Quietrock

[caesar]

A quick story taken from the F. Toole book (page 480).

A listening room had been built, and the friendly builder thought he was doing us a favor by adding an extra layer of gypsum board on the interior surface. The “favor” was discovered too late, and the room was used in that condition for a couple of years, during which it acquired a reputation for having somewhat boomy bass and upper-bass/lowermidrange coloration. The evidence was in measurements. Eventually, we had the interior of the room stripped and the originally intended single layer of gypsum board installed.

Hi Ron, what are your walls made of now? Construction is risky business. Construction is a big commitment that can take one on that unfortunate path.

I also have experienced rooms done with green glue that have that have excessive boominess and never-ending echoes. And you can't just hit an "Undo" button to completely erase and reverse all of the work that was done.

Instead, flexibility of peppering the room with many portable ASC tubes and diffusion pieces may be the best option, as you already have openings to help the bass escape.

Good Luck

 

[Ron Resnick]

Are you suggesting that because I have a large opening on each side wall that my situation is out of the category of having to have flexible walls to absorb low frequencies, and out of the category of building solid, stout walls to hold low frequencies in?


Yes, but I need a basic starting point to do something with the walls:

-- one layer of common drywall

-- two layers of common drywall with Green Glue in the middle

-- common drywall with over mass-loaded vinyl

-- 530 Quietrock

-- fill in crevices and cavities in wood framing with regular insulation or blue jeans insulation

In my complicated room I could do both: I could glue just one sheet of common drywall on the concrete front wall and the first third of each side wall which is cinderblock for solidity and holding in the low frequencies, and then when the side walls switch to wood framing I could use one layer of Quietrock or two layers of common drywall with Green Glue in the middle (and then the last third of each side wall near the listening position is open ).

How is that for "splitting the baby"?

 

[microstrip]

What was Toole's explanation as to why two layers of drywall caused these acoustic problems, whereas one layer would not have caused the same problems?

In that situation was the builder of the room trying to create flexible walls to absorb bass frequencies?

The book has not the full details on the room, it is not possible to know exactly. But he was illustrating the case that the problem of most rooms is too much bass at some frequencies and they need some kind of bass absorption.

Panels with air cavity are resonators and typically absorb bass one octave bellow and above their tuning frequency - see http://www.mh-audio.nl/ACalculators.asp#showcalc for approximate formulas. I used them with success to build to tame a 37 Hz second order mode in my room. You can easily the effect of doubling the mass of the panel from 10 to 20 kg/m2 with a gap of 10 cm - it moves the center of absorption from 62 to 40Hz. We should also consider that filling the cavity with fibreglass or mineral wool tends to lower the resonant frequency by up to 50 per cent (quoting from the referred link).

 

[joey_v]

Don't know about you Ron, but all this room stuff is giving me a headache

 

[Ron Resnick]

Me too, Joey!

Mark, Why do you suppose Quietrock all but disavows the use of Quietrock for sound absorption purposes?

Quietrock 530 is 5/8" thick and has a thin layer of steel in the center. Quietrock 510 is 1/2" thick and has a thin layer of visco-elastic polymer in the center. Quietrock ES is 5/8" thick and has a thin layer of visco-elastic polymer in the center.

How do we know that these Quietrock boards better sound and vibration absorbers than common drywall?

 

[Ron Resnick]

I think if anyone is hoping to accurately control room modes by vibrating sheetrock { of any type} wall panels they are dreaming ! - I have never seen anyone trying to calculate such an effect and I suspect it is not possible - better to have density and rigidity, keep all the bass in the room and then deal with it via traps, speaker placement , listening position etc.
At least you start from a (partially) known position

my 2 cents

phil

phil,

How does one "keep all the bass in the room" when one-third of each side wall of the room towards the listening position is open to other rooms?

Doesn't that defeat the whole concept of using density and rigidity to keep the bass in the room?

What, in your view, is the best wall structure solution when large openings in the rear of the room will allow bass waves to "escape"?

 

[Ron Resnick]

Ron,

For the low frequencies its all about mass, ergo the benefits of mass loaded vinyl and Roxul. Roxul is very dense (not sure about Ultratouch). The KNC Clips are about 1" off side walls and the hangers for the ceiling are 1 7/16". You may want to chat with Nyal. He is a member here. My room is dead, dead quite.....no hvac, no fridge, no outside noise, nothing. It is really cool for dynamic range and immersion.

Pb,

When you write your listening room is "dead, dead quiet" does it nonetheless sound natural? Or does it sound unnaturally damped when you are in it?

 

[Ron Resnick]

yes, I have Quietrock.....to be specific.....I have Quietrock 545. which is the 1" and 3/8th thick affair with a 1/4" layer of aluminum.

in 2010 I found I had uneven and overdamped bass response side to side due to excessive bass trapping and uneven loading of the walls; one side was an outside wall, the other inside (this was our best guess of causes and effects). so the goal was to establish consistent room boundaries in the front sides and front window wall. we already had the whole room (all walls and ceilings) cocooned in a double layer of 5/8" sheetrock, and my cabinetry was built out from that. so that was the base layer on top of the studs.

so we ripped out the huge designed in 10' x 15' front and side bass traps.

we considered multiple layers of more sheetrock, but then came across Quietrock 545 (at that time it was also called 'THX' 545 in reference to the Home Theatre application). 545 was more effective than 6 stacked sheets of 5/8" sheetrock, and would take up as much less space. and it's aluminum layer suggested it would really help to establish clear room boundaries. so we did install something like 12-16 sheets of Quietrock 545 on the front half of the sidewalls and the window wall. it was glued and screwed to the sheetrock cocoon, then 3/4" finish grade maple plywood was screwed and glued to that. we also made window inserts of the same sandwich and those are in use (which is a separate story in itself).

so.....I have the---studwall (insulated with 702 corning)-> 2 sheets of 5/8" sheetrock -> Quietrock 545 -> 3/4" plywood.....all glued and screwed.

and we have room boundaries that are super solid and....well....amazing bass authority and articulation. and with the barn being a separate building I don't have noise issues to deal with; but even if there are chain saws or other heavy equipment being used in my neighborhood I hear nothing.

your contractor will hate you since it's so heavy to deal with and it will tear up saw blades with that aluminum layer so it's a real pain to work with. but that part is over quick, and you have your solid walls. and it's the time and labor that is the expense; using the right materials has minimal cost differences.

as far as vinyl as your acoustic treatment; it has it's attributes....but if you are chasing ultimate sound.....it's a big bass trap (lots of loose mass) and will deaden the sound since it's mushy and absorbs at an unpredictable rate and can react to changes in temp and humidity. I think at the listening end it's a good choice, but not at the 'business'-speaker end. but that is just my opinion, I've not had Lp lined shelves around the speaker end......could be just right in certain situations.

Mike, I understand the design now.

You used the Quietrock 545 and the maple plywood to neutralize the mysterious low frequency imbalance between your exterior side wall and the interior sidewall, and to create acoustical symmetry of the side walls.


1) In addition to your window wall (your front wall) did you continue this treatment on the side walls all the way to the rear wall, or only on the front half of the sidewalls?


2) Do you think the maple plywood layer was essential to creating stout side walls and creating symmetrical acoustic room boundaries? Or do you think the Quietrock 545 would have achieved most of the same objective?

Putting it differently, which was more critical to employ to create the new, symmetrical acoustic room boundaries -- the Quietrock 545 or the 3/4" plywood?


3) What do you think you would you have done in your actual situation to resolve the side wall imbalance if the rear third of both of your side walls were permanently open to other spaces?

I ask because I have asymmetry to deal with also. The rear third of each of my side walls is symmetrically open to adjacent rooms. The front third of each side wall is symmetrically built out of cinder block. But the middle third of the left wall is wood framing and the middle third of the right side wall is cinder block.


4) Did you treat your entire ceiling the same way (2 sheets of 5/8" sheetrock -> Quietrock 545 -> 3/4" plywood, glued and screwed)?


5) Lest you think I have reached maximum neuroticness on this topic, Mike, think again!

I see the layer of 1/4" of aluminum in the Quietrock 545 is not in the middle of the sandwich:





How did you decide whether to hang up the Quietrock 545 with the aluminum layer closer to the plywood layer or further away from the plywood layer?

. . . For those starting from scratch, my preference would be to see a heavy and rigid outer shell using Baltic Birch ply and/or MDF with wood or steel stud framing with isolation of some form to the flexible, but damped mass of the inner walls, more commonly 2-3 layers of drywall with green-glue. This gives the outer layer of isolation, but then allows the inner layer to eat up some energy from low frequency modes reducing their intensity (less difference peak to valley in level).

. . .

In what I've seen of your space, your biggest focus should be on maintaining any degree of left to right symmetry where you can. In cases like yours that might often come by NOT trying to make things overly rigid when you have a weaker boundary on the opposing surface, or beefing up the areas which do have matching rigid boundaries.

Mark, Maybe the Quietrock 545 on the cinder block sections of my side walls, continuing over the wood framing sections of my side walls, would equalize the asymmetry, and create new, symmetrical acoustic boundaries?

I do not have enough space to build each wall out from the studs with an isolation channel of clips and hangars to hang 5/8" drywall and then Quietrock 545 (1 3/8") and then 3/4" plywood. Mark, Which do you think is more critical to employ to create the new, symmetrical acoustic room boundaries -- the Quietrock 545 or the 3/4" plywood?

If I used the Quietrock 545 and the 3/4 plywood, could I forego the insulation channel? Could I forgo the first (inside) layer of 5/8" drywall?

Which components do you think are more important to achieve a rigid, isolation exterior, but also achieve some low frequency absorption from an inner layer?

 

[Pb Blimp]

Me too, Joey!

Mark, Why do you suppose Quietrock all but disavows the use of Quietrock for sound absorption purposes?

Quietrock 530 has a thin layer of steel in the center so how do we know that 5/8" Quietrock 530 is a better sound and vibration absorber than common drywall?

Ron, This is a broad generalization but might help to think about it this way:

The harder something is the more it reflects.
The softer something is the more it absorbs.
The heavier something is the lower the frequency it can reflect or absorb.

As such,

Hard and light reflects high frequencies - ex. sheetrock
Hard and medium weight reflects mid to high frequencies -ex. quietrock 530
Hard and heavy reflects low to high frequencies - ex. quietrock 545

Soft and light absorbs high frequencies - ex. fiberglass board
Soft and medium weight absorbs mid to high frequencies - ex. roxul
Soft and heavy absorbs low to high frequencies- ex. floating walls on clips and springs a with mass loaded vinyl.

With that in mind, STC is a measure of how much sound is blocked by a substrate (i.e.,sound that is absorbed and/or reflected) measured on the opposite side of the substrate and NRC is how much sound is absorbed by a substrate (i.e., noise reduction by the substrate within the environment). So given this, it makes perfect sense that quiet rock 530 is used to stop transmission of noise through a substrate because it is an effective reflector not an absorber. It has a high STC relative to normal sheetrock but a low NRC relative to fiberglass board. It would make no sense to test it for NRC because it is a hard reflector designed for STC.

That all said, IMO this is all best evaluated by a computer modeling the math based on room dimensions, speaker and listening positions within the room to optimize the correct level of absorption, reflection and diffraction to manage room modes and reflections across the frequency spectrum so the room is flat and lively (i.e., NOT over dampened). Nyal dialed up all room dimensions, 7 helmholtz traps, 3 rpg bass plates and a bunch of strategically located absorbers and diffraction panels all on floating walls backed by mass loaded vinyl and roxul. I know I sound like a broken record but I really think you should consider reviewing your situation with somebody that can perform this kind of work. It was not more expensive than a good interconnect. Best money I have spent in this hobby.

 

[Mike Lavigne]

Mike, I understand the design now.

You used the Quietrock 545 and the maple plywood to neutralize the mysterious low frequency imbalance between your exterior side wall and the interior sidewall, and to create acoustical symmetry of the side walls.

that's it.

1) In addition to your window wall (your front wall) did you continue this treatment on the side walls all the way to the rear wall, or only on the front half of the sidewalls?

only the front 40%.

it's on the 10 forward feet of both sides of the sidewall, and then continues for 6 feet on the window wall (including the window inserts) on either side of the center curved diffuser.

it is not anywhere back of this forward area where previously there had been a huge (10' x 15') bass traps. the idea was to reinforce the wave launch nearest the speakers. and the rest of the room had very heavy built in cabinets (using 3/4" finish grade ply) mostly filled with media. so it was impractical and unnecessary to worry about the rear walls with the Quietrock. we would have had to remove all the cabinetry and install it behind them.

2) Do you think the maple plywood layer was essential to creating stout side walls and creating symmetrical acoustic room boundaries? Or do you think the Quietrock 545 would have achieved most of the same objective?

Putting it differently, which was more critical to employ to create the new, symmetrical acoustic room boundaries -- the Quietrock 545 or the 3/4" plywood?

the objectives were to (1) create the equal room boundaries side to side, and (2) to maintain the dimensions as they were (not unduly change wall thickness). and we wanted to match the rest of the room in terms of 'look'. which was all this same finish grade 3/4" plywood, even including the ceiling. so there was no consideration of having the Quietrock on the outside. I have no idea whether the aluminum layer is inside or outside. and as heavy as the Quietrock 545 is, the 3/4" ply is also very heavy. someone could do the calculation on which is heavier.

the idea was.....hey.....what is the most robust fairly thin product(s) that can overcome the challenge of loose bass hookup and make both side more the same? it's what we came up with. and it worked.

3) What do you think you would you have done in your actual situation to resolve the side wall imbalance if the rear third of both of your side walls were permanently open to other spaces?

I ask because I have asymmetry to deal with also. The rear third of each of my side walls is symmetrically open to adjacent rooms. The front third of each side wall is symmetrically built out of cinder block. But the middle third of the left wall is wood framing and the middle third of the right side wall is cinder block.

my best guess is that the cinderblock will be dominant in terms of wave launch. but it's only a guess. likely until you are in the room with music, knowing the final solution in terms of bass optimization with be unlikely.

4) Lest you think I have reached maximum neuroticness on this topic, think again!

hah! fat chance of that.

i'm confident you have no maximum of neuroticness; and there are absolutely no limits here on WBF.....lots of bandwidth. (just teasing....you kinda have asked for it)

I see the layer of 1/4" of aluminum in the Quietrock 545 is not in the middle of the sandwich:

How did you decide whether to hang up the Quietrock 545 with the aluminum layer closer to the plywood layer or further away from the plywood layer?

as I mentioned above, I don't recall. it's possible I posted about it in 2010-2011 (when I made the changes) and it's there somewhere in the web record.

Mark, Maybe the Quietrock 545 on the cinder block sections of my side walls, continuing over the wood framing sections of my side walls, would equalize the asymmetry, and create new, symmetrical acoustic boundaries?

this could be a future addition if you find it could be helpful.

 

[pjwd]

phil,

How does one "keep all the bass in the room" when one-third of each side wall of the room towards the listening position is open to other rooms?

Doesn't that defeat the whole concept of using density and rigidity to keep the bass in the room?

What, in your view, is the best wall structure solution when large openings in the rear of the room will allow bass waves to "escape"?

Ron -correct - i was commenting on the notion of using various wall panels as bass absorbers rather than your particular case - the quietrock type products are perfect for creating a sound proof man cave which you then treat acoustically to absorb bass energy, deal with first reflections etc. To determine what they (or any other sheet wall system) does as a resonating panel system for absorption you would have to construct an exact replica of the system and measure it.
In your case the bass energy is going to "see" a very large space so there is probably limited need for bass absorption as you suggest ( if connected spaces are small and have a small opening they may resonate and may need absorption ) If you have rigid walls opposite each other you will have modes in that zone but I would be careful about bass absorption as a a a part of the wall system without the advice of an acoustic consultant as you may end up with too much.

My guess is that a decorative finish directly over concrete would be fine and apply funds to a known propriety system if needed

As has been noted before dipole speakers really help to take the room out of the equation so your treatments should be quite simple
To support a good stereo image symmetry is key - my guess is that is your major challenge but it does give you something to do


As a side note in our main house we have a system in our living room that is connected to the rest of the house - they are dipole speakers with no room treatments except for a very absorptive ceiling
in our holiday house we have the full sound isolated man cave ( 25dB ambient ) with acoustic treatments - in the latter you can hear amazing detail, plenty of bass and the imaging is spectacular but I get most enjoyment out of the living room system as it is a part of everyday living but you can sit in the sweet spot and really focus on the music
In the living room the ceiling and roof construction that is very lightweight, multiple openings to other spaces and quite a few windows ( transparent below 250hz or so ) has never had a long reverb in fact it is a bit too lossy in the bass hence my suggestion for some caution

cheers

Phil

 

[Rodney Gold]

I investigated the sheetrock and green glue wall treatment , double thickness plasterboard etc when doing my room.. I decide to adopt another solution

I covered all my walls with panels from acoustic solutions

http://www.acousticsolutions.co.za/

I used a 3" batten with isolated screws for wall mounting the battens and the same for the panels to the battens
I used a 1" isover rockwool of 48kg/m3 density to be behind the panels fitting into the batten gaps

The panels are made of 16 mm veneered mdf , they have slots cut into them for some diffusion/dispersion and the slots are pierced to allow sound to go thru them and be absorbed in the air gap tween them
There is some thin acoustic material behind the panels

My area of coverage is around 50m2 or 500 sq ft ..... I can reduce it by hanging artwork which will effectively block off some of the diffusion and absorption .. so you can tune the room...
If you look at the pics you can see a giant area of ceiling covered by the panels .. was removed as it was pulling the ceiling down.

The rockwool inside the airgap is low density so the room wont absorb so much as to make the room sound dead
The cost was around $100 a sq m including battens , isover stuff and installation

The net effect is amazing .. the room is very quiet now.. but not at all dead .. the treatment made the room isolate itself from the outside in that you can play real loud and the ambient noise floor in the room is very very low.

The comments folk make is how natural their voices sound but how quiet the room is.. if you walk up to the wall , your voice sounds natural till you get close and when right at the wall. your voice almost disappears , like its getting sucked in...

These are NOT bass traps , but they do resonate and the resonance gets damped , so they do remove some bass energy
They are also not broadband or specific absorbers and neither are they diffusers..albeit they do have a bit of both ..
You still have treat the room with bass traps and purpose made diffusers and absorption .. but the start point is elevated.
I use no side treatment with my speakers barring the paneled wall itself , they are far away from the walls and have a very wide dispersion hut do use tube traps and bass traps and absorptive panel behind me

The room treats the music very well , the sound is large scale and has amazing imaging..

Here are some pics

Room before

room after..ceiling panels been removed

Slotted panels

Isover rockwool stuff

Battens and isover

Room as it looks now... 2nd pic is older..but nothing much barring the speakers has changed

 

[Ron Resnick]

Why don't more acousticians suggest MikeL's and Mark Seaton's prescription of stout, rigid exterior of Baltic birch plywood with an absorbent interior layer of common drywall or a sound absorbing model of Quietrock (i.e., EZ or 510)?

Interestingly it looks like Baltic birch plywood has a slightly higher sound absorption coefficient than drywall.

 

[Mike Lavigne]

Why don't more acousticians suggest MikeL's and Mark Seaton's prescription of stout, rigid exterior of Baltic birch plywood with an absorbent interior layer of common drywall or a sound absorbing model of Quietrock (i.e., EZ or 510)?

Interestingly it looks like Baltic birch plywood has a slightly higher sound absorption coefficient than drywall.

I had an existing, purpose built, well sized and shaped, symmetrical, measured room with (a) known problem(s) in need of a solution. I was removing huge built in bass traps and had that unfinished space to work with.

we were still making an educated guess on the cause of the problem, and therefore an educated guess on what might work.

OTOH most designers approaching a space don't really have knowledge of how the finished room will work in the bass with specific speakers ahead of time to fine tune a particular issue. it's nearly impossible to predict how structural issues might affect the bass balance.....lot's of guess work.

my point is that it's easier to fix a specific issue in an otherwise effective space than anticipate what might need to be done. so Quietrock + 3/4" ply would not be a likely choice to design in without a specific need to solve.

observe how many concert halls get built and then redone acoustically not long afterwards. they live in the space and fine tune. it's normal.

 

[microstrip]

Ron, This is a broad generalization but might help to think about it this way:
(...)
That all said, IMO this is all best evaluated by a computer modeling the math based on room dimensions, speaker and listening positions within the room to optimize the correct level of absorption, reflection and diffraction to manage room modes and reflections across the frequency spectrum so the room is flat and lively (i.e., NOT over dampened). Nyal dialed up all room dimensions, 7 helmholtz traps, 3 rpg bass plates and a bunch of strategically located absorbers and diffraction panels all on floating walls backed by mass loaded vinyl and roxul. I know I sound like a broken record but I really think you should consider reviewing your situation with somebody that can perform this kind of work. It was not more expensive than a good interconnect. Best money I have spent in this hobby.

Excellent advice, but some rooms are too irregular to be modeled with the usual CAD acoustic modelers and it seems to me Ron's room is one of them. But a quick measurement (broken record II ) will supply data enough to analyze and identify the critical issues.

Can you supply us some information on your Helmholtz traps, such as size and tuning?

 

[Hi-FiGuy]

Don't know about you Ron, but all this room stuff is giving me a headache

I say finish the room as is and set the kit up and see how it sounds and yhen adjust.
You could way overthink this spend a ton of money on drywall that weighs 200 lbs a sheet and hate it and rip it all out.
You have such an odd shaped room there is, in my opinion way to many variables to attempt to nail it on one effort.
Dont paint and finish trim until you nail the basics, who knows you might be pleasantly surprised.

 

[Ron Resnick]

I investigated the sheetrock and green glue wall treatment , double thickness plasterboard etc when doing my room.. I decide to adopt another solution

I covered all my walls with panels from acoustic solutions

http://www.acousticsolutions.co.za/

I used a 3" batten with isolated screws for wall mounting the battens and the same for the panels to the battens
I used a 1" isover rockwool of 48kg/m3 density to be behind the panels fitting into the batten gaps

The panels are made of 16 mm veneered mdf , they have slots cut into them for some diffusion/dispersion and the slots are pierced to allow sound to go thru them and be absorbed in the air gap tween them
There is some thin acoustic material behind the panels

My area of coverage is around 50m2 or 500 sq ft ..... I can reduce it by hanging artwork which will effectively block off some of the diffusion and absorption .. so you can tune the room...
If you look at the pics you can see a giant area of ceiling covered by the panels .. was removed as it was pulling the ceiling down.

The rockwool inside the airgap is low density so the room wont absorb so much as to make the room sound dead
The cost was around $100 a sq m including battens , isover stuff and installation

The net effect is amazing .. the room is very quiet now.. but not at all dead .. the treatment made the room isolate itself from the outside in that you can play real loud and the ambient noise floor in the room is very very low.

The comments folk make is how natural their voices sound but how quiet the room is.. if you walk up to the wall , your voice sounds natural till you get close and when right at the wall. your voice almost disappears , like its getting sucked in...

These are NOT bass traps , but they do resonate and the resonance gets damped , so they do remove some bass energy
They are also not broadband or specific absorbers and neither are they diffusers..albeit they do have a bit of both ..
You still have treat the room with bass traps and purpose made diffusers and absorption .. but the start point is elevated.
I use no side treatment with my speakers barring the paneled wall itself , they are far away from the walls and have a very wide dispersion hut do use tube traps and bass traps and absorptive panel behind me

The room treats the music very well , the sound is large scale and has amazing imaging..

. . .

That is a very interesting panel product, Rodney. I have never seen slotted panels like that before.

 

[Ron Resnick]

I say finish the room as is and set the kit up and see how it sounds and yhen adjust.
You could way overthink this spend a ton of money on drywall that weighs 200 lbs a sheet and hate it and rip it all out.
You have such an odd shaped room there is, in my opinion way to many variables to attempt to nail it on one effort.
Dont paint and finish trim until you nail the basics, who knows you might be pleasantly surprised.

But I have to put something on the walls (common drywall, some model of Quietrock, wood paneling) so it makes sense to try to figure out a solution which may have at least some chance of being the correct solution.

 

[Pb Blimp]

Excellent advice, but some rooms are too irregular to be modeled with the usual CAD acoustic modelers and it seems to me Ron's room is one of them. But a quick measurement (broken record II ) will supply data enough to analyze and identify the critical issues.

Can you supply us some information on your Helmholtz traps, such as size and tuning?

Micro - I checked with Nyal and he prefers I not show construction docs but you can peruse this and always reach out to him at Acoustic Frontiers.

View attachment AF Design.pdf

 

[Pb Blimp]

Rodney,

Dat room is purdy!