Distance to the wall

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Distance to the wall

Postby archive » Mon Apr 12, 2004 3:43 am

From: "Jose Ramon San Juan" <sanjuanjr@x????xxx.xxx
Date: Fri Jan 14, 2000 9:41 pm
Subject: Distance to the wall

I've read somewhere about the convenience of leaving a free space between the
wall or ceiling and the absoption boards but I can't find this now. Can
somebody help me? Does it depend on the thickness of the board or on the
frequencies we want to reduce?
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Postby archive » Mon Apr 12, 2004 3:43 am

From: SRF7@x??x.xxx
Date: Sat Jan 15, 2000 1:37 am
Subject: Re: Distance to the wall

In a message dated 1/14/00 6:29:49 PM Eastern Standard Time,
sanjuanjr@r... writes:

> I've read somewhere about the convenience of leaving a free space between
the >wall or ceiling and the absorption boards but I can't find this now. Can
somebody >help me?

Maybe

>Does it depend on the thickness of the board

Yes

>or on the frequencies we want to reduce?

Yes

The bottom line is that an absorptive material works better hung off the
wall. Better at what frequency you ask. Well, .. that depends, the nature
of the material determines what sounds pass thru the material and the nature
of the cavity formed by its offset aspect determine this micro-spaces
acoustic properties .. then there is the question of what will pass back thru
and back into your room.

Simply stated, a 4" panel of 703 absorbs a good deal more if hung off the
wall, the further, the better, and the shape of the cavity behind the panel
will define the frequency at which the cavity resonates (sucks up more sound
... the bigger the lower the freq.). For broadband absorption a variable
depth cavity (like a panel across a corner will be effective (because the
depth in variable) across a broad range of freq.s

Hope this helps

Scott R. Foster
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Postby archive » Mon Apr 12, 2004 3:44 am

From: Jon Best <jrbest@e...>
Date: Sun Jan 16, 2000 3:30 pm
Subject: Re: Digest Number 66

Actually, this kind of brings up something I still don't really have straight
in my head- what are the pros/cons/differences between hanging some absorption
set away from the wall with the space behind it closed off vs. with the space
behind it open on the
sides? i.e., a free-hanging piece of 703 or equivalent that you can pass your
hand behind, or a boxed in, deep frame fronted with the same 703 in the same
relation to the wall?

Jon Best
Sales Weasel From Mars
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Postby archive » Mon Apr 12, 2004 3:44 am

From: john/blackcabin <blackcabin@x????xxx.xxxx
Date: Sun Jan 16, 2000 4:55 pm
Subject: Re: Digest Number 66

Jon Best wrote:
>
> From: Jon Best <jrbest@e...>
>
> Actually, this kind of brings up something I still don't really have straight
in my head- what are the pros/cons/differences between hanging some absorption
set away from the wall with the space behind it closed off vs. with the space
behind it open on the
> sides? i.e., a free-hanging piece of 703 or equivalent that you can pass
your hand behind, or a boxed in, deep frame fronted with the same 703 in the
same relation to the wall?

And while on the subject (sorta)...

1) What are the pros/cons to stuffing a box type absorber with batts
of fiberglas ?

2) Would one stuff said absorber regardless of the material used for
the baffle ie. "703", plywood/masonite, etc?

3) What are the pros/cons to using a fiberglas (loose or ridgid)
product with a paper or foil backing ?

4) Should the backing be installed adjacent to the wall or the
baffle ?

john
--
the little house that rocks
www.blackcabin.com
931-358-0114

"All rock musicians and soundmen are deaf in some form or fashion. No
one can do these jobs for a living for many years without frying
something out."
- Tommy Womack from the "Cheese Chronicles" -
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Postby archive » Mon Apr 12, 2004 3:44 am

From: "Mucha, Kevin S (Kevin)" <kmucha@l...>
Date: Mon Jan 17, 2000 3:45 pm
Subject: RE: Distance to the wall

On a somewhat related note I would like to comment that I have just
had very pleasant results utilizing a panel resonator at my place. I was
having large problems with airline noise leaking in. I filled a cavity at
the peak of my ceiling with 4" 703 (some air space allowed as well) and then
sealed a layer of masonite below to form a triangle and it worked remarkably
well. Actually became evident how much sound loss I was losing through my
entrance door. Looks like I'll need to add another to form a mini sound
lock.

Kevin Mucha
Coerce Recording Services
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Postby archive » Mon Apr 12, 2004 3:45 am

From: SRF7@a...
Date: Mon Jan 17, 2000 5:49 pm
Subject: Re: Digest Number 66

In a message dated 1/16/00 11:54:38 PM Eastern Standard Time,
blackcabin@m... writes:

> And while on the subject (sorta)...
>
> 1) What are the pros/cons to stuffing a box type absorber with batts
> of fiberglas ?
>
> 2) Would one stuff said absorber regardless of the material used for
> the baffle ie. "703", plywood/masonite, etc?

Stuffing broadens the Q (effective range) of the absorber .. if you are
trying to address a single peak, a unstuffed resonator would be better. I
wish someone would supply formulae for a "honeycomb" box as alluded to by a
prior poster to the list ... as I recall he described a unit much like a
speaker box with throated ports which could be tuned by port size and depth
for very narrow Q's. An intriguing idea ... interesting to consider however
that with a tight Q you will actually increase the reverb time of the target
frequency (the box will store then reemit the captured frequency). This
would be reduced by a stuffed box, but that would broaden the Q ... I guess
you really can't buy a free lunch.

>
> 3) What are the pros/cons to using a fiberglas (loose or ridgid)
> product with a paper or foil backing ?

The backing acts as an absorptive diaphragm which can be helpful if the
resonant freq. of the backing is a target frequency ... if the resonant freq.
of the backing is a hi-Q target freq. then turn the backing toward the room,
if not then turn the backing away (or even better save money by buying
un-backed batts and use the savings to buy thicker batts, or beer.

> 4) Should the backing be installed adjacent to the wall or the
> baffle ?

depends ... see above ... the resonant frequency of paper backed R-11 was
quoted in this list several weeks ago, but I'm not sure if I recall ... seems
it was about 250 Hz, but don't rely on my memory.

Scott R. Foster
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Postby archive » Mon Apr 12, 2004 3:45 am

From: "Jose Ramon San Juan" <sanjuanjr@r...>
Date: Tue Jan 18, 2000 2:28 am
Subject: Distance to the wall

Hello, Scott. Thanks for your advice, very helpful as always. I think that you
must to know that finally I made the salomonic division of my room that you
recommended. :-))
But now I have another question, more specific, about the same subject. The
stuff I have bought seems to be very efficient with the low frequencies placed
at 60 mm to the wall (0,15 at 63Hz; 0,5 at 125 and 0,98 at 250 and 500) Can I
improve these coefficients by increasing the distance? Is it worth?
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Postby archive » Mon Apr 12, 2004 3:46 am

From: Dan Nelson <dprimary@e...>
Date: Tue Jan 18, 2000 3:41 am
Subject: Re: Distance to the wall

Generally if you increase the distance the low frequency absorption is
increased. What material is it? you will probably will get greater low
frequency absorption by increasing the thickness of the material than by
increasing the space behind it. Don't forget about the low frequency
absorption of any
drywall in the room as well.

Did you have an attached drawing or spec sheet ? The list doesn't allow
attachment but if you email it to me at dan@s... I can post it on the
studiotips site.

Dan Nelson
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Postby archive » Mon Apr 12, 2004 3:48 am

From: "Jose Ramon San Juan" <sanjuanjr@r...>
Date: Tue Jan 18, 2000 4:15 pm
Subject: Distance to the wall

----- Original Message -----
From: Jose Ramon San Juan <rsanjuan@r...>
To: <acoustics@o...>
Sent: Tuesday, January 18, 2000 5:01 PM
Subject: RE: [acoustics] Distance to the wall

> Generally if you increase the distance the low frequency absorption is
> increased. What material is it? you will probably will get greater low
> frequency absorption by increasing the thickness of the material than by
> increasing the space behind it. Don't forget about the low frequency
> absorption of any
> > drywall in the room as well.
>
> I can't increase the thickness because the stuff is modulated. If curious
> you can see Ipakell W and Ipakell B-201 at
> http://www.acusticaint.com/Absorb.htm
>
> > Did you have an attached drawing or spec sheet ? The list doesn't allow
> attachment but if you email it to me at dan@s... I can post it
on
> the studiotips site.
>
> I am sending to you two gifs refferring to the absorption coefficients of
> Ipakell B-201
> (kell 201gf.gif) and Ipakell W (kellwgf.gif). The first explain the
> differences related to the distance to the wall.
>
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Postby archive » Mon Apr 12, 2004 3:50 am

From: Dan Nelson <dprimary@e...>
Date: Tue Jan 18, 2000 5:37 pm
Subject: Re: Distance to the wall

I have posted the absorption coefficients to the file area, the link below
will also take you to the manufacturer.
I would say that increasing the space to 120mm would increase the low
frequency absorption about .75- .8 I would call the manufacturer and see if
they know they may have more data.

Dan Nelson
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Postby archive » Mon Apr 12, 2004 3:51 am

From: "Jose Ramon San Juan" <sanjuanjr@r...>
Date: Tue Jan 18, 2000 7:40 pm
Subject: RE: Distance to the wall

> From: Dan Nelson <dprimary@e...>
>
> I have posted the absorption coefficients to the file area, the link below
> will also take you to the manufacturer.
> I would say that increasing the space to 120mm would increase the low
> frequency absorption about .75- .8 I would call the manufacturer and see
if
> they know they may have more data.

Sorry, Dan, but I don't understand what you mean by .75 -8. What frequencies
will be affected anyway?

Jose Ramon San Juan
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Postby archive » Mon Apr 12, 2004 3:52 am

From: Dan Nelson <dprimary@e...>
Date: Tue Jan 18, 2000 9:36 pm
Subject: Re: Distance to the wall

Sorry about that, I forgot half the sentence. Now that I look at it again it
looks like it would increase the 125hz absorption coefficient to 6-.7 sabins
judging how much increases based upon the amount the low frequency absorption
increased at each increase of spacing on the graph. But still it is just an
estimate and the manufacturer may have more information. This is for the
Ipakell B-201 for the other one I don't know.

Dan Nelson
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Postby archive » Mon Apr 12, 2004 3:52 am

From: SRF7@a...
Date: Wed Jan 19, 2000 2:56 am
Subject: Re: Distance to the wall

In a message dated 1/17/00 9:58:11 PM Eastern Standard Time,
sanjuanjr@r... writes:

<< The stuff I have bought seems to be very efficient with the low
frequencies placed at 60 mm to the wall (0,15 at 63Hz; 0,5 at 125 and 0,98 at
250 and 500) Can I improve these coefficients by increasing the distance? Is
it worth?
>>

What is the stuff?

Whats the stuff for?

I'm lost ( not really news for those who know me, but it seemed worth
mentioning)

Scott R. Foster
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