A few data points on Richlite vs. MDF

My previous work with Richlite was mostly with their sandwich composites (Richlite face cladding over Bamboo or Birch Plywood). However, Fern & Roby have a floorstanding full-range design wherein the front panel/baffle board is solid .75-in. Richlite. I want my next project to be, all panels out of Richlite.

My current project is a 2-way with the BBC Monitor Shoebox form factor. As a "Mule," I am modifying the PE/Denovo .23 cu.ft. CNC MDF Kit. The form factor is dictated by the choice of the Purifi PTT5.25 woofer. With an Fs of 32Hz and a Mms of 19.6 grams, a ported enclosure would have to be rather large, and the port would probably require a bend, such Purifi's previous open-source design. Purifi recommends two PTT5.25 passive radiators in an enclosure net of intrusions of 5.5 Liters.

As a baseline, I calculated the weight of the PE/Denovo .23 cu.ft. CNC MDF Kit as 9 pounds. (PE quotes 8.2 pounds.) I then calculated:

A Denovo .23-sized cabinet with a .75-in. Richlite shell (388 sq.in./2.69 sq.ft.) and a .75-in. Richlite front panel (96 sq.in./.66 sq.ft). would weigh 16.23 pounds (13.04 lbs. shell and 3.19 lbs. front panel) (before driver cutouts and assembly).

A Denovo .23-sized cabinet with a .75-in. Richlite shell (388 sq.in./2.69 sq.ft.) and a 1.0 Richlite front panel (96 sq.in./.66 sq.ft). would weigh 17.26 pounds (13.04 lbs. shell and 4.22 lbs. front panel) (before driver cutouts and assembly).

A Denovo .23-sized cabinet with a .5-inch Richlite shell (388 sq.in./2.69 sq.ft.) and a .75 in Richlite front panel (96 sq.in./.66 sq.ft) would weigh 12.01 pounds (3.19 lbs. front panel and 8.82 lbs. shell) .

Conclusion: The Richlite cabinet with the .5-in. shell and .75-in. front panel (12.01 lbs.) weighs 32% more than the MDF baseline cabinet (9.07 lbs.).

That suggests that cabinet vibration or resonances should not be an issue. And in any event, a cross-brace fabricated from Richlite Stratum Bamboo 1.0-inch is contemplated.

The reason some cases have front panels thicker than the shell boards is so that routering .75 x .25 in. dadoes at the top and bottom of the front panel would allow for the back .25 inch of the front panel to be inset into the four-sided shell, and glued up for greater clamping strength and rigidity. Leaving a .5-inch reveal.

FWIW & YMMV.

all my best,

john
 
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GM

Member
Joined 2003
This stuff 'reads' similar to the high voltage (> 10 kV) insulation board we used except a lot more decorative, though couldn't find its spec sheet, but hope it has similar MOE, etc., in which case it will make 19 mm no void plywood near balsa wood limp in comparison, i.e. stiff enough to not need any bracing and 'ring' so far above a woofer's passband in will be inert.
 

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