Hello,
I'm about 85% through with this woofer build, so for better or worse,
the design won't be changing by a great deal.
I think it should work at least "OK".
It is essentially like a Linkwitz Thor, except two boxes (stereo bass).
The old 12" Peerless XLS in a sealed box, around 1.2 Cubic feet or so.
I'll be using a Marchand Bassis for bass EQ.
So.....
I'm building a box-within-a-box, each box is 3/4-in MDF, the space
between is about 5/8-in on 5 sides (4 sides and the back).
The damping layer will be heavy sand, Chromite sand.
Finally, here is my question:
Should I coat the MDF surface on the inside of the outer box and
the outside of the inner box with an epoxy sealer ?
This would be in theory an anti-abrasive surface for the sand, since
I don't know how much the vibrating sand might etch the wood
over time.
Thank you for your thoughts !
I'm about 85% through with this woofer build, so for better or worse,
the design won't be changing by a great deal.
I think it should work at least "OK".
It is essentially like a Linkwitz Thor, except two boxes (stereo bass).
The old 12" Peerless XLS in a sealed box, around 1.2 Cubic feet or so.
I'll be using a Marchand Bassis for bass EQ.
So.....
I'm building a box-within-a-box, each box is 3/4-in MDF, the space
between is about 5/8-in on 5 sides (4 sides and the back).
The damping layer will be heavy sand, Chromite sand.
Finally, here is my question:
Should I coat the MDF surface on the inside of the outer box and
the outside of the inner box with an epoxy sealer ?
This would be in theory an anti-abrasive surface for the sand, since
I don't know how much the vibrating sand might etch the wood
over time.
Thank you for your thoughts !
Well with only a 5/8 gap have you considered just getting some 5/8 MDF and glue and making it solid? Or maybe find 3/4 rubber mat so it’s a nice squeeze?
Here are some concerns I have.
A- I would have multiple strips of wood on all sides to keep the spacing correct, the bass over time is likely to shift the loose sand and change the spacing.
B- epoxy paint with sand to provide a seal on the mdf is good, mdf will absorb the moisture and could weaken the cabinet if there is enough moisture. Also the rough texture may help the sand from moving.
C- do your best to remove as much moisture from the sand
Good luck and let us see pictures, build and completed. Please
A- I would have multiple strips of wood on all sides to keep the spacing correct, the bass over time is likely to shift the loose sand and change the spacing.
B- epoxy paint with sand to provide a seal on the mdf is good, mdf will absorb the moisture and could weaken the cabinet if there is enough moisture. Also the rough texture may help the sand from moving.
C- do your best to remove as much moisture from the sand
Good luck and let us see pictures, build and completed. Please
Over-thinking it.
Congrats on pulling out the old sand box. Heavy, messy, but worked well. Very popular back in the sono-tube days.
That said, My XLSS subs are 1/2 birch ply inner, 1/2 MDF core, with 1/4 oak ply on the outside. Heavier than I can manage any more, but dead as a doornail. Only using one now as this house just did not have room for the second. Yup, the Chinese chest is the sub.
Congrats on pulling out the old sand box. Heavy, messy, but worked well. Very popular back in the sono-tube days.
That said, My XLSS subs are 1/2 birch ply inner, 1/2 MDF core, with 1/4 oak ply on the outside. Heavier than I can manage any more, but dead as a doornail. Only using one now as this house just did not have room for the second. Yup, the Chinese chest is the sub.
Attachments
Good Morning Gents,
Handiman, you bring up a point I had a question about. Now, the inner box
is not free-floating, it will be fastened to the front face, and also in the center
of the rear face, where the wires will pass through.
However, I had not planned any attaching points on the sides. We are talking
roughly a 14 x 14 inch area. Any attaching points would act like a brace,that is not a bad thing but is it really necessary for vibration control ?
To me, the sand has two functions, vibration control and sheer weight.
I think each cabinet might end up close to 80 pounds each, really don't know yet.
Handiman, you bring up a point I had a question about. Now, the inner box
is not free-floating, it will be fastened to the front face, and also in the center
of the rear face, where the wires will pass through.
However, I had not planned any attaching points on the sides. We are talking
roughly a 14 x 14 inch area. Any attaching points would act like a brace,that is not a bad thing but is it really necessary for vibration control ?
To me, the sand has two functions, vibration control and sheer weight.
I think each cabinet might end up close to 80 pounds each, really don't know yet.
Sand works better than any other deadener I've ever heard, it's amazing. I've never seen anyone paint or seal the insides for protection against the sand, but now what you mention it the idea is intriguing.
Let us know what you come up with.
Let us know what you come up with.
Pano,
My first idea was to use lead shot, but I did a rough calculation
on weight and it looked way too heavy ! I would have to redesign the
boxes to have less than 5/8-inch space to fill. But I think lead shot would
be an excellent dampener.
My first idea was to use lead shot, but I did a rough calculation
on weight and it looked way too heavy ! I would have to redesign the
boxes to have less than 5/8-inch space to fill. But I think lead shot would
be an excellent dampener.
I've used sand and seen it used by others. It's amazing what it sand can do. Some people mix lead shot in with it, but I don't know how much more effective that is. Be sure to pack the sand, it will settle over time with vibration, you want it to be as tight as possible to begin with.
Anecdotally, being a show tech for 45 years I have pushed many 1000s of road cases over all sorts of hard surfaces, like concrete, ice, wood, tile, marble, stone. A wooden road case full of sand bags is not only maddeningly heavy, it makes no sound. Dead quiet. The only thing that comes close is a trunk full of electrical cable. Masses of rubber covered copper is also insanely heavy and sonically inert. A cart full of steel plates is heavy, but very loud.
Just my day to day experience with rattling (or not) materials.
Anecdotally, being a show tech for 45 years I have pushed many 1000s of road cases over all sorts of hard surfaces, like concrete, ice, wood, tile, marble, stone. A wooden road case full of sand bags is not only maddeningly heavy, it makes no sound. Dead quiet. The only thing that comes close is a trunk full of electrical cable. Masses of rubber covered copper is also insanely heavy and sonically inert. A cart full of steel plates is heavy, but very loud.
Just my day to day experience with rattling (or not) materials.
I posted in another thread not long ago. A friend and I did something similar (years ago) but used bitumen to fill the space between. also used two short strips on the base and for support and cable entry. Poured bitumen in from the top and covered with hard wood top to look like a table. A bit lighter than sand but absolutely no vibration.
Kevin
Kevin