12" Sealed Sub - stuff or not to stuff

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IH8usrnames,

I am curious what technique and tools you use to get the curvature on your cabinets? I've seen suggestions of kerfing and/or steaming to do that, followed by putting the workpiece into a mold to define the exact curvature. Or did you just use stacked pieces of veneer glued together? Looks like some high quality work in any case!
 
ToS,

I've always thought that fills should be retained as far away from the driver as posible. Their action is one of nonlinearity by design. Much like horn loading, I think its best to let the driver(s) fully couple with the cab volume before interacting with dampening materials.

Although, way back B&W had the matrix line. Think of the cardboard dividers in a case of wine, then precision filled with formed batting material instead of loose pile poly-fill. I always thought that was a optimally crossbraced /dampened design.
 
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ToS,

I've always thought that fills should be retained as far away from the driver as posible. Their action is one of nonlinearity by design. Much like horn loading, I think its best to let the driver(s) fully couple with the cab volume before interacting with dampening materials.

Although, way back B&W had the matrix line. Think of the cardboard dividers in a case of wine, then precision filled with formed batting material instead of loose pile poly-fill. I always thought that was a optimally crossbraced /dampened design.

I have been thinking along the lines of a cylindrical cabinet filled with concentric rings of cardboard arranged exponentially both in spacing and size of apertures. Between the rings I plan to put small amounts of long haired sheep wool held in place with toothpicks. My reckoning is the rings of cardboard will dissipate the rear shock wave to the cylinder walls, and the sheeps wool will soak up any resonance. This is what my imaginarium tells me.

I tend to agree about allowing the driver to couple with the cabinet. ToS
 
There is nothing wrong with kerf bending but its not for me and I cannot imagine it is nearly as strong as proper form bending in a press.

I made a 2-1/2" wide test piece using 6 layers of MDF to form an arch about 15" from tip to tip. I weigh 220lbs and can stand on that arch, while it does deflect it has not broken. I have stood on it several times, had others stand on it and still holding strong.

If a 6 layer 2-1/2" piece can hold me, imagine the strength of 7 layers in an arc 16" wide!

I used seven layers of mdf.
Each layer is slightly less than 1/8".
The finished material is a bit over 13/16".

I used a venturi style vacuum system and polyurethane bag to form the panels over MDF forms I created. The glue is titebond II Extend - it offers more open time allowing for projects such as this.

Quick video of the process.
In the background you can see some other panels.

Link >>>>> Curved Panel - Vacuum Bag <<<<< Link
 
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I am at the research and design stage of building my first woofer, and am interested in this aspect of construction. My instinct suggests that although filling a cabinet with stuffing will work and do the job, it may in fact work better when combined with the intricacies of internal construction. Otherwise it seems a bit haphazard to me. When I look at organic forms in nature, it is difficult to see where a structure starts and ends. Nothing in nature looks bolted on, and within context, speaker stuffing looks to me like a bit of a bolt on.

I could be wrong, I often am, and that's OK. ToS

The more I learn about speakers the more I realize there is a LOT of flexibility in design and there is the golden rule that all ears hear differently.
I have bought a lot of speakers, most have minimal to no stuffing. I blame that on economics of scale and just being cheap.
The one exception I have seen is on 3 way speakers the mid speaker is almost always in a small enclosure and just crammed with stuffing.
Stiffening enclosures definitely helps, I always add extra braces to my bass guitar cabs.

Stuffing adds clarity, anything not absorbed will bounce around and eventually find its way out through the speaker or the port. Always out of phase.
At worst over stuffing will drop a DB or two is volume but the clarity you gain is worth it.
 
Personal experience:

I used (4) Bag End sealed 18" subs for small PA work. Just rectangular boxes @ 3 cubic feet each.
They are not stuffed from the factory.

Last year I put polyfill in 2 of them as an experiment. The difference was subtle, but not good at all. I don't quite remember what the sound was like (maybe less punchy) but I immediately pulled the fill out. (And I REALLY expected them to sound better.)

YMMV, though I suspect ths will be the case for any sealed cabinet.
 
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Great video, I have the parts for a vacuum press, just not sure I ever want to build another set of speakers.

I'm listening to the ones I built in that video right now. They sound fantastic but because I have a couple veneer blemishes I might build another set.

I have Dirac on my NAD preamp - it shows I'm getting flat response down to 20hz from them.

I have loads of other projects that will require curved bits that are not audio related.
 
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