Sign in with
Sign up | Sign in
Your question

acoustic foam mounting options

Last response: in Home Audio
Share
Anonymous
March 1, 2005 7:36:21 PM

Archived from groups: rec.audio.pro (More info?)

I'm attempting to convert a poor sounding room (10 x12 box with plaster
stucco walls, plastered ceiling and wood floor) into a useable space to
take some of my work home with me. I intend to do some pre-production,
editing and non-critical mixing tasks here - but right now the room is
infuriating. Serious flutter echoes and big bass buildup (especially
in the rear). First step is I've acquired 48, 12"x12"x4" thick wedge
tiles. I understand that by placing them off the wall I allow
absorbtion to take place on the way in and back out. Anyone found a
simple, inexpensive method of mounting these types of tiles with a gap
behind them? How much of a gap? Also, in the future these tiles will
be taken to a new location - so any adhesive that leaves them in chunks
when I dismantle this system is out of the question. Thanks for your
input.

Dan Fox
Anonymous
March 2, 2005 12:38:42 AM

Archived from groups: rec.audio.pro (More info?)

"Daniel Fox" wrote...
....
> I understand that by placing them off the wall I allow
> absorbtion to take place on the way in and back out. Anyone found a
> simple, inexpensive method of mounting these types of tiles with a gap
> behind them? How much of a gap?

Dunno about spacing out from the wall, but...

> Also, in the future these tiles will be taken to a new location -
> so any adhesive that leaves them in chunks when I dismantle this
> system is out of the question.

I just installed 64 sq ft of Sonex in a temporary location. I used
2 1/2 inch drywall screws and big ("fender") washers on about
12 inch centers. Should be completely removable leaving only
small holes that can be patched.
Anonymous
March 2, 2005 7:20:01 AM

Archived from groups: rec.audio.pro (More info?)

offpeak808 wrote:
> Is this the same Bob Ross who worked at Fantasy and recorded me in
92? We
> did that cool track "Definately not jazz" and put that Bo Diddly beat
in
> "Iko Iko."


Uh...I don't think so. In 1992 I was working mostly out of a Brooklyn
studio called Andersound. Also did some freelancing in Manhattan
studios but frankly I barely remember their names, Fantasy doesn't seem
familiar.

On the other hand, "Definitely Not Jazz" sure sounds like the sort of
piece I would've been involved with!∆
Related resources
Anonymous
March 2, 2005 7:29:47 AM

Archived from groups: rec.audio.pro (More info?)

Richard Crowley wrote:
> "Daniel Fox" wrote...
> ...
> > I understand that by placing them off the wall I allow
> > absorbtion to take place on the way in and back out. Anyone found
a
> > simple, inexpensive method of mounting these types of tiles with a
gap
> > behind them? How much of a gap?
>
> Dunno about spacing out from the wall, but...
>

To quote the Bible ...er, I mean, F. Alton Everest's Master Handbook of
Acoustics, "the absorption of porous materials is much greater with
an airspace between the material and the wall." And elsewhere he writes
"Low-frequency absorption can also be improved by spacing the absorbent
out from the wall...Spacing 1-inch material out 3 inches makes its
absorption approach that of the 2-inch material."

The ASTM even has designations for how acoustic absoption is mounted on
a surface that indicate whether or not it is spaced off the surface.
Anonymous
March 2, 2005 12:26:08 PM

Archived from groups: rec.audio.pro (More info?)

"Daniel Fox" <upryz1@gmail.com> wrote in message
news:1109723780.971612.110600@f14g2000cwb.googlegroups.com...
> I'm attempting to convert a poor sounding room (10 x12 box with plaster
> stucco walls, plastered ceiling and wood floor) into a useable space to
> take some of my work home with me. I intend to do some pre-production,
> editing and non-critical mixing tasks here - but right now the room is
> infuriating. Serious flutter echoes and big bass buildup (especially
> in the rear). First step is I've acquired 48, 12"x12"x4" thick wedge
> tiles. I understand that by placing them off the wall I allow
> absorbtion to take place on the way in and back out. Anyone found a
> simple, inexpensive method of mounting these types of tiles with a gap
> behind them? How much of a gap? Also, in the future these tiles will
> be taken to a new location - so any adhesive that leaves them in chunks
> when I dismantle this system is out of the question. Thanks for your
> input.
>
> Dan Fox

My foam panels are attached directly to the wall with drywall screws and
large rubber fender washers as another poster suggested. However, were I to
redo it, I think this approach has more advantages. I would construct a 2
foot by four foot frame of 3/8 inch plywood cut into two or three inch wide
strips. I would staple a sturdy wire cloth to the frame, which would keep
the frame from distorting diagonally. I would put 3/8" weather strip on the
frame opposite the wire cloth to cushion the frame against the wall. I'd
mount the foam by sewing it to the wire cloth, which would put the foam two
or three inches away from the wall. Then, I'd hang the units like pictures
on the wall. Cheap. Easy to construct. Totally portable. And only two
holes in the wall required per unit. Then, after making the first one, I
fix whatever didn't work like it thought it would and make the rest ;-)

Steve King
Anonymous
March 2, 2005 4:17:22 PM

Archived from groups: rec.audio.pro (More info?)

Is this the same Bob Ross who worked at Fantasy and recorded me in 92? We
did that cool track "Definately not jazz" and put that Bo Diddly beat in
"Iko Iko."
March 2, 2005 7:28:51 PM

Archived from groups: rec.audio.pro (More info?)

"offpeak808" <offpeak808@hotmail.com> writes:
>Is this the same Bob Ross who worked at Fantasy and recorded me in 92? We
>did that cool track "Definately not jazz" and put that Bo Diddly beat in
>"Iko Iko."

The "Fanatasy" Bob Ross is an old bud from Detroit --- he was the keyboardist
for the band Brainstorm (they had a hit in the discos) though IIRC he had
studied horn as a kid. He's an EXCELLENT musician/writer/arranger.

I've lost touch since I left Cal, but I heard he went independent after
Fantasy -- and was still working on the coast --- maybe down around LA.
Anonymous
March 2, 2005 10:40:41 PM

Archived from groups: rec.audio.pro (More info?)

Bob Ross wrote:
> "Low-frequency absorption can also be improved by spacing the absorbent
> out from the wall...Spacing 1-inch material out 3 inches makes its
> absorption approach that of the 2-inch material."

That will extend the lowest frequency that it can absorb, but may reduce
the absorption at higher frequencies. For smooth wideband absorption, I
believe keeping the air gap no bigger than the thickness of the material
is a good rule of thumb, but I haven't done the maths.

--
Anahata
anahata@treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
Anonymous
March 2, 2005 11:51:57 PM

Archived from groups: rec.audio.pro (More info?)

anahata wrote:
> Bob Ross wrote:
> > "Low-frequency absorption can also be improved by spacing the
absorbent
> > out from the wall...Spacing 1-inch material out 3 inches makes its
> > absorption approach that of the 2-inch material."
>
> That will exten d the lowest frequency that it can absorb, but may
reduce
> the absorption at higher frequencies. For smooth wideband absorption,
I
> believe keeping the air gap no bigger than the thickness of the
material
> is a good rule of thumb, but I haven't done the maths.
>

Then what are you basing this conjecture on? See Everest, especially
Figure 9-9, Figure 9-14, Figure 9-16, and Figures 9-35 compared to
9-36. In all of these examples the absorption coefficiant at 1kHz and
4kHz (as well as, obviously, at low frequencies) is higher the farther
from the wall the material is spaced..
March 3, 2005 1:34:28 AM

Archived from groups: rec.audio.pro (More info?)

I just bought some 3 inch acoustic foam tiles a la Auralex to put on the
sheetrock ceiling. Any good advice to install it without messing too
much with my landlord's ceiling? Thanks.
Krubb

anahata a écrit:
> Bob Ross wrote:
>
>> "Low-frequency absorption can also be improved by spacing the absorbent
>> out from the wall...Spacing 1-inch material out 3 inches makes its
>> absorption approach that of the 2-inch material."
>
>
> That will extend the lowest frequency that it can absorb, but may reduce
> the absorption at higher frequencies. For smooth wideband absorption, I
> believe keeping the air gap no bigger than the thickness of the material
> is a good rule of thumb, but I haven't done the maths.
>
Anonymous
March 3, 2005 1:15:13 PM

Archived from groups: rec.audio.pro (More info?)

In article <422685C4.8040700@videotron.ca> prodmac@videotron.ca writes:

> I just bought some 3 inch acoustic foam tiles a la Auralex to put on the
> sheetrock ceiling. Any good advice to install it without messing too
> much with my landlord's ceiling?

Buy the building.

Glue them to sheets of 1/4" plywood, then hang the plywood from the
ceiling using picture frame wire and eye hooks screwed into plastic
anchors. That will leave just small holes that are easy to spackle
over when you move out. If you glue the tiles to the ceiling, you'll
never get them off cleanly.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
March 3, 2005 1:43:28 PM

Archived from groups: rec.audio.pro (More info?)

Bob Ross wrote:
> Then what are you basing this conjecture on?

The theory is that you get optimum absoption when there's material at a
quarter wavelength from the wall (maximum air velocity at that point)
and a dip in absorption at twice that frequency where the material-wall
distance is half a wavelength (pressure peak instead of velocity peak).
I'm not making it up - I think I read it on Ethan Winer's site but
wherever it was it makes sense to me.

But I'm happy to be proved wrong...

> See Everest,
[...] In all of these examples the absorption coefficiant at 1kHz and
> 4kHz (as well as, obviously, at low frequencies) is higher the farther
> from the wall the material is spaced..

Just goes to show that as usual in acoustics the exceptions seem to
carry more weight than the rules :-)

--
Anahata
anahata@treewind.co.uk -+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827
Anonymous
March 4, 2005 10:40:10 AM

Archived from groups: rec.audio.pro (More info?)

David Grant wrote:

> Unfortunately you chose to purchase foam which is more expensive,
possibly
> flammable, and usually less effective than OC703 rigid fibreglass. If
you do
> further treatment I suggest you consider this.

This is only a first step. Next will be to build some winer-style
traps with 703.
>
> My recommendation would be to mount (glue?) these tiles on thin 2'x4'
MDF
> panels. You'd need 6 tiles per panel, so you'd get 8 panels with 48
tiles.

Hmmm. If I mount the tiles on MDF (or plywood for that matter) then
wouldn't the whole concept go out the window because the rear
absorptive surface of the tile is covered by the board? The waves
would just pass through the foam, bounce off the board they are mounted
on and go back out with no air gap in the picture... Correct me if i'm
wrong.

Dan
Anonymous
March 4, 2005 1:26:49 PM

Archived from groups: rec.audio.pro (More info?)

"Daniel Fox" <upryz1@gmail.com> wrote in message
news:1109723780.971612.110600@f14g2000cwb.googlegroups.com...
> I'm attempting to convert a poor sounding room (10 x12 box with plaster
> stucco walls, plastered ceiling and wood floor) into a useable space to
> take some of my work home with me. I intend to do some pre-production,
> editing and non-critical mixing tasks here - but right now the room is
> infuriating. Serious flutter echoes and big bass buildup (especially
> in the rear). First step is I've acquired 48, 12"x12"x4" thick wedge
> tiles. I understand that by placing them off the wall I allow
> absorbtion to take place on the way in and back out. Anyone found a
> simple, inexpensive method of mounting these types of tiles with a gap
> behind them? How much of a gap?

If you're targeting specific frequencies then you can calculate the air gaps
based on the wavelength of these frequencies.

If you need broadband absorption, which I almost guarantee is the case for a
room that size, then the best thing to do is to mount your absorbing
material diagonally across the corners of your room. This provides a varying
air gap - small where the material meets the wall and large at the center of
the material - and hence gives good absorption across a range of
frequencies.

Unfortunately you chose to purchase foam which is more expensive, possibly
flammable, and usually less effective than OC703 rigid fibreglass. If you do
further treatment I suggest you consider this.

My recommendation would be to mount (glue?) these tiles on thin 2'x4' MDF
panels. You'd need 6 tiles per panel, so you'd get 8 panels with 48 tiles.
Hang the panels from heavy duty picture hangers, strattling the corners
which your ear tells you need absorption most desperately. I'd actually
suggest only making 6 panels, and use the remaining 12 tiles to absorb first
reflections coming off your side walls and ceiling.

See Ethan Winer's acoustics FAQ at http://www.ethanwiner.com/acoustics.html

Take it from me it's a worthwhile read if you're serious about creating a
good sounding small room.

Cheers,

Dave
Anonymous
March 4, 2005 1:41:39 PM

Archived from groups: rec.audio.pro (More info?)

"David Grant" <NO_SPAM_PLEASE_jmd_2003@msn.com> wrote in message
news:V6%Vd.8895$RM2.2930@read1.cgocable.net...
>
> "Daniel Fox" <upryz1@gmail.com> wrote in message
> news:1109723780.971612.110600@f14g2000cwb.googlegroups.com...
> > I'm attempting to convert a poor sounding room (10 x12 box with plaster
> > stucco walls, plastered ceiling and wood floor) into a useable space to
> > take some of my work home with me. I intend to do some pre-production,
> > editing and non-critical mixing tasks here - but right now the room is
> > infuriating. Serious flutter echoes and big bass buildup (especially
> > in the rear). First step is I've acquired 48, 12"x12"x4" thick wedge
> > tiles. I understand that by placing them off the wall I allow
> > absorbtion to take place on the way in and back out. Anyone found a
> > simple, inexpensive method of mounting these types of tiles with a gap
> > behind them? How much of a gap?
>
> If you're targeting specific frequencies then you can calculate the air
gaps
> based on the wavelength of these frequencies.
>
> If you need broadband absorption, which I almost guarantee is the case for
a
> room that size, then the best thing to do is to mount your absorbing
> material diagonally across the corners of your room. This provides a
varying
> air gap - small where the material meets the wall and large at the center
of
> the material - and hence gives good absorption across a range of
> frequencies.
>
> Unfortunately you chose to purchase foam which is more expensive, possibly
> flammable, and usually less effective than OC703 rigid fibreglass. If you
do
> further treatment I suggest you consider this.
>
> My recommendation would be to mount (glue?) these tiles on thin 2'x4' MDF
> panels. You'd need 6 tiles per panel, so you'd get 8 panels with 48 tiles.
> Hang the panels from heavy duty picture hangers, strattling the corners
> which your ear tells you need absorption most desperately. I'd actually
> suggest only making 6 panels, and use the remaining 12 tiles to absorb
first
> reflections coming off your side walls and ceiling.
>
> See Ethan Winer's acoustics FAQ at
http://www.ethanwiner.com/acoustics.html
>
> Take it from me it's a worthwhile read if you're serious about creating a
> good sounding small room.
>
> Cheers,
>
> Dave

P.S the MDF obviously faces towards the corner.
Anonymous
March 4, 2005 5:45:50 PM

Archived from groups: rec.audio.pro (More info?)

> Hmmm. If I mount the tiles on MDF (or plywood for that matter) then
> wouldn't the whole concept go out the window because the rear
> absorptive surface of the tile is covered by the board? The waves
> would just pass through the foam, bounce off the board they are mounted
> on and go back out with no air gap in the picture... Correct me if i'm
> wrong.
>
> Dan

You're somewhat right. However I believe most (if not all) the frequencies
that you will be targeting with these absorbers ("bass traps") will pass
through the MDF. To reflect low frequencies you need substantial mass (like
a wall) so MDF shouldn't be a problem. You just need to make sure the
backing is sturdy but not too heavy. If you wish to use the tiles to absorb
mid to high frequencies you won't want any backing on them, but for a room
that size bass will usually be your biggest problem.
Anonymous
March 5, 2005 1:09:54 PM

Archived from groups: rec.audio.pro (More info?)

Dave,

> I believe most (if not all) the frequencies that you will be targeting
with these absorbers ("bass traps") will pass through the MDF. To reflect
low frequencies you need substantial mass (like a wall) so MDF shouldn't be
a problem. <

It's difficult to contradict someone who was so nice in recommending my
Acoustics FAQ! But in fact MDF is quite massive, and even MDF that's "only"
half an inch thick will reflect enough to negate the air gap. Even much
thinner materials like 1/8 inch wood or Masonite should be avoided there.

--Ethan
Anonymous
March 5, 2005 2:37:51 PM

Archived from groups: rec.audio.pro (More info?)

"Ethan Winer" <ethanw at ethanwiner dot com> wrote in message
news:o 7SdnWbrSONZVrTfRVn-rQ@giganews.com...
> Dave,
>
> > I believe most (if not all) the frequencies that you will be targeting
> with these absorbers ("bass traps") will pass through the MDF. To reflect
> low frequencies you need substantial mass (like a wall) so MDF shouldn't
be
> a problem. <
>
> It's difficult to contradict someone who was so nice in recommending my
> Acoustics FAQ! But in fact MDF is quite massive, and even MDF that's
"only"
> half an inch thick will reflect enough to negate the air gap. Even much
> thinner materials like 1/8 inch wood or Masonite should be avoided there.
>
> --Ethan

Hi Ethan, thanks for the correction, but I'm somewhat confused. My
understanding was that such materials were virtually unreflective at low
frequencies, hence they could be modeled as not existing at low frequencies.
How much reflection constitutes "enough" to negate the air gap? More
importantly, can you give any qualitative description of how absorption at
low frequencies varies with backing mass; does absorption go down sharply
with the slightest addition of backing mass? Would the OP not at least get
some benefit from doing things this way?

Dave
Anonymous
March 5, 2005 5:27:52 PM

Archived from groups: rec.audio.pro (More info?)

Well, not to contradict anyone here, but MDF, as a working material, is
dense enough at 3/4" that it requires two people to handle it. Now as a
young man I worked in custom kitchen cabinets and 3/4" marine plywood
weighed in at 90 lbs per 4X8 foot sheet, which I carried over my head, and
MDF is HEAVIER than that. It's very good at containing sounds within a
room, which certainly suggests highly reflective characteristics at LF
ranges, so it's not something I'd use for a bass trap. I believe Ethan's
website shows this by the materials he already suggests.

For soundproofing a room, particularly with 2 1/2" sheets and Z channel, it
would be great, but the room itself wouldn't sound nice. Or, more
appropriately, the room would still require much assistance at sounding
nice.

--


Roger W. Norman
SirMusic Studio
http://blogs.salon.com/0004478/

"David Grant" <NO_SPAM_PLEASE_jmd_2003@msn.com> wrote in message
news:AflWd.5948$If1.1059046@read2.cgocable.net...
>
> "Ethan Winer" <ethanw at ethanwiner dot com> wrote in message
> news:o 7SdnWbrSONZVrTfRVn-rQ@giganews.com...
> > Dave,
> >
> > > I believe most (if not all) the frequencies that you will be targeting
> > with these absorbers ("bass traps") will pass through the MDF. To
reflect
> > low frequencies you need substantial mass (like a wall) so MDF shouldn't
> be
> > a problem. <
> >
> > It's difficult to contradict someone who was so nice in recommending my
> > Acoustics FAQ! But in fact MDF is quite massive, and even MDF that's
> "only"
> > half an inch thick will reflect enough to negate the air gap. Even much
> > thinner materials like 1/8 inch wood or Masonite should be avoided
there.
> >
> > --Ethan
>
> Hi Ethan, thanks for the correction, but I'm somewhat confused. My
> understanding was that such materials were virtually unreflective at low
> frequencies, hence they could be modeled as not existing at low
frequencies.
> How much reflection constitutes "enough" to negate the air gap? More
> importantly, can you give any qualitative description of how absorption at
> low frequencies varies with backing mass; does absorption go down sharply
> with the slightest addition of backing mass? Would the OP not at least get
> some benefit from doing things this way?
>
> Dave
>
>
Anonymous
March 6, 2005 1:04:56 PM

Archived from groups: rec.audio.pro (More info?)

David,

> My understanding was that such materials were virtually unreflective at
low frequencies <

You didn't state a thickness for the MDF so I assumed at least 1/2 inch. I
cannot tell you exactly how reflective 1/2 inch MDF is at various low
frequencies, but I'm pretty sure it reflects down to 50 Hz or lower. The
real issue is how much it reflects, since all materials reflect at least a
little. Even 1/8 inch masonite reflects at 100 Hz.

> How much reflection constitutes "enough" to negate the air gap? <

That's a great question and I have not tested this. I have seen data for
sheet rock, which is "in the ballpark" with MDF, and that is very reflective
at low frequencies.

> does absorption go down sharply with the slightest addition of backing
mass? <

In order to know for sure you or I or someone else would have to build a
bunch of panels with different thicknesses and test them all. Last year I
measured rigid fiberglass with a heavy cardboard backing, and even that was
enough to screw up the absorption a little.

Something similar came up recently at the Sound on Sound forum when it was
suggested that a window to the outside gives some amount of bass trapping
because it reflects low frequencies less than sheet rock. The problem is
this is very difficult to measure, especially below 100 Hz.

One of these days I hope to test this using the ETF software and a subwoofer
to measure the comb filtering off a large glass door. My plan is to measure
the door open, with glass (closed), and also with sheet rock stacked in
front of the door. Its a huge pain to do that, which is why I haven't done
that yet. :-(

--Ethan
!