# Rockwool and rigid fiberglass substitutes?



## Mikeythai (Aug 23, 2010)

I want to begin to acoustically treat my HT room. I live in SE Asia and cannot find rockwool or rigid fiberglass insulation.

I can find plenty of pink fluffy insulation, though. Are there any substitutes for either rockwool, or rigid fiberglass insulation? Or can I pack in the pink fluffy enough that it will do the job.

I have no treatment at present and assume I will start with corner bass traps and full range panels on the walls.


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## Mike0206 (Jul 14, 2013)

You can definitely use pink fluffy. That's what I've used. I believe most people go with rigid cause the they can make the panels smoother. I've used r-30 pink fluffy with great results.


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## bpape (Sep 14, 2006)

For thicker treatments the fluffy will work fine. For anything < 6", I would use something more dense like mineral wool, 3lb rigid fiberglass, etc.


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## Mikeythai (Aug 23, 2010)

That is good news. Space is not an issue. What kind of density is optimal? I mean, should I sort of lay it into the panels and bass traps, or try to pack it in a little?


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## bpape (Sep 14, 2006)

3lb/cu ft is kind of the sweet spot in performance vs cost.


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## Mikeythai (Aug 23, 2010)

I went out today and priced all the materials and it looks like I can do this for a pretty reasonable cost. 1x2 wood is cheap, then I want to use chicken wire to hold in the insulation, and porous fabric is pretty cheap too.

If my wall panels are 6" thick, made with pink fluffy, what kind of space do I want to leave between the panel and the (stone) wall?

And am I correct that triangular corner bass traps should be mounted flush in the corners?


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## bpape (Sep 14, 2006)

You can leave anything up to 1.5x the thickness of the panel behind it. Corners, yes, flush into the corner.


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## Mikeythai (Aug 23, 2010)

If I want to start with the primary reflection points, how do I figure out the optimal panel size? And I know about the mirror technique, but does that work for the mounting height for the panels? Room is 15 x 15 x 11 and I am currently running 5.1 with a rear center seating position (about 4 feet from the center of the back wall). I hope to upgrade to 7.1 soon.


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## bpape (Sep 14, 2006)

The point you see will be for height and wall position front to back also. Thickness, never hurts to go at least 4" thick if you have the space.

Bryan


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## Mikeythai (Aug 23, 2010)

I have a lot of room, am planning on 6" thickness with pink fluffy. I was really wondering about height and length for the panels. The cloth material comes in a 1.5 M width and I was thinking 1.5m x 2m

Also if my corner bass traps will use pink fluffy, what is a good thickness? I was thinking of putting them in 3 corners from the floor to the ceiling.

I know a lot of this will depend on the results frem req wizard, but I have not spent any real time with that because I still don't have a sub and have zero acoustical treatment.


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## bpape (Sep 14, 2006)

for reflection points I would use something more dense than fluffy. Fluffy only works well in pretty thick situations. 6" is kind of borderline. 4" of 3lb with a couple inch air space behind will work better.

Bass control - no real restriction The thicker you go, the lower it will work. Just understand that with the fluffy you will get a hump in absorbtion even more than the normal corner hump.


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## Mikeythai (Aug 23, 2010)

Unfortunately I don't think I can get anything more dense than the pink fluffy insulation. I was planning on weighing it carefully then packing it into the frames to achieve 3 lbs per cubic foot. And then making the panels 6" thick. Is there a sweet spot for the distance between the panel and the wall? In your earlier post you mentioned up to 1.5 X thickness of the panel. Are you saying the 1" gap would be optimal with the different material?

And if there is a hump in absorption is that describing better absorption of certain frequencies, or diminishing absorption overall after a certain amount of treatment has been put in a space?


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## bpape (Sep 14, 2006)

I was just trying to save space. Sure, you can go 1x or 1.5x the material thickness. A very common side wall treatment is 4" with a 4" gap, though 6" with a 2" gap will be slightly better and take the same space (and not look as odd).


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## charlieblue (Aug 17, 2013)

Mikey, lurking elswhere I've been reading interesting stuff on bass trapping... theory has it that (very) thick & fluffy beats less thick but more rigid, for same total trap depth. If you have a dedicated HT room, and neither space or fluffiness is a problem, you could do great bass traps but with a somewhat extra depth. Think 12" + 8" gap, or even 20" with no gap. This will give even absorption from very low to very high frequencies. If room becomes too dead for mid and high frequencies, which it will, eventually, then add reflective panels & diffusion as needed to return some liveliness to the sound.


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## bpape (Sep 14, 2006)

Just to be clear, once energy is gone, you can't get it back. Adding diffusion will not add any energy back to the space. Best to balance using limp damped membranes to cut off some of the bass control in the 100-300Hz range and leave the energy above it tact so can absorb it only where needed like reflection points.


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## charlieblue (Aug 17, 2013)

Good point, Bryan... best preserve useful energy ! 

I was thinking, trap as much of the very low frequencies as possible (easy for Mikey building from scratch and having no space restrictions, not so easy for quite a few of us) then cover the bass traps with panels / diffusors to reflect MF & HF back into the room... much like covering corner traps with plastic.. 

Hope that wont kill the energy all together ... : )

Regards,

Charlie


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## bpape (Sep 14, 2006)

Depends on what the diffusers are to determine if they will pass the bass energy to the absorbers behind or just act like a wall.


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## Mikeythai (Aug 23, 2010)

Okay guys, thanks for the pointers. I am learning how to use REW at the moment, and buying a new AVR shortly, and will treat my room as well. Also I am taking a week off after the LLT build which drained me a little.


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