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Rockwool Density for bass traps vrs general absorption / General Advice

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Rockwool Density for bass traps vrs general absorption / General Advice

Postby Dodger » Wed Oct 14, 2020 8:08 am

Hello,

Im looking at finally doing some good level treatment in my room. but on a budget of course... so homemade :bouncy:

Ive attached a super rough idea of what I would like todo.

I plan to build traps to this specification https://www.coreybautistaaudio.com/diy- ... anel-guide So each panel will be 6inchs thick with 100mm rockwool inside giving a small air gap behind. which i believe is a good think ? 4 x general absorbers with 1.2m x 0.4m rockwool slabs in and 8 bass traps of the same dimensions but stacked on top of each other to go floor to ceiling.

This is my room layout https://drive.google.com/file/d/1pjIPHB ... sp=sharing
and where i plan to put my treatment

And this is my current sonar works setting with no treatment. I plan to keep using sonar works but it will work better in a treated room and have todo less processing itself as you can see most of issues are in the low end. But i also know without a waterfall plot this is only half the story unfortunately I don't have a measurement microphone at the moment. If anyone really wants more info I could do one with RoomEQ and a 414 https://drive.google.com/file/d/1LKZhhA ... sp=sharing

Ive been looking at this https://www.wickes.co.uk/Rockwool-Sound ... m/p/148842 Get 12 todo 8 bass traps and 4 general panels

I cant find the density for the above? I've read that 65kgm^3 (Or RW3) is best for general absorption but 100kgm^3 (RW5) is better for bass traps but might reflect higher frequencies? or will what i have found above be ok? the advantage of above is that its a good chunk cheaper than anything else i have found...

Also I couldn't make my mind up on what todo about first reflection points. with the window being completely down 1 side thought it best to leave both un-treated that way it should be more even with stereo image?

Generally just trying to check quickly my overall plan and get advice on which Rockwool to buy.

Also any recommendations on fabric to cover them and where to buy in the uk?

Thanks!!

Jack
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Luke W » Wed Oct 14, 2020 8:34 am

I'd avoid the stuff from Wickes that you've linked to, if I remember correctly the density is a fair bit lower than RW3. As for deciding between RW3 and RW5, it's well worth a read though the posts by Studio Support Gnome in this thread:

https://www.soundonsound.com/forum/viewtopic.php?f=24&t=67971#p624571

With regards to the window issue, if it were me I think I'd make a freestanding panel along that side so that both first reflection points will be treated. It's not just a case of the sides being untreated, they're also different materials/constuction entirely, so your image is likely to be a bit wild anyway :thumbup:

It's also worth a mention that it doesn't have to be a Rockwool branded product, just a mineral wool of the appropriate density. In some places it may be easier to get hold of alternatives from companies like Knauf, for example.

I'm sure more knowledgeable people will be along with some more detailed answers, but hope that helps a little.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby blinddrew » Wed Oct 14, 2020 10:39 am

I'm definitely not more knowledgable than Luke but I agree with what he says. :)
Treating the side walls is going to be key I think so I'm going to ask if it's possible to rotate the desk so that you're looking out of the window?

For rockwool I ended up going to Jewson, they needed to order the right density in but it was painless and well priced.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Watchmaker » Wed Oct 14, 2020 12:07 pm

This link will give you material comparisons. It's a US company but you can easily find UK equivalents.

https://www.atsacoustics.com/cat--Fiberglass-and-Mineral-Wool-Batts-and-Boards--106.html

Owens Corning has a .pdf called the "Noise Control design guide" which, due to idiotic programming by every developer in the world, I can't actually link to without invoking Google advertising (all hail our new insect overlords!) but if you google it, you can enjoy your own experience. It is well worth a read.

I have recently used both 2" 703 and 3 1/2" Rockwool "Safe and Sound" for panels using essentially the same method as you're planning. The rockwool appears to have better low frequency absorption. Both are effective, easy to use and work well. The rockwool is a bit floppier and is ~16" wide whereas the 703 is not floppy and 24" wide. I had to add a brace inside each panel with rockwool to manage excess floppiness but no biggie.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Matt Houghton » Wed Oct 14, 2020 12:16 pm

Studio Support Gnome will, I'm sure be along to correct me on this, but, as a quick summary...

RW3 is best for panels.

RWA45 will do as good a job, but it's a bit floppy, meaning it needs a lot more support from the frame, which probably means more expense on the frames. OTOH, depending where you live, it's easier to get hold of in smaller quantities than RW3, which generally comes as pallets/half pallets from builders' merchants.

RW5 is stiffer still, but IIRC it's a little less effective as an absorber (to do with the gas flow resistivity, not the density). That said, I recently used some RW5 panels I had left over from another project for my ceiling cloud, where the stiffness helped and it's working well.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby James Perrett » Wed Oct 14, 2020 1:25 pm

The last time I had to buy Rockwool I found that Studiospares were best for small quantities. All the builders merchants had to order it and it could take a few weeks for it to be delivered.

Cara fabric is popular for covering bass traps. It is easy to use and has the right acoustic properties. However, the price has increased a bit recently. I usually buy from soundproofingexpert (aka Making Waves) on Ebay.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Sam Spoons » Wed Oct 14, 2020 2:15 pm

I built mine in 50mm RW3 which was a bit hard to source but no problem with the small quantity (5 or 6 packs IIRC). Cara is well worth the cost, easy to work with and get a pro finish without prior experience.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Hugh Robjohns » Wed Oct 14, 2020 3:51 pm

I used the Camira Lucia fabric on my bass traps and broadband panels, rather than Camira Cara. The weave on Cara is quite coarse whereas Lucia is much finer. Both are easy to use, but I preferred the look of Lucia given that the panels are inherently all quite close to the my listening position. The colour swatches are slightly different between the two ranges, too.
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Re: Rockwool Density + Thickness ? for bass traps vrs general absorption / General Advice

Postby Dodger » Thu Oct 15, 2020 6:47 am

Luke W wrote:I'd avoid the stuff from Wickes that you've linked to, if I remember correctly the density is a fair bit lower than RW3. As for deciding between RW3 and RW5, it's well worth a read though the posts by Studio Support Gnome in this thread:

Noted

https://www.ikoustic.co.uk/products/wal ... XMQAvD_BwE Thinking this then? Anyone know of a somewhere to get 400mm width? 600mm will tall take abit too much space out of my room Ill cut down and use the off cuts for other panels if not.

Luke W wrote:it's well worth a read though the posts by Studio Support Gnome in this thread:

https://www.soundonsound.com/forum/viewtopic.php?f=24&t=67971#p624571

Thanks I had read that previously to posting was just want to clarify as that post contained a lot of words I didn't really get :headbang:

Luke W wrote:With regards to the window issue, if it were me I think I'd make a freestanding panel along that side so that both first reflection points will be treated. It's not just a case of the sides being untreated, they're also different materials/constuction entirely, so your image is likely to be a bit wild anyway :thumbup:


Ok ill try and think something up. Plan to do it in 3 stages anyway bass first then front and back then ill look at the sides. Its a rented house so my aim is to have everything freestanding if possible.

Sam Spoons wrote:I built mine in 50mm RW3 which was a bit hard to source but no problem with the small quantity (5 or 6 packs IIRC). Cara is well worth the cost, easy to work with and get a pro finish without prior experience.

How does 50mm vrs 100mm stack up? for both absorbers and bass traps?

Hugh Robjohns wrote:I used the Camira Lucia fabric on my bass traps and broadband panels, rather than Camira Cara. The weave on Cara is quite coarse whereas Lucia is much finer. Both are easy to use, but I preferred the look of Lucia given that the panels are inherently all quite close to the my listening position. The colour swatches are slightly different between the two ranges, too.

That looks nice but oooft bit expensive :crazy: Ill shop around any see any slightly cheaper recommendations?

Also looking at what to wrap them in (as most guides seem to recommend wrapping the rockwool in something so your not breathing it in.) I was thinking just some cling film ? As it will be pretty much transparent ?

Thanks again!!
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Sam Spoons » Thu Oct 15, 2020 12:00 pm

The RW works as an absorbent by allowing air to move into the matrix of the panel and dissipating the energy of the sound waves as heat, wrapping the RW in clingfilm will prevent air movement into the material and significantly reduce it's efficiency as an absorber. Definitely a bad idea. If you must do something a coat of diluted PVA painted on will secure any loose fibres without totally preventing air movement through the surface. But the fabric covering is sufficient to prevent loose fibres escaping.

50mm spaced 50mm off the surface is likely to be a little less effective than 100mm flush but not anywhere near 50% as the energy near the wall is zero.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Hugh Robjohns » Thu Oct 15, 2020 1:48 pm

Sam Spoons wrote:... wrapping the RW in clingfilm will prevent air movement into the material and significantly reduce it's efficiency as an absorber. Definitely a bad idea.

That does sound logical... but actually, testing suggests it's not the case.

Provided the clingfilm is not under great tension it would be free to move slightly under the influence of sound waves and thus set up sympathetic air movements within and through the rockwool. In effect, the clingfilm would act as a damped membrane and would still absorb energy from impacting sound waves.

Whether a clingfilm-wrapped arrangement it would be as efficient as material-wrapped rockwool I can't say... but it would provide peace of mind for anyone with significant concerns about potential health risks associated with rockwool.

If you must do something a coat of diluted PVA painted on will secure any loose fibres without totally preventing air movement through the surface. But the fabric covering is sufficient to prevent loose fibres escaping.

This is my feeling too...
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Dodger » Sun Oct 18, 2020 6:26 pm

Thanks again for all your help so far!

Started building the frames today. I'll post pictures and updated Sonarworks results for anyone interested! Might even try a REW before and after if anyone is interested.

Still just stressing (probably slightly over thinking and freaking out) about fabrics... Really dont think i cant really stretch to the Cara fabric if i can find a decent alternative. Been looking at either these after spending too long this afternoon googling..??

https://www.diy.com/departments/verve-w ... 814_BQ.prd

https://www.ikea.com/gb/en/p/ditte-fabr ... -33080380/

Also had a quick look into muslin options but that all looked quite thick?

Anyone fancy giving me there two cents?

Wont bother with any plastic wrapping as that seems not to be needed.

Thanks again for all your help!
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby blinddrew » Sun Oct 18, 2020 6:44 pm

The verve stuff is what i used for the backs of mine. It's actually very easy to work with and if you do balls it up it hasn't cost you much.

It's also good at stopping weeds. ;)
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby DanDan » Sun Oct 18, 2020 7:29 pm

I have tested one and two layers of Clingfilm and found no detectable reflection up to 20KHz. Many people have added thicker plastic, card, or even hardboard to LF traps. It seems to increase LF absorption while of course reflecting back some HF life into the room.
Whatever I might do personally, I would have concerns about recommending plastic film in rooms filled with electronic equipment. I have also read that the often recommended weed control fabric ignites vigorously. I reckon that overhead traps could do with a fibre containment layer. Polyester batting is readily available and very cheap. Same material as in Quilts and Mattress Protectors. It is acoustically perfect and intrinsically fire retardant. Under fabric it can soften edges and wrinkles too.
For LF traps Bedsheets are fine. I would only fuss about fabric in the cloud or side reflection absorbers. For a little extra, angling them is no harm at all.
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Re: Rockwool Density for bass traps vrs general absorption / General Advice

Postby Sam Spoons » Sun Oct 18, 2020 10:02 pm

While Cara is easy to work with and get a professional looking result, if cosmetics are less of a concern panels covered with dust sheets, weed control or other similar fabric will be just as effective.
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