[Hakka]

I have been doing a bit of research on that materials used to acoustically treat HT rooms, most of the products that are used don't seem to be available in Australia.
Now that there's quite a few Aussies on this forum, what materials do you use and where did you get them from??

The only things I've been able to find here are products made specifically for room treatment, only problem is they cost a fortune.

Thanks.

Harry.

 

[Alan Brown]

You should be able to find rigid fiberglass "duct board" from heating and ventilation suppliers. It is typically 2 foot x 4 foot x 1 and/or 2 inches thick. Here in the US, we find it in 2 densities. The higher density is better.

One variety is black and treated to prevent the glass fibers from going airborn in a high velocity air duct. Another variety is untreated. The untreated is best because the pores are not blocked and absorbs sound better.

Cover this board material with acoustically transparent fabric. Here, it's called "panel fabric" because it's used for covering office cubicle partitions or panels.

 

[Prof.]

Hakka,

I found this article some time ago on making your own acoustic panels, using fibreglass duct board..
It's something that I'm looking at doing also for both bass traps and wall treatment..
It should be available from Air-conditioning Installers..
Hope it helps..
http://mywebpages.comcast.net/kidder/Audio/Room/PANEL/Panels.htm

 

[Hakka]

Thanks for the info, I rang a few local air con suppliers to see what was available. I mentioned 'acoustic panels' to one bloke and he told me exactly what I need. Going to pick them up now I'll let you know how it goes.

Harry.

 

[Hakka]

There were 2 densities available and two thicknesses 25mm and 50mm. I went for the high density 25mm. One side has a peforated foil covering, the other side is bare. The salesman said the perforated side is the sound absorbing side. I hope the foil doesn't reflect light back through the material.
I have a pic on my phone but for some reason I can't email it to my PC. I will attach the pic tomorrow.

While we were there he had a metal duct, approx 1.5m long, with a 25cm square opening at each end. The duct was lined on all sides with the high density 50mm duct board. He put his head in one end and I put mine in the other, when he spoke I could barely hear him, it was like the volume had been turned way down. I was very suprised at how effective this stuff is at absorbing sound.

 

[Prof.]

Is the material called "Duct Board" or do we know it by another name?
Also what size sheets does in come in?
I'll be very interested to hear how it works out for you..

 

[Hakka]

Yes, it is called duct board, the sheets size is 1200mm x 2400mm, cost $40 per sheet. It is available in 2 thicknesses (25mm, 50mm) and 2 densities. It has a foil backing on one side, the foil can be perforated or non perforated, I dont think it will matter which one you get.

I was advised to have the foil side facing out but after googling 'acoustic panels' I decided to go the other way.

I made 2 panels about 1m square, I just cut the duct board to size and wrapped it in material. I am planning to make 3 panels 1200mm x 2400mm, these will be mounted in wooden frames, I will place one on the front wall and one on each sidewall. This should cover all first reflection points for the front speakers.

 

[Prof.]

Thanks for that info....$40.00 for 1200x2400 a sheet sounds fairly reasonable...

He shows (on that link I posted) the foil side as the back of the panel, and I've also seen it used as bass trap in the same way, so I guess this is how it should be used..

Making acoustic side panels using a full sheet at the first reflection point seems a bit excessive...unless you have a very "live" room..

One sheet cut in half down the length, and the two pieces placed on top of each other, should make a very good bass trap, and I think this is what I will try first..when I've found a local supplier...

Did you notice any improvement with the test panels?

 

[Hakka]

Making acoustic side panels using a full sheet at the first reflection point seems a bit excessive...unless you have a very "live" room.

I've done a bit of research and I found the general consensus for room treatment(absorbtion) is to treat the side walls from the ground to just above ear level and to treat the entire front wall (leave the backwall bare). The majority of my front wall is covered by the screen so I will just treat it up to the bottom edge of my screen, which is about 4 inches above my tweeters and ears.

My room is solid brick, with the sidewalls rendered, there is no flex in the walls like there is with plaster.

I think it would be a lot harder to make these with the foil side facing out, it is a lot easier to attach the material to the foil side than the uncovered side.

I *think* the system sounded better with the panels in place on the side walls but I didn't AB test it. There seems to be more detail in the high frequencies than before, also the soundstage seems bigger.

 

[Prof.]

I *think* the system sounded better with the panels in place on the side walls but I didn't AB test it. There seems to be more detail in the high frequencies than before, also the soundstage seems bigger.

That sounds good (no pun intended) that you can discern some improvement with those metre square panels..
I have a good soundstage but I do get some blurring in the mid highs. Hopefully this material will improve that...

Looking forward to hearing your results when you've made your panels..

 

[Prof.]

I just found this post by Terry Montlick from the AVS forum..

There is no acoustical difference between using rigid fiberglass duct board and flexible fiberglass duct liner. There is some slight difference in going from lightest 2.25 pcf linacoustic to heaviest 6 pcf, but this is very minor and can be ignored in most situations.
_______________________________________________________________________________________

Make sure the foil is facing against the wall and not towards the theater room, and it will have absolutely no disadvantage.
_______________________________________________________________________________________

Regards,
Terry

__________________
Terry Montlick Laboratories
Complete Home Theater Acoustical Services
Design, Evaluation, Alpha Certification
www.tmlaboratories.com

That pretty well confirms which side the foil should face...and the flexible duct liner will be easier for me to transport..

 

[Hakka]

I've got most of the materails I need so I will start making the panels tonight. I will take photo's of the process and post them on here. I decided to make the panels 100cm x 60cm to make them easier to handle.

 

[Prof.]

Thanks for that...I'll be very interested to see the pics...

 

[Hakka]

pic 1
Here's the duct board, its been cut to 100mm x 60mm sheets. It is the 25mm high density duct board

pic 2
The duct board is wrapped in polyester batting to stop particles becoming airborne. Cut the batting to a size about 12 inces longer and 12 inches wider than the duct board.

pic 3
Use Caulk to attach it to the foil side of the duct board.

pic 4
I made the frame from 42mm x 18mm timber. I used some masonite packing sheets from work for the backboard. Run a bead of Caulk around the frame where it meets the backboard to stop it rattling/buzzing. Screw it all together.

pic 5
Almost finished, I used Caulk to stick the panels into the frames. They just ned to be covered in acoustically transparent material. I will post a fial pic when I get them covered.

Harry.

 

[Prof.]

Nice job Hakka....went together nicely..
What are you intending to use for your top cover?
If you are having them black, then grille cloth is ok...but if you want a different colour, what do you use?

 

[Hakka]

I think I'll cover them in black grill cloth type material, preferably the same stuff my subwoofers are covered in if I can find it.
I have 6 of these in my room at the moment, 3 on each sidewall. I did some A/B testing with and without the panels and they do make a huge difference to the soundstaging and detail. I have 5 more still in construction, 3 for the front wall and 1 more for each sidewall.

 

[Prof.]

Grille cloth can be expensive, if you're doing a lot of panels and I've only ever found it locally in 1Mx1M. sheets.
When I was doing my screen wall and prosceniums, I had to find something similar to grille cloth, i.e. acoustically transparent, and certainly bigger than 1M.square.
I found a material called Black Stretch Interlok...It comes in 1500m.m wide rolls and was about $9.00/metre..
It has two-way stretch and was very easy to apply to the large side panels..
Acoustically, it's almost identical to grille cloth and has a nice "silky" feel to it..
I found it at Spotlight, and is definately worth considering...

I'm planning on doing 6 panels in my theatre..4 of them will have the duct board and the other two will just have Polyfill,( my theatre is already quite dead acoustically) and I'll be using the same material to cover them..

 

[Hakka]

That might be the stuff I used on the subs, I got it at spotlight but could't remember what it was called.

 

[Hakka]

I still haven't got around to cobering them yet but here's a pic of them installed in the theater room.

 

[terry j]

hi harry

thanks for the tip on what the panels are called, I've been to an aircon supplier and asked for dense fibreglass, he didn't have any idea what I was talking about. ( he must have been dense?)

Quick question on your methodology, would not leaving off the masonite have improved the bottom end performance without degrading any results higher up?, or am I way off base here. ( should I have said 'way off bass??)

loking forward to finished pictures and measurements

lots of love

terry