Polarity Checking; Amplification & Power Handling - Tannoy VQ 60 User Manual

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.
There are also commercially available polarity checkers that can be used (IviePAL™, NTI™). If you are
commissioning a system using a spectrum analyzer such as SMAART™, SYSTUNE™, CLIO™, MLSSA™ by
checking the impulse response for the first positive swing. Be sure that EQ and crossover filtering has been
removed before checking.
If problems are encountered, inspect the cable wiring in the first instance. If you are using amplifiers from more
than one manufacturer, check the polarity at the amplifiers as well as the loudspeakers.
5 AMPLIFICATION & POWER HANDLING
As with all professional loudspeaker systems, the power handling is a function of voice coil thermal capacity. Care
should be taken to avoid running the amplifier into clip (clipping is the end result of overdriving any amplifier).
Damage to the loudspeaker will be sustained if the amplifier is driven into clip for any extended period of time.
Headroom of at least 3dB should be allowed. When evaluating an amplifier, it is important to take into account its
behavior under low impedance load conditions. A loudspeaker system is highly reactive and with transient signals
it can require more current than the nominal impedance would indicate.
Generally a higher power amplifier running free of distortion will do less damage to the loudspeaker than a lower
power amplifier continually clipping. It is also worth remembering that a high powered amplifier running at less
than 90% of output power generally sounds a lot better than a lower power amplifier running at 100%. An amplifier
with insufficient drive capability will not allow the full performance or the loudspeaker to be realized.
It is important when using different manufacturers amplifiers in a single installation that the have very closely
matched gains, the variation should be less than +/- 0.5dB. This precaution is important to the overall system
balance when only a single active crossover is being used with multiple cabinets; it is therefore recommended
that the same amplifiers be used throughout.
On the specifications pages you will find the VQ loudspeakers power handling capacity quoted in three
categories:-
Average (RMS), Programme, & Peak
We recommend using the programme power listed in the loudspeaker specifications to choose the correct
amplifier. To realize the VQ loudspeakers full potential, the amplifiers rated continuous power should be equal to
the loudspeakers programme power at its nominal impedance.
VQ Series Recommended Amplifier Power
VQ60/100
Low Frequency
Passive MF/HF
Mid Frequency
High Frequency
VQ DF
Passive MF/HF
Mid Frequency
High Frequency
VQ MB
Power Requirement
2000W into 4 ohms
400W into 8 ohms
400W into 8 ohms
200W into 8 ohms
400W into 8 ohms
400W into 8 ohms
200W into 8 ohms
2000W into 4 ohms
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