Tannoy V12HP - Manual (Page 5)

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 sq. mm (12 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:-
CABLE RUN (m) C.S.A. OF EACH
CONDUCTOR (mm) CABLE
RESISTANCE Ω % POWER LOSS
INTO 8Ω LOAD % POWER LOSS
INTO 4Ω LOAD
10 2.5
4.0
6.0
0.14
0.09
0.06
1.7
1.1
0.73
3.5
2.2
1.5
25 2.5
4.0
6.0
0.35
0.22
0.14
4.3
2.7
1.8
8.6
5.4
3.6
50 2.5
4.0
6.0
0.69
0.43
0.29
8.6
5.4
3.6
17.0
11.0
7.2
100 2.5
4.0
6.0
1.38
0.86
0.58
17.0
11.0
7.2
35.0
22.0
14.0
4. Polarity Checking
It is most important to check the polarity of the wiring before the speaker system is flown. A simple
method of doing this without a pulse based polarity checker for LF units is as follows: Connect two
wires to the +ve and -ve terminals of a PP3 battery. Apply the wire which is connected to the +ve
terminal of the battery to the speaker cable leg which you believe to be connected to pin 1+ of the
speaker connector and likewise the -ve leg of the battery to pin 1-.
If you have wired it correctly the LF drive unit will move forward, indicating the wiring is correct. All
that remains now is to connect the +ve speaker lead to the +ve terminal on the amplifier and the -
ve lead to the -ve terminal on the amplifier. If however the LF driver moves backwards, the input
connections need to be inverted.
If problems are encountered, inspect the cable wiring in the first instance. It should also be noted
that different amplifier manufacturers utilise different pin configurations and polarity conventions, if
you are using amplifiers from more than one manufacturer, check the polarity at the amplifiers as
well as the loudspeakers.