Quick Acoustic Verification - journey continues - AVS Forum
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post #1 of 23 Old 03-07-2012, 04:37 PM - Thread Starter
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So I started this thread in the "wrong" forum perhaps...just hoping for a final validation from a few of the experts around hear.

My question is quite simple....

As you can see I have a partially finished "theater". I have rockwool in the soffit above the seating area, mainly for sound proofing. I know I could do much more, but it is what it is.

I was going to do a few bass traps after completion, but it was suggested that perhaps I should use rockwool i.e. safe n sound in the soffits, front columns and front theater wall vs. just the R13 pink stuff I was planning.

I am not looking for sound proofing in those areas, but simply to help my acoustics.

It was suggested that the rockwool behind the drywall would be better than pink fluffy stuff.

Can any of the experience folk help me validate this. I have no problem spending the extra bucks or so at this time, but then again I HATE to waste a few hundred bucks if it is not going to help.

Thanks much!
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post #2 of 23 Old 03-07-2012, 05:00 PM
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If it's covered in drywall then it won't act as an absorber to help room acoustics. No insulation behind drywall helps the acoustic performance of the room.

Dont bother with roxul. Tests have shown that it is not superior to fiberglass for sound isolation. You should be aware that just putting insulation in the walls isn't going to soundproof your theater. Will it help a little, yes, but you'll have to look into other methods like double drywall and decoupling if you are serious about it. Also just putting it in one area (the soffit) will not help at all as the sound will just exit everywhere else. If you're going to put in insulation put it everywhere or don't bother unless it is for thermal or required by a building code.

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post #3 of 23 Old 03-07-2012, 05:05 PM
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Quote:
Originally Posted by toofast68 View Post

It was suggested that the rockwool behind the drywall would be better than pink fluffy stuff.

I think it has a slower fire spread rating so if you are anticipating a fire it would be a good choice. I would not use it as anything benefiting the theater sound.
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post #4 of 23 Old 03-07-2012, 05:11 PM - Thread Starter
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Thanks guys...looks like I could have saved a few dollars on the safe n sound, oh well...it is what it is.

OK, moving forward.

I am not really trying to soundproof this room at all, with such an open plan it is nearly impossible.

This only leaves one question...I was planning on using pink stuff in the soffits to make sure they don't become echo chambers somehow.

Is this the wrong thinking ? Should I just leave them hollow ?

Yes, I know I am far from being perfect...just trying to understand at this point to fill or leave the soffits hollow.

Thanks again gang!
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post #5 of 23 Old 03-07-2012, 05:49 PM
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Never leave an empty cavity for the reasons you stated. Fill it loosely with the cheapest insulation you can find.
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post #6 of 23 Old 03-07-2012, 06:00 PM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post

Never leave an empty cavity for the reasons you stated. Fill it loosely with the cheapest insulation you can find.

As always - THANK YOU!

Now, back to building - if I could just stay out of this forum
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post #7 of 23 Old 03-09-2012, 08:46 AM - Thread Starter
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Ok, so progress sort of...now I am even more confused.

So I contacted some "experts" to try and help me out. They gave me advice that was counter to most of what I read on this forum under the acoustical sticky.

Mainly it was around completely treating the screen wall...what I've read on this forum suggested that it is not worth it...I think I was told that it is extremely critical to do ?

HELP ?

Who do I believe....and how do I figure out what is best ?
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post #8 of 23 Old 03-09-2012, 10:31 AM
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"Completely treating the screen wall" is usually not aesthetically acceptable unless you can hide all of the treatments behind an acoustically transparent ("AT") screen. Search this forum for "minimalist screen wall" for examples.

Quote:


what I've read on this forum suggested that it is not worth it

I'm not sure I would agree that there is a broad consensus on this forum that treating the front wall is "not worth it." There are many examples of well-respected theaters -- including theaters where the acoustical plan was professionally prepared -- that use treated front walls behind an AT screen wall.

Incidentally, you might be able to get some bass trapping out of your soffits if you cover one surface adjacent to the wall or ceiling with AT fabric, instead of drywall.

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post #9 of 23 Old 03-09-2012, 11:01 AM - Thread Starter
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Ok, so I have a multi-purpose theater room, not dedicated by all means. The screen is retractable....and I have (will have) a 60" plasma for every day quickie viewing.

SO - I am fighting my wife on looks vs. function and so far she is buying in on function.

Point is - this post tells me I should KEEP ON TRYING to go for a "dedicated" screen wall to be acoustically treated...i.e. all 703 with GOM covering per say.

Also, as for the soffit as bass trap....do you mean the ones on the ceiling or the side columns ? I was plannig on treating the inside of the columns much like the front wall...with material inside and GOM on the inside wall...drywall on face and sides facing the OTHER rooms.

Does that seem like a solid plan ?
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post #10 of 23 Old 03-09-2012, 11:13 AM
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Look here for how GIK sells soffit bass traps.
You'd stuff those ceiling soffits with fluffy insulation, possible covered in 6mil plastic to not over absorb mid-hi freq, then use fabric for your HT facing sides.
http://gikacoustics.com/gik_soffit.html
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post #11 of 23 Old 03-09-2012, 12:25 PM - Thread Starter
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Mmmm...well not sure if I can convince my wife to give up the "hard soffits"...but I can try.

It won't do any good just leaving the "bottoms" with cloth and the inside/outside drywall ?

Also, what about the soffit above the seating area....what if I filled that and had GOM per say on the face of that....before someone told me that won't help, but might it ?
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post #12 of 23 Old 03-09-2012, 12:46 PM
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Quote:


...well not sure if I can convince my wife to give up the "hard soffits"...but I can try

...she gets up on a step ladder every day and checks their hardness? Just asking.

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post #13 of 23 Old 03-09-2012, 12:58 PM
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I'm no expert about bass traps but it seems like the most common viewpoint on this forum is that bass traps are most effective when located in corners -- wall-to-wall, wall-to-ceiling, etc.. Soffits fit the bill because they normally occupy a wall-to-ceiling corner.

If you have columns that are not located in corners, I don't know how effective they would be as bass traps.

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post #14 of 23 Old 03-09-2012, 01:03 PM - Thread Starter
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OK, I do have COLUMNS up front that are basically a corner with the front wall.

You can see that in this picture.
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post #15 of 23 Old 03-09-2012, 01:24 PM
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toofast68;
Can you post a basic floor plan, hard to visualize from the pictures your true HT/basement.

Will help for better feedback.
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post #16 of 23 Old 03-09-2012, 01:34 PM - Thread Starter
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for sure....hopefully this is enough :-)

If you want more, just yell.

This is the total space, plus the "theater area"

Thanks again gang for helping!
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post #17 of 23 Old 03-10-2012, 10:34 AM - Thread Starter
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Quote:
Originally Posted by Dennis Erskine View Post

...she gets up on a step ladder every day and checks their hardness? Just asking.

Funny....actually my wording wasn't great...I meant the finished look of drywall vs. fabric that with my skill set might look like crude.

However...I am thinking that I will drywall the outside and front of the columns up front. Fill them with fluffy stuff and then put GOM material on the INSIDE wall of the column. Should become a giant bass trap correct ?

Then I am still debating about the entire screen wall as well...so hopefully the pics will help generate some final guidance.
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post #18 of 23 Old 03-11-2012, 10:00 PM
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toofast68;
With your layout clearly the soffits in your layout are not ceiling/wall boundaries like in the GIK drwg, rather multiroom partition dividers.
Seems best advice is fill them with pink fluffy so they are not resonating boxes, and drywall them as your original plan.
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post #19 of 23 Old 03-12-2012, 05:45 AM - Thread Starter
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Quote:
Originally Posted by mtbdudex View Post

toofast68;
With your layout clearly the soffits in your layout are not ceiling/wall boundaries like in the GIK drwg, rather multiroom partition dividers.
Seems best advice is fill them with pink fluffy so they are not resonating boxes, and drywall them as your original plan.

OK, perfect...

I assume "treating" the theater wall with 703/GOM is still a WAY BETTER choice vs. Drywall ?

Or will my room layout mitagate the effects ?

I will post an updated picture this afternoon as well.
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post #20 of 23 Old 03-12-2012, 10:26 AM
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Having a theater space that is so open on the sides is not common on this forum. It will likely create some issues with the sound, especially surround sound. It will also be a challenge to get enough bass output to have an impact in that huge volume.

You might want to consider the effect of putting a big, reflective plasma TV in the middle of your front wall acoustic treatment.

Between the open sides and the plasma on the front wall, I'm not sure it would be worth it to treat the front wall.

Have you looked into bass shakers to augment the LFE?

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post #21 of 23 Old 03-12-2012, 11:00 AM - Thread Starter
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Quote:
Originally Posted by dwightp View Post

Having a theater space that is so open on the sides is not common on this forum. It will likely create some issues with the sound, especially surround sound. It will also be a challenge to get enough bass output to have an impact in that huge volume.

You might want to consider the effect of putting a big, reflective plasma TV in the middle of your front wall acoustic treatment.

Between the open sides and the plasma on the front wall, I'm not sure it would be worth it to treat the front wall.

Have you looked into bass shakers to augment the LFE?

In all honesty I have 2 12" subs...I am not even running them HOT...and I have plenty of bass. So I don't think I am super worried about the bass.

Also, I am newbie when it comes to acoustics...perhaps I don't know what I don't know.

I just wanted to try to the best of my ability and given the room issues...deal with the sound issues.

If making the screen wall drywall has NO IMPACT on the room, then hey my wife will be happy. Even though I have her convinced this will sound a bunch better.

Also, you are correct, I will have a 60" Plasma dead smack behind the screen....oh and the screen is not acoustically transparent...so what affect does that have in the scope of things ?
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post #22 of 23 Old 03-12-2012, 01:05 PM
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Look up SBIR, that would be one reason for treating your front wall with absorption/GOM.
From this thread http://www.avsforum.com/avs-vb/showt...0#post19947420

Quote:


I have this general suggestion for those wanting to learn about acoustics:

A) read this Acoustics/Treatment Reference Guide , via gearslutz, its a easy read in layman terms, starts you off with basics and good foundation with practical discussion. Studio acoustics and Home Theater acoustics.
From that, simple/straight forward advice via Jens Eklund:
Quote:


1. Learn how to make measurements: REW - Room EQ Wizard Home Page
Don't do anything without measurements.

2. Define your MLP (Master listening position). Confirm with measurements.
(Mike R modified for HT viewpoint)

3. Identify and treat your modal and SBIR - Speaker Boundary Interference Response related issues and educate yourself about different bass-absorbing techniques.
Other info: SBIR by Bryan Pape

4. Treat areas that otherwise creates early reflections.

5. If the room is big enough, add diffusers (but read up on how to use diffusers before going nuts).

Always base your decisions regarding different treatment, on measurements. Avoid thin porous only absorbers (including wall to wall -carpet, drapes etc.) unless a measurement indicates the need for it.

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post #23 of 23 Old 03-12-2012, 01:53 PM - Thread Starter
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mike...thank you so much.

No matter what, my mind is now set :-)

I will be treating the entire front wall.

I am sure I will revisit this thread as my build continues.

I will still post some new pics hopefully later on tonight, updating my plan.
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