are there any type of adhesives to specifically be avoided with this general class of rigid insulation?
well for one, expanding foam can't always be guaranteed to fully fill all cavity shapes, and I've certainly seen some types swell unbraced thin panels - 1/8" plywood or MDF used as dividers. it can also be very messy to clean up
insulation foam sheets will be uniform thickness / density and are generally easy enough to cut with a heavy duty utility knife ( a bit messy on table saw - definitely wear a mask)
I'll try and answer as many of these Q's as I can.
The iso's we have up here are cream coloured or black. It comes with either a paper or inorganic fiberglass scrim facer. It has a lower compressive strength than XPS but will bend further before breaking because of that facer. It doesn't burn like XPS but does give off a more toxic smoke when heated. Iso has a higher initial R value per inch but is less stable long term. It starts out at about 8 per inch and after 10 years goes down to about 6 so it is usually rated at 6. XPS starts at 5 and remains fairly stable. XPS is more prone to chemical disintegration. Iso doesn't drive you crazy when you run a knife through it like XPS does. Iso is supposedly closed cell but will absorb moisture and XPS, for all intents and purposes, won't unless the initial formulation is faulty. They have similar mass. Iso you can use pretty much any type of adhesive as you are gluing the facer. With XPS you have to be careful but there are many items that can be used depending on the application. In roofing XPS is used primarily loose laid in an inverted and ballasted system. Just check the label and ask the local Home Depot dude which to use. I think the spray foam adhesives are good and so is construction adhesive.
The iso's we have up here are cream coloured or black. It comes with either a paper or inorganic fiberglass scrim facer. It has a lower compressive strength than XPS but will bend further before breaking because of that facer. It doesn't burn like XPS but does give off a more toxic smoke when heated. Iso has a higher initial R value per inch but is less stable long term. It starts out at about 8 per inch and after 10 years goes down to about 6 so it is usually rated at 6. XPS starts at 5 and remains fairly stable. XPS is more prone to chemical disintegration. Iso doesn't drive you crazy when you run a knife through it like XPS does. Iso is supposedly closed cell but will absorb moisture and XPS, for all intents and purposes, won't unless the initial formulation is faulty. They have similar mass. Iso you can use pretty much any type of adhesive as you are gluing the facer. With XPS you have to be careful but there are many items that can be used depending on the application. In roofing XPS is used primarily loose laid in an inverted and ballasted system. Just check the label and ask the local Home Depot dude which to use. I think the spray foam adhesives are good and so is construction adhesive.
Thanks for the nice summary of the foams and what they are like Cal. My impression is that isocyanurate resembles egg carton foam in texture. I am glad it has paper facers - that makes it easy to glue and work with. It probably takes paint better than bare foam. I really want to try this for my next bigger speaker build. Maybe a big MLTL with an 8 in driver or even a big tall double back facing horn.
Egg cartons are made of XPS. Iso is like that crunchy foam at the bottom of a fake flower arrangement that you stick the ends of the wires into. 
Both type of facer that I know of are not an ideal surface to paint. The fiberglass would telegraph through and the paper one is not that smooth.I don't know about the stuff in the ads you've posted, that might be different. Also if you want it to be all facer, you'll have to mitre your joints.
Both type of facer that I know of are not an ideal surface to paint. The fiberglass would telegraph through and the paper one is not that smooth.I don't know about the stuff in the ads you've posted, that might be different. Also if you want it to be all facer, you'll have to mitre your joints.
I mentioned on the other polystyrene speaker thread that Wharfedale produced a range of speakers in the 80s that had a foam core with formica outer and inner. It was a cheaper version of Celestion's aerolam cabinets which were then all the rage.
A Google may track down references. Brand new ideas are thin on the ground.
Traditionally one of the best materials for loudspeakers is sand between two thin-wall panels. Gilbert Briggs (founder of Wharfedale) did this in the 50s and there are some tables in the Colloms books giving the relative effectiveness of it compared to other materials.
A Google may track down references. Brand new ideas are thin on the ground.
Traditionally one of the best materials for loudspeakers is sand between two thin-wall panels. Gilbert Briggs (founder of Wharfedale) did this in the 50s and there are some tables in the Colloms books giving the relative effectiveness of it compared to other materials.
yes i understand that, but that is issue with HOW the user implements the foam. For me CLD MUST be 2 boxes that contact at no point other than the constrained layer. Its very difficult to achieve, hence the discussion. Cabinet bonds at 'corners' are of great importance, and achieving this with sheet foams is very difficult. This is why I believe success is easier with rubbers or green glue. Making 2 cabs that fit into each other, the inner using perf hardboard, allows venting of gas and excess material. Yes its awful stuff to clean up, thats the worst aspect.
Unfortunately, by far the best materials for such constrained layer techniques are almost impossible to aquire, and would have equally severe implementation issues. I wish I could show you guys some of the data I've had access to / worked with over the past few years (non-audio, but certain analogies to be drawn).
FWIW, I've recently started looking into some hybrid construction methods, and am currently getting quite interested in a high-mass, high stiffness front baffle with differential materials to provide a decent wavelaunch platform and grounding for a lighter, high-stiffness main carcass, braced & damped as appropriate for the box geometry, dimensions & BW. What once was old...
Pity I can't actually afford a decent set of speakers of my own.
Oh well. Maybe one day.
FWIW, I've recently started looking into some hybrid construction methods, and am currently getting quite interested in a high-mass, high stiffness front baffle with differential materials to provide a decent wavelaunch platform and grounding for a lighter, high-stiffness main carcass, braced & damped as appropriate for the box geometry, dimensions & BW. What once was old...
Pity I can't actually afford a decent set of speakers of my own.
Oh well. Maybe one day.There is no way to build a CLD speaker with complete panel isolation. The edges of the panels will have to be dado'd into corner posts.
I think that Scott is thinking along the lines of my original construction technique, at least for the baffle. Today, I would do 12mm Russian birch/Liquid Nails/cement board. The sides/back could be 6mm plywood/whatever damping material I decide on. Perhaps a few 1/2" dowels connecting sides.
Bob
I think that Scott is thinking along the lines of my original construction technique, at least for the baffle. Today, I would do 12mm Russian birch/Liquid Nails/cement board. The sides/back could be 6mm plywood/whatever damping material I decide on. Perhaps a few 1/2" dowels connecting sides.
Bob
Scott and Bob, I certainly agree that total panel isolation is unlikely within typical scopes of the ability of DIYers. Also the aim of making dissimilar baffle and panel strucures is noteworthy. I can see the validity in such an approach. My thinking is a rigid outer box (minus baffle) and an inner box. To hold the inner in place, shims or or battening at corners would be necessary (so not perfect but at least theyre located where panel deflection is least). I do not know the structure Bob is planning, so Im not trying to say x is better than y. Consistent foam density of sheet goods is the main advantage IMO, though part of me thinks thats a counter intuitive assumption re its performance. My way just seems the easiest implementation, and I like easy gypsum board and ply would certainly be worth trying (ive had good experience using that combo). Not sure what difference the cement loaded MDF ive seen, would make, other than add mass.
I will certainly be interested to see how it works out.
Scott, you cant afford decent speakers? You design enough (dont you?) and sell enough (surely?), I know the UK is rapidly turning into an economic bloodbath but im sure I earn far less lol
gypsum board and ply would certainly be worth trying (ive had good experience using that combo). Not sure what difference the cement loaded MDF ive seen, would make, other than add mass. I will certainly be interested to see how it works out.
Scott, you cant afford decent speakers? You design enough (dont you?) and sell enough (surely?), I know the UK is rapidly turning into an economic bloodbath but im sure I earn far less lol
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Foam Panels can be Permanently and V effectively Glued ... using Glidden "Gripper" Acrylic type paint primer, No fumes of note. Yess it's true... and proven.
Subsequent bond is outstanding, requiring complete panel destruction to physically seperate.. Plus the stuff seems to work without Air exposure/drying.. the achilles' heel of most foam useable glues. Do allow 48 hour time for max cure though.
Subsequent bond is outstanding, requiring complete panel destruction to physically seperate.. Plus the stuff seems to work without Air exposure/drying.. the achilles' heel of most foam useable glues. Do allow 48 hour time for max cure though.
Unfortunately, by far the best materials for such constrained layer techniques are almost impossible to aquire, and would have equally severe implementation issues. I wish I could show you guys some of the data I've had access to / worked with over the past few years (non-audio, but certain analogies to be drawn).
FWIW, I've recently started looking into some hybrid construction methods, and am currently getting quite interested in a high-mass, high stiffness front baffle with differential materials to provide a decent wavelaunch platform and grounding for a lighter, high-stiffness main carcass, braced & damped as appropriate for the box geometry, dimensions & BW. What once was old...
Pity I can't actually afford a decent set of speakers of my own.
Please could you provide extra details about this. I should be ordering my altec 604's soon and want to match them with a suitable high quality enclosure
Cabinet isolation was attempted by a Mordaunt Short design in the UK in the 1980s. The front baffle/drivers were mounted on a frame which formed the floor stand. The rest of the cabinet was mounted on it but decoupled from it.
Another technique from the University of Liverpool used wooden panels with a ceramic tile on each for stiffness. The panels were decoupled from each other with cork.
Another technique from the University of Liverpool used wooden panels with a ceramic tile on each for stiffness. The panels were decoupled from each other with cork.
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