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PASSIVE CROSSOVER IMPEDANCE
When passive crossover components are used in multiple-speaker systems, the crossover
system's impedance must be considered along with the speakers impedance in determining
amplifier loading.
For 6dB per Octave systems (where a single capacitor in a series is used for high-pass or single
inductor [choke] in series is used for low-pass) the net impedance of the system will be increased
and problems are unlikely.
12dB per Octave systems (where both an inductor and a capacitor are used with each speaker) can
cause trouble. A 12dB choke capacitor pair forms a series-resonant circuit to ground whose
impedance at resonance is determined by the speaker's dynamic independence. For instance, if the
speaker is openordisconnected, the crossover input impedance is theoretically ZERO at resonance
- a direct short!
Since speaker impedance varies considerably from rated values at various frequencies, it is
common to find that "standardized" 12dB per Octave crossovers (which are designed for pure
resistor loads) have serious impedance dips near their crossover frequencies, possibly causing
overheating and fuse-blowing in the amplifier.
We recommend that you be cautious in using 12dB/Octave
specifically designed to have minimual impedance variations for the speakers in use.
SPEAKER POWER RATINGS
It is common knowledge that more speakers are damaged due to too little power from the amplifier,
and sending a distorted "clipped" signal to the speaker. The distortion components of a clipped
waveform create a tremendous amount of heat which can, and often does, damage the voice coil.
This happens when the user thinks he/she can turn the volume knob up all the way. The amplifier
inputs can be adjusted to allow this, and that is highly recommended. Using an oscilloscope, the
installer can adjust the gain controls on the amplifier until the signal just clips at maximum volume.
Excessive power can also damage speaker voice coils, but most speaker specifications are
conservative, and speakers can handle a great amount of power if clipping is avoided.
The power rating for speakers should correspond to the rated output of the amplifiers:
At high power levels some woofers, which are rated to handle the power, "pop", "clang", "snap", or
otherwise show signs of bottoming. These speakers are designed to use the "air spring" of an
enclosed box to prevent bottoming. This applies to almost all woofers originally designed for home
or professional use. One solution is to use speakers designed for "infinite baffle"use, which have very
stiff suspensions. The best solution is to build enclosures for the woofers.
AMPLIFIER
MODE
Punch 30
Stereo
Bridged Mono
Bridged Mono
Punch 45
Stereo
Bridged Mono
Bridged Mono
Punch 75
Stereo
Bridged Mono
Bridged Mono
Punch 150
Stereo
Bridged Mono
Bridged Mono
5
crossover systems unless they are
IMPEDANCE POWER
4-ohm
15 Watts
8-ohm
25 Watts
4-ohm
50 Watts
4-ohm
22.5 Watts
8-ohm
45 Watts
4-ohm
70 Watts
4-ohm
37.5 Watts
8-ohm
75 Watts
4-ohm
120 Watts
4-ohm
75 Watts
8-ohm
150 Watts
4-ohm
180 Watts
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