|
 The
power density of components found in today's electronics keeps temperatures
high, especially among those stored in tight quarters. For example, our
Denon AVR-5308CI has seven 150-watt THX-certified power amplifiers in
a single chassis. The challenge is to keep these components cool enough
to be reliable for years to come. Ignoring this can drasticallly shorten
the life of the internal electrical components due to thermal stress.
To address this, a company called Active Thermal Management (ATM)
has introduced several products that offer solutions for both cabinets
(Enclosure Coolers) as well as for individual components (Equipment Coolers).
We will cover the Cool-it II product, which is designed to keep
a component cool by blowing air into the top of the chassis. This cooling
system sits on top of the component and requires that there be some ventilation
around the unit. It is ideal for components that have limited ventilation
and localized heat buildup. This particular model will not be effective
in a sealed enclosure simply because the hot air will just circulate as
opposed to bringing in cooler air into the chassis.
The Cool-it
II runs very quietly thanks to the design that limits the voltage
to the dual 120mm brushless DC fans. These fans are rated at 12VDC, but
only run at a mere 6.5VDC due to the 22 ohm power resistor installed in
series with the voltage from the power adapter. The result is a very low
noise level of only 19dBA. The Cool-it II only has an ON and OFF
mode and does not throttle the fans at different speeds. The transformer-based
power adapter is rated for 9VDC at 0.5 amps. The Cool-it II has
an inline power connector that makes it easy to disconnect from the bulky
power adapter. The unit measures only 15.75" wide x 6.75" deep
x 2 1/8” high.
 We
installed the Cool-it II on the top of our Denon AVR-5308CI THX
receiver inside of our StudioTech Ultra U-22T
cabinet. Normally this receiver has pretty good ventilation thanks to
the large vents on the chassis. However, due to the lower impedance of
our M&K speakers connected to the receiver, the unit runs hotter than
normal. This is where the cooling system helps keep our electronics in
check. The fans on the Cool-it II have 1-inch stand-offs that provide
an air gap between the fans and the top housing plate. This allows air
to move in from the sides and down into the unit. The fans sit flush on
top of the unit it is cooling. The design works well and moves a good
amount of air into the chassis. Since the design uses a thermal sensor
to turn the fans on, there is no need to switch power to the cooling system.
It can stay plugged in and runs only when needed.
 Thermal
Sensor
We placed the thermal sensor on the hottest part of the receiver near
the amplifier heatsinks using the high strength cube magnet provided with
the system . For test purposes, we placed a digital thermometer probe
next to the temperature sensor to measure when the Cool-it II turned
on. At 89 degrees Fahrenheit, the fans began to run and air quickly circulated
through the large chassis. Fan noise was minimal near the unit and inaudible
when placed in the cabinet where we use the receiver.
 Need
More Air Flow?
Users must do this at their own risk as Active Thermal Management
does not authorize any modifications to the Cool-it II and it may
very well void the warranty. If users want to have more air flow, it is
possible to change the power resistor on the terminal strip to a different
value to change the fan speed. The fans can run at full speed by shorting
the resistor completely, but the fan noise may become an issue. The trade-off
in changing the resistor value is air flow versus fan noise. Both the
fans and the power adapter are well within the design limits to handle
this. However, the power resistor must be properly selected to handle
the power dissapation, so we recommend contacting Active Thermal Management
if a change is required.
Conclusion
The Cool-it
II is a simple yet effective product to keep your expensive electronics
reliable for years to come. Active Thermal Management has many
solutions for a variety of applications for both cabinets as well as individual
components. Larger cooling systems are also available if needed. We recommend
checking out their website
for more information. The system is very quiet and only adds about 2-inches
to the height of the component. In addition, power consumption is very
low (we measured less than 5 watts). The Cool-it II is an affordable
($139.95) cooling system and is the perfect addition to our expensive
($5500) Denon A/V receiver that we cannot afford to have fail on us.
-
Kevin Nakano | 
