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Help chosing the right density insulation

Postby Helmutcrab » Fri Sep 07, 2012 4:52 pm

Hi,

Im currently using knauf ecowool universal rock mineral wool slabs (60kg/m3) to make 1200 x 600mm 4" and 6" broadband panels.

Could anyone please tell me if its worth using 100kg/m3 (rs100) for these 4" and 6" broadband panels instead of the 60kg/m3 with regards to the low end ?
The data from the old rocksilk product suggested to me (rightly or wrongly) that at 50mm thickness atleast, 100kg/m3 was better (0.65) than the rs45 and rs60 (both 0.45) when it had a cavity behind at 125hz, but worse at 75mm with a solid backing (0.44 verses 0.5 and 0.55), but there is insufficient data on this for the new product.

Many thanks,

Peter
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Re: Help chosing the right density insulation

Postby thefruitfarmer » Fri Sep 07, 2012 11:19 pm

Helmutcrab wrote:Hi,

Could anyone please tell me if its worth using 100kg/m3 (rs100) for these 4" and 6" broadband panels instead of the 60kg/m3 with regards to the low end ?


Most people use RW3 @ 60kg/m3....

You can use the denser Rockwool, I used RW5 @ 120kg/m3 IIRC...

The denser Rockwool will absorb more bass but it reaches a point where it starts to reflect the higher frequencies, then you may have to put foam on the front of your trap to compensate..

The sweet spot is at 60kg/m3...

I have a room with some RW3 panels and some RW5 panels....

The RW5's do seem to absorb slightly more bass and any relections were dealt with quite easily. They are heavy though and best fitted on the floor corners with the RW3 on the ceiling corners.

It depends how big your room is, if it is a small room then I would use more RW5.
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Sat Sep 08, 2012 6:23 am

thefruitfarmer wrote:
The sweet spot is at 60kg/m3...


Not necessarily true. Density actually has not much to do with it - the important variable in absorbers is the material's gas flow resistance (which can be a hard figure to obtain). And even then, there isn't a 'perfect' GFR per se, it depends on depth. At 2", really dense material with a high gas flow resistance works well. However, at 24" thick, really light, porous material works better. You can check out this calculator and play with resistance values and depths to determine the best for your absorbers: http://www.stanleyhallstudios.co.uk/pacalc/
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Re: Help chosing the right density insulation

Postby thefruitfarmer » Sat Sep 08, 2012 7:54 am

GIK Acoustics wrote:
thefruitfarmer wrote:
The sweet spot is at 60kg/m3...

Not necessarily true.


But if this guy builds some traps out teh 60kg/m3 Rockwool he will get something functional...

Without going in to the science of it most people use the RW3 to make a 100mm thick trap out of one of the slabs...

I reckon this guy just needs to know what material will work and then just to build a few traps to hear the difference, rather than be baffled with the science.
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Sat Sep 08, 2012 8:50 am

thefruitfarmer wrote:But if this guy builds some traps out teh 60kg/m3 Rockwool he will get something functional...

Agree'd!
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Re: Help chosing the right density insulation

Postby Helmutcrab » Sat Sep 08, 2012 5:26 pm

Thefruitfarmer,

Cheers for your experiences , they are very helpful to me. Ive heard it said before around here that 100kg/m3 does have worse performance in upper frequencies, so i will bear that in mind thanks.

Hi Alexander,

As you say GFR is hard to find, and whilst knauf provided some absorb. coefficient figures for this relatively new ecose product i was unable to get any meaningful figures to make an informed decision ie no figures for 100mm and no 50mm with cavity figures. It is a small room i have with some serious bass issues so bass performance is paramount from the panels i am making.

Could you please tell me if its worth using 4" panels of 100kg/m3 over the 60 please ?. That would be really helpful to me.

Also, do you find the 100kg/m3 knauf ecowool does actually have worse absorption above 4K over the 60kg ?

Many thanks,

Peter
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Tue Sep 11, 2012 3:58 am

Helmutcrab wrote:
Hi Alexander,

As you say GFR is hard to find, and whilst knauf provided some absorb. coefficient figures for this relatively new ecose product i was unable to get any meaningful figures to make an informed decision ie no figures for 100mm and no 50mm with cavity figures. It is a small room i have with some serious bass issues so bass performance is paramount from the panels i am making.

Could you please tell me if its worth using 4" panels of 100kg/m3 over the 60 please ?. That would be really helpful to me.

Also, do you find the 100kg/m3 knauf ecowool does actually have worse absorption above 4K over the 60kg ?

Many thanks,

Peter


Hi Peter,

At 4" the difference should be minimal. I would advise 100kg/m3 for 50mm thick panels, 60kg/m3 for 100mm-150mm thick panels, and lighter for larger than 6". If bass is a serious issue, I would advise making them thicker than 100mm. 100mm is considered the 'minimum' for some bass absorption. Straddled corners will work great, and an air gap for panels hung on the wall will help as well.

Good luck!
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Re: Help chosing the right density insulation

Postby Helmutcrab » Tue Sep 11, 2012 10:48 am

Alexander,

You are a star !!!

Thank you very much for your help with this - it means alot to me as its so difficult gaining knowledge on a specific product without tests.

Im making 23 panels - 6" across corners and 4" to 6" elsewhere - all these will have a gap of atleast 4" behind them and the rear of all panels will have a 70gsm kraft paper attached to the rock wool via pva solution spray.

By the way, your products are very reasonably priced in uk and if i had the money i wouldnt hesitate to fill my room with them, and helping out the small fry like me speaks volumes as to the type of company you are.

All the best,

right, back to my d.i.y grind :headbang:
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Re: Help chosing the right density insulation

Postby SafeandSound Mastering » Tue Sep 11, 2012 5:21 pm

I used RW3 for all panels and bass traps in my studio and am very pleased with the results. Easy to work with and good performance when used in bulk for broadband bass traps,

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Re: Help chosing the right density insulation

Postby Helmutcrab » Tue Sep 11, 2012 6:29 pm

Thanks very much for that. Its good to know SafeandSound ,as thats what im planning on using too.

Cheers

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Re: Help chosing the right density insulation

Postby Mixedup » Tue Sep 11, 2012 8:37 pm

I've used 100mm 100kg/m3 RockSilk panels. Those at mirror points have Auralex foam in front for extra control of the HF. And then cotton fabric in front of that, because foam is ugly!

Doing a grand job.
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Wed Sep 12, 2012 6:21 am

Helmutcrab wrote:Alexander,

You are a star !!!

Thank you very much for your help with this - it means alot to me as its so difficult gaining knowledge on a specific product without tests.

Im making 23 panels - 6" across corners and 4" to 6" elsewhere - all these will have a gap of atleast 4" behind them and the rear of all panels will have a 70gsm kraft paper attached to the rock wool via pva solution spray.

By the way, your products are very reasonably priced in uk and if i had the money i wouldnt hesitate to fill my room with them, and helping out the small fry like me speaks volumes as to the type of company you are.

All the best,

right, back to my d.i.y grind :headbang:


Peter,

Thanks for your kind words. We try to help out as much as possible, even for those DIYers. 23 panels is quite the quantity! How large is the room? If you're under 70m^3 or so you may want a few less panels at a larger thickness (like keeping most of them 6"). But if it is a large room, you will be doing it some justice for sure. Will we get to see some pictures of them completed?

Good luck!
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Re: Help chosing the right density insulation

Postby Helmutcrab » Wed Sep 12, 2012 8:41 am

Cheers Mixed up - i may end up having to do the same for my side RFZ panels as there is so little room there i will undoubtedly whack myself into the panels when im routing cables.

Hi Alexander and thanks again for helping,

My room has sloping ceilings and is L shaped but i think its roughly only about 38.3 m3 (it is small). After your advice yesterday i measured to see how many panels i can make 6". I think its about 12-13 (including corner panels).

The reason for so many panels is that it is an odd shaped single recording (acoustic drums, guitars, vocals etc) and mixing room and i want to use artificial reverb for ambience so will be trying to get as much of it as a RFZ as possible. (the estimate includes 4 panels as ceiling clouds).
The plan is (with the kraft paper) that if i cant take how dead it is when mixing i will atleast have the option of turning some of the panels around to get some reflections. Plus, it may help alittle with the low end as they are spaced off the wall (even when paper is facing the wall).

Here is a plan of my room by the way, from another recent post here. (please ignore the proposed mixing position and movable trap)

Image

I will get a photo up of the first trap once it is finished and then the room once it is done - this may take some time !!..........

Thanks again,

Peter
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Thu Sep 13, 2012 7:36 am

Helmutcrab wrote:
The reason for so many panels is that it is an odd shaped single recording (acoustic drums, guitars, vocals etc) and mixing room and i want to use artificial reverb for ambience so will be trying to get as much of it as a RFZ as possible. (the estimate includes 4 panels as ceiling clouds).
The plan is (with the kraft paper) that if i cant take how dead it is when mixing i will atleast have the option of turning some of the panels around to get some reflections. Plus, it may help alittle with the low end as they are spaced off the wall (even when paper is facing the wall).

Hi Peter,

I see your predicament now. And with recording and mixing, I understand the want and need for many acoustic panels. I like your idea about the kraft paper and being able to turn the panels around when need be. This would be really useful when recording too...you could turn some panels around when you want a more "live" sound, or turn the absorptive side towards the microphone for when you want intimate mic'ing (like fingerpicked guitar or something of the sort).

As far as your RFZ goes, I wouldn't suggest turning any of the panels with the kraft facing the inside of the room. For panels behind you and the like, it should be fine. But the RFZ should be that - no reflections in that area. So long as you don't over absorb high frequencies elsewhere in the room, you will be fine.
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Re: Help chosing the right density insulation

Postby Helmutcrab » Thu Sep 13, 2012 8:18 am

Hi Alexander,

Many thanks for taking the time to look that over.
Thats a good point about not over absorbing the highs. I think it will involve turning rear wall panels around sometimes between recording and mixing.

Cheers,

Peter
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Fri Sep 14, 2012 7:14 am

Peter,

Not a problem! Good luck with your room - we always hear that acoustics have been the best investments made in studios. Hopefully your experience will be the same and you can achieve some great results in your room. Keep us updated on how it works out! :D
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Re: Help chosing the right density insulation

Postby Helmutcrab » Mon Sep 17, 2012 5:28 pm

Hi Alexander,

I have one last question if you dont mind.

As you know, im using pva/water solution spray to adhere the kraft paper to the back of my panels, but I was also thinking of spraying the rest of the rock mineral wool slabs all over (including the front of them) with a 1:10 pva/water solution ( and a drop of washing up liquid) to prevent some of the outer fibres from shedding or turning into dust over time. I'd like these traps to last me a good while and will need to move them around.

Ive read some people around here do it for bass traps, but do you happen to know if doing this on broadband absorbers will adversely affect the performance of them across the frequency spectrum ?. Im thinking it might do as its effectively sealing the traps and making them non porous ?

Thanks very much,

Peter
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Re: Help chosing the right density insulation

Postby GIK Acoustics » Tue Sep 18, 2012 6:41 am

Helmutcrab wrote:Hi Alexander,

I have one last question if you dont mind.

As you know, im using pva/water solution spray to adhere the kraft paper to the back of my panels, but I was also thinking of spraying the rest of the rock mineral wool slabs all over (including the front of them) with a 1:10 pva/water solution ( and a drop of washing up liquid) to prevent some of the outer fibres from shedding or turning into dust over time. I'd like these traps to last me a good while and will need to move them around.

Ive read some people around here do it for bass traps, but do you happen to know if doing this on broadband absorbers will adversely affect the performance of them across the frequency spectrum ?. Im thinking it might do as its effectively sealing the traps and making them non porous ?

Thanks very much,

Peter

Hey Peter,

Not too sure honestly. It would be hard to test every type of bonding/spray glue etc type agents on the panels to know, and I would expect it to act differently for different type of materials (like fiberglass vs. mineral wool, light vs. rigid boards, etc) so it would be hard to give any word as fact on this. I would assume such a light layer wouldn't affect performance much, but that is only an assumption. I have seen tests that show a light layer of plastic 6 mils (mils, not millimeter) thick did not affect performance much at all until over 10kHz. However, my advice would be to stick with what is proven to work, and that is open and porous. If you are concerned about it, as I understand, just use a bit tighter weave of fabric for the traps. Speaking of fabric...what type of fabric do you plan on using for these?
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Re: Help choosing the right density insulation

Postby Helmutcrab » Tue Sep 18, 2012 10:05 am

Thanks very much for spending the time to answer that Alexander - it is much appreciated.

I was going to use a more open weave non dyed Hessian/burlap than Jute (or other tighter weave) just because these tighter weave fabrics seem to be expensive over here, especially for 30m worth. I might use a thin (2-4 oz) layer of polyester wadding under the hessian to collect any dust. That might be my best option, because like you say, if its not been tested , we cant know for sure and it would be a bit heartbreaking to make them all only to find they didnt work too well ! (thats interesting about the very thin plastic though).

Much obliged

Peter
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Re: Help choosing the right density insulation

Postby James Perrett » Tue Sep 18, 2012 2:17 pm

Look for Cara fabric from Making Waves on Ebay - much cheaper than any other source and it comes direct from Interface Fabrics next day. I've used this directly over mineral wool in two studios and there have been no issues with fibres.

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