Drying sand thoroughly can be problematic and time consuming. I found a few minutes in the microwave heated it through, and just pouring it between bowls while hot resulted in bone dry sand. Very effective in damping but my wife is now convinced there's madness in the family.
Another option is the steel "Soundbites" product sold for damping hollow speaker stands. Very effective, but keep well away from drive units until sealed into the baffle, once magnetically attracted and attached to the drive unit it is there to stay,if it gets inside the unit is ruined. Same can go for sand though.
The whole baffle does not need to be damped in this way. A few significant patches will effectively damp vibration, and rectangular pockets on the back are easy to make, fill, and seal properly.
Another option is the steel "Soundbites" product sold for damping hollow speaker stands. Very effective, but keep well away from drive units until sealed into the baffle, once magnetically attracted and attached to the drive unit it is there to stay,if it gets inside the unit is ruined. Same can go for sand though.
The whole baffle does not need to be damped in this way. A few significant patches will effectively damp vibration, and rectangular pockets on the back are easy to make, fill, and seal properly.
In Martin's Open Baffel 2 build he uses a 12 db xover. I
was considering biamping it and wondered if I could just
use a 6db xover instead of 12db. Or if I tried this would I
probably need to change the xover points ?
was considering biamping it and wondered if I could just
use a 6db xover instead of 12db. Or if I tried this would I
probably need to change the xover points ?
One way to damp an open baffle is to sandwich 1/4” mass-loaded vinyl between two layers of wood, which I think would be called a “constrained layer” damping. I did this using well seasoned 1.5” thick fir lumber. Total thickness about 3”. The drivers are between the wood layers with extra gaskets and no fasteners; but this is very fussy to do. Not for the time conscious builder or woodworking novice. It was a pandemic project, LOL.
Seems like plywood could be used instead of thick lumber---maybe with more layers of board and mass-loaded vinyl to achieve a desired thickness.
The layers on my project were not glued together, so the drivers could be removed. No reason why they couldn't be glued, if the drivers were conventionally mounted.
Seems like plywood could be used instead of thick lumber---maybe with more layers of board and mass-loaded vinyl to achieve a desired thickness.
The layers on my project were not glued together, so the drivers could be removed. No reason why they couldn't be glued, if the drivers were conventionally mounted.
Not sure it works well in that layout if the screws touch the CL layers, so you must make bigger hole around the screws for this CL layer. And it should avoid the plan to sing by invisible flexing. So better to brace it behind, eventually do CL between the braces. (theorically)
Also due to the surface w/o press it will be hard to make the elastic glue (Sikaflx and all) thin enough an iso thickness distributed. this layer behind shoulld be very thin an metal <= 0.5 mm and the front with a very thin mdf layer 5 mm max or simply hard veenering with the same glue couldd heellp in theory (same hole spacing in order it doesn't touch the screws.
But this is very theorical I believe bacause of the omni out of phase nature of surch loudspeakers0. It is cool also like T Gravsen did it with a liitlieer plan for the speaker on a bigger plan. certainlier easier to do here like him and just CL on the driver square plan (whivh will need renforcment at the back for rigidity due to its smallness.
OSB is ugly but cheaap and rigid as well as well damped if you suit the front of the baffle with nicer looking : faux leather, felt, veenering and so on.
my 2 cents
Also due to the surface w/o press it will be hard to make the elastic glue (Sikaflx and all) thin enough an iso thickness distributed. this layer behind shoulld be very thin an metal <= 0.5 mm and the front with a very thin mdf layer 5 mm max or simply hard veenering with the same glue couldd heellp in theory (same hole spacing in order it doesn't touch the screws.
But this is very theorical I believe bacause of the omni out of phase nature of surch loudspeakers0. It is cool also like T Gravsen did it with a liitlieer plan for the speaker on a bigger plan. certainlier easier to do here like him and just CL on the driver square plan (whivh will need renforcment at the back for rigidity due to its smallness.
OSB is ugly but cheaap and rigid as well as well damped if you suit the front of the baffle with nicer looking : faux leather, felt, veenering and so on.
my 2 cents
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It may be that mine does not qualify as a constrained layer, precisely, but maybe just “workable damping between two layers of wood”. I think the fact that the vinyl is dense, soft and flexible compared to the wood, it likely interrupts vibrations. The mass-loaded vinyl does not ring like wood when struck or otherwise agitated. The situation may be roughly analogous to placing a finger on a vibrating cymbal or drum-head, etc.
I used this same type of mass-loaded vinyl sheet, sandwiched into a home wall partition.
It was placed between 3/4” plywood and 1/2” drywall, total thickness 1.5”. The inhibition of sound transmission was about as good as a standard stud wall partition, which is 4.5” thick. I set some large cabinets back into the space that the wall cavity would usually occupy, and their 3/4” plywood backs were part of the above mentioned 1.5” assembly.
I used this same type of mass-loaded vinyl sheet, sandwiched into a home wall partition.
It was placed between 3/4” plywood and 1/2” drywall, total thickness 1.5”. The inhibition of sound transmission was about as good as a standard stud wall partition, which is 4.5” thick. I set some large cabinets back into the space that the wall cavity would usually occupy, and their 3/4” plywood backs were part of the above mentioned 1.5” assembly.
Another way to keep woofer vibrations away from an open baffle panel, is to keep a driver from touching the large front baffle that mounts the other drivers.
In a 4way OB build, I isolated the18” woofer by having it mounted to an arched-top U-frame assembly.This frame is separable from the baffle for transport. When installed for use, the 18” woofer comes up to the back of the baffle, but is not attached to it, thus minimizing the direct transfer of vibrations.
The U-frame assembly has a sort of sub-base plate that holds the crossover. That sub-base plate attaches to a lower base plate (which forms an “L” shape with the baffle). So vibrations can move from the 18” driver to the baffle by that route, but the transfer is less than if the driver were mounted to the baffle. I think that the floor contact may damp some of the energy too. The baffle is 1 7/8” thick cherry.
There may be a simpler way to achieve this, but this is what I came up with at the time. It makes this large speaker easier to transport to club events, etc.
In a 4way OB build, I isolated the18” woofer by having it mounted to an arched-top U-frame assembly.This frame is separable from the baffle for transport. When installed for use, the 18” woofer comes up to the back of the baffle, but is not attached to it, thus minimizing the direct transfer of vibrations.
The U-frame assembly has a sort of sub-base plate that holds the crossover. That sub-base plate attaches to a lower base plate (which forms an “L” shape with the baffle). So vibrations can move from the 18” driver to the baffle by that route, but the transfer is less than if the driver were mounted to the baffle. I think that the floor contact may damp some of the energy too. The baffle is 1 7/8” thick cherry.
There may be a simpler way to achieve this, but this is what I came up with at the time. It makes this large speaker easier to transport to club events, etc.
Sounds like a good idea to me. I used cork, which could use more mass to it. I bet it makes a nice, dead panel.
I have used OSB with a sizing step- diluted titebond 2 woodglue. Just dilute and brush thinly on the whole surface and let dry. The end product is much more stable and durable, but it takes space and hassle to do, but is a cheap way to turn nice flat, cheap OSB into a more workable product. The glue not only acts as a surface sealant but also prevents any flaking and adds some additional damping.
I didnt know what OSB was, so I had to look it up. Here's a good explanation -
https://www.paoson.com/blog/en/types-of-osb-boards-for-woodworking/
https://www.paoson.com/blog/en/types-of-osb-boards-for-woodworking/
Cheap/ugly is good for test boxes/baffles. With open baffle, one might want experiment with size and shape.
I like the way OSB looks (smooth side, with the printing sanded off).
Has anyone seen 1" or 1 1/8" (1.125) OSB? other than stair treads?
I like the way OSB looks (smooth side, with the printing sanded off).
Has anyone seen 1" or 1 1/8" (1.125) OSB? other than stair treads?
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Above reminded me that stair treads are a convenient/accessible way to get wide, sanded hardwood boards. Two could be edge-glued to make a 23" wide panel (22" with bull-nose removed). For those without a planar, having just one glue-line to sand-out is way easier than multiple pieces.
Stair treads are usually a few pieces edge-glued at the factory. Big-box store stair treads are now often made by more complex/ less traditional methods, that may not look so nice on the edges, especially on the end grain, or if a bevel or round-over is added to an edge or a cut-out.
The traditional ones may typically be sourced from contractor oriented hardwood flooring outlets. Online prices may be high to pay for shipping. Also, may be very high if ordered through a lumber yard that gets them from a "stair parts" vendor.
Stair treads are usually a few pieces edge-glued at the factory. Big-box store stair treads are now often made by more complex/ less traditional methods, that may not look so nice on the edges, especially on the end grain, or if a bevel or round-over is added to an edge or a cut-out.
The traditional ones may typically be sourced from contractor oriented hardwood flooring outlets. Online prices may be high to pay for shipping. Also, may be very high if ordered through a lumber yard that gets them from a "stair parts" vendor.
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No, but I've seen tables, specifically the tops of such. Very thick, nice finish on the listener facing side. Got a pair I wouldnt mind being rid of, as I'll likely never use them for anything other than a table in the future. I'm in the PNW, shipping very unlikely. 30" x 60" x 1.25"
What material are they made from? I have a lot of material left from jobs and such, so I won't need them, but I am curious.
I am in Seattle area.
Thick and light. 30-40mm XPS as core with wood veneer skins as baffle for very dead OB panel seems perfect in concept
MDF. I was able to make a pair of 42" "tombstone" OB panels, along with extra material to make front tip-toes and back legs from the table tops. I also had enough extra material to partially surround or "hood" my upper Lii Audio F15s and add some significant mass about the driver at the panel top. Later I added Goldwood 18"s on the bottom.
I used a protracted router to score the cutouts, then chased that with a Jig saw to get cleanish circular cutouts. The backside of the speaker flanges simply mount to the front baffle surface, which is a bone white color. They're wrapped with "T" plastic molding all around the outside edge, so no work was needed to dress the panel edges. I was able to find a spray paint can that matches the color, to get 16" and 18" metal pizza grilles looking nicer against the baffle. Assembled, I need to use a hand truck to move them, so there's some heft there for the drivers to push against.
I suppose it would be fun to hang them from the rafters in our RV garage, with the pair of 8" whizzers I've got sitting new in the box, but...I dont need to do that. Already have a set of MLTLs suspended horizontally using bicycle hoists out there.