John Sayers' Recording Studio Design Forum Archive

I have to build some corner absorbers this week and I need to check that the rockwool I have chosen will be suitable. it is Rockwool ProRox SL960 (Formerly RW5) Slab at 50mm thickness. I will be making a fixed triangular frame and then cutting the slabs to size and stacking before pinning the muslim sheet to the front and then the covering batons.

Here is the data sheet location for the prorox: http://www.insulationexpress.co.uk/docu ... 310713.pdf

My question is, is the rockwool suitable for what i intend or should i use a different rating/density?
Also on some of the builds, some people have put plastic sheeting in front of the rockwool then the material, is this just to keep fibres in or does this have an acoustic property when placed over the corner absorber?

I thought it was more sensible to ask these questions rather than build it and hope for the best.

I currently have a celing mount large cloud absorber that is sloped to the front of the monitors, in the corners i have hinged absorbers to change the angles, on the side walls i have some smaller absorber panels, and at the rear i have a large 6ftx4ft absorber with a sofa below it.

When i sit at my desk the sound is clear and sweet, yet when i sit on the sofa it becomes over bassy and muddy.

I am going to purchase an ARC kit this week so i can take measurements as the only mic i have is an se2000 mic and I doubt this is suitable to test with.

I can take some pictures and measurements later today if that helps for further advice.

I built the studio room following the many threads and advice on the forum, it is a decoupled room with airlock door entry, the main door is around 10 inches thick and is packed with rockwool, two layers of 25mm marine ply and on the inside 2 layers of 15mm gypsm board. then the interior door is a mass door built to john brandts designs and filled with sand, with a seal running all the way around the frame.

The interior walls are 2 layers of 15mm gypsum on framing, with the filled 100mm spacing to the concrete blockwork, the whole studio sits on its own dedicated reinforced concrete slab at the rear of my house.

Thanks again.

edit: ok i have spent some time reading some more threads, i understand the reason for the plastic sheeting is to prevent the loss of too much mid/high end and thus making the room too dead. (glad thats clarified!) At the moment i just need to know if the above prorox is suitable for a corner absorber.

it is Rockwool ProRox SL960 ... My question is, is the rockwool suitable for what i intend or should i use a different rating/density?

That's a little on the heavy side for good bass trapping. The SL930 would probably be a better bet, as it is less dense. The SL920 would probably be even better, but the don't give the acoustic data for that model, so it's hard to say for sure.

some people have put plastic sheeting in front of the rockwool then the material, is this just to keep fibres in or does this have an acoustic property when placed over the corner absorber?

For horizontal things over your head (eg: ceiling traps, ceiling cloud, horizontal superchunks in wall/ceiling corners) it keeps the fibers in, so they don't filter down over time and mess up your gear, and in all uses it does help keep the higher frequencies in the room, instead of them being killed too much by the absorption. There are other ways of accomplishing the same thing, though, if you don't like the idea of plastic.

When i sit at my desk the sound is clear and sweet, yet when i sit on the sofa it becomes over bassy and muddy.

Muddy bass near the rear wall is fairly common, and is simply due to the location of the sofa with respect to the wall, and the amount of treatment on that wall. The only sure way of dealing with that is to have very deep treatment back there (several feet), and/or to move the sofa away from the wall as far as possible. At the very least you need large superchunks in the two rear corners and a thick layer of absorption over the rest of the rear wall, floor to ceiling.

But before you do any of that, I'd suggest doing a REW test of the room exactly as it is right now, both at the mix position and in several locations along the center line of the room, all the way to the back wall. For example, take a REW reading every foot from the mix position to the back wall. Post the MDAT file here, and also some photos of the room, so we can understand it better.

I am going to purchase an ARC kit this week so i can take measurements

I'm not sure what an "ARC kit" is, but it sounds like it might be one of those rather useless room correction things, so if that's it, then don't! Room acoustics cannot be corrected by software or hardware, since the vast majority of room acoustic issues are in the time domain, not the frequency domain, and therefore it is impossible to correct them with EQ, no matter how you apply it. So forget the marketing hype of the "room correction" manufacturers, since what they are trying to sell you is a physical impossibility. Yes, it can make a slight difference for one specific location in the room, but at the expense of all other locations in the room. EQ can correct some acoustic issues, but not the ones that matter most. So don't waste your money on that, if that's what you mean by "ARC kit".

Just get a good quality acoustic measurement mic, such as the Presonus PRM1, the DBX RTA-M, or even the lower-end Behringer ECM-8000. That's all you need, along with your DAW and the REW software, which is free.

- Stuart -

Hi stuart.

Ok i will go for the lower rated prorox thanks for the advice. I really need to measure the room and also upload some photos so you can see what im dealing with. One other thing is my yamaha 02r console sits on an argosy gseries console unit, do you think that reflections and the cavities in there are adding to the bassy sound at the back of the room?

The arc software was as you guessed one of those room correction things, ok that idea has now been binned i will get hold of a good calibrated mic as soon as i can and then do the checks. I will measure the position out and then do what ever i need to, can you point me to a link that explains the required process for testing stuart?

Apart from that when i st at the console the sound is clear and crisp, and the mixes translate well to other monitors in other studios and domestic hifi units etc.

Thanks for the input its appreciated, I have some more reading to do regarding reading the room with the softwear, best get that right than waste time with multiple retests!

thanks again, will get back to you later.

my yamaha 02r console sits on an argosy gseries console unit, do you think that reflections and the cavities in there are adding to the bassy sound at the back of the room?

There might be some resonance things going on under there, but they aren't responsible at all for the bass at the rear of the room: that's just a natural consequence of the room boundaries, and how acoustics works. Bass always builds up at walls and in corners, since that is where all the room modes terminate. The only way to deal with that is to place deep treatment in those places.

I will measure the position out and then do what ever i need to, can you point me to a link that explains the required process for testing stuart?

When you download REW, also download the manual. It might even be included automatically in the more recent versions. That manual has a section on how to set up your system, and how to calibrate it to your sound card. But you also need to calibrate it to the real world, so you will need a hand-held sound level meter. You use that to measure the real level in the room, and then inform REW what that level is, so it has an accurate point of reference. I'm not sure if that is in the manual or not: if not, then let me know: I did write up a procedure for that a while back, so I can dig it out again and post it here for you.

- Stuart -

Hi stuart.

I am sorry i havent got back to this thread for a while, life sorta has a way of getting in the way and changing your path randomly!

However the room sounds good now, i made a changes and have now become more accustomed to the sound.
Over christmas i mastered an album for client in there and after cross checking on many other monitors and setups the room is good for what i need.

When i get some time i will share some pictures with you.

many thanks for all the help and advice from the members of this forum.

pk

Cool! I'm looking forward to seeing those pics!


- Stuart -