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Super Soffit.. 50 hz ?
Old 14th February 2017
  #1
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Super Soffit.. 50 hz ?

Hello everyone,

First of all let me thank all of you for your contribution to this website and this forum, I have learned a lot of miscellaneous information about acoustics thanks to this community.

I am currently in the process of treating a pretty small room, & after analyzing everyone's different bass trap designs I concluded that GIK's Soffit trap had amazing results in the 50hz range. Knowing that low frequencies are the biggest problem and being someone who has devoted their entire life to the low end of the frequency spectrum I want the best possible low end response time that I can get. From my research I have concluded such:

Denser materials (6 PCF) typically perform much better below 100hz than other acoustic insulation like typical 3 PCF material,

So let's say I theoretically took Knauf Earthwool Insulation (6 PCF 24"x48"x2")
cut each piece in half, and stacked them floor to ceiling, and built a frame around it (with a possible built in limp mass membrane).. Would I efficiently absorb waves below 100hz?

I want to design my room to absorb as much bass as humanly possible, add monster traps to all the early reflection points, and build a massive amount of diffusors for the rest of the room.

Do any of the veterans on this page have any suggestions for me? Should I consider adding some sort of limp mass membrane to maximize my super soffit design?

I attached a janky portrayal of how I want to build the corner traps
Attached Thumbnails
Super Soffit.. 50 hz ?-14870269405297.png  
Old 14th February 2017
  #2
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DanDan's Avatar
Cornered

A simple fibre trap in a corner will work well. I have 32" wide StudioTips SuperChunks here. They have decent effect even down at 35Hz.
As the size gets bigger it is better, very luckily for the wallet, to use low density low Gas Flow Resistivity fibre. My SSC's are 3pcf.
Up to about 4 inches of depth most of us seem to go for 6pcf, 100KG. But above that size I would definitely start reducing density.
DD
Old 14th February 2017
  #3
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Quote:
Originally Posted by DanDan View Post
A simple fibre trap in a corner will work well. I have 32" wide StudioTips SuperChunks here. They have decent effect even down at 35Hz.
As the size gets bigger it is better, very luckily for the wallet, to use low density low Gas Flow Resistivity fibre. My SSC's are 3pcf.
Up to about 4 inches of depth most of us seem to go for 6pcf, 100KG. But above that size I would definitely start reducing density.
DD
Thank you for your input my friend! Fortunately I make music for a living, and have been saving up money! I have been purchasing Knauf 6 PCF earthwool board by the pallets directly from the distributor so I'm getting high quality material for a really good price, so I'm willing to sacrifice money for absolute performance in this case.
Old 14th February 2017
  #4
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DanDan's Avatar
Dense

Unfortunately dense material doesn't work well at greater depths.
Best bang per buck here would be to make 6inch deep corner straddling traps. Floor to Ceiling. All four vertical corners and continue to ceiling corners if you have the fibre. Surface area is similarly important to depth. The cloud is vital as are side reflection killing panels.
Lots of simple panel traps work well. Here's a clever design from a client of mine. https://www.gearslutz.com/board/bass...trap-ever.html
DD
Old 14th February 2017
  #5
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It was from my understanding that denser materials work better for lower frequencies, and that " the more bass traps the better. "

I plan on adding 4-6 inch thick panels on my early reflection points, above me, and then filling every single corner with the Soffit style trap.

Are you saying what I'm doing will not work?
Old 14th February 2017
  #6
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DanDan's Avatar
No

Quote:
It was from my understanding that denser materials work better for lower frequencies
A common misunderstanding. They do when the depth is small, e.g. up to say 100mm. But above that lighter materials perform better. This is not an actual threshold, it is a sliding scale thing.
Try some predictions for yourself.
Multi-layer Absorber Calculator
https://www.gearslutz.com/board/stud...y-numbers.html
More importantly NASA and others have shown this to be true in large scale tests.
This is a great boon. Large traps built using dense material would be very expensive and would not work well.
DD
Old 14th February 2017
  #7
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So DanDan do you believe that products like GIK's Soffit Bass trap were made using much less dense material? I would like to do the square design for corners, should I stick with 16 inch by 16 inch? & Should I use 3 PCF or 1.6 PCF?

Would 24x24 be more effective than 16x16?

Thank you for your feedback
Old 14th February 2017
  #8
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DanDan's Avatar
Predictions

You are welcome Mikey. Using those two links you can predict and chose the optimum size etc.
DD
Old 14th February 2017
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Excuse my ignorance but I have no idea how to operate this calculator, :(
Old 14th February 2017
  #10
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Upon further research I have concluded that either 3 PCF or 1.6 PCF in the corners will work best.

My simple question is which one will work better?
Old 14th February 2017
  #11
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Quote:
Originally Posted by DanDan View Post
Thanks for providing those links and posting on a few other threads about this subject. I have 4" AFB and am trying to determine if I should use square/rectangles soffit style, vs 4-8" thick panels straddling the corners with another 4" behind that with air gaps. The calculator should help, assuming I can find the specs for the 4" AFB. Andre posted specs for 3" elsewhere.

"I received a reply from Roxul re: GFR for their materials. The only material that they had data for was AFB. AFB is 2.8 pcf and has airflow resistivity at 3" of 16,600 mks rayls/m and for 1.5" 15,000 mks rayls/m."
Old 14th February 2017
  #12
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Upon further math & consideration, I'm beginning to believe the Soffit Trap was designed with 3 PCF material. Please correct me if I am wrong
Old 14th February 2017
  #13
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DanDan's Avatar
Guesses

That's a fair guess, but do try running those numbers in the calculator some more. A straddling panel will address some modes at 45 degrees, and has a varied airgap behind it. A square or rectangular soffit sees the sound differently. Then there is the damped membrane effect of a straddling panel.
In short the straddler is great value for money but for a 4" peaks at about 70-80Hz. A large SSC or even better a square deep Soffit Trap reaches down lower.
For a 2 foot wide/deep Soffit I would have no qualms about using fibre less dense than 3pcf.
https://www.gearslutz.com/board/stud...q-4-avare.html
DD
Old 15th February 2017
  #14
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Thank you DanDan! I have approximately 48 pieces of 2"x24"x48" 3PCF mineral wool, and approximately 36 pieces of 2"x24"x48" 6PCF mineral wool,

I think I'm going to build all my soffit corners ( 24"x24" for 4 main corners and 16"x16" for the other 8 corners) with 3 PCF material,
and use my 6PCF material to build my 4" early reflection traps & clouds.

Is there a point in covering the square shaped traps with a limp mass membrane? Or will these traps work without a membrane?

My understanding is that a membrane prevents the upper frequencies from being absorbed going more room for the bass to become " trapped. "

Does kraft paper work as a membrane? Or must I use something like MLV (Sheetblok ect.)
Is there a general guideline to this or should I just avoid this concept altogether being as nooby as I am.
Old 15th February 2017
  #15
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adrumdrum's Avatar
 

Treating a room is not just adding a bunch wool in the room.
Here's how to treat a room:
https://www.gearslutz.com/board/10434774-post13.html
https://www.gearslutz.com/board/10536953-post22.html
I also recomend to fill the larger airgaps behind the "panel shell". Very low density wool.

If you know that 50hz is a very large problem in the room it is possible to include membrane traps behind the panels, but these need to be placed exactly where the problem is wherte it is air preassure resonance at that freq.
minimum area of membrane traps is usally recomended to be around 0,6x2 meters.

I get the feeling that you are quite serious about treating your room and then I recommend to not just guess about what the treatment will do.
Old 15th February 2017
  #16
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Thread Starter
All due respect adrumdrum I am not just adding mineral wool everywhere. I've specified that I'm treating early reflection points and adding a cloud above my mix position.. On top of that I want to add as many bass traps as possible. The rest of the room will be treated with 2D QRD diffusors. My understanding is that membranes are limiters added to bass traps to help them absorb more low frequencies.. you sound like you're talking about a tuned membrane which I want absolutely nothing to do with. This post is mainly me trying to reverse engineer the concept behind GIKs signature little soffit trap
Old 15th February 2017
  #17
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Guessing

We have tests showing great performance from what looks like 705 or 703, formed into large 32"wide StudioTips SuperChunks. I see useful absorption at 35Hz from my version, 48KG Isover fibre.
It should be noted though, that these address the room at 45 degrees, and the maximum amount of trap is IN the corner. Maximum depth is about 17inches which occurs at only one peak, all the rest being shallower.

The GIK SoffiTraps test results look good. One might suspect what type of fibre is used, perhaps based on their DIY offerings. Or one could ask.

Adding HF blocking to the exposed surface of any traps will reflect some HF. To be honest though I wouldn't expect to actually hear a difference unless there was a substantial area of such. Kraft Paper or think card should be fine, as are Laths. For some reason, confirmed recently by a clients observation, plastic can be a bit harsh or pingy.

Mike, you have a treatment plan, the usual suspects, which pretty much always work, although diffusion...? Have you tested the room? There are other basics we might have started with. Dimensions, what materials the boundaries are made of, is this a CR or a LR or both?

DD
Old 15th February 2017
  #18
Gear Head
 

DD, or anyone that understands the calculator DD provided a link to, when the linked calculator is set to an angle of incidence, say 45, is this calculating the volume of a super chunk if only 1 layer is used?

Example, if I'm seeking to calculate for a super chunk that is 24" x 24" x 33.9" (610mm x 610mm x 861.06mm), I would input 17" (431.8mm) into the calculator for thickness with the flow resistivity for the given material, set the angle of incidence to 45 and compute. Is that correct?
Old 15th February 2017
  #19
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"Angle of incidence" means the angle of the sound wave that's going in the trap. 45 degrees travels for longer time inside the trap than zero degrees (90 degrees from the wall), so it will be absorbed for a longer time like in a thicker trap.
It's always "flat on the wall" traps sumulated in the calculator.
Old 15th February 2017
  #20
Gear Head
 

Thank you, adrumdrum.
Old 15th February 2017
  #21
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Thread Starter
Quote:
Originally Posted by DanDan View Post
Mike, you have a treatment plan, the usual suspects, which pretty much always work, although diffusion...? Have you tested the room? There are other basics we might have started with. Dimensions, what materials the boundaries are made of, is this a CR or a LR or both?

DD
Dan based off of your advice and upon further research I believe I will be building 24x24x34" super chunks out of OC-703 equivalent.. Mainly because I'm sort of overwhelmed with all the data I'm learning and I know that super chunks work and I know that I can easily make them....

That being said.. Glenn.. Or anyone from GIK, can you guys just sell me the blueprints for a Soffit Trap? Sell me advice on how to build my own? I don't want to sell them I just want to build a bunch of them for all the other corners other than the 4 main corners..

I'm assuming you guys are just using 1.6 PCF ecose board, cut the boards into thirds ( 16" ) And stack 8 pieces into a 16" by 16" by 24" cube and stack them in the simplest possible wood frame you can build?

Seriously tho guys I will pay for this info $$

Granted I can just buy one of your traps & rip it apart to reverse engineer it but I'd rather respect your art and pay for the blueprint..

Best regards, Mikey

(Please don't threaten to sue me)
Old 15th February 2017
  #22
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You will get better prformace with 2" or 4" 703 as front layer and soft pink wool behind.(Edit: or something similar from other brand than OC)

For back wall corners squer traps is good, But for the front of the room I would recommend to build the traps 30 degrees covering the outer 1/3 of front wall. It will work better with the speakers. See the attached drawing:
Attached Thumbnails
Super Soffit.. 50 hz ?-30-traps.jpg  
Old 15th February 2017
  #23
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DanDan's Avatar
Personal

Quote:
Dan based off of your advice and upon further research I believe I will be building 24x24x34" super chunks out of OC-703 equivalent.. Mainly because I'm sort of overwhelmed with all the data I'm learning and I know that super chunks work and I know that I can easily make them....
These are my goto recommendation. But, inspired by Glenn's SoffiTrap and test data, I have moved on to the bigger square or rectangular designs. Or indeed full wall trapping as you will see in Boggy's work. (Typically 60cm deep and using what looks like the lightest Knauf Ecose batts) You could ask him.
Note adrumdrum's suggestion. I prefer the freedom to have the speaker touch the Front Wall. But note if one takes his idea a bit further you will eventually end up a full wall trap with a speaker sunk into it.
More, including area, is better, when it comes to LF, and the shape doesn't matter much. Even simple attic rolls left in their wrapping, stacked up in corners, work well.


DD
Old 16th February 2017
  #24
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So I'm confused at this point because you keep switching between recommending the super chunk and the soffitrap.. I think I'm just going to go with the original 2x2 foot soffit floor to ceiling idea and try to find the least dense product ( probably knauf ecose earthwool 1.6 PCF because this is the most affordable material I can source )

Thank you for all your expert advise my friends. This calculator is making more sense as I begin to play with it
Old 16th February 2017
  #25
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DanDan's Avatar
Confusion

I understand. To be honest I am probably a bit confused between the two almost identical threads going on at the moment.
I have had good success with the bigger 32 inch wide SSC's using Isover High Performance Duct Cladding. So I confidently recommend that. Note this is a high absorption product and Fibreglass often does better than Rock.
I have also had good success using Knauf Ecose but I cannot exactly recall the density or exact product that the client ended up with. I am fairly sure it was Knauf Ecose Earthwool, 32KG, i.e. 2pcf. I will try to contact them to clarify that for you.
The Calculators are great, but the above examples actually happened. I tend to favour the real evidence, even though it is not comparative.

DD
Old 17th February 2017
  #26
Gear Head
 

Pardon my ignorance and lack of ability to find a definitive answer on Google, but is the basic construction of a soffit trap made up of four sides of an absorptive material and a hollow center? Or does the core of it need to be comprised of the absorptive material as well? Most photos I have found are just showing stacked up squares of an absorptive material. thanks.

Last edited by keysandguitars; 17th February 2017 at 04:59 AM.. Reason: Typos
Old 17th February 2017
  #27
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DanDan's Avatar
Soffit

Understandable, I guess most actual Soffits are hollow. The term Soffit Mounted in terms of speakers flush mounted in a wall is also very confusing.
Stacked up squares of light batt or the roll version contained in an open frame would be best. The fours sides idea would place half of your active fibre touching the wall. Not a great use of an expensive material.
DD
Old 17th February 2017
  #28
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adrumdrum's Avatar
 

Quote:
Originally Posted by MikeyHayek View Post
So I'm confused at this point because you keep switching between recommending the super chunk and the soffitrap.. I think I'm just going to go with the original 2x2 foot soffit floor to ceiling idea and try to find the least dense product ( probably knauf ecose earthwool 1.6 PCF because this is the most affordable material I can source )

Thank you for all your expert advise my friends. This calculator is making more sense as I begin to play with it
What is the size of your room?
Old 17th February 2017
  #29
Gear Head
 

Quote:
Originally Posted by DanDan View Post
Stacked up squares of light batt or the roll version contained in an open frame would be best. The fours sides idea would place half of your active fibre touching the wall. Not a great use of an expensive material.
DD
Thanks DD. It appeared to me that these soffits, say from the GIK videos, are being mounted directly against the wall. So if I were to go the DIY route, you're suggesting making the soffits and standing them in the corner, but off of the wall a few inches?

Last night I cut down a couple bags of 4" roxul AFB into squares. I figured I'd either end up making soffits, or super chunks. I'm still struggling to know if AFB is considered dense or not and if it's good for superchunk or soffit purposes.

Here are the specs from Bob Gold's page.
AFB 4" (100mm) 2.5 pcf (40 kg/m3)0.86 1.11 1.20 1.07 1.08 1.07 1.10

Depending on the verdict, maybe this could work for the OP if it's easier to source?
Old 17th February 2017
  #30
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DanDan's Avatar
Best Bass Trap

It is very likely to certain that Glenn has optimised his design using actual testing and comparison. Indeed RealTraps seem to have resulted from such an experiment, which Ethan published.
But is no test out there comparing SSC's with SoffiTraps and other LF trap designs. There is also no test which shows the performance of any one of the options using different fibres.
So there is really no point in the question, "which is best".

Without testing all we can do is theorise and guess, using the GFR and Calculators.
There are more sophisticated paid apps. e.g. SoundFlow.

Ultimately though, much of this musing tends to be done before researching what is actually available to buy.

Probably best to check that first and pick the option closest to a sure thing.

This post by seedee is advice to act on IMO.

Quote:
The thicker - the less GFR Gas Flow Resistivity / AFR Air Flow Resistivity

GFR is not always, but mostly is pro rata with density

General guidelines:
40cm and thicker -> get pink fluffy or URSA ONE Pure 40 PN, it's the 'lighest' available fibre
-> GFR = 7000- 5000 Pa·s/m²

less than 40cm -> start getting 'denser' stuff
-> GFR = 30000 - 15000 Pa·s/m²


10cm -> use owens corner 703/705
-> GFR = 45000 - 40000 Pa·s/m²
DD
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