lowrider, others
VENTILATION.
The design is a ’shed’, not an enclosure, with a roof strong enough to support 125 lbs, i.e. Amps over Preamps (nice short interconnects). Lower equipment sits ’loose’ within. Lots of Air Flow.
The design has rubber feet below and above the side panels, for side air flow in and out. Coincidentally Vibration Isolation. There is clearance below the top support (only snug above the tuner’s flywheel, most preamps do not have them). The top support blocks heat rising up at the center area by design, limiting heat above that area. There are slots on both sides of the top support to allow additional air flow out the open space above the side panels. There is space between the top support and the glass, and more space at the front and rear portions with no top support. Front, Bottom and Rear Completely Open.
Preamps, Tuners do not make as much heat as you think. Look at the minimum ventilation of modern designs.
McINTOSH ENCLOSURES (most OEM’s Walnut Enclosures)
I contacted McIntosh, they confirmed their original enclosures for tube preamps and tuners had no top or side vents, and that I could use a non-top vented enclosure, even for my mx110z or other tube preamps or tuners. My mx110z Tuner/Preamp has 17 tubes, most preamps a lot fewer.
http://www.mcintoshaudio.com/specifications/cabinets.htm Face plates blocked any front air-flow in those enclosures.
Panloc rails restricted side air flow.
http://www.mcintoshcompendium.com/Compendium%20Docs/Other/PDFs/PANLOC.pdfPartial opening in the bottom and open back, that was it.
Top Vents were added for Low Powered Tube Receivers, (25-30-35 wpc) front still blocked by faceplates and panloc still restricting side air flow. Fisher, others, no panloc, had a bit more side clearance for air movement.
Later, low powered SS Receivers could be used in the Top Vented Enclosures, same thing: front blocked, panloc at the sides. Unlike Tube components with rear bodies ’low and open’, the SS units had complete metal cases restricting air flow within that case and within the outer enclosure.
To make things easy, make, store, sell, ship: they started using top vented enclosures for preamps as well as receivers.
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HEAT BELOW the UPPER UNIT
The real issue is to keep the temperature below the upper unit from being excessive. Using an indoor/outdoor sensor, my (hotter than most) 17 tube mx110z below, after hours of continuous play, it stayed just below 100 F on the top of the glass surface below my 45 wpc Cayin. Taller feet could be placed under any upper unit for greater clearance of course.
Any custom height is possible for the ’shed’ below, I made 3 heights based on (where’s my notes?). Oh yeah, the maximum height my woodworker could get out of raw 1x4; 1x6; 1x8 lumber (a bit taller than conventional 3-1/2; 5-1/2; 7-1/4).