Perth.hifi

Making muy own acoustic panels

134 posts in this topic

Hi everyone

 

Looking to make my own acoustic wall panels for my home theatre / muic room.

 

Wanting too get Donne images printed on canvas sheets for the panels and add some 25mm autex insulation batts i have left from building the new home.

 

Is canvas ok? Been reading mixed comments that canvas reflects too much sound. Is this correct?

 

On a tight budget hence why I'm building them myself.

 

Balsa wood for frames, or any wood will do?

 

I'm in Perth if there is any one willng to build me frames as I'm time poor. Haha

 

Thanks

 

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I think the suitability of canvas would depend on the room and its particular issues. When I put panels up, I actually wished they weren't attenuating so much of the really high frequencies, and at some stage will try putting some thin plastic behind the cotton covers. Can you do some experiments with samples of the coverings? Also just as a tip if you are DIYing and want a simpler build, if you use use Polymax/Martini Absorb XHD or XXHD the panels are rigid enough to not need frames, though you will get slightly rounded corners and see some of the texture of the panel below.

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I think the suitability of canvas would depend on the room and its particular issues. When I put panels up, I actually wished they weren't attenuating so much of the really high frequencies, and at some stage will try putting some thin plastic behind the cotton covers. Can you do some experiments with samples of the coverings? Also just as a tip if you are DIYing and want a simpler build, if you use use Polymax/Martini Absorb XHD or XXHD the panels are rigid enough to not need frames, though you will get slightly rounded corners and see some of the texture of the panel below.


Hi Steve

Cheers. To clarify.

Your saying canvas is a no?

Your saying the 25mm Autex Batts are not ok?

Your proposal available from where? Cost approx?

Can i print movie poster images on them?

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Posted (edited)

If the canvas is actually slightly reflective, I would imagine it would be at higher frequencies only(but you'd need to confirm with tests) and could actually be better in certain rooms where you don't want to absorb the highs as much. So, could be better or worse, but wouldn't assume either way.

 

I haven't used the Autex, but just thought I'd add my experience with the Martini. If you contact Martini they will let you know where you can get them. Bunnings also sell a version of it now https://www.bunnings.com.au/csr-martini-absorb-xhd-r1-5-2400mm-x-1200mm-x-50mm-17-28m2_p0811175 (6 sheets in that pack) There's a big thread around here somewhere discussing them. You'd cover them like you were going to with the framed Autex, and print on that covering, but if you are trying to save money and can handle a slightly less sharp edge, you can get away without using the timber frame. You could also possibly use a heavy posterboard or similar from an art supplier to make a rigid edging.

Edited by Stevesie
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You want the cover to be acoustically transparent I.e sound wave travels through the cover and gets (partially) absorbed by the batts.

Canvas would be too dense a weave imo, you want a weave that you can feel your breath move through. You will get improved performance mounting the panels ~70mm off the wall. I have pictures of my panels in my room in my thread. I used light pine as the frame, 75mm batts from memory. Dowels in corners keep the frames proud of the wall (and can be adjusted) and frames are hung on "L" brackets. 

 

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canvas and printed canvas will let bass through but reflect higher frequencies - depending on the density of the weave.

 

The "blow" test is a rough guide for whether higher frequencies will be reflected - if you can blow through the fabric it will absorb rather than reflect high frequencies.

As mentioned above, you may want the fabric to reflect higher frequencies

 

autex is fine, but if you want to absorb lower it needs to be deeper - to work below say 250Hz, 100mm thick is a good start

 

What you don't want is an absorber panel with fabric that reflects higher frequencies, but is too thin (and/or small) to absorb lower frequencies - lots of work for no absorption :(.

 

To give some idea of the absorption properties of different density/thickness fiberglass or poly, this calculator is handy

http://www.acousticmodelling.com/porous.php

 

You need to know the gas flow resistivity of the insulation - some figures here

https://www.gearslutz.com/board/studio-building-acoustics/625978-common-gas-flow-resistivity-numbers.html

Fluffy insulation is around 5000 - 6000

Polymax XHD is around 14000

 

The Acoustic Model tool is just a guide - it doesn't cater for the size of the absorption, just thickness and air gap.

 

Which Autex do you have?

25mm sounds too thin to be "fluffy" insulation - is it a blanket style product or individual batts?

 

You need some idea of what you're trying to achieve with the treatment and design accordingly.

 

Attached is a DIY guide for absorption traps - I wouldn't call them "bass" traps - but the usual practice of gapping them from the wall (eg straddling corners), will get reasonable performance down to 200Hz or so

DIY-BASS-TRAPS-MADE-EASY.pdf

 

Some recent posts on this forum have called into question the usual gapping approach for absorption if the material is not held in place appropriately - I've never used any backing for my absorption, but don't doubt the maths/knowledge/experience of the forum member who provided some interesting comments on room absorption/gapping etc.

 

In summary:

  • 25mm insulation is much too thin if bass/mid bass absorption is required
  • tight weave canvas will start to reflect high frequencies at some point, and painted canvas will lower the frequency where reflection starts 
  • credit to you for trying to combine treatment with something that looks good - my room treatment is a disaster in the looks department.

 

cheers

Mike

 

 

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I'm feeling flat. Haha... thought I'd utilise the 25mm batts. Type AAB 48-25. BEING 48KG weight and 25mm thickness.

See link....

Could I double up the batts?

https://www.google.com.au/url?sa=t&source=web&rct=j&url=http://www.apexceilings.co.nz/uploads/7/0/3/3/7033939/quietstuf_autex_acoustic_blanket.pdf&ved=0ahUKEwjsvM74uMvTAhWJlZQKHY6HB2QQFggfMAI&usg=AFQjCNGluDnwn95IXT_Md_IWFsnuvphlkg&sig2=fFZyVfHhtVWPfWzm5HRp9g



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possibly the 48-25 means 48kg/cubic metre 25mm thick - if that's the case then that will work fine.

Read the blurb and let us know.

 

yes you can double/triple/quadruple the batts.

 

100mm depth is good - 150mm or 200mm better if you want it working below 200Hz.

 

How much left over insulation do you have?

Do you have a bass issue?

 

IME most rooms benefit from some broadband absorption in the bass/mid bass region (say below 300Hz).

Traps for this region need to be deep and large - as a guide 100mm deep and 600mm wide would be minimum size.

 

Around 200-300Hz in most domestic (ie small) listening rooms is the "transition zone" - below the transition zone the room dominates and you have modal behaviour - where absorption straddling corners works well if large (wide and deep) enough to trap bass.

 

Absorption at 1st lateral (sidewall) reflection points is designed for above the transition zone where sound waves travel more like beams of light in straight lines - thinner absorption can work in this scenario as the wavelengths are shorter and the frequency higher.

 

When I treat a room I always target the bass first and measure (decent sized traps straddling corners will typically clean up the 100 - 300Hz region very well).

IME get the bass right first and minimal treatment is required after.- others have different approaches to room treatment.

 

cheers

Mike

 

 

 

 

 

 

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I've got enough batts for a single layer, to make 6 wall art panels.... thou would have to purchase more for double or triple layers....

Main reason for this project, is to reduce river, echo, clean up harshnesd in sound alittle ( highs ). The focal 826v towers can be alittle harsh at high volume levels.

In regards too bass, I'm constantly upping it our dropping it to suit what movie I'm watching or music I'm listening too. Bass is causing done vibrations in walls and ceiling more so.....

I've got a room that simply cant be touched in ceiling as I'm under the upper floor slab. Installed lots of insulation above and a dropped ceiling with nose mounts, but clearly something has gone wrong.

Walls are also insulated with framing on noise mounts... again I've done allot of work, but things have gone wrong...





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Here's a few shots of my room. Had a design done awhile back, but completely over budget... thus shows recommendations. But art thus stage I'm just doing rear side walls ad back walls, for decoration of rooms... I'm going to get fabric material with movie prints on it locally ....be45eb5d8c430dd2f5fe193a3d99e5e0.jpgca776501fd179cc5eac3bc731b02af65.jpg6a17fb8fc16add97a05a5a3fa61cfd80.jpg

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I wouldn't put too much absorption at the rear of the room... that's where some diffusion is best applied.

The raised seating plinth lends itself to being adapted as a bass absorber trap but you would need some professional room measurements and advice to successfully implement that.

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Why is this process so expensive. Its just insulation. Haha

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Posted (edited)

Some great info here, I have always been trying to get the time to add some panels to my small HT Room.

I didn't realize Bunnings sell the Martini insulation.  Looking at the specs the best price / performance looks to be from the HD 75.  Is there any other reason besides rigidity to go for the XHD?

I might buy a pack and try them on the walls first before making any frames.

I have read previously that the RIM_Fabrics_Trilogy material was okay, has anyone used this before?

 

 

Acoustic Insulation Spec.png

Edited by Dogbert
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Posted (edited)

Here's a not very good photo of what the Martini XHD looks like without frames. The fabric is the cheapest Lincraft cotton I could get. It's just pulled tight and pinned on the other side using dressmaker's pins every 10cm or so. 

 

panels.jpg

Edited by Stevesie
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Posted (edited)

Very tidy work stevesie:thumb:

Edited by mtf

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40 minutes ago, mtf said:

Very tidy work stevesie:thumb:

 

Thanks! :)

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Posted (edited)

On 2017-5-3 at 3:19 PM, Dogbert said:

 

I have read previously that the RIM_Fabrics_Trilogy material was okay, has anyone used this before?

 

 

Yep, great stuff.  Really nice to work with too i.e. doesn't fray nor stretch. 

Edited by Peter the Greek

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Hi

Would I be best with the XD or the XHD, also, can this be used for both absorbing and diffuser? If not what needs to Happen to make a diffuser with this material?

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Posted (edited)

15 hours ago, Perth.hifi said:

Would I be best with the XD or the XHD, also, can this be used for both absorbing and diffuser? If not what needs to Happen to make a diffuser with this material?

 

The XHD looks the go, but depends I guess on what you want. Here is a useful and not so long article that might help you with your decisions

 

https://homeacoustics.org/2017/04/acoustical-treatment-primer-absorption/

 

You can give the insulation diffusive properties by covering it with strips of tape, plastic film, paper etc in 150mm vertical strips i.e. 150mm covered, 150mm uncovered and so-forth. Other DIY methods are significantly more work, but easily achievable. As I said, read the article. If you have more questions get the book he references

Edited by Peter the Greek
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If i were to cut out squares ad create a maze like pattern in the insulation batt, would this be sufficient? Or must the surface have a mix of projections to diffuse the sound.

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You wouldn't use an insulation batt to make a diffusion panel. Diffusion panels reflect sound in a controlled way to scatter the energy around the room, insulation batts absorb and turn the sound into heat. This might be worth a read to get the basic understanding http://www.gikacoustics.com/articles/

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Hi
Ok, any there any simple to read guides for a diffusion panel, could I perhaps use a grid of insulation in a fabric covered panel to for adiffusion panel?

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Might be best to just forget the diffusion panel unless you buy something ready made, and just go with your plan of building some broadband absorbers.

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Those GIK articles (links above) are really worth a good read - just take your time as there often seems to be some contradiction between absorbtion panels and diffusion panels as Steve mentioned - much of the promo info applies more to 'pro-audio' use where the acoustical requirements are quite different to homehifi - a few guys here on SNA are playing around with the relatively new 'leanfuser' that deliver similar/better performance to the traditional type of diffusers at a more affordable price

 

Using gaps in the absorbtion panels (grid of insulation) doesn't really give diffusion - it just changes the merits of the absorbtion - can be quite useful, mind you, but it's not the same as diffusors - a similar thing to using mid-range and treble reflective strips on front of the absorber panels 

 

There isn't any simple answer to the wide variety of room treatments in pro-audio and it's the same in home hifi - no two rooms behave the same and our individual music tastes add to the variety of acoustics - it's often been written that between 40 - 60% of the sound we listen to at home is determined by our room environment rather than just changing components - unfortunately, the use of dsp (digital signal processing) is only partially useful and 'knocking up' a couple of simple absorbers is very effective and a great way to start your 'room acoustic journey' - a good bit of fun tho ...

 

I think those Martini panels are available at Bunnings nowadays - they're designed for this sort of use but all sorts of other material will do just as well - it still stays in my mind the effect of just poking cushions into the room corners had on the sound (see Michael Green Audio and 8th nerve gear) 

 

   ...   my 2 cents

 

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