Bass trap help

[GIK Acoustics]

Light fluffy fiberglass insulation will be your best bet for traps 400mm thick. If you're in Canada or the US, Roxul Safe'n'Sound is also great for traps that are that thick.

Rigid fiberglass would not be the best bet for 400mm. I'm not sure of the gap idea you are talking about - are you talking about baffles being suspended inside the trap? Those will work well, but I'm not sure whether they would be more or less effective than a low flow resistivity material.

[Maschined]

Hi Alexander,

Thank you for the advice. I am in the uk and we are thinking of using knauf acoustic roll. http://www.knaufinsulation.co.uk/med...ustic-roll.pdf does it matter that this is glass and not rock?

The idea for the raised step comes from this post Forums - Can my floor be a bass trap? it's the 4th comment down.

As soon as we get this first round of DIY in place we'll actually be heading over to you guys for some final fine tuning and diffusors

[Maschined]

Does anyone have any ideas about the above? Sorry for the bump but we are hoping to start building the traps and floor tomorrow.

[Rondeath]

Alexander, little confusing
for broadband absorbers too thick(40cm), it is not wise to use rigid glass wool is used as an common absorber (like ~15or20cm)?

[AwwDeOhh]

Originally Posted by Rondeath

Alexander, little confusing
for broadband absorbers too thick(40cm), it is not wise to use rigid glass wool is used as an common absorber (like ~15or20cm)?

Generally speaking, thin traps (ie, thin is anything 4-6" thick or less) you want rigid.
If you want a deeper trap (and thus better bass absorption) use lighter weight insulation (ie, the pink fluffy stuff). look at some of the porous absorber calculators for a visual.

[Syncamorea]

Originally Posted by Maschined

We are also building a step up at the back of the room. This will be 100mm high and 2m x 3.5m floor surface. We will use plywood for the step and fill it with fibre glass. Again I would be grateful for any suggestions on the density. I read on the decware forum an idea of layering rigid sheets with bubble wrap to create alternating fibreglass/ air layers, does this sound like a good idea?

Will there be an opening into that 0.1 x 2 x 3.5m step volume? I don't see a large effect happening if it is sealed.

The fiberglass provides an air layer - that's why it insulates heat/cold and also why it absorbs sound. Rigid sheets are fairly expensive, so I'd use them in specifically targeted zones. Layering with bubble wrap may give some mid and high frequency reflection, depending on how close it is to the outer surface of the treatment.

[Rondeath]

Originally Posted by AwwDeOhh

Generally speaking, thin traps (ie, thin is anything 4-6" thick or less) you want rigid.
If you want a deeper trap (and thus better bass absorption) use lighter weight insulation (ie, the pink fluffy stuff). look at some of the porous absorber calculators for a visual.

thanks for d reply dude
about this fluflly stuff, it would be compressed?

im tryin to search this absorber calculators, but what is the use?
And this coefficient air flow resistivity, it needs to be analyzed to build traps?
Thanks

[AwwDeOhh]

Originally Posted by Rondeath

thanks for d reply dude
about this fluflly stuff, it would be compressed?

im tryin to search this absorber calculators, but what is the use?
And this coefficient air flow resistivity, it needs to be analyzed to build traps?
Thanks

It depends on how thick a trap you're making, but generally 'no' you don't compress it. Again, if you're making thinner traps, the rigid is the way to go. If you have a foot or more space, fluffy insulation (non compressed. actually you want to put supports every so often so the weight doesn't settle it over time) will work much much better for low end control.

As for the Excel based porous absorber calculator:
Porous Absorber Calculator V1.59 you need to know the Gas Flow Resistivity..
and generally this isn't easy to find data. Fortunately there's a thread here that has a lot of the info already:

Could someone help out interpreting material's gas flow properties

(note: the Rayls/m that the calculator uses, is equivalent to Pa s²/m². And with kPa s²/m² , the "K" stands for 1,000x). So basically just know that 12,000 rayls/m is the same as 12,000 Pa s²/m² is the same as 12 kPa s²/m².

Also of interest this post from Avare with useful links:
Sticky with links?


~Hope that helps!

[GIK Acoustics]

Originally Posted by Rondeath

And this coefficient air flow resistivity, it needs to be analyzed to build traps?

No, only for comparing theoretical absorption coefficients for different materials. The only way to actually see how they perform is to of course, test them! This is why we get all of our products tested at accredited laboratories, so we can be sure they perform well before we sell them.

[Rondeath]

AwwDeOhh, thanks so much for the reply and for the links. im very happy.
GIK(Which one? :D), thanks so much too.
Its good to understand the theory.
Thanks guys

[Maschined]

Thanks for all the replies so far. I have attached a layout of the studio we have and here are the suggested materials we will go for.

First Reflections (side & cloud) 100mm material with 75mm cavity - Knauf RS60 (I only have the data for 75mm thick)
Thickness 125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz NRC
75mm 0.55 1.1 1.2 1.15 1.15 1.05 1.15

Corner Traps and soffits along back wall/ ceiling intersect. 400mm x 400mm - Knauf Loft Roll 40, this is 12kg/m3 (Andre recommended this density in another post)

Back wall panels : 150mm thick with no cavity - Knauf RS128 (this is data for 50mm thick with 50mm air cavity)
Thickness 125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz NRC
50mm 0.65 0.8 0.85 0.95 0.95 1 0.89

The remaining side panels 100mm thick with 75mm cavity : Knauf RS100 (data for 50mm thick with 50mm air cavity)
Thickness 125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz NRC
50MM 0.65 0.95 0.8 0.9 0.95 1 0.9

It would be great to hear any opinions before we take the plunge and order this lot :-) I am wondering if we should use the RS100 for the back wall panels also. I read Glenn from GIK mention that their monster traps use 128kg/m3 at 150mm thick, hence the idea of the RS128 on the back wall.

Thanks for reading.