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
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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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.
Here's Richlite's Technical Data web page.
There is one Sound Transmission Test Report, of a 4 x 8 foot .5-in panel.
It's a five-page report, but I Grabbed the results (attached). Above 2500Hz, the Transmission Loss goes from 32 to 50.
I chatted by phone with a honcho at Ferm & Roby, and he said that they did not choose Richlite capriciously or randomly.
Thanks for your interest,
john
There is one Sound Transmission Test Report, of a 4 x 8 foot .5-in panel.
It's a five-page report, but I Grabbed the results (attached). Above 2500Hz, the Transmission Loss goes from 32 to 50.
I chatted by phone with a honcho at Ferm & Roby, and he said that they did not choose Richlite capriciously or randomly.
Thanks for your interest,
john
Attachments
Mass will tend to lower the frequency, the stiffness will tend to bring it back up.
Thanks.
I should have mentioned that the design calls for all inside surfaces except for the"floor" to be covered with Danny Richie's GR Research "No-Res" material, and that the floor under the crossover will have a 1/8" soundproofing putty pad on it.
john
I should have mentioned that the design calls for all inside surfaces except for the"floor" to be covered with Danny Richie's GR Research "No-Res" material, and that the floor under the crossover will have a 1/8" soundproofing putty pad on it.
john