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Dedicated Theater Design & Construction > Acoustical Treatments Master Thread
BlakeN's Avatar BlakeN 11:24 PM 07-23-2009
Sorry if this has been asked before but after reading +50 pages and some searching my eyes are killing me.

Does anyone have any links to lower wall treatment construction using something like Insul-Shield?

I am not familiar with that material can you just cover it in GOM or does it need a frame.

Thanks

Ethan Winer's Avatar Ethan Winer 12:07 PM 07-24-2009
However you can get absorbing materials in the right places is fine. But covering the very bottom of the side walls is not useful unless you're using very thick materials. In that case you're making bass traps, not reflection absorbers.

Reflections occur at specific places, and those are where the treatment should go. Much more here:

Early Reflections
How to set up a room

--Ethan
KERMIE's Avatar KERMIE 01:42 PM 07-24-2009
Ethan,

Is really the main reason for NOT doing the bottom half is the risk of making the room too dead or is there much more at risk here?
Ethan Winer's Avatar Ethan Winer 03:00 PM 07-24-2009
^^^ Well, mostly it's just a waste because little sound reflects off the walls down that low.

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan
allredp's Avatar allredp 03:16 PM 07-24-2009
Quote:
Originally Posted by Ethan Winer View Post

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan

Hey Ethan,

Great help as usual!

Could you give some parameters of "small" rooms?

My room is 27' x 15' x 8' - does that qualify for small?

Thanks much.
pepar's Avatar pepar 09:19 PM 07-24-2009
Quote:
Originally Posted by allredp View Post

Hey Ethan,

Great help as usual!

Could you give some parameters of "small" rooms?

My room is 27' x 15' x 8' - does that qualify for small?

Thanks much.

"a room the size you'll find in most homes"
Dennis Erskine's Avatar Dennis Erskine 07:49 AM 07-25-2009
Quote:


Could you give some parameters of "small" rooms?

If you move 2' and the sound changes, it's a small room. Your room will be a small room.
Franin's Avatar Franin 07:51 AM 07-25-2009
Quote:
Originally Posted by Ethan Winer View Post

^^^ Well, mostly it's just a waste because little sound reflects off the walls down that low.

However, I prefer a room to be more toward dead anyway, at least if the room is on the small side. Small room ambience sounds pretty bad, and it covers up the good larger ambience that's generally present in good recordings. So for a room the size you'll find in most homes, having it on the dead side actually makes the music sound larger and more lifelike.

--Ethan

I was just going to ask the same question regarding making a room dead. My bottom half of the wall has Carpet and Underlay which is divided by skirting( actually it was more aesthetic purposes). I have the room treatments in place which were placed by a certified HAA ( these guys specialize in room treatments and room calibrations over here in Western Australia). I was going to cover the top half of the walls with Acoustic wall tiles to deadned the room. Do you think that is wise decision or is there other products to use.

These are ones im talking about:
Quote:


Fonic Acoustic Tiles are specially designed and tested to improve the frequency response and decay time of mid to high frequencies in Recording Studios, Home Theatres and Public spaces. They are typically used on walls and ceilings at reflection points to reduce interference and flutter echoes.


Ethan Winer's Avatar Ethan Winer 11:23 AM 07-25-2009
Quote:
Originally Posted by Franin View Post

My bottom half of the wall has Carpet and Underlay ... I was going to cover the top half of the walls with Acoustic wall tiles to deadned the room.

That's not a good idea because you don't want or need to make all of the walls absorbent. Not only is that much surface coverage not a good idea, but the materials you propose are not thick enough. The general goal in room treatment is to have decay times that are more or less uniform across the audible range. Thin materials absorb only higher frequencies. So the room is too dead sounding and the bass still rattles around and is boomy etc. The graph below is from my recent video Hearing is Believing, showing how extensive diffusion, coupled with absorption, helps make the decay times more uniform.

--Ethan
LL
Dennis Erskine's Avatar Dennis Erskine 11:38 AM 07-25-2009
Ethan is not entirely correct, nor is he entirely incorrect either. There are two purposes for the use of absorption in a playback space. One is to solve direct acoustical issues. For example, SBIR when speakers are near a boundary, back reflections from an AT screen, or, in some cases, to knock down the effect of early reflections (usually diffusion is more useful). In this case, the placement of the absorptive treatments becomes part and parcel of their performance.

The second reason is to reduce the overall reverberation time in the room. In this case, the position of the absorptive material is less important than its very presence in the room. For this purpose, ear height and below would work.

In actual practice, you may absolutely want absorptive materials to stay out of early reflection points. An example would be the use of diffusors to expand sound stage width, depth or to enhance the surround channels. At the same time, absorption needs to be placed in the room to reduce reverberation time. This would be a real case where absorptive panels in less than obvious locations is required.
Franin's Avatar Franin 12:45 PM 07-25-2009
Quote:
Originally Posted by Ethan Winer View Post

That's not a good idea because you don't want or need to make all of the walls absorbent. Not only is that much surface coverage not a good idea, but the materials you propose are not thick enough. The general goal in room treatment is to have decay times that are more or less uniform across the audible range. Thin materials absorb only higher frequencies. So the room is too dead sounding and the bass still rattles around and is boomy etc. The graph below is from my recent video Hearing is Believing, showing how extensive diffusion, coupled with absorption, helps make the decay times more uniform.

--Ethan

Thank you for your response I will leave it as it is then.
allredp's Avatar allredp 07:08 PM 07-25-2009
Quote:
Originally Posted by pepar View Post

"a room the size you'll find in most homes"

Caught that in Ethan's original post, but wondered if there were some general parameters for "small" like cubic feet, etc. But, thanks for the reply.

Quote:
Originally Posted by Dennis Erskine View Post

If you move 2' and the sound changes, it's a small room. Your room will be a small room.

Ah, that makes sense in practice. It is true, at least of bass in my room.

Thanks for the clarifications, though I'm still curious if there are some numbers to put to "small" or "large" which would help establish whether a room should be damped-down vs. left more natural.
nathan_h's Avatar nathan_h 11:26 PM 07-25-2009
When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.
KERMIE's Avatar KERMIE 10:37 AM 07-26-2009
Two Questions:

1. What makes a good "membrane" to cover corner bass traps in the rear

2. Why do you use it on the bottom of walls (like FSK)?
erkq's Avatar erkq 10:53 AM 07-26-2009
Quote:
Originally Posted by nathan_h View Post

When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.

Ha, ha! Not always. I had a buddy (lifestyles too different to maintain friendship) who build a 3 story concert hall with a replica of some old-school European pipe organ as part of his ranch house. It was the darndest thing to walk from a nice, but definitely NOT McMansion house into this incredibly ornate concert hall. Stanford used his facilities for a while after the Loma Prieta earthquake damaged their organ recital hall.
pepar's Avatar pepar 11:16 AM 07-26-2009
Quote:
Originally Posted by erkq View Post

Ha, ha! Not always. I had a buddy (lifestyles too different to maintain friendship) who build a 3 story concert hall with a replica of some old-school European pipe organ as part of his ranch house. It was the darndest thing to walk from a nice, but definitely NOT McMansion house into this incredibly ornate concert hall. Stanford used his facilities for a while after the Loma Prieta earthquake damaged their organ recital hall.

Well now, that *would* be a concert hall then, wouldn't it?
Ethan Winer's Avatar Ethan Winer 11:19 AM 07-26-2009
Quote:
Originally Posted by Dennis Erskine View Post

The second reason is to reduce the overall reverberation time in the room. In this case, the position of the absorptive material is less important than its very presence in the room. For this purpose, ear height and below would work.

Good point Dennis, ands this brings up a related issue. In my experience treating "normal" furnished rooms, there's less need for overall reverb reduction. Once absorption has been placed at the reflection points, and in corners for bass trapping, that's often enough. But you are correct that all treatment is not necessarily position-specific.

--Ethan
allredp's Avatar allredp 11:45 PM 07-26-2009
Quote:
Originally Posted by nathan_h View Post

When talking about acoustics: Large room = concert hall.

Small room = anything you'd find in a home, even a McMansion.

Well I certainly don't have a McMansion, eh! Thanks.
Weasel9992's Avatar Weasel9992 08:57 AM 07-28-2009
Quote:
Originally Posted by allredp View Post

Caught that in Ethan's original post, but wondered if there were some general parameters for "small" like cubic feet, etc. But, thanks for the reply.

Everest says 2500Ft3. Dennis' answer was the right one from a practical standpoint though.

Frank
eiger's Avatar eiger 09:57 AM 07-28-2009
All -

Does anyone have experience with the panels from Ready Acoustics? Quality?

On their website I see "ReadyTraps" panels and "Chamelon C2" panels. Both of these are for mid to high frequencies. The ReadyTraps are significantly cheaper and looks like you can get a bundle.

Anyone know the differences between these models? I'm looking to address my side and front walls so guessing this is the right area I need to be looking if I'm not planning DIY components.

Posted my room configuration a couple pages back. Thx!
nathan_h's Avatar nathan_h 01:36 PM 07-28-2009
Quote:
Originally Posted by eiger View Post

All -

Does anyone have experience with the panels from Ready Acoustics? Quality?

On their website I see "ReadyTraps" panels and "Chamelon C2" panels. Both of these are for mid to high frequencies. The ReadyTraps are significantly cheaper and looks like you can get a bundle.

Anyone know the differences between these models? I'm looking to address my side and front walls so guessing this is the right area I need to be looking if I'm not planning DIY components.

Posted my room configuration a couple pages back. Thx!



After reviewing the test data and materials from both, I compared the price of the roughly equivalent models from Ready Acoustics and GIK Acoustics and chose GIK. Before I completed my purchase, however, I took them up on their offer of a free phone consultation to discuss my room and needs (based on photos I sent them). That was very helpful in terms of getting the most impact for the limited budget I had.

But Ready Acoustics has some DIY options, and some construction methods that GIK doesn't offer. So it's not a easy question to answer.

I've also used Real Traps in my room and found the construction/fit/finish to be superior to the competition. It was, however, a little too "industrial" looking for the lady of the house. If you factor in re-sale value, and/or like the solid look, Real Traps is worth considering.

I think all of these (and some other) reputable brands will give you good results, if you intelligently choose which products you buy, and if you carefully select their placement in your home for the right impact.
Ictusbrucks's Avatar Ictusbrucks 11:21 AM 07-29-2009
Quote:
Originally Posted by erkq View Post

Prices are very approximate... from memory... just to give you an idea. This stuff is pretty cheap.

I use:

1. Room EQ Wizard is free and GREAT! I run it on Windoze.

2. LinearX M31 calibrated mic. Comes with it's calibration curve you can enter into Room EQ Wizard if you want. About $100

3. Behringer MiniMIC modeling mic pre-amp. I don't use any of the modeling settings, of course. It was just a nice cheap mic pre-amp with an analog VU meter. It's good to 6Hz! About $89

4. Then I got an M-Audio Transit to get the pre-amp output into the laptop's USB port and Room EQ Wizard's test tones into the audio system. About $50

5. Last, I use Behringer's Feedback Destroyer Pro to adjust out those bothersome "humps". It's a multi-band parametric eq that works extremely well for tuning sub-woofers. About $99


Hi erkq/Pepar,

Sorry to bug you about this again but I just finally ran some measurements last night with my Galaxy CM140 SPL meter and REW using my Laptop.

Unfortunately my laptop only has a Mic in... no line in. So I dont thinnk the curves I got mean much, as its only saying ~45-50db until I hit the 1khz range, then it gets to the 75db area. And this is with my subwoofer turned up to room-shaking levels. And I did calibrate things to the proper level beforehand.


But I am still confused about what the M-Audio Transit does. In the quoted post you said you're going Mic-Preamp-> Transit -> USB.

So would the M-Audio transit allow me to bypass the laptops soundcard somehow? Or do I need to lug down my desktop machine to get a line input?

What Pepar said in this post seems to contradict what erkq said:

Quote:
Technically, no actually, you are using the line in and line out of the "soundcard." The mic's preamp does not pug into a mic input; it goes into the line input. Line output goes to the device/channel being tested.


pepar's Avatar pepar 11:31 AM 07-29-2009
Quote:
Originally Posted by Ictusbrucks View Post

Hi erkq/Pepar,

Sorry to bug you about this again but I just finally ran some measurements last night with my Galaxy CM140 SPL meter and REW using my Laptop.

Unfortunately my laptop only has a Mic in... no line in. So I dont thinnk the curves I got mean much, as its only saying ~45-50db until I hit the 1khz range, then it gets to the 75db area. And this is with my subwoofer turned up to room-shaking levels. And I did calibrate things to the proper level beforehand.


But I am still confused about what the M-Audio Transit does. In the quoted post you said you're going Mic-Preamp-> Transit -> USB.

So would the M-Audio transit allow me to bypass the laptops soundcard somehow? Or do I need to lug down my desktop machine to get a line input?

Thanks!
Ryan

I picked up an M-Audio MobilePre USB on ebay for ~$80. Not familiar with the Transit, but a quick visit to their site suggests that it might work. With the stereo line in and stereo line out - as opposed to discrete connectors for each channel - you need to look at your 3-pole-to-whatever adapter to make sure that you are using the same channel for both in and out.

Yes, any measurements you made with your laptop sound are throwaways. Onboard laptop audio solutions lack the necessary bi-directionality which is why external "soundcards" are needed. I know that there are Firewire interface units, but most use USB. Firewire is more "pro" and that usually means it is more sophisticated and more $$$.

If you are using a mic preamp in addition to the USB soundcard, the mic preamp needs to plug into a line input. One of the reasons I bought the MobilePre USB is so that I could plug a mic into the mic input and do away with the mic's preamp. I've just learned that I am not supposed to do that, but that is another subject entirely and is unrelated to your question.
Ictusbrucks's Avatar Ictusbrucks 11:36 AM 07-29-2009
Quote:
Originally Posted by pepar View Post

With the stereo line in and stereo line out - as opposed to discrete connectors for each channel - you need to look at your 3-pole-to-whatever adapter to make sure that you are using the same channel for both in and out.


Thanks for the reply.

Do you mean making sure that both in/out are using L or R??

I am planning on doing everything at just 1/8" mini. I have a Mini-to-RCA cable so I have separate L and R cables going into the receiver.

Do you still think I need a separate adapter or could I just reverse the RCA cables if it doesn't work? And to be clear, is this a 'works or doesn't work' thing, or are we talking about innacurate measurements?

Also not sure exactly what a 3-pole adapter is, I couldn't find it on google, only standard Y adapters. Are you talking about something that would separate stereo into separate L/R channels? Do they even make that for mini?
Ictusbrucks's Avatar Ictusbrucks 11:39 AM 07-29-2009
Quote:
Originally Posted by pepar View Post

If you are using a mic preamp in addition to the USB soundcard, the mic preamp needs to plug into a line input.



Nope, no preamp for me since I am using an SPL meter... Am I confused? Do I still need a preamp with a Galaxy Cm140 SPL meter?
pepar's Avatar pepar 11:43 AM 07-29-2009
Quote:
Originally Posted by Ictusbrucks View Post

Thanks for the reply.

Do you mean making sure that both in/out are using L or R??

I am planning on doing everything at just 1/8" mini. I have a Mini-to-RCA cable so I have separate L and R cables going into the receiver.

Do you still think I need a separate adapter or could I just reverse the RCA cables if it doesn't work? And to be clear, is this a 'works or doesn't work' thing, or are we talking about innacurate measurements?

Also not sure exactly what a 3-pole adapter is, I couldn't find it on google, only standard Y adapters. Are you talking about something that would separate stereo into separate L/R channels? Do they even make that for mini?

For using measuring software like REW, pick Left or Right, and use that channel's input and that channel's output. If you have mono 1/8" minis, then they will only use one of the channels - I forget if it is left or right - so you won't need to do anything else but plug in. If your minis go to left and right RCA phono plugs, you do need to pick a channel to use.

Mono 1/8" minis are 2-pole ("tip-and-sleeve" in old jargon - two circuits, one hot and one ground), stereo minis are 3-pole ("ring, tip-and-sleeve" - three circuits, one left, one right and one ground).
pepar's Avatar pepar 11:46 AM 07-29-2009
Quote:
Originally Posted by Ictusbrucks View Post

Nope, no preamp for me since I am using an SPL meter... Am I confused? Do I still need a preamp with a Galaxy Cm140 SPL meter?

Then you have a line level output and need to plug into a line level input. There is a preamp built into the SPL meter.
Ethan Winer's Avatar Ethan Winer 12:40 PM 07-29-2009
Quote:
Originally Posted by nathan_h View Post

I've also used Real Traps in my room and found the construction/fit/finish to be superior to the competition. It was, however, a little too "industrial" looking for the lady of the house. If you factor in re-sale value, and/or like the solid look, Real Traps is worth considering.

Thanks very much Nathan. In case you're not aware, we have some newer products that are more "spouse friendly" than our usual panels, including a bass traps disguised as a large planter.

--Ethan
Ictusbrucks's Avatar Ictusbrucks 07:04 PM 07-29-2009
Just FIY: I got the Creative SB X-Fi USB soundcard and worked with REW without even installing the drivers. It was the only decent one that BestBuy had in stock so I took a chance and it seems fine.

It didn't specify whether it was full duplex or not, but it did work with REW. However, my baby daughter was sleeping so I had to do the measurement at super-low-volume. Even so, the results look better than before using the laptop's mic input. I'll probably have to wait until this weekend to take measurements at the right volume though.
KERMIE's Avatar KERMIE 07:59 PM 07-29-2009
My neighbor insists that these louvered shutters from an old barn house that was torn down work very well as diffusers.

he has about 8-10 of them across the back half of the room on his ceiling and back wall. They are on top of 1" rigid fiberglass and all covered in black GOM. I have not been in a room of his size with or without them to compare. I think it sound good but...

he used them because they were free and it only took up 2" of total depth

every other one is opened (angled) forward/backward, up/down depending on ceiling or back wall.



any thoughts
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