I've decided on sandwich walls for my new sub enclosure (~32 litres with one Peerless 10" XLS and one 10" passive): thick MDF / sand / thin MDF
I undersand that sand is useful in this scenario as it will convert motion energy to heat, but would concrete be better with the increased rigidity it provides?
Also, how thick should the panel layers be? I was thinking 18mm MDF / 18mm sand / ~6mm MDF, but I don't know if the end panel should be a different material or whether the different thickness will be enough to ensure different resonance properties?
I undersand that sand is useful in this scenario as it will convert motion energy to heat, but would concrete be better with the increased rigidity it provides?
Also, how thick should the panel layers be? I was thinking 18mm MDF / 18mm sand / ~6mm MDF, but I don't know if the end panel should be a different material or whether the different thickness will be enough to ensure different resonance properties?
I think sand is overkill.
With a subwoofer, it is a trivial matter to brace the cabinet enough to get the first resonance above the operating range, assuming you won't cross higher than 100-125Hz. Sand will mass-load the panels and could actually bring the first resonance down into the operating range.
With all those layers, you have many times the chance for a cabinet buzz or a loose joint.
Keep it simple, simon....
Cheers
With a subwoofer, it is a trivial matter to brace the cabinet enough to get the first resonance above the operating range, assuming you won't cross higher than 100-125Hz. Sand will mass-load the panels and could actually bring the first resonance down into the operating range.
With all those layers, you have many times the chance for a cabinet buzz or a loose joint.
Keep it simple, simon....
Cheers
I'm not an expert on sand for power dissipating purposes, however my general understanding is that the coulombic friction between adjoining sand particles dissipates power and acts as a damper for the enclosure. So, with that understanding, I think it'd be best if the sand had some freedom of movement, i.e. I would just pour the dry sand in and pack it a little to make sure there's no large air pockets.
Ron E said:I think sand is overkill.
With a subwoofer, it is a trivial matter to brace the cabinet enough to get the first resonance above the operating range, assuming you won't cross higher than 100-125Hz. Sand will mass-load the panels and could actually bring the first resonance down into the operating range.
With all those layers, you have many times the chance for a cabinet buzz or a loose joint.
Keep it simple, simon....
Cheers
I'm completely with Ron E on this one.
The sand will be ineffective in a subwoofer application.
Decent bracing and descent eventual sub c/o slope is the way to go.
Your sub will also be smaller in every dimension by 2" which is a lot.
sreten.
If you are going with the sandwich 18/18/6 should be more than sufficient AFAIK. Outer and inner walls will be decoupled by the sand, so you need not worry about resonance. I would look at the inner panel purely as a means to keep the sand together, so it could be even less than 6 mm thick.
Rudolf
I've built several sand filled enclosures with great results. Just leave a hole in the top of the box play the speaker for a while and the sand will fill the voids then top-off the sand. The box is very inert and does not resonate on the outer shell as the sand dampens it well. It takes a whole lot of energy to get something that heavy to vibrate. Also, use sterile play sand from the local home center, the grains are smaller and more uniform.
I also agree with the idea of having the sand SOMEWHERE in the enclosure, but not inside the walls.
I also have built a few large towers with the bottome third or quarter of the tower being a seperate enclosure packed with sand. I truly believe this helped the stability of the box, and kept the bass sounding tight and clean. you might also try doing what (I think) Velodyne did a few yeard ago and mount the enclosure to a slab of marble or something else heavy like that. I think one of the major killers of a powerful sub is the enclosure not having the guts to hold perfectly still while the driver is doing its work. I don't mean resonances like a certain mdf panel vibrating, I mean the whole enclosure moving with the sub a bit and taking away from the travel of the driver.
I also have built a few large towers with the bottome third or quarter of the tower being a seperate enclosure packed with sand. I truly believe this helped the stability of the box, and kept the bass sounding tight and clean. you might also try doing what (I think) Velodyne did a few yeard ago and mount the enclosure to a slab of marble or something else heavy like that. I think one of the major killers of a powerful sub is the enclosure not having the guts to hold perfectly still while the driver is doing its work. I don't mean resonances like a certain mdf panel vibrating, I mean the whole enclosure moving with the sub a bit and taking away from the travel of the driver.
There have been enclosure designs that have used sandwiches made with sheet lead and sheet soft copper as well as sand. The physics works well. The soft heavy material dissipates any energy it absorbs without converting it to sonic energy forms.
The real problems are extreme weight and a very complex carpentry problem if there are any bevels or strange angles.
The sand must be sterile and dry. Use the top side hole trick mentioned above, and top off in 6 months or so.
I have read that the box is dead quite in the lower frequencies.
The real problems are extreme weight and a very complex carpentry problem if there are any bevels or strange angles.
The sand must be sterile and dry. Use the top side hole trick mentioned above, and top off in 6 months or so.
I have read that the box is dead quite in the lower frequencies.
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