703, 705, rockwool!?

Hi guys. Havent posted in a long time as ive had MAJOR delays on the studio. :evil: However i still come on about once a week to watch all your studios progress, which kinda spurs me on. Hopefully in the next couple of weeks things are gonna start and ill put a FULL post on my thread explaining where the studio stands now. Just got a quick question about materials for acoustic treatment. Is the general rule of thumb that; :arrow: Rockwool is mainly used for isolation due to it being very dense. :arrow: 703/ 705 is a type of rigid fibreglass sheet (705 being more dense) :arrow: Pink fluffy is... well the pink fluffy stuff found in most comon insulated houses, and is good for insulating cavities? My questions; Can i use rockwool for corner trap/ broadband absorber pannels (with fluffy stuff behind?) see pic (thanks len :wink: ) Is a slot res. made the same as above, just with slots? Cheers guys. oZ

Ive heard the rigid fiberglass boards are good to use if you cant get acoustical mineral fiber boards. I dont think the flluffy insulation would be more effective than plain old air. Thats the way I would do it if I couldnt get auralex so cheap.

Rockwool and rigid fiberglass are acoustically interchangeable by density; so 3 PCF is optimum for acoustic treatments. In most areas fiberglass of that density is more expensive than rockwool/mineral wool/slag wool. For inside a wall, 2.5 PCF (like Thermafiber SAFB) is ideal for music, but standard weight (around 0.8 PCF) fluffy fiberglass will only lose 1-2 dB at most, and is quite a bit cheaper usually. For outside walls, paper faced fluffy fiberglass should go paper out for hot zones (more air conditioning than heat) and paper in for cool zones (more heat than air conditioning) For inside walls, (between rooms) use NON-faced insulation. For double frame walls, it's best to use fiberglass strapping across the inner edges of both frames and a slight compression of insulation when the first layer of wallboard goes up; this keeps some air flow possible within the wall for any drying that may be necessary, it keeps the insulation from sliding down in the stud cavities, and it helps keep the insulation against the panel faces for vibration damping which improves isolation a few dB. HTH... Steve

Here are data sheets for Thermafiber Sound Attenuation Fire Blankets (SAFB) - Nominal Density (2.5 pcf) and Roxul Acoustical Fire Batt (AFB) - ≥2" (2.5 pcf). --Keith :mrgreen:

Hi guys. Thanks for the great answers. My questions were related specifically to acoustic treatment, as the design for isolation between rooms has been already sorted (with great help from this forum and British Gypsum). Contractors and dry-liners are responsible for the first fix of the walls, tape and caulk, etc. However it is my responsibility to fit the acoustic treatments within the rooms (bass-traps, slot wall resonators, soffits, etc). So basically for broadband absorbers, soffits, bass hangers, slot wall/ helmholz resonators i can use either rockwool or rigid fiberglass as long as its 3 PCF (rockwool being cheaper tho)? The basic designs for the corner traps are very similar to lens http://www.johnlsayers.com/phpBB2/viewt ... &start=150 (hense the borrowed pic :lol: ) If you could cast your collective knowledgeable eye over these rough pics, just to check ive got the right idea, that would be great. Thanks for all the help so far. Oz

Whats the verdict then? oz

You're good to go - if you can afford it though, I'd fill the entire corner with the 3 PCF stuff; just cut into squares, then cut those into triangles and stack 'em horizontally in the corner floor to ceiling. If that's too expensive for the budget, the fluffy fill behind the 3 PCF stuff will still help more than an empty corner... Steve

Thanks steve. Just wanted to make sure i get the idea of all this stuff! As soon as 'the powers that be' pull out the finger, hopefully construction will get underway, which means i can start getting everything together. Thanks for all the time and advice guys, and as soon as some physical developments start, i'll put up a construction diary. Hope all of your respective projects are goin well. Oz

is mineral wool and mineral fiber the same thing? are there any different kinds. a local company carries mineral wool 2-4 2in sheets for 32$ for 6 sheets. they also carry what they say is oc 703 = john mansville duct board.

Ozzy, bear in mind that you might struggle getting hold of 703 in the UK. You can substitue this with RW3 (Rockwool). You should be able to get this at Travis Perkins. You might have to ask them to check if they give you a blank stare when you ask for it. si

Calling anything Johns Manville makes "OC 703 might get them sued; OC stands for Owens-Corning, a completely different company. Acoustically tho, nearly any mineral wool, mineral fiber, rigid fiberglass, slag wool, rock wool, sheep wool, cotton wool, etc, have so close to the same characteristics that they are interchangeable. Any of these in the SAME DENSITY will give very close to identical results, with possible SLIGHT differences in absorption characteristics - but if you follow the accepted practices of mounting, placement, etc, seen on these and most OTHER acoustic related (NON-commercial) sites, you'll be fine. One exception - products like "duct board" usually have some sort of coating applied to minimise shedding of fibers, since they're intended for use inside of DUCTS - this will change at least higher frequency absorption, so this should be taken into account when calculating TOTAL room absorption at all frequency bands... Steve

thanx for your help........