Community VERIS Series - Operation and Installation Manual - Page 14
IMPORTANT:
If the operator continues to run the system at excessive levels, or worse, if
the operator raises the drive level to compensate for the drop in output caused by the
protection circuitry, eventually an additional stage of protection will engage that shuts down
the system entirely (note that this additional stage of protection will never engage until
after
the second stage has been triggered). If the system shuts down entirely, the operator
can immediately restore sound by simply reducing the drive level to the system.
Advantages of Community’s DYNA-TECH Circuitry
There are numerous advantages to this type of multi-stage protection circuitry. The trip
point is pre-set to engage at exactly the same time on all speakers that are powered from
the same amplifier. The initial stages of DYNA-TECH protection circuitry do not rely on, and
are not affected by heat build-up. Some manufacturers use circuit breakers that require
heat build-up before they trip; this limits their ability to protect a cold speaker. The trip
points of such breakers are also affected by ambient temperature, their own internal
heating curves, and small variations in speaker impedance or crossover component
tolerances, all of which can cause unpredictable behavior.
Because the first and second stages of Community’s DYNA-TECH circuits are not thermally
sensitive, they react nearly instantaneously to protect against an excessive increase in
level. Moreover, the protection disengages almost immediately when the drive level to the
system is reduced; it is not necessary to wait for a circuit breaker to cool down. This
means that your loudspeaker can operate at its full dynamic range and still react quickly to
protect against excessive musical peaks, avoiding damage to the system. It also means
that your loudspeaker is protected from the moment the power amplifier is plugged in and
turned on, regardless of the ambient temperature.
As mentioned above, the protection circuitry provides a third level of protection for the
entire loudspeaker to guard it from severe misuse. If the system is operated in the second-
stage mode of protection for a long period of time, or if the input level is increased to try to
overcome the volume drop from the second-stage protection circuitry, a solid-state circuit
breaker will trip and remove all signal from the loudspeaker until the input level is reduced.
Because this circuit breaker
is
heat sensitive, it provides a final level of protection that
takes heat into account as well as power. However, unlike most implementations of circuit
breakers that take time to cool down before resetting, DYNA-TECH circuits respond
instantly to a reduction in level, restoring the system to its full dynamic range without
needing to wait for the circuit breaker to reset itself.
COOL-COIL™ TECHNOLOGY
The cone drivers used in the VERIS subwoofers utilize Community’s patented Cool-Coil™
heat evacuation technology. A proprietary process, Cool-Coil employs an airflow director to
remove heat from the voice coil, thereby increasing both the performance and reliability of
the cone drivers. In particular, the effect of Power Compression is significantly improved by
Cool-Coil technology. Power Compression occurs when drivers respond non-linearly to
applied power, producing less and less output as their voice coils heat up and their
impedance rises.
High voice coil temperatures have other undesirable effects on performance. Most materials
used in drivers, particularly adhesives and insulation, suffer some diminished properties
under extremes of heat. Thermal expansion can result in warpage and misalignment of
components. A voice coil in which the diameter has increased due to thermal expansion
will often no longer be round, and certainly has a greater possibility of rubbing against the
magnetic structure.
Any amount of cooling that can be applied to a woofer will be beneficial. One very
commonly used cooling method is venting of the pole piece of the magnet structure.
The motion of the cone assembly will pump air in and out of the cavity under the dust cap.
This air passing through the pole vent helps to cool the magnet structure. Community has
improved on this common cooling method by introducing an airflow director (US patent
6,390,231) into the air path. Figure 3 shows a conventional woofer motor with a vented
pole piece, and also a similar motor with the addition of an airflow director. The voice coil
former in the airflow motor is aluminum, and is taller than normal. This extended
aluminum former becomes a cooling fin for the voice coil, and the airflow director causes
the air to pass in close proximity to the former. By directing the air to flow over the hot
aluminum former, more heat is removed from the voice coil than simply allowing the