Advice for Classic GR MarKen12p build

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M

madings

Member
Joined 2009
#1
I’m new to speaker building and would like to build the Classic GR MarKen12p.

http://frugal-phile.com/boxlib/P10free/CGR-Mar-Ken12p-310817.pdf

I’m unable to find 12mm wool felt, but have found two alternatives

  1. 8mm felt from Jantzen (recycled fibers of unspecified composition, but Troels Gravesen says on his website that he uses it).
    http://www.jantzen-audio.com/wp-content/uploads/Damping-Materials-Catalogue.pdf
  2. 5mm felt (90% wool), more expensive but still reasonably priced

Can I use two layers of the 5mm for a total of 10mm, or would 3 layers be preferable?

When the notes say “All internal panels lined with ~1/2" (12mm) wool felt (preferred), 3/4" (19mm) poly-fluff batting, or 1" (25mm) fiberglass”

Does this mean all internal surfaces, including both sides of the brace?
 
#4
Regarding damping of internal brace; IIRC that panel should be installed offset sufficiently that one face is is on the vertical centre line, and damped with a layer of fibrous material thinner in density than the felting used on six internal enclosure faces. I never anything thicker than 1/2” or so cellulose batting.
 
#5
The dampinh on the walls is required. Putting somethign with lowish desity over the centre side of the holey braces helps absorb anything going side-to-side.

Multiple layers is fine (but a PITA ;^)

You’ll likely want to atatch the layer stogether, don’t use much

Add layers until you hit 12-15mm.

dave
 
#6
Thanks!

So when damping the brace, should I also cut holes in the damping material like those on the brace?

For a lower density material for the brace, I can get this 25mm pure wool backed by cloth, with a density of 20 kg/m3, compared to 160 kg/m3 for the felt, so certainly much lower density.

I don't know how this compares to cellulose batting in density or damping, but it's 25mm/1in in thickness. Could that work for the brace dampening, or is 25mm too much?


Unfortunately ordering from McMasterCarr isn't practical as I'm in the EU -- generally the same things are available here, just harder to find with all the different languages...
 
#8
That was my thoughts too
Fabric Stores will carry Quilt Batting in sheets for quilts or comforter blankets.

Different thickness and fabric blends
Usually Poly or Cotton or a blend

Basically the same Poly type material sold as the brand name
Poly Fill for speaker builds.

Poly Fill is a loose Poly fill more common with stuffed animals or pillows.

But as mentioned the Quilt batten/ Batting comes formed in a sheet
and more suited for lining walls
 
#11
Thank you for all the replies, this is very helpful. I can definitely get this kind of quilt batting from a fabric store, so I'll use that for the brace.

I already got the drivers, so will try to get some birch plywood this weekend and get started on the build. Can't wait to hear them when they're done 🙂
 
#12
Finally I have collected all the tools and materials I needed for the build and am making some progress.

For the felt lining on the sides and back interior walls, should it extend only down to where the port begins (red line) or all the way to the bottom (blue line)?

IMG_0387_small.jpeg
 
#16
Hello all,

Sorry for resurecting this thread, but I have a similar problem as the OP. I'm working on the same cabinet, but for the Alpair 12P. In my area, natural 12mm wool felt is insanely expensive, could I use 12mm polyester wool felt instead? Or would it be better to use 20mm polly-fluff batting?

Thanks
 
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