be a very balanced four-sided square in no particular order:

1. Sound isolation
2. Sound absorption
3. Aesthetically pleasing
4. Financially sound

With #4, it doesn't mean cheap, but if name brand product 'A' in the acoustic treatment area is two times more expensive as product 'B' that you can get in bulk at a discount store or more common, and has a negligible difference in the said acoustic goals - that's the kind of stuff I'm trying to find out ahead of time. The basement finishing job itself is taking me to the cleaners but I'm getting what I pay for. They guarantee for 50 years, and the materials they use for the walls and floor (besides the wooden door to the laundry room) are moisture proof, mold-proof, and inorganic.

The company is going to be doing the job about a week from now, and I'd like to be able to get the ceiling piece done in its' entirety pretty quickly shortly after they are done so I can really start working and be done with the construction part, just having to worry about bass trapping, diffusion and absorbing reflections with treatment on the walls as I go. I work between 70-100 hours a week between gigging, teaching, recording, etc so time and simplicity are of great value in my scenario as well.

Regarding materials, if possible (which may not be), I want to use a substitute for drywall in the mass/isolation department. As expressed, I don't want to cover the joists or lower the ceiling anymore, and want access to wiring and ductwork as well w/o having to cut through drywall to replace / repair, so the traditional drywall ceiling with resilient channel is not the route I'd like to go. Ceilings are just shy of 7 inches and don't want to lose anymore height.

Also regarding drywall, as mentioned earlier, I'm trying to keep everything in the basement inorganic and moisture proof. I know there's probably no way around this from the insulation angle, as Rockwool, or fluffy are compromised when they get wet. Mass loaded vinyl, PVC molding etc come to mind.

Have you guys had any experience with or have any opinions about this stuff for the ceilings?:
https://www.youtube.com/watch?v=wv4IMnySxyc

There were two solutions with the same goals in mind I've come across in the various forums which seemed very similar to my situation. Both had great drawings of their ideas, both offer isolation, High, mid, and low-frequency absorption, and I'm a very visual guy, so diagrams are everything to me:

Solution A: Ran across this in Sayer's thread from a poster named knightly and it seemed to follow Grevais' (Mass-Air-Mass with additional A after the last M).



This seems to be the be-all end all that I've found if you want to leave the joists exposed for absorption and isolation. Three concerns / adjustments I would have in my specific scenario:

1. Money and time factor it would take to do this on my end (I need to get working soon after the finishing is done and will have a bit more budget, but not a ton).
2. I only have 7 inch joists (cavity is 14inches across BTW), so this would have to be modified
3. All this treatment seems like it would greatly help, but it seems to me that the largest issue, the joists, will still be booming in my case. They are directly connected (coupled) to the subfloor and the transmission of the impact immediate. Awesome for isolation of sound going up, not so much sound coming down.

Solution B: This seemed to address the joists and use M-A-M from a poster named eirikur here from the gearslutz forum:



I want to add that the frustrating thing about all of the threads that I've come across regarding this topic - there seems to be a ton of sound, solid planning and then very little report on results and/or adjustments needed after the fact after work is done (how does it SOUND, recording results, band rehearsal, to what degree it kept noise in the work environment and kept noise out from other areas etc).

Soo…all of the above being said with the intended usage of the space and four finishing goals in mind, do you guys have any thoughts and / or creative solutions on materials or specific approaches you could recommend? Diagrams would be very welcomed and appreciated.

Regarding addressing the impact problem from above:
The floors are hardwood right now, an impact magnet, and the living room a resonance nightmare, as is most of the house. I'm going to carpet the floor in the living room upstairs after the basement is done - thinking a very thick carpet with an acoustic underlayment. I've run across Silent Source, SONOPAN Panels, Acousticblok. Any recommendations in this realm to get the most impact absorption for the buck?

Regarding electrical and wiring:
The finishing contractor is updating the lighting fixtures and the wiring as well in the finished space. Regarding how the electrical, lights, outlets and fixtures should be run (separate circuits, placement of wiring in ceiling, types of recessed lighting fixtures) is there any thing you folks could recommend to keep in mind for the '1 to 5 year down the road' philosophy that I have them do? I don't want to be looking at this job in any way at the end saying, 'I wish I would have thought of that.'

Link to lighting fixtures they typically use:
Cooper Lighting H27ICT 6-Inch Shallow Ceiling IC 120V Line Voltage Housing - Recessed Light Fixture Housings - Amazon.com

They also offer an option to Dryfall paint (black or white) the ceiling. Depending on how much $ I need to invest in treating the ceiling for the acoustic goals, I've considered this as well, because it seems like the treatment of the ceiling could turn into quite a project which could take longer than I expected. There will be this nice, finished area and then bare, exposed wood y'know? I like the industrial look and that might not be that bad for a bit in the interim. They said they would charge me $550 to paint the ceiling - not so sure that's a good value either.

Thanks to this forum and it's contributors for existing, and for being a wonderful source of knowledge and information for guys like me who want to get it right the first time. This room is very important to me and is (already) literally the headquarters of my family's income. Any help you guys could give is very much appreciated!! Thank you!

 

[Tadpui]

Soundproofing takes 3 main components:
- mass, mass, more mass (OK, that's 3 by itself...)
- flanking paths - giving the vibrations places to dissipate rather than transfer to the rest of the house's structure
- preventing air movement

There's probably another element or two that I'm forgetting (it's been about 18 months since I studied up for my home studio). I don't think that you can expect very much attenuation with walls that are directly connected to the floor and ceiling, and with open joists on one side. It'll dampen the high frequencies pretty well, but bass will pass through it like it's not even there. That means drums, bass, and guitar leaving the room, and footfalls entering the room from above. You've got to decouple your walls and ceiling from the floor above, deaden the air between them, and put a couple of layers of drywall on either side if you're going to get any appreciable attenuation of lower frequencies. Seal up all of the joints and junction boxes with acoustical caulking.

There are a few good books on the subject, although I only have experience with one of them: Build It Like The Pros, by Gervais. I'd recommend picking up a book or two, read them cover-to-cover, and then re-evaluate what your expectations are. Soundproofing is pretty expensive, and if you skip any of the critical elements of it, then it's not going to be even remotely soundproof and you'll just end up with a really expensive room that doesn't behave much differently than a much cheaper conventionally constructed room.

 

[Furious G]

Thanks Tadpui. My expectations for isolation are pretty darn low. I know I'm not going to soundproof the room, or isolate/eiliminate the impact noise from the living room upstairs. It's just unrealistic to expect that given the given environment and the balance of things I want it to do. Because I don't want to do a resilient channeled drywall ceiling and lose any more ceiling height, that's a sacrifice, and I know the consequences of that choice. I know the joists are going to be low frequency / impact resonators because they are coupled to the subfloor above (hence looking for perspective on the best treatment in respect to carpeting / matting the floor above in the living room). I know that mass and decoupling are basically Gods in terms of soundproofing and isolation.

Mainly, I'm looking for ideas that expand, add or subtract from the two diagrams I presented that would help in the isolation, but more specifically in balancing the four goals, in as equal portion as possible:

1. Sound isolation
2. Sound absorption
3. Aesthetically pleasing
4. Financially sound

To add an implied 5th goal - 5. DIY novice (and novice is being generous) friendly. I'm a fast learner, but as stated before, I don't have a ton of free time to allocate to turning this into a lab experiment, so to speak. I've got to get this done pretty efficiently and turn my attention to other areas of the house (happy wife…happy…well, y'know the story).

Right now based on all ideas and information I've collected, where I'm at:

Add 1-2 layers of drywall (thicker the better?) glued to the subfloor in-between the joists, using acoustic caulking to connect it to the joist sides. Use 703 (or Rockwool - not sure which one) mounted (cleated or nails for support) to bottom of joists covered with a breathable fabric. Carpet the living room floor with thick carpet (not sure of specifics) laid over acoustic matting (again, have no specific material in mind).

As far my expectations with said treatments towards those goals?
1. Sound isolation - drywall attached to subfloor, better than what is there. Carpet and matting above will help with footfalls. Don't know if doing the drywall piece is even worth it though - guessing the difference in isolation and impact noise will be nominal.
2. Sound absorption - highs absorbed by breathable fabric, mids by insulation, whole ceiling's airspace turns joists into bass trapping cavities. Check. Winner of the 5 goals with this approach.
3. Aesthetically pleasing - Ethan Winer's 'The Ultimate Home Studio' video shows the end result of this treatment - looks pretty nice
4. Financially sound - Not too expensive so far
5. DIY novice friendly - I know a carpet guy to do the upstairs, and the fabric / insulation idea for me is not intimidating.

Thoughts on Rockwool vs the 703? Rockwool seems to have slightly better bass absorption, which might help for the rumbly footfalls and 'heavier' side stuff that I will be tracking from time to time.

Is it even worth considering beefing up the subfloor with a couple layers of drywall? Based on the physics of sound my gut tells me it's not going to do much (which was the basis of the two aforementioned drawings). Feels like putting ointment around the border of a wound instead of directly on the center of it.

 

[mjbphotos]

The problem I see with your ideas - 7' ceiling to work with ( I assume you meant 24 feet -not inches - in your first post.) Sounds like you've got 2x8 joists, so little room to implement either of the possible isolation solutions. If you are recording/mixing in this room, you're going to need ceiling clouds (2" thick rockwool panels), too.

 

[Furious G]

Yes on the 24 feet typo. I found both of those diagrams on the forums as 'springboard' ideas or starting points - they are not mine.

As I said in first post:

2. I only have 7 inch joists (cavity is 14inches across BTW), so this would have to be modified

It seems the best thing for me to do is to stuff the cavities with one layer of Safe 'n' Sound towards the bottom of the joist, cover it with a breathable fabric (suggestions?), leaving the 3-4 inch air gap towards the top of the joist. Get some high, mid absorption and low frequency trapping in one shot. I won't get much isolation or soundproofing benefit from this, particularly in dampening impacts from above or bass freq going up from this because the joists are in direct contact with the subfloor and I'm not adding any mass (correct so far?).

Again, the whole drywall / green glue / multi insulation ideas I posted are definite overkill and would have to be modified to be practical for my situation, which is what I was looking for suggestions on. Putting drywall in between the joists would just lower the already existing space and small the bass trapping area, not really giving me an appreciable difference in dampening correct?

Where I can attack the impact noise is at its' source - the living room upstairs. The living room is hardwood floor on top of subfloor. Need the best treatment for the buck (suggestions on floor matting pre-carpet anyone?). Looking to place carpet on top of whatever acoustic underlayment will be the most effective in terms of dampening and hopefully providing a little isolation. Thoughts or suggestions?

 

[mjbphotos]

Get OC 703 or 705 or Roxul AFB, 60 or 80, rather than Safe 'n' Sound - they have better low frequency absorption. Burlap or cotton sheeting are cheap cloth to cover the insulation/ceiling. Burlap stretches, so is harder to work with. There are also specialty fabrics you can buy - check out Guilford of Maine. More money, but can look very nice when installed well.

 

[Jake_JW]

Using fabric on it's own between the joists might sag a little over time. I have a similar setup in my studio (though above I have a vaulted ceiling, rather than a kitchen floor).

You can try putting something like plywood with drilled/sawed holes in to help the fabric hold the rockwool up if aesthetics are a concern. Also stops the fabric getting nicked by people wielding cymbal stands/overhead stands/swords. Anything rigid and with enough holes will do but it definitely helps things look tidy.

I'll put up a picture of mine later on when I'm back there.

 

[Furious G]

Thanks guys.

Did some digging getting Roxul Rockboard 60 and OC 703 in my area. Can't really get it anywhere without getting super dinged for a shipping charge (Amazon) or shipping being factored into the price already (Sears). None of the local DIY chains or Mom & Pop stores carry it. Same with the OC 703 / 705.

Figured with my room size (288 squ ft - I always factor in a little extra - about 30 squ ft in this case), I would need about 6 cases of 6 for one layer of the Rockboard 60 . Amazon about $500, Sears about $600, ATS Acoustic about $440 with shipping.

Priced Safe 'n' Sound at Lowe's / Home Depot (available for pickup / free shipping)

$46.27 a Roll / $37.02 in quantity of 15+
One bag covers approx 60 squ ft - 288 / 60 = 4.8 rolls
Safe 'n' Sound 3in layer = 5 x $46.27 = $231
Safe 'n' Sound 6in layer (2 batts per joist) + extra bonus insulation to cover unfinished side $555.30

So dealing with about double the cost for the Rockboard 60 (and OC 703)

Comparing absorption on (available) LF data sheets for the products:
Roxul Rockboard 60 2" =
.32 @ 125Hz / .81 @ 250Hz / 1.06 @ 500Hz / 1.02 @ 1000Hz / .99 @ 2000Hz / 1.04 @ 4000Hz / NRC .95
Roxul Safe 'n' Sound 3" = .
.52 @ 125Hz / .96 @ 250Hz / 1.18 @ 500Hz / 1.07 @ 1000Hz / 1.05 @ 2000Hz / 1.05 @ 4000Hz / NRC 1.05
OC 703 2"
.63 @ 125Hz / .56 @ 250Hz / .95 @ 500Hz / .79 @ 1000Hz / .60 @ 2000Hz / .35 @ 4000Hz / NRC .75

We all know NRC's don't compensate for LF < 125Hz but it seems the curve on the Safe 'n' Sound slopes more a little more favorably to the sub-bass stuff, and has the best balance of mid & HF absorption, unless there is something I'm missing, or don't know / understand. According to the published numbers and the pricing, Safe 'n' Sound seems to be the best balance (bass trapping is one of many things the ceiling needs to do ideally) that I'm going for with the original priorities:

1. Sound isolation
2. Sound absorption
3. Aesthetically pleasing
4. Financially sound
5. DIY Novice friendly

The only thing I'm not really sure on is whether or not to use one layer of Safe 'n' Sound or two. The company itself said there would not be a significant STC difference (about 3-4). I've searched for the NRC figures of one layer vs two specific to this product and been unsuccessful. What would be equally as valuable would be the IIC rating of Safe 'n' Sound relative to my sitch too.

Regarding the ceiling, thank you, mjbphotos and Jake_JW SO much for posting ideas on this. This is the only area of the ceiling treatment that I don't at leas have a semi-solid idea on as far as material. I checked out Guilford of Maine (thanks for the ref), and it looks like they have some VERY nice stuff. The bigger concern I have is what Jake hit on the head. With fabric, I have three potential worries.

1. It will sag, no matter how durable. Gravity always wins. Aesthetics suffer. Not a once and done. Have to do it again.
2. It will become a dust magnet, and vacuuming the area will lead to the first worry because it will pull at the fabric
3. If I ever have to access the duct work / electrical, besides pulling the Roxul out, a ceiling 'repair' will be a bigger pain than drywall with the fabric to 'reset.'

I am really looking for an 'outside the box' solution to this part of the equation, and it's a bit of a challenge. A more micro mesh breathable material that 'acts' like fabric but allows easier accessibility. Looks nice. Not drywall. More modular than a long run of fabric. Micro-mesh vinyl or steel (like a window screen)?. Spitballing a bit out loud here. Wood with holes is a good suggestion (and also can be painted), but it is has organic material in it, which is something I am completely avoiding (less the wooden door that leads to the laundry room). This is another reason I'm steering toward Roxul - fire resistance, not as much itchy, more moisture resistant than fiberglass, can be dried out and put back if it gets soaked (god forbid a plumbing leak of this size coming from upstairs). Ideally, if you are finishing the basement, you want to use inorganic materials. Solve water movement problems, tame humidity, give mold nothing to feed on.

Returning to wood, besides the holes, it would place a rigid, reflective surface in the sound transmission chain, in front of the Roxul, which would reduce the effectiveness of the bass trapping of the joists as well as the mid and HF absorption yes?

I would love to see a picture of your ceiling Jake_JW, with any and all details you could provide, no matter how trivial they might seem, when it came to your process of deciding how to treat your ceiling and why you did it this way in your sound environment. Pictures, graphs, unbiased / unpaid reviews - results and videos speak a million words to me. Whatever you remember - exactly what materials you used, measurement of joists, (depth, width of cavities, etc). Specific materials and quantities of them.

Most importantly, feedback on how it SOUNDS (before and after treatment if you can remember) or probably more accurately DOESN'T sound. Adjustments you made afterwards if expected result after ceiling treatment was not to your liking. How long you've been mixing / recording / rehearsing in the space.

I've had one heck of a time on the forums trying to find results after people went through the prep and planning process (some threads were 50-70+ posts long), specifically relative to this joist treatment forgoing the drywall / resilient channel treatment. Found about 10 threads where there was a ton of useful information in the planning stage, but when someone (including myself) asks a couple years later on the thread, 'how did it work out," usually there is no answer. In one case there was, "this thread is over 5 years old - why don't you start your own on this topic?" A poster had just asked something along the lines, "I'm doing something similar in my basement - curious to see how everything worked out." I don't believe the question was intended to hijack the thread. He seemed to be asking the thread starter for details regarding achieved results.

 

[mjbphotos]

Yeah, shipping is a bear, but its worth it - use this place to order the RIGHT stuff: Acoustic Panels by ATS Acoustics

You're not seeing replies back from the original posters on those threads mentioned because they spent a ton of time and money to find that the noise (kids upstairs!) still gets through.

 

[Furious G]

Regarding the second part of what you said, I am starting to think that as well. As I expressed to Tadpui's response, I am a realist and know I'm still going to be annoyed, just want to be a little less annoyed, by the footfalls.

Regarding ATS Acoustic, I mentioned them in my last response in regards to pricing the materials you suggested:

I would need about 6 cases of 6 for one layer of the Rockboard 60 . Amazon about $500, Sears about $600, ATS Acoustic about $440 with shipping.

All three of these places (Amazon, Sears, ATS Acoustc) sell Roxul Rockboard 60, so when you say "RIGHT stuff," I'm not sure I understand. You suggested some materials:

"Get OC 703 or 705 or Roxul AFB, 60 or 80, rather than Safe 'n' Sound"

Was there another treatment I missed that you recommended? The ones you mentioned (such as Roxul 60) are distributed from the parent company to multiple vendors.

You also stated, "they have better low frequency absorption." Based on the published numbers and how I'm using the absorptive material, for the balance of high, mid AND low absorption, I haven't found any evidence that supports this, especially relative to my goals. Safe 'n' Sound seems to be the best OVERALL performer for balance in what I'm trying to achieve, no?

 

[Tadpui]

My ceiling is totally decoupled from the floor above (bedroom), with a couple of layers of drywall + green glue, plus safe 'n sound between the decoupled floor and ceiling joists. And about the only noise that still comes through the floor is footfalls. I can hear my 50 lb poodle gallop down the hallway above, and occasional footfalls in the bedroom/bathroom above. Those damn footfalls are tough to get rid of. Luckily the bedroom and hallway are carpeted. If it was the clicky-clacky laminate wood flooring like I have in my studio, it would probably be unbearable. But as it is, in my room they might not be loud enough to ruin a vocal take, but in such a quiet environment it's loud compared to the soft whir of my CPU cooler, which is the only other audible noise in the room.

My ceilings ended up being about 7'6" (they weren't a full 8' to begin with), so I can understand not wanting them any lower than 7'. It would be a little claustrophobic. What we did in my basement was run a 2nd set of joists between the existing joists. The bedroom floor above rests on the original joists, and my studio ceiling is suspended from the new joists. Neither set touches the other. The new joists are only about 2" lower than the originals, so I only lost about 2" of height with this setup.

 

[Furious G]

As an aside, just found a decent resource if it can help anyone else in my situation, (or anyone else who wants documentation on this sort of thing). The document is called "Controlling the Transmission of Impact of Sound through Floors." Gives a pretty comprehensive coverage of approximate IIC ratings for different floor assemblies and materials. Looks like it was published by the Institute for Research in Construction - National Research Council of Canada. Seems largely fact based / field test minded.

Link:
https://www.nrc-cnrc.gc.ca/ctu-sc/files/doc/ctu-sc/ctu-n35_eng.pdf

 

[JimmyS1969]

Looks like 1 hour 45 minute drive to SPI in Perrysburg. The location here in Denver carries the Roxul and OC703/5 mentioned at a great price. I would contact them first and see if a bit of a drive can save you a bunch of shipping costs.

I have a session starting soon so don't have much time. I have a drum room treated with open ceiling joists in basement similar to what you are dealing with. I will give more detail as to my results later.

Perrysburg
USA, OH
43551 (419) 661-8877

 

[Furious G]

Thanks jimmys69. Went to the website and found the location. Every dollar counts in this equation, as I just sold my soul to give my wife a new kitchen and had to waterproof the basement before even thinking of this fun stuff.

I will definitely reach out to them tomorrow or via email. Definitely leaning towards the Roxul and steering away from the OC703/5. Looking at the specs for all the products - it seems that the Safe 'n' Sound is going to be the best option for my overall treatment goals, unless there's something I'm missing or don't understand up to this point. Roxul said the main two distributors of the Safe 'n' Sound were Home Depot and Lowe's in the area, both of which I can go to the store and grab. I'm wondering if the SPI would be willing to sell 5-10 rolls of that product to lil' ol me who is not a contractor. Worth a shot to reach out to them though yeah?

I look forward to hearing more about your drum room, and details surrounding it. If you have any pictures, that would help me tremendously too. I am really concerned about the material at the base of the joists and it is the only question mark left in the equation. All fabrics will sag, and eventually become dust magnets. Trying to find an unconventional solution that is both aesthetically pleasing, rigid, modular and does the same job the fabric will do. Some sort of micro-mesh vinyl if it exists maybe?

 

[mjbphotos]

You also stated, "they have better low frequency absorption." Based on the published numbers and how I'm using the absorptive material, for the balance of high, mid AND low absorption, I haven't found any evidence that supports this, especially relative to my goals. Safe 'n' Sound seems to be the best OVERALL performer for balance in what I'm trying to achieve, no?

The numbers are for 2" thick Roxul and OC - 4" is always recommended where space allows (double up the panels).

 

[Furious G]

The numbers are for 2" thick Roxul and OC - 4" is always recommended where space allows (double up the panels).

Gotcha. Thanks for clarifying. I'm definitely going to be using the rigid panel stuff for bass trapping and panels around the room. The tricky part about a 2' x 4' panel for a joist that is 14" wide is the inevitable cutting and sizing (#5 DIY Novice - with limited time and money), and the cost of the materials. I understand there are industry standards when it comes to the pro studio. I'm trying to find the balance.

Using what I could gather as 'accurate,' I plugged OC and Roxul S&S (these will have to be refigured of course if I don't have the accurate flow resistivity numbers:

1 - Blue: 4" OC 703 (2 layers) @ 27,000 Pa.s/m2 (NASA number) + 3" air gap
2 - Green: 2" OC 703 (1 layer) @ 27,000 Pa.s/m2 + 5" air gap
3 - Red: 6" Roxul S&S (2 layers) @ 8,000 Pa.s/m2 + 1" air gap
4 - Orange: 3" Roxul S&S (1 layer) @ 8,000 Pa.s/m2 + 1" air gap

Result: Multi-layer Absorber Calculator

Called Roxul today and their tech guy said that although they don't publish it, the flow resistivity for Safe 'n' Sound should be around 15,000 Mks rayls / m. Not knowing for sure if this is the same as Pa.s/m2, I did another graph anyway:

1 - Blue: 4" OC 703 (2 layers) @ 27,000 Pa.s/m2 (NASA number) + 3" air gap
2 - Green: 2" OC 703 (1 layer) @ 27,000 Pa.s/m2 + 5" air gap
3 - Red: 6" Roxul S&S (2 layers) @ 15.000 Pa.s/m2 + 1" air gap
4 - Orange: 3" Roxul S&S (1 layer) @ 15,000 Pa.s/m2 + 1" air gap

Multi-layer Absorber Calculator

According to both graphs, I really hope the 15,000 Mks aryls / m from Roxul was right. The red line with the 6" of Safe 'n' Sound looks to be the smoothest, most balanced, absorptive curve. The 703 starts edging it around 50Hz, but not by much.

Being the 'don't tell me it sounds better let me hear it / don't tell me it's a better absorber, I need to understand the physics and see the numbers (chart / graph) kinda guy, I've come to really love the Multi-Layer Absorber Calculator. This thing has taken me on a very time consuming hunt however that I'm not enjoying - the hunt to try to find the accurate Gas Flow resistivity figures - listed as Pa.s/m2 in the calc.

My brother is the Dr. in Physics (literally) - I'm the music guy - I keep seeing rayls/m posted for materials flow resistivity. Are rayls/m = Pa.s/m2? In other words, can you plug a rayls/m factor for a material into the Porous Absorption calc and it be accurate? If this is not the case then how do you convert rayls/m to Pa.s/m2? On Wiki I'm seeing CGS Rayl, MKS Rayl. So far, what I've got is Mks rayls / m = Pa.s/m2. Also, if a listing doesn't have the "MKS" listed in front of the Rayl, is it assumed?

For newbs like me, it would be so helpful (and probably too easy - nothing worthwhile is ever easy right) to find the accurate numbers for this calculator for materials in one place. Is there any place out there in web world from a third party that has them all in one place, and accurately? You obviously won't get accurate acoustic results if you don't plug in the right variables to start with. Would it be worthwhile to start another thread to get all this in one place?

I've seen the Bob Golds resource (which is awesome) but don't see anything with rayls or Pascals. Is there another besides this one?

http://www.bobgolds.com/AbsorptionCoefficients.htm

Additionally and finally, amongst the threads, I'm seeing a variance of figures. For example with OC 703, I've seen: "between 16,000-25,000," and just came across a study that avare in Gearslutz found by nasa that stated 27,000.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19880003624.pdf

I've also seen it posted, that depending on the time of day, you may get different figures for gas flow resistivity from the companies (OC) themselves.

To sum all this up, I simply just want the right flow resistivity figures (and preferably the source from which they were generated as well) for Safe 'n' Sound, Rockboard 40,50,60 OC 703/705 in the unit the Absorption Calculator needs so I can 'play' with this calculator (correctly). Anyone?

 

[Furious G]

And…(drum roll, another (different) flow resistivity figure for OC 703, apparently right from the company: 17324 mks rayls / m

 

[JimmyS1969]

And…(drum roll, another (different) flow resistivity figure for OC 703, apparently right from the company: 17324 mks rayls / m
View attachment 96279

I'm Replying to this post as it will take less space. lol! Sorry for the late reply. Had the flu and blah blah.

Ok, so many of us have gone through the research of what is best in any given situation with the science that makes it so. It really come down to trying an approach based on facts and the results obtained by them. Some of it is personal... Anyway.

I was lucky enough to have great advice from jhbrandt LINK here when I was building the drum room. I initially planned on paying him for his services but my 'small scale' project was not something he felt needed to do other than steer me in the right direction. He did infer that I buy his book which of course I did.

-You may want to contact him directly. He will not bullshit you in any way. Though he is a very busy man and worth every penny he requests.

So, without my real need for isolating sound from the basement room to the upstairs/or otherwise and the advice I was given, what I found to be the most cost effect and efficient for the drum room was to use Roxul 80 @4" thickness between the 8" joists. I could have added mass to the bottom of the subfloor above if I desired a bit of transmission of sound reduction by adding layers if inserted dense material, but the low end will always travel through the structure. It just was not warranted in my case.

So the basic of the install was cutting 4" Roxul 80 1/2 to 1" larger than the opening between the joists across the whole usable ceiling of the drum room. In my case, 24" centers with 10" (actual 9.5) joists. The Roxul (though not as rigid as OC705) is more than sturdy enough to hold it's place without any type of anchoring or support. Proven by 3 years of use and not a single sag. I'll admit, I cut a couple short and a few nails held it up.

These were all placed 1" above the bottom level of the joists leaving an air gap of 5.5" above the Roxul. The ceiling was then covered with fire retardant cloth. I myself was not concerned about pretty so I didn't trim it off all pretty with wood. Drummers don't seem to care about pretty in my experience, and all I care about is making the room sound good. Also, since I was in a basement where the joists are supported by the concrete foundation, added the full depth at the walls with the same Roxul, thus forming superchunk style corner traps @ two of the adjacent walls.

I used only 5 - 4"x2'X4' panels hanging from the joists for reflection control in the room. Hanging 5" off the concrete walls-staggered from each short side of the room. Oops, the room is 28'x13'X8.3'. The actual space I treated in the room that I call usable is 13'X17'. The other portions are storage and the damn laundry room. Just draped cloth on those ends so it don't look like a Gomer Pyle drum room. The floor is just concrete (reflective flooring is best) though a thin tight looped carpet works well under drum kits for stability.

The results have been amazing for me. There is no issue with reflections at the ceiling from overhead mics that are common with recording in a drywall ceiling room this short. In fact it really sounds like a 'bigger room' than it is. I mounted boom stands on the ceiling joists to get the overhead mics out of the way and as far up as possible.

Now, how does this relate to a control room or multi use recording room? Good question. Well first you will not need a 'cloud' dropping from the ceiling. All reflections from floor to ceiling will be basically eliminated so controlling the flutter echo and 'first point reflections from monitors will be just a matter of experimentation as to how the room sounds and tests after introducing the acoustic treatment. The fact that you have the ability to fully treat the ceiling seems to me a win/win situation. You can always add reflection. Always best to adsorb as much low end as possible. I have never heard of anyone complaining that their ceiling didn't have enough reflections.

Bass traps in corners are something that through all of my research and personal experience, can not be overdone. Especially in rooms with short wall distances. You have a long wall as I do in my control room. I do not have bass traps at the far end from my monitors as it is 29 feet away. I do notice a strong resonant frequency at 120Hz about 3/4 the length of the room, but I don't mix there. Usually musicians recording like the bass buildup in that part of the room so I don't care. I also have a couch, thick rug, bookshelf, and big PA system on the back wall when rock bands are tracking drums so they can blow their ears out if they want.


Hope any of this helps man.

 

[Furious G]

jimmys,

Thanks a ton for taking time to detail your whole experience beginning to end, and it's result. Lots of good, specific stuff and very helpful. Have a couple of follow-up questions throughout if that's ok.

This whole basement process (starting w the waterproofing) has been about finding that balance between everything - just a big optimization problem, and as expressed by many here, the science of acoustics seems sometimes counter-intuitive.

Regarding jhbrandt, have run into several of his posts and they have been very helpful - (including the recent link you provided). Such an amazing knowledge base in this communitity and it's great that those in the know take time to share.

Regarding subfloor, I'm at pretty much the conclusion you came to. Almost like having a Band-Aid vastly smaller that the wound it's supposed to cover. Seems most economically sound and practical to treat the impact noise at it's source with carpeting and padding. Again, not hoping for miracles. I'm a dad of two rambunctious kids who love to play, and outside of gigging, work primarily from home when teaching / recording / mixing.

Question 1: Why did you choose the Roxul over OC, and why Roxul 80 as opposed to Safe 'n' Sound and completely filling the cavities? My first guess is it had to do with the width of the joist cavities and you needing more rigidity for that, yeah? Was it a spec decision? Bass weighted (guessing a big priority for drum room)? Advice from jhbrandt?

I guess the thing I'm not understanding is the science as it relates to my overall case / needs (need this to behave basically like a control room) behind going with rigid board in the ceiling, OC or Roxul vs the Safe 'n' Sound product. I compared the specs of all the substances at 3" (I know you used 4")

Roxul Rockboard 80 3" =
.75 @ 125Hz / .82 @ 250Hz / .89 @ 500Hz / .94 @ 1000Hz / 1.00 @ 2000Hz / 1.00 @ 4000Hz / NRC .90
Roxul Rockboard 60 3" =
.78 @ 125Hz / .89 @ 250Hz / 1.04 @ 500Hz / .98 @ 1000Hz / 1.01 @ 2000Hz / 1.02 @ 4000Hz / NRC 1.00
Roxul Safe 'n' Sound 3" = .
.52 @ 125Hz / .96 @ 250Hz / 1.18 @ 500Hz / 1.07 @ 1000Hz / 1.05 @ 2000Hz / 1.05 @ 4000Hz / NRC 1.05
OC 703 2" (guessing the bottom end figures bump when you do two layers)
.63 @ 125Hz / .56 @ 250Hz / .95 @ 500Hz / .79 @ 1000Hz / .60 @ 2000Hz / .35 @ 4000Hz / NRC .75

I know these figures don't account for the sub bass <125 where all the bass chaos magic happens. I could get the rigid board stuff and folks keep telling me it's worth it, and better in LF absorption, but I don't understand that quantifiably in the numbers and science of what I'm trying to accomplish. Based on the numbers I'm seeing, Safe 'n' Sound absorbs more completely from 250Hz up than any of the rigid board product (almost too much in some areas it seems esp around 500Hz). For my case, I would imagine the mids and highs absorption would do well for clicks from toys rolling around on the floor, airborne noise, human speech, etc, as well as what's going on down here. Very important part of the equation as well.

Question 2: The low bass is where Safe 'n' Sound starts losing in absorption to the other products, which is what I must be still missing critical information about. Is it going to be an earth-shattering amount of bass not absorbed that I can't deal with with bass traps in the room, and how much is more? Before starting this research project, I was just going to throw 1-2 layers of the Safe 'n' Sound in the ceiling and cover it with fabric. I got the ceiling idea originally from Ethan Winer's (mad props again to Ethan) videos where they stuff the ceiling with just fluffy and cover it with fabric.

Question 3: After all this, I STILL don't know if I should do one or two layers of S&S. Talked to the Roxul rep today - they didn't have NRC figures for two layers of S&S - just told me that the product has a diminishing return as far as STC, which makes sense to me. Any opinion on this my friend?

It seems for ease of install (7" deep, 14" wide cavities - product fits right in), pricing (one layer $250, two $500) and availability (can grab it from HD or Lowes in my area) that the Safe 'n' Sound product is the best bet for me. Folks have said that rigid board is better, and worth it. I could, and would drive out to an industrial seller if it made sense to do so. Like I said, I still must be missing something.

Thank you for making parallels between our rooms even though we are using them for different things, and relating them - also very helpful. Regarding the cloud - that's funny. Someone had said I will need a cloud additionally on top of this ceiling treatment. That really left me scratching my head as to if they had read the very long post I took the time to detail.

Question 4: Was wondering about the traps at the far end myself. From what I've gathered, my order of treatment (post ceiling) should be, first reflection points, bass traps behind by mixing area, diffusion by back stair wall, bass traps in back of room. Probably can't do everything at once so have to do things gradually most likely. Thoughts?

Question 5: Do you have any pictures of your room?

Question 6: Regarding the pretty part of my equation - because of it's multi-functional nature, I still need to figure out an 'outside the box' solution to the ceiling membrane. If it's fabric, it's fabric. Afraid though, as people have mentioned on this thread, that fabric will sag, possibly be a dust magnet. Looking for an inorganic based (vinyl, steel etc), semi-rigid, micro meshy type material that looks great - LOL.:roll eyes: Any suggestions?

The finishing is happening this coming Monday. If I get my butt in gear and figure out at least the insulation part, I could negotiate to have these guys help me with the ceiling as well. Need to know exactly what I'm doing with it though.

Thanks again, and mad respect for the time and detail!

G

 

[mjbphotos]

Note: the actual dimension (measure twice, cut once) between your joists is probably 14-3/8" (16" on center, 2Xs are actually 1-5/8 wide). So if you cut each 48" piece of Roxul into 3 pieces 14-3/8" you'll have little waste. Note that the S&S is not really 24" x 48", either, its something like 23"x47" - measure the insulation when you get it!