Hi Vicki,
The foam I am able to find locally is green (whatever that means!). It is c=
alled high-density foam (they also sell "regular" density, which is white),=
and although the clerks in the store had no idea about open or closed cell=
, it is absorbent like a sponge, so I guess it is open-cell. It isn't nearl=
y as dense as I expected, less so, I think, than the foam mattress pad I me=
ntioned. It is quite squishy. The 4" x 6" x 9" scrap I bought weighs 125 gr=
ams.
Could I possibly have the right thing? I can return it if I bought the wron=
g material, but how can I tell? Does anyone know?
Many thanks,
John Crockett
Westminster, Vermont
--- In vickipowys <> wrote:
>
> Hi John (& John),
>
> I looked at your link John C, all the foam they make seems to be
> white. I recall Rob Danielson found a US source that had 'High
> Density Open-cell Foam' that was dark grey in colour, the colour was
> the way of identifying the type of foam i.e. different colours for
> different types of foam. You should not need to buy a whole sheet of =
> it, there must be a foam place that will custom cut it. At one time
> Rob was sending out blocks of grey foam to anyone who wanted it.
>
> The foam you are after should not be at all heavy, I note that some
> of the more dense foams are actually quite heavy.
>
> I agree with everything John H has said about the claims made by
> Crown, I don't think anyone really quite knows what goes on. But it
> is logical that high frequency sounds would be more easily blocked by =
> the foam, than would low frequency sounds.
>
> Don't forget that the (metal) wrap around the foam also blocks
> sound. The original Crown was made of plastic but the blocking
> effect would be the same.
>
> Vicki Powys
> Australia
>
>
>
>
> On 10/07/2012, at 5:07 AM, hartogj wrote:
>
> > Hi John
> >
> > Yes, it has been discussed before on this list, but before you
> > search the archives have a look at Rob Danielson's boundary mic
> > blog at:
> > http://diystereoboundarymics.blogspot.com/
> >
> > I seem to recall a Crown description of the SASS saying that the
> > low frequencies pass around the array and through the nose in a way =
> > that sum thus boosting the low end a bit. This balances those lower =
> > frequencies with the higher frequencies that are amplified by the
> > boundary plates, and provides a flatter overall frequency
> > response. Disclaimer: I am probably not remembering that
> > accurately, and even if I am, it may have just been Crown marketing =
> > hype.
> >
> > John Hartog
> > rockscallop.org
> >
> >
> > --- In "John Crockett"
> > <jladd@> wrote:
> >>
> >> Hi Vicki
> >>
> >> That's interesting, and surprising. I, too, expected the nose foam =
> >> to be more dense. I am currently using about a 4cm thick piece of
> >> the #1 foam on top of the mic capsules as a wind baffle, and it
> >> seems to be pretty much acoustically transparent. Is the nose
> >> baffle only attenuating some frequencies, or none at all? Is it
> >> thick enough that it separates the channels even though it is
> >> fairly transparent?
> >>
> >> I guess what I am using in my prototype (my foam #4) is probably
> >> low or medium density closed cell foam. I guess, but I don't know! =
> >> It is not absorbent, it is fairly but not extremely rigid, and the =
> >> cells are large. Lots of air space, but the plastic cell walls are =
> >> fairly rigid. And I added some cardboard around that to create
> >> even more separation between the two channels. I rather like the
> >> image it produces (airplane noise aside), which is what matters in =
> >> the end, but it sounds like that is not the intent of the Crown
> >> SASS. What is the theory? What is acoustically separating those
> >> two omni capsules?
> >>
> >> If this has all been explained in detail somewhere, can you
> >> provide a link to that discussion?
> >>
> >> Unfortunately I am not aware of any foam supply stores anywhere in =
> >> New England. I've tried searching online and I'm just not sure
> >> what I am looking for. This is the sort of thing I find online:
> >>
> >> http://www.onlinefabricstore.net/specialty-stores/automotive-store/
> >> automotive-upholstery-padding-and-supplies/automotive-upholstery-
> >> foam/open-cell-foam/high-density-open-cell-foam.htm?N=3D11774
> >> +4294963398
> >>
> >> This looks a lot like my foam #2 - the mattress foam, but it's
> >> hard to tell looking at pictures online. Is this what I want?
> >>
> >> I wish someone could send me a tiny sample of the right stuff so I =
> >> know what it looks and feels like. Then I could go to a fabric and =
> >> upholstery store and see if they have it. Please contact me off
> >> list if that is possible! I'll pay postage!
> >>
> >> Many thanks! (Sorry for all the exclamation marks but I am truly
> >> grateful to everyone who contributes to this fascinating and
> >> informative group).
> >>
> >> John
> >>
> >> --- In vickipowys <vickipowys@>
> >> wrote:
> >>>
> >>> John,
> >>>
> >>> You would need to go to a foam supply store, rather than a building
> >>> store. In Australia we have Clark Rubber chain stores who
> >>> specialize
> >>> in foam, not sure who does in US.
> >>>
> >>> You can tell if it is open cell if the foam absorbs water like a
> >>> sponge.
> >>>
> >>> The idea in the original SASS design is that some sound can pass
> >>> through the open-cell foam. However I know of several people
> >>> who, in
> >>> misunderstanding the SASS design, have built the front 'nose' out of
> >>> something solid e.g. closed cell foam or balsa-wood. And the sounds
> >>> samples I have heard are just great, so perhaps it does not matter
> >>> hugely.
> >>>
> >>> I would say that your number 1) would be most like the open-cell
> >>> foam
> >>> used for the nose of the original SASS.
> >>>
> >>>
> >>> Vicki Powys
> >>> Australia
> >>>
> >>>
> >>>
> >>> On 09/07/2012, at 7:01 AM, John Crockett wrote:
> >>>
> >>>> If I can re-open this thread,
> >>>>
> >>>> I'm still unclear about exactly what high-density open-cell foam
> >>>> is. My local building supply store hasn't a clue.
> >>>>
> >>>> I have several types of foam lying around the house.
> >>>>
> >>>> 1) One is very soft and pliable, like the foam windscreens that
> >>>> come with most microphones. It came as packing material.
> >>>>
> >>>> 2) Another is a bit denser and thicker, the sort of foam that is
> >>>> used for mattresses.
> >>>>
> >>>> 3) Then we have what in the USA is called blue board. This is a
> >>>> very dense, small cell, rigid foam that comes in sheets of various
> >>>> thicknesses and is used for building insulation (we have some left
> >>>> over from insulating our cellar). Sort of similar to styrofoam.
> >>>>
> >>>> 4) Finally I have sort of an odd thing that came as cushioning
> >>>> material in a box with an electronic device. It is rigid, like the
> >>>> blue board, but the cells are much larger than that in the blue
> >>>> board and therefore it is a bit springy when pressed. It is not as
> >>>> rigid as styrofoam.
> >>>>
> >>>> 5) Oh, and somewhere I have a block of stiff, small-celled foam
> >>>> that is used to go between a kayak or canoe and the roof of the
> >>>> car.
> >>>>
> >>>> Are any of these "high-density, open-cell" foam? If not, what does
> >>>> this creature look and feel like?
> >>>>
> >>>> I built a prototype sass array using EM172 capsules, and #4 above
> >>>> for the nose baffle, and it works well as far as I can tell, but
> >>>> for the real thing (built for AT3032 mics), I'd like to get it
> >>>> right.
> >>>>
> >>>> Many thanks!
> >>>>
> >>>> John
> >>>>
> >>>> John Crockett
> >>>> Westminster, Vermont
> >>>>
> >>>> --- In Peter Shute <pshute@>
> >>>> wrote:
> >>>>>
> >>>>> I made it to Clark Rubber tonight, and sure enough it wasn't as I
> >>>>> expected. According to this store, high density foam comes in
> >>>>> colours, and acoustic foam is grey and only 2" thick.
> >>>>>
> >>>>> Then I spotted a light grey scrap in a bin, exactly the size I
> >>>>> wanted, but twice as long. It felt like the acoustic foam, so I
> >>>>> think it's the right stuff. They weren't sure what it was and
> >>>>> thought a customer had left it behind after bringing a piece in
> >>>>> for cutting, and let me have it for $3.
> >>>>>
> >>>>> There's something a bit disturbing about an industry that's
> >>>>> inconsistent about what it calls its products.
> >>>>>
> >>>>> Peter Shute
> >>>>>
> >>>>>
> >>>>> --------------------------
> >>>>> Sent using BlackBerry
> >>>>>
> >>>>> ________________________________
> >>>>> From:
> >>>>> To:
> >>>>> Sent: Tue Feb 28 10:17:03 2012
> >>>>> Subject: Re: [Nature Recordists] Re: Foam for SASS
> >>>>>
> >>>>>
> >>>>>
> >>>>> Peter,
> >>>>>
> >>>>> re filling inside of SASS box - well I've overcome that problem by
> >>>>> making my SASSes out of solid blocks of closed-cell foam (it's
> >>>>> lighter weight too) - see my website. If you've made a wooden SASS
> >>>>> you could fill the gap with closed cell foam.
> >>>>>
> >>>>> Vicki
> >>>>>
> >>>>> On 28/02/2012, at 9:08 AM, Peter Shute wrote:
> >>>>>
> >>>>>> Excellent, if I can tell by colour then they can't trick me. It
> >>>>>> sounds pretty cheap, so I'll get enough for future experiments.
> >>>>>>
> >>>>>> Can you recommend what to fill the inside of the box with?
> >>>>>>
> >>>>>> Peter Shute
> >>>>>> ________________________________
> >>>>>> From: <naturerecordists%
> >>>>>> 40yahoogroups.com>
> >>>>>> <naturerecordists%
> >>>>>> 40yahoogroups.com>] On Behalf Of vickipowys
> >>>>>> Sent: Tuesday, 28 February 2012 8:54 AM
> >>>>>> To: <naturerecordists%
> >>>>>> 40yahoogroups.com>
> >>>>>> Subject: Re: [Nature Recordists] Re: Foam for SASS
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> Yes Peter, Clark Rubber call their stuff 'high density foam'
> >>>>>> and it
> >>>>>> is grey in colour (as opposed to medium density foam which
> >>>>>> comes in
> >>>>>> many colours). The acoustic foam is black. My nearest Clarks used
> >>>>>> to be at Bathurst (2 hours away) but they closed and now I
> >>>>>> have to
> >>>>>> get it via mail order from Dubbo where they can never cut it
> >>>>>> straight. I agree Clark's website is pretty useless. If you
> >>>>>> can get
> >>>>>> Clarks to cut it in blocks around the size you want, you can then
> >>>>>> taper the sides according to Rob's specifications, using a razor
> >>>>>> knife with a new blade extended all the way out. And tidy up
> >>>>>> the cut
> >>>>>> surfaces with a little piece of fine sandpaper.
> >>>>>>
> >>>>>> Vicki
> >>>>>>
> >>>>>> On 28/02/2012, at 8:17 AM, Peter Shute wrote:
> >>>>>>
> >>>>>>> Thanks, Vicki. You mean the one they're calling high density but
> >>>>>>> which isn't acoustic foam? If that works then it would be better
> >>>>>>> not to have to glue it.
> >>>>>>>
> >>>>>>> It's a pity I can't see the stuff on their web site before I go
> >>>>>>> there, or even just order it online to save myself the
> >>>>>>> trouble, but
> >>>>>>> the web site is a mess. A search for high density foam takes
> >>>>>>> me to
> >>>>>>> anything but what I expect to see.
> >>>>>>>
> >>>>>>> Peter Shute
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> From: <naturerecordists%
> >>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>> 40yahoogroups.com>
> >>>>>>> <naturerecordists=
> >>>>>>> %
> >>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>> 40yahoogroups.com>] On Behalf Of vickipowys
> >>>>>>> Sent: Tuesday, 28 February 2012 8:06 AM
> >>>>>>> To: <naturerecordists%
> >>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>> 40yahoogroups.com>
> >>>>>>> Subject: Re: [Nature Recordists] Re: Foam for SASS
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> Peter,
> >>>>>>>
> >>>>>>> I have always used the grey high-density foam from Clark Rubber,
> >>>>>>> which is fairly close in texture to the original foam that
> >>>>>>> was used
> >>>>>>> in the Crown SASS design. And you won't have to glue either.
> >>>>>>>
> >>>>>>> Vicki
> >>>>>>>
> >>>>>>> On 28/02/2012, at 7:28 AM, Peter Shute wrote:
> >>>>>>>
> >>>>>>>> Good enough for me then. I'll try to get there tonight and get
> >>>>>>>> some
> >>>>>>>> of the acoustic foam.
> >>>>>>>>
> >>>>>>>> The plans also say to fill the void with "dense absorptive
> >>>>>>>> material
> >>>>>>>> like rubber backed carpet padding". Does that mean similar
> >>>>>>>> material
> >>>>>>>> to that used for the baffle? I.e. can I just get a bit more
> >>>>>>>> of it
> >>>>>>>> to put in there?
> >>>>>>>>
> >>>>>>>> Peter Shute
> >>>>>>>>
> >>>>>>>> ________________________________
> >>>>>>>> From: <naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com>
> >>>>>>>> <naturerecordist=
> >>>>>>>> s
> >>>>>>>> %40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com>] On Behalf Of hartogj
> >>>>>>>> Sent: Tuesday, 28 February 2012 7:19 AM
> >>>>>>>> To: <naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com>
> >>>>>>>> Subject: [Nature Recordists] Re: Foam for SASS
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Hi Peter,
> >>>>>>>> The open cell foam in the nose baffle is part of the original
> >>>>>>>> Crown
> >>>>>>>> SASS design, and that design has proven good for natural
> >>>>>>>> soundscape
> >>>>>>>> recording. I think the reason for sticking with the open cell
> >>>>>>>> design is mostly for the sake of consistency. Some low
> >>>>>>>> frequencies
> >>>>>>>> will pass through the foam nose, some frequencies are absorbed,
> >>>>>>>> and
> >>>>>>>> some will be reflected. The qualities of these transitions will
> >>>>>>>> depend on the specific material used.
> >>>>>>>>
> >>>>>>>> John Hartog
> >>>>>>>> rockscallop.org
> >>>>>>>>
> >>>>>>>> --- In
> >>>>>>>> <naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com><naturerecordists%
> >>>>>>>> 40yahoogroups.com>, Peter Shute <pshute@> wrote:
> >>>>>>>>>
> >>>>>>>>> I'm building a SASS array to Rob Danielson's design (https://
> >>>>>>>>> pantherfile.uwm.edu/type/www/audio-reports/
> >>>>>>>>> BoundaryMicExperiments/
> >>>>>>>>> images/PBB2N-Plans_SASS-LikeDimensionsSept2010.gif), and I
> >>>>>>>>> have
> >>>>>>>>> some questions about the foam used for the nose (baffle?)
> >>>>>>>>>
> >>>>>>>>> The plans say to use high-density open-celled foam, and I
> >>>>>>>>> don't
> >>>>>>>>> know how to identify the stuff. I rang the local supplier
> >>>>>>>>> (Clark
> >>>>>>>>> Rubber, which Australians would know), and they said they
> >>>>>>>>> can cut
> >>>>>>>>> a piece for a few dollars. But when I mentioned what it was =
> >>>>>>>>> for,
> >>>>>>>>> they said it would be better to use acoustic foam, which
> >>>>>>>>> doesn't
> >>>>>>>>> cost much more.
> >>>>>>>>>
> >>>>>>>>> They said it's similar, but denser. It also comes in thinner
> >>>>>>>>> sheets, so I'd have to glue two pieces together.
> >>>>>>>>>
> >>>>>>>>> Will it be better. Does it even matter?
> >>>>>>>>>
> >>>>>>>>> If the aim of the foam is to block sound from the other
> >>>>>>>>> side, why
> >>>>>>>>> open cell? Does it work better for that?
> >>>>>>>>>
> >>>>>>>>> Sorry if these are basic questions, I don't know anything
> >>>>>>>>> about
> >>>>>>>>> foams, their acoustic properties, and how this array works.
> >>>>>>>>>
> >>>>>>>>> Peter Shute
> >>>>>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> ------------------------------------
> >>>>
> >>>> "While a picture is worth a thousand words, a
> >>>> sound is worth a thousand pictures." R. Murray Schafer via Bernie
> >>>> Krause.
> >>>>
> >>>> Yahoo! Groups Links
> >>>>
> >>>>
> >>>>
> >>>
> >>
> >
> >
> >
> >
> > ------------------------------------
> >
> > "While a picture is worth a thousand words, a
> > sound is worth a thousand pictures." R. Murray Schafer via Bernie
> > Krause.
> >
> > Yahoo! Groups Links
> >
> >
> >
>
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