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" <> 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=11774+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>
> > >>>>> <naturerecordists
> > >>>>> %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
> > >
> > >
> > >
> >
>
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