KLING & FREITAG K&F ACCESS T9 - Manual (Page 13)

User’s Manual ACCESS SYSTEM
KLING & FREITAG GMBH ©1995-2009 Version 6.0, 17.03.2009 Page 13 of 60
4. The Subwoofers
4.1 Short-Circuit Fuses in the K&F Subwoofer Systems
4.1.1 Risks of using High Performance Power Amplifiers
In recent years, power amplifiers have achieved increasingly higher levels of perform-
ance. Some of them can be operated with low-impedance loads. There are, therefore,
strong power amplifiers that can reliably work with impedances below 1
Ω. This devel-
opment has led to an increased safety risk during defective operations.
When there is a defect, such as a short circuit in the speaker chassis or on the crossover,
it is possible that the power amplifier --- despite existing protective switches --- will not
shut off. Long cable lengths and contact resistance on the plug connections may already
have an electrical resistance of 1
Ω. As a result, the power amplifier cannot ‘‘recognise’’
the operations as being defective and, therefore, delivers unacceptable high currents. In
the worst-case scenario, this may lead to fire damage (hot and charred wiring / connec-
tors as a result of overloaded wires and connectors, etc.).
The current safety regulations
are lagging behind this development and are thus not up-to-date with this modern
technology.
Normally, the K&F System Controller prevents the speaker from being overloaded. The re-
sults of such a defect cannot be avoided by the controller.
In order to give consideration to this development, Kling & Freitag now equips its sub-
woofer systems with short circuit fuses at the signal input. These fuses do not offer
protection for the speaker, but do reduce the risk of consequential damage in the case
of a short circuit.
For systems, which are not serially equipped with a short circuit fuse, Kling & Freitag
offers simple add-on kits so that you can adapt your existing subwoofer systems to the
current power amplifier development.
4.1.2 Identifying the Models with Short-Circuit Fuses
The subwoofer systems, which are serially equipped with short-circuit fuses can be iden-
tified as follows; both mentioned stipulations must be fulfilled:
4.1.3 Add-On Kits for Subwoofers without Short-Circuit Fuses
All subwoofer systems, which are not serially equipped with short circuit fuses, can be, if
required, easily and inexpensively upgraded even by yourself.
An instruction manual for this upgrade is delivered with the add-on kit.
POWER: 700W
WT: 51,5kg
XO-ON OFF
SER.-NO.:
25080000070
IMP: 6
Ω
8
Ω
Zmin: 4
Ω
6
Ω
-
1 - 2 -
1+
2+
+
IN
all pins
parallel
to out
The first two
digits must be at
least 25.
The next two
digits must be at
least 08.