And reading the thread again my posts were unnecessary, not much knowledge on the stuff 
well, hopefully provokes reading and thinking for all
Reading a bit, and thinking a bit thin sheets should work fine as well. Thick layer in the middle why not, performance seems to depend on materials, thicknesses, sizes and what not, even temperatures, which is luckily rather constant on home loudspeakers. In practice one could do some experiments and find most effective solution. For example, if panels aren't resonating audibly from the get go there is no need to stress about it. Or, if one has to make light weight box then its probably something to take very serious about. Or, if the application is such that panel resonances are obvious. Perhaps I don't know the magnitude of the stuff, which would be interesting to make tests on.
Quick review on papers and some products let me believe the damping effect can be optimized for some bandwidth. I could imagine a panel on a speaker cabinet would have some main resonance, the most audible one. It probably changes with bracing, size of the panel, and one could probably target the damping for it. If we assume this main audible resonance was already somehow not very audible, out of band perhaps then the optimization process would be kind of extra work without too much benefit. If it was smack on audible then yeah.
Its very easy to hear difference in a knuckle test though. Not sure if it means there is audible difference with the speaker playing, haven't compared / measured side by side. Making a box traditionally and then slapping some panels in is easy, and makes knuckle test difference. Using thin metals and rubber and all that, perhaps better but already quite much work and would perhaps justify multiple configuration experiments for given application, to find out what actually works best, dampen the worst offender, or reduce weight / cost / work / something to optimum.
well, hopefully provokes reading and thinking for all Reading a bit, and thinking a bit thin sheets should work fine as well. Thick layer in the middle why not, performance seems to depend on materials, thicknesses, sizes and what not, even temperatures, which is luckily rather constant on home loudspeakers. In practice one could do some experiments and find most effective solution. For example, if panels aren't resonating audibly from the get go there is no need to stress about it. Or, if one has to make light weight box then its probably something to take very serious about. Or, if the application is such that panel resonances are obvious. Perhaps I don't know the magnitude of the stuff, which would be interesting to make tests on.
Quick review on papers and some products let me believe the damping effect can be optimized for some bandwidth. I could imagine a panel on a speaker cabinet would have some main resonance, the most audible one. It probably changes with bracing, size of the panel, and one could probably target the damping for it. If we assume this main audible resonance was already somehow not very audible, out of band perhaps then the optimization process would be kind of extra work without too much benefit. If it was smack on audible then yeah.
Its very easy to hear difference in a knuckle test though. Not sure if it means there is audible difference with the speaker playing, haven't compared / measured side by side. Making a box traditionally and then slapping some panels in is easy, and makes knuckle test difference. Using thin metals and rubber and all that, perhaps better but already quite much work and would perhaps justify multiple configuration experiments for given application, to find out what actually works best, dampen the worst offender, or reduce weight / cost / work / something to optimum.
My hero speakerdesigner Albert Von Schweikert (R:I.P) wrote about this in 2009 when he study the problem.
https://www.audiocircle.com/index.php?topic=70291.0
https://www.audiocircle.com/index.php?topic=70291.0
Plus the bending of the side-walls ;-)Exactly that have i done, both on 80mm front baffle and 50mm side "baffle"
Regarding the cld layer, the visco part is most important.
@jawen , is it mdf on chipwood ? Works fine ? I remember my Kef 104/2 were made of chipboard as well... but the mdf front bafle for MTM section. they quite disseapered sonically in the room. Very quiet cabinet.
Wonder also about OSB and internal shear between sheets. SUre it is not elastic but wonder if it happens at very low frequencies where the force is max due to WL of bass driver radiation.
Wonder also about OSB and internal shear between sheets. SUre it is not elastic but wonder if it happens at very low frequencies where the force is max due to WL of bass driver radiation.
Yes its mdf glued on chipwood, and mdf, mdf, glue, chipwood on front baffle.
Haven´t come that far yet to test it "full out", but its like a "Panzarwagon".....Weight is not so funny however hahaha.
152 cm in high, 68 cm wide and 61 cm deep ( topp is 17 cm x 31 cm, 2 walls in pyramidshape )
Weight 150 kg each
, so sandwich cabinette is not all "for the good".
There is a point with weigth at remembering Planet10 's input : weigth is lowering the resonance of the cabinet you want at the opposit upper in the midrange.
Stiff front baffle made of denser HDF or doubled ply seems to work fine, while the bottom and sides could be thinner (and braced but not so the front bafle) ! SO coupliing of a thick and heavy front bafle seems the best way with big bass drivers.
Me who xant to try faceted cabinet, I do not see how to make this with a table saw, so MDF king here for front baffle with Gravsen' hand wood cisel technic. But Damn, even HDF today is very expensive !
Stiff front baffle made of denser HDF or doubled ply seems to work fine, while the bottom and sides could be thinner (and braced but not so the front bafle) ! SO coupliing of a thick and heavy front bafle seems the best way with big bass drivers.
Me who xant to try faceted cabinet, I do not see how to make this with a table saw, so MDF king here for front baffle with Gravsen' hand wood cisel technic. But Damn, even HDF today is very expensive !
You need a plunge saw to do that, table saw is perfect for "ordenary" rectangular shapes but useless to other shapes.
Yea, know weight is good with speakers, but thats when they all finished and standing on the right possitions hahaha
Swedish but ust as you see how it works
Exactly right; the majority of attempts at CLD here and on other forums miss the VISCO part of viscoelastic, and end up using either a boundary layer that is either elastic or dries hard. That's not to say there's anything wrong with such a simpler sandwich construction, I use it often myself. But it's not 'true' CLD.
Possibly worth reading for more info:
https://www.sorbothane.com/technica...-elastic-materials-and-viscoelastic-materials
https://www.adhesivesmag.com/articl...d-treatments-using-typical-adhesive-materials
http://assets.press.princeton.edu/chapters/s9774.pdf
Knocking on hells door :
Checkout/listening around 03: 52sec for resonating cab sound in comparison to expensive B&W speakers , and info about KEF Q150 vs Q350 around 08:51sec ...
Lay the KEFs on the side on a DIY stand and add a 6mm glass plate (on both sides) with 2-3mm vibration absorber mat in between ... and these speakers need some better damping in the cab!
Checkout/listening around 03: 52sec for resonating cab sound in comparison to expensive B&W speakers , and info about KEF Q150 vs Q350 around 08:51sec ...
Lay the KEFs on the side on a DIY stand and add a 6mm glass plate (on both sides) with 2-3mm vibration absorber mat in between ... and these speakers need some better damping in the cab!
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Some more info about the original Q350 measured with the industry standard 100k$ Klippel NFS :
https://www.audiosciencereview.com/forum/index.php?threads/kef-q350-speaker-review.13484/
Quick suggestions - close the back port with the two-part foam pieces that comes with speaker or use yown stuff to tweak the performance ... and add some internal absorbent material! The FResp will be nearly flat then as you can see in the next posting!
https://www.audiosciencereview.com/forum/index.php?threads/kef-q350-speaker-review.13484/
Quick suggestions - close the back port with the two-part foam pieces that comes with speaker or use yown stuff to tweak the performance ... and add some internal absorbent material! The FResp will be nearly flat then as you can see in the next posting!
The original Q350 use a very simple 1st order filter for both drivers (woofer/tweeter) , has a nice looking step response and tweeter is ferrofluid cooled ... brand new with warranty for under 400 Euro/pair in germany .
Placing the Q350 near a wall on a stand will make it sound too heavy in the lower range!
But , fortunately our experienced DIY buddy Alex in germany developed a better balanced filter network based of his own measurements :
https://www.hifialex.de/pimp-kef-q350/
Use Google Translation for reading the content on his web site!
Btw - the Q350 has far more directivity than the Q150 and the tweeter curves off-axis are much more smoother and well distributed over angle! (hard to beat)
The coax part number from the Q350 is SP1709 !! (6.5inch/Z-4Ohm)
Another info - the Q950 model uses a 8 inch Uni-Q coaxial driver with 38mm diameter!
good luck & have fun
Placing the Q350 near a wall on a stand will make it sound too heavy in the lower range!
But , fortunately our experienced DIY buddy Alex in germany developed a better balanced filter network based of his own measurements :
https://www.hifialex.de/pimp-kef-q350/
Use Google Translation for reading the content on his web site!
Btw - the Q350 has far more directivity than the Q150 and the tweeter curves off-axis are much more smoother and well distributed over angle! (hard to beat)
The coax part number from the Q350 is SP1709 !! (6.5inch/Z-4Ohm)
Another info - the Q950 model uses a 8 inch Uni-Q coaxial driver with 38mm diameter!
good luck & have fun
I have used visco-elastic stuff from http://www.swedac-acoustic.se/en/vibration-damping/
With good success
Both sheet and kit
With good success
Both sheet and kit
Swedac glue and foam, highly recommended!
This bass cab is shown under construction, all walls are lined with the adhesive foam and then Glava sound board and 5cm of Basotect is added in center of the volume with a hole for the resistance slot that is using aquarium filter foam.
This bass cab is shown under construction, all walls are lined with the adhesive foam and then Glava sound board and 5cm of Basotect is added in center of the volume with a hole for the resistance slot that is using aquarium filter foam
.
clean design ! What's that white foam material ??
Although why Sweedac glue should be special ? All that glue are made the same, they seems made of polyurethan to have the visco behavior whatever the brand... same urethan base than the damper sheets from Sorbothane trade mark. Btw something cheap and that should work imho both as internal standalone CLS doubling internal panel with damping behavior and raw for prototype is the polyurethan dense foam panel used in house building under the concrete floating floor as isolation decoupled structure (floating floor structure) than can be found everywhere.
I also saw at Muji some sponges made of open cell urethan foam from 2 density which could make excelllent damping behind mids or open back tweeters (call that the meta material for poors with cahotic labyrinth non tunned by Matlab or the marketing dpt from Kef)
Some talked a lot of melamine foam as well as internal panel damping in spite of glass fibers (that work well but are a pain for the health for the diyer)
! What's that white foam material ??Although why Sweedac glue should be special ? All that glue are made the same, they seems made of polyurethan to have the visco behavior whatever the brand... same urethan base than the damper sheets from Sorbothane trade mark. Btw something cheap and that should work imho both as internal standalone CLS doubling internal panel with damping behavior and raw for prototype is the polyurethan dense foam panel used in house building under the concrete floating floor as isolation decoupled structure (floating floor structure) than can be found everywhere.
I also saw at Muji some sponges made of open cell urethan foam from 2 density which could make excelllent damping behind mids or open back tweeters (call that the meta material for poors with cahotic labyrinth non tunned by Matlab or the marketing dpt from Kef)
Some talked a lot of melamine foam as well as internal panel damping in spite of glass fibers (that work well but are a pain for the health for the diyer)
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Hum, few big enterprise make glue for everyone they rebrand. I think I will spent somee bed readings at SIKA and 3M technical centers that have both 90% of the industrial construction market (aeronautic, boat, cars, buildings, factories...).
sorbothane according the link above have this wanted viso internal behavior (urhetan again that seems better than any rubbers for internal loss and isolation behavior...)
sorbothane according the link above have this wanted viso internal behavior (urhetan again that seems better than any rubbers for internal loss and isolation behavior...)
That’s Swedac UAR.clean design
The glue is proven to maintain it’s properties over time (does not harden) much better than most other brands.
Swedac Acoustic is a well established serious supplier to the construction, marine and land transportation sectors, it’s not a hifi brand.
There are other companies in the EU and USA with similar products though, so in that sense not unique.