Cable choice consists mainly of selecting the correct cross sectional area in relation to the cable length and the load impedance. A small cross sectional area would increase the cables’ series resistance, inducing power loss and response variations (damping factor).
Connectors should be wired with a minimum of 2.5 mm2 (13 gauge) cable. This will be perfectly satisfactory under normal conditions. In the case of very long cable runs the wire size should exceed this, refer to the following table for guidance: -
|
|
|
| C.S.A. OF |
|
|
|
|
| CABLE |
|
| % POWER |
|
| dB LOSS |
|
| % POWER |
|
| dB LOSS |
|
| CABLE |
|
| EACH |
|
|
|
|
|
|
| LOSS |
|
|
|
| LOSS |
|
|
| |||
|
|
|
|
| AWG |
|
| RESISTANCE |
|
|
|
| INTO 4Ω |
|
|
|
| INTO 8Ω |
| ||||
| RUN (m) |
|
| CONDUCTOR |
|
|
|
|
|
| INTO 4Ω |
|
|
|
| INTO 8Ω |
|
|
| ||||
|
|
|
|
|
|
|
| Ω |
|
|
|
| LOAD |
|
|
|
| LOAD |
| ||||
|
|
|
| (mm2) |
|
|
|
|
|
|
| LOAD |
|
|
|
| LOAD |
|
|
| |||
| 10 |
| 2.5 |
| 13 |
| 0.13 |
| 3.9 |
| 0.17 |
| 2.0 |
| 0.09 |
| |||||||
|
|
| 4 |
| 11 |
| 0.08 |
| 2.5 |
| 0.11 |
| 1.3 |
| 0.06 |
| |||||||
|
|
| 6 |
| 9 |
| 0.05 |
| 1.6 |
| 0.07 |
| 0.8 |
| 0.04 |
| |||||||
| 25 |
| 2.5 |
| 13 |
| 0.33 |
| 9.3 |
| 0.42 |
| 4.9 |
| 0.22 |
| |||||||
|
|
| 4 |
| 11 |
| 0.21 |
| 6.1 |
| 0.27 |
| 3.1 |
| 0.14 |
| |||||||
|
|
| 6 |
| 9 |
| 0.13 |
| 3.9 |
| 0.17 |
| 2.0 |
| 0.09 |
| |||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||
| 50 |
| 2.5 |
| 13 |
| 0.66 |
| 17.0 |
| 0.81 |
| 9.3 |
| 0.42 |
| |||||||
|
|
| 4 |
| 11 |
| 0.41 |
| 11.4 |
| 0.53 |
| 6.1 |
| 0.27 |
| |||||||
|
|
| 6 |
| 9 |
| 0.26 |
| 7.5 |
| 0.34 |
| 3.9 |
| 0.17 |
| |||||||
| 100 |
| 2.5 |
| 13 |
| 1.31 |
| 29.1 |
| 1.49 |
| 17.0 |
| 0.81 |
| |||||||
|
|
| 4 |
| 11 |
| 0.83 |
| 20.5 |
| 1.00 |
| 11.4 |
| 0.53 |
| |||||||
|
|
| 6 |
| 9 |
| 0.52 |
| 14.0 |
| 0.65 |
| 7.5 |
| 0.34 |
|
5. Voltage and Power Selection (Distributed Line Operation)
When using 70.7V or 100V
When the relevant voltage tappings have been selected, add the individual power in Watts at all speakers and select and amplifier with a rating equal to or exceeding the total power in Watts. All of the transformer primaries should be connected in parallel to the output of this amplifier. If for example, you select the
It is recommended that a generous power safety margin (3dB of headroom) be left so that the system does not have to operate continuously at its full rated output power
In order to comply with relevant fire safety regulations (i.e. BS 5839:1998), it is required that in the event of fire, that failure of the circuit to which the loudspeaker is connected does not occur before evacuation of the building is complete. Suitable measures include:
a)use of terminal blocks (for connection to primary) with a melting point of not less
than 650°C, for example constructed from ceramic materials;
c)use of terminal blocks of a lower melting point but protected with thermal insulation;
d)use of terminal blocks such that, on melting, an
6