Music Player Network Home Guitar Player Magazine Keyboard Magazine Bass Player Magazine EQ Magazine
Topic Options
#1646780 - 02/28/04 11:34 PM bass traps in corner with windows
HiRoller Offline
Senior Member

Registered: 08/19/02
Posts: 401
Loc: Portland, OR USA
First off, thanks and congrats to Ethan for this forum and everything else.

I'm treating an 11x11x8 bedr.. oops control room with your DIY traps/absorbers. The only problem is one back corner of the room has 2 36"x45" windows right in the corner (one on each wall). There is approximately 33" below and 12" above the windows to work with.

I was going to make a portable self-contained 2'x4' low bass trap with a 3/4" plywood panel on the back and hang it in front of the windows, but in another post on this forum you said that it needs to be secured to the wall to be effective.

The easy way out is to just buy some foam bass traps and stick them in the corner above and below the windows, but I am trying to avoid foam. Any thoughts?
_________________________
my band: Mission 5

Top
#1646781 - 02/29/04 12:02 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Roller,

> I was going to make a portable self-contained 2'x4' low bass trap <

You need a lot more than one! \:D

> you said that it needs to be secured to the wall to be effective. <

It's not that panel traps must be secured as much as they need to be placed at the room boundaries. But a window is already sort of a bass trap because it's less massive than the wall, so bass frequencies tend to pass through it.

As an exeriment, play some bass-heavy music and go outside and walk past the window. If you hear more bass leaking through when you're right outside the window, that proves some of the low frequencies are passing through. Which means you don't necessarily need a bass trap right on the window.

> The easy way out is to just buy some foam bass traps and stick them in the corner above and below the windows, but I am trying to avoid foam. <

Yes, there are better solutions than foam. I suggest you use thick dense rigid fiberglass instead of wood panel traps or foam. In a room that size you'll get excellent results from rigid fiberglass panels if you place them straddling the corners. Besides working much better than foam and to a lower frequency, rigid fiberglass is cheaper too. Though you need to cover it with fabric for appearance and to keep the fibers inside.

If you haven't yet seen my Acoustics FAQ, it's second in the list on my Articles page:

http://www.ethanwiner.com/articles.html

This article is very long, but it explains all about acoustic treatment and bass traps in plain English with no math or jargon.

--Ethan

Top
#1646782 - 02/29/04 04:11 PM Re: bass traps in corner with windows
HiRoller Offline
Senior Member

Registered: 08/19/02
Posts: 401
Loc: Portland, OR USA
Thanks for the reply.

I played some 70-100Hz sine wave test tones and stood outside the windows. It's louder in front of the windows than the walls, which is good (except for my neighbors). Inside though, there is alot of bass buildup in that corner.

Inside the room my ghetto test method for bass freq's is to play sine waves through my studio monitors and measure SPL around the room with a Radio Shack digital sound level meter.

In the non-windowed rear corner I have a 2'x4' low bass trap and 2'x4' high bass trap above it. I would have liked to do a 2'x8' trap of each but theres not enough room.

Before the traps there was approximately a 12dB increase in the corners at 70-100Hz. The traps have smoothed it out quit a bit.
_________________________
my band: Mission 5

Top
#1646783 - 03/01/04 01:16 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Roller,

> my ghetto test method for bass freq's is to play sine waves through my studio monitors <

There's nothing ghetto about that! Seriously, you're way ahead of some pro acousticians I know who do not realize the value in playing static sine waves.

--Ethan

Top
#1646784 - 03/01/04 01:49 PM Re: bass traps in corner with windows
Griffinator Offline
TPS cook & bottle washer
20k Club

Registered: 03/28/02
Posts: 20318
Loc: Lynchburg, VA, USA
Quote:
Originally posted by Ethan Winer:
Roller,

> my ghetto test method for bass freq's is to play sine waves through my studio monitors <

There's nothing ghetto about that! Seriously, you're way ahead of some pro acousticians I know who do not realize the value in playing static sine waves.

--Ethan
Cool. That's how I got my numbers on my system (and discovered an absolutely horrendous standing wave @ 400Hz in the front right corner of my room, within 4 feet of my right monitor!)

Top
#1646785 - 03/02/04 04:59 AM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
Quote:
Originally posted by Ethan Winer:
Yes, there are better solutions than foam. I suggest you use thick dense rigid fiberglass instead of wood panel traps or foam. In a room that size you'll get excellent results from rigid fiberglass panels if you place them straddling the corners. Besides working much better than foam and to a lower frequency, rigid fiberglass is cheaper too. Though you need to cover it with fabric for appearance and to keep the fibers inside.
Hey Ethan, congrats on the board. You hae been very helpful to many of us here for quite some time. You are Da' Man. (Acoustically speaking that is)

Anyway, I had seen someting about the corner traps on one of the room threads on Craigs board and I am still a bit confused.

Do you have to build a wooden frame for them?
Do you fill the entire trap space with the fiberglass or just the outside?

Would 1/2 inch plywood placed as a 45 degree angle cap in the back corners of a small room, then lined with the fiberglass have any added benefit in terms of bass absorption?

Thanks in advance.
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top
#1646786 - 03/02/04 12:50 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Jotown,

> Do you have to build a wooden frame for them? <

No. Rigid fiberglass panels placed across the room corners work well all by themselves. You'll want to do something to dress up their appearance a bit, and you need a way to attach them to the walls and/or ceiling. But any method you come up with is fine.

--Ethan

Top
#1646787 - 03/02/04 03:00 PM Re: bass traps in corner with windows
Tedly Nightshade Offline
MP Hall of Fame Member

Registered: 01/03/02
Posts: 4649
Loc: applegate,OR,UNITED STATES
I have some big windows that reflect higher frequencies too much at times- maybe it's the comb filtering that's so unpleasant?. Seems like there's a good potential for turning a window into a sound trap by covering it with a pleated curtain- I wonder what the best kind of material would be and, considering that much bass is already escaping through the windows (mine are double-glazed, actually it's pretty quiet outside), whether the pleats would really gain me anything. My windows are recessed 6" as it is.

I've had this idea for a while, is it theoretically sound? (no pun intended, but I love 'em anyway!)
_________________________
A WOP BOP A LU BOP, A LOP BAM BOOM!

"There is nothing I regret so much as my good behavior. What demon possessed me that I behaved so well?" -Henry David Thoreau

Top
#1646788 - 03/02/04 05:18 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Ted,

> I wonder what the best kind of material would be <

The thicker the better. Pleats likely help, but being recessed probably makes no difference. Even better than heavy fabric is acoustic foam, and even better than foam is rigid fiberglass.

--Ethan

Top
#1646789 - 03/02/04 07:23 PM Re: bass traps in corner with windows
Tedly Nightshade Offline
MP Hall of Fame Member

Registered: 01/03/02
Posts: 4649
Loc: applegate,OR,UNITED STATES
Quote:
Originally posted by Ethan Winer:
Ted,

> I wonder what the best kind of material would be <

The thicker the better. Pleats likely help, but being recessed probably makes no difference. Even better than heavy fabric is acoustic foam, and even better than foam is rigid fiberglass.

--Ethan
I thought maybe the space between the window and the curtain might amount to something- if I hung the curtains 6" in from the wall, there would be 1 foot between curtains and window, more in some places if the curtain was pleated. That kind of dead space ought to amount to something?
_________________________
A WOP BOP A LU BOP, A LOP BAM BOOM!

"There is nothing I regret so much as my good behavior. What demon possessed me that I behaved so well?" -Henry David Thoreau

Top
#1646790 - 03/03/04 12:10 AM Re: bass traps in corner with windows
HiRoller Offline
Senior Member

Registered: 08/19/02
Posts: 401
Loc: Portland, OR USA
Quote:
Originally posted by Jotown:
Quote:
Originally posted by Ethan Winer:
Yes, there are better solutions than foam. I suggest you use thick dense rigid fiberglass instead of wood panel traps or foam. In a room that size you'll get excellent results from rigid fiberglass panels if you place them straddling the corners. Besides working much better than foam and to a lower frequency, rigid fiberglass is cheaper too. Though you need to cover it with fabric for appearance and to keep the fibers inside.
Hey Ethan, congrats on the board. You hae been very helpful to many of us here for quite some time. You are Da' Man. (Acoustically speaking that is)

Anyway, I had seen someting about the corner traps on one of the room threads on Craigs board and I am still a bit confused.

Do you have to build a wooden frame for them?
Do you fill the entire trap space with the fiberglass or just the outside?

Would 1/2 inch plywood placed as a 45 degree angle cap in the back corners of a small room, then lined with the fiberglass have any added benefit in terms of bass absorption?

Thanks in advance.
Here is a link to Ethan's DIY bass traps:

http://www.ethanwiner.com/basstrap.html
_________________________
my band: Mission 5

Top
#1646791 - 03/03/04 01:02 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Ted,

> I thought maybe the space between the window and the curtain might amount to something <

Okay, now I see what you're getting at. Yes, that will help a little. But a curtain, even a heavy one, is not as effective as a real absorber made of rigid fiberglass.

--Ethan

Top
#1646792 - 03/03/04 02:23 PM Re: bass traps in corner with windows
Tedly Nightshade Offline
MP Hall of Fame Member

Registered: 01/03/02
Posts: 4649
Loc: applegate,OR,UNITED STATES
Quote:
Originally posted by Ethan Winer:
Ted,

> I thought maybe the space between the window and the curtain might amount to something <

Okay, now I see what you're getting at. Yes, that will help a little. But a curtain, even a heavy one, is not as effective as a real absorber made of rigid fiberglass.

--Ethan
To be specific (I see that helps!) I want to eliminate the reflections off the glass- the bass absorbtion is just gravy, but we can all use a lot of bass absorbtion.

*What kind of frequencies are reflected off of glass? Sounds to me like mostly mids and highs. That's why I thought maybe a heavy curtain could do the trick? My experiments seem to indicate yes...*

I have some windows that are candidates for a rigid fiberglass insert to be stuck in the window frame, and I'll do that with those. Others are too high to approach this way, and curtains that can be easily opened or closed are the easiest to do there.
_________________________
A WOP BOP A LU BOP, A LOP BAM BOOM!

"There is nothing I regret so much as my good behavior. What demon possessed me that I behaved so well?" -Henry David Thoreau

Top
#1646793 - 03/04/04 12:32 AM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
Quote:
Originally posted by Ethan Winer:
Jotown,

> Do you have to build a wooden frame for them? <

No. Rigid fiberglass panels placed across the room corners work well all by themselves. You'll want to do something to dress up their appearance a bit, and you need a way to attach them to the walls and/or ceiling. But any method you come up with is fine.

--Ethan
Thank you kindly, now one more dumb question. Is the rigid fiberglass you are referring to the kind that comes in rolls? And if so which brand/density do you recomend for this purpose?

Thanks in advance.
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top
#1646794 - 03/04/04 11:40 AM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Jo,

> Is the rigid fiberglass you are referring to the kind that comes in rolls? <

No, rigid fiberglass is similar to the fluffy stuff, but it's squeezed and formed to pack a large thickess down to a much thinner panel. It's not really rigid like a piece of wood - it can be bent and it holds its shape. There's a photo in the Acoustics FAQ, second in the list on my Articles page:

http://www.ethanwiner.com/articles.html

Click Rigid Fiberglass in the Table of Contents to jump to the right place.

--Ethan

Top
#1646795 - 03/05/04 08:18 PM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
Quote:
Originally posted by Ethan Winer:
Jo,

> Is the rigid fiberglass you are referring to the kind that comes in rolls? <

No, rigid fiberglass is similar to the fluffy stuff, but it's squeezed and formed to pack a large thickess down to a much thinner panel. It's not really rigid like a piece of wood - it can be bent and it holds its shape. There's a photo in the Acoustics FAQ, second in the list on my Articles page:

http://www.ethanwiner.com/articles.html

Click Rigid Fiberglass in the Table of Contents to jump to the right place.

--Ethan
And where is the best place to buy rigid fiberglass? And what grade should I ask for?
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top
#1646796 - 03/05/04 10:31 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Jo,

> And where is the best place to buy rigid fiberglass? And what grade should I ask for? <

If you'd read the FAQ as I suggested you'd already have it and be building traps. \:D

--Ethan

Top
#1646797 - 03/06/04 05:48 AM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
I have been trying to access your FAQ page all week from the link provided in this thread. It will not load. I guess I will try again.

Sorry to bother you.
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top
#1646798 - 03/06/04 05:55 AM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
I just tried to access your articles page, your faq, and http://www.ethanwiner.com from my desktop as well as my laptop. They still won't load.

Curve Dominants site loads fine and so are all the other sites I have visited this week.

Maybe your website needs some bass traps?

If I could have accessed your site I wouldn't be still asking questions.

Again sorry to bother you.
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top
#1646799 - 03/06/04 12:07 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Jo,

> I have been trying to access your FAQ page all week <

Sorry, I didn't realize you had tried. There's no problem with my web site. I check it dozens of times per day, and it has not been down. Where are you located? Maybe it's a routing problem between you and Connecticut?

Related, your avatar and signature images do not display on my computer, even though everyone else's avatars appear. So if you see them, that really proves it's a routing problem. Which neither of us can do anything about. Hopefully it will be fixed soon.

--Ethan

Top
#1646800 - 03/06/04 05:07 PM Re: bass traps in corner with windows
Ethan Winer Moderator Offline
MP Hall of Fame Member

Registered: 06/12/00
Posts: 8905
Loc: New Milford, CT, USA
Jo,

Below is the part from my Acoustics FAQ that explains rigid fiberglass and suggests how to find it.

--Ethan

Quote:
There is some confusion about the term "rigid fiberglass" because it is not really rigid like a piece of wood or hard plastic. Rather, the term rigid is used to differentiate products such as 703 from the fluffy fiberglass commonly used for home insulation. Rigid fiberglass is made of the same material as regular fiberglass, but it is compressed to reduce its size and increase its density. Rigid fiberglass that is one inch thick contains about the same amount of raw material as 6 to 12 inches of regular fiberglass. The photo below shows a piece of 703 one inch thick folded slightly. As you can see, it is rigid enough that it doesn't flop over when not supported (right side of photo), but not so rigid that it can't be bent or squeezed.

Now that you know what rigid fiberglass is, where the heck do you buy it? You probably won't find it at your local hardware store or lumber yard, but many insulation suppliers stock it or can order it. Start by looking in your telephone directory under Insulation. You can find the name of an Owens-Corning dealer near you by calling 800-GET-PINK (800-438-7465) or from the Locator page on the Owens-Corning web site. Other companies, such as Knauf, Armstrong, and Delta, make similar products, and they often cost less than fiberglass from Owens-Corning. You can contact them directly to find a distributor near you.

When assessing rigid fiberglass, it is important to know its density so you can compare equivalent products. Owens-Corning 703 has a density of about three pounds per cubic foot (45 kilograms per cubic meter), and 705 is about six pounds per cubic foot (90 kilograms per cubic meter). Therefore, products from other companies that have a similar density will have similar absorption characteristics at the same frequencies. Note that some companies call their products mineral wool, mineral fiber, or rockwool, but acoustically they are equivalent to fiberglass.

Rigid fiberglass is great stuff, and you can cut it fairly easily with a razor knife, but it's not very pleasant to work with because the fibers can make your skin itch. While handling it you should wear work gloves, and you won't be too cautious if you also wear a dust mask. The usual way to mount rigid fiberglass to a wall is with sheet rock screws and large diameter washers with a small hole, often called fender washers. These washers are needed to prevent the screw heads from pulling through the fiberglass. Fender washers are available at Home Depot and other hardware stores. If your wall is made of cement or brick, you can instead use construction glue like Liquid Nails to attach small strips of wood to the wall, and then screw the fiberglass to the strips. Since fiberglass works better when spaced away from a wall or ceiling, wood strips make sense even when you're able to screw directly into the wall.

Once the fiberglass is attached to the wall, you can build a wooden frame covered with fabric and place the frame over the fiberglass for appearance. If that's too much work, you can cut pieces of fabric and staple them to the edges of the wood strips. Nearly any porous fabric is appropriate, and one popular brand is Guilford type FR701. Unfortunately, it's very expensive. One key feature of FR701 is that it's made of polyester so it won't shrink or loosen with changes in humidity when stretched on a frame. But polyester is a common material available in many styles and patterns at any local fabric store. Another feature of FR701 is that it's one of the few commercial fabrics rated to be acoustically transparent. But since you're not using it as speaker grill cloth to place in front of a tweeter, that feature too is not necessary.

Shiny fabrics having a tight weave should be avoided because they reflect higher frequencies. The standard test for acoustic fabric is to hold it to your mouth and try to blow air through it. If you can blow through it easily, it will pass sound into the fiberglass. Burlap is one inexpensive option, but nearly any soft fabric will do nicely and will also keep the glass fibers safely in place.

Top
#1646801 - 03/07/04 08:24 AM Re: bass traps in corner with windows
Jotown Offline
MP Hall of Fame Member

Registered: 07/04/02
Posts: 4413
Loc: The Galactic Center (26 Sagit...
Thanks for the info.

I am not sure what is up with the website. I clicked on several links on threads in Craigs board and they all come up.

I will be at my ex'es today and I will try it from there.

Thanks again.
_________________________
Jotown:)

"It's all good: Except when it's Great"

Top


Moderator:  Ethan Winer