Bi-wiring, bi-amping, bridging

Bi-wiring:
Here several speaker cables from the amplifier led to the speaker. As a result, the cable cross-section is increased and the cable influences caused by a cross-section that is too small can be reduced.

bi-amping:
Here is the frequency range vor der final stage divided into two areas and each frequency range is amplified by its own power amplifier. Then a speaker cable goes from each power amplifier to that Chassis, for which it amplifies the frequencies.

bridging:

Here, a loudspeaker is connected to two amplifiers in order to achieve a higher level Performance to obtain. In addition, you need a phase inverter. Theoretically, the power of the two amplifiers is not doubled by bridging but quadrupled.

Bi-wiring/bi-amping only makes sense if the loudspeaker's crossover is built in such a way that the connections for the various chassis are routed to the outside.

With 2-way boxes, there are usually connections for the low and high frequency range. With 3-way boxes, there are often only connections for the low and high frequencies, because here the midrange and the Tweeter together on one Connection be placed. However, there are also speaker boxes with connections for each frequency range separately, i.e. not just 2 pairs of connections, but 3 or 4. With 3 pairs of connections one speaks of tri wiring/Tri Amping. With 4 connection pairs Quattro-Wiring.

Notes on bi-wiring:

Bi-wiring is a simple matter, risk-free and usually not particularly noticeable in terms of hearing differences (with - without - bi-wiring). Since the same output stage is still used for all chassis and frequency ranges, there is no real advantage, apart from the higher cable cross-section. If the power amplifier is equipped with several speaker outputs, then bi-wiring is a good idea.

Notes on bi-amping:

Bi-amping is a complex thing. To separate the frequency ranges according to the precursor you need a special switch. A speaker crossover is not suitable for this. These devices are z. B. with "Active Crossover“ or Behringer CX3400 Super X Pro. Such crossovers usually have a high edge steepness (24 db/octave) and extensive setting options (frequency, Phase, level, Delay…). From the preamp Is that possible Signal into the crossover and from the crossover into as many power amplifiers as there are connections on the loudspeakers, so with bi-amping you need two stereo power amplifier.

Depending on the frequency range, you can use different amplifiers, usually you will use a much more powerful amplifier for the bass range than for the middle and treble range. In the middle and high range you can z. B. fall back on a Class-A amplifier, often less than 2 times 50 watts are sufficient.

Now you have to remember that the loudspeaker also has a built-in crossover, although this crossover is usually primitive compared to the active crossovers. It only has passive components. Runtime corrections, phase corrections are difficult to carry out, for an active crossover this is child's play. But this crossover in the loudspeaker cannot be switched off, and this makes bi-amping relatively difficult to operate.

A simpler form of bi-amping is to dispense with the crossover described above. Then you only use the crossover in the speaker. This is probably the most commonly used form of bi-amping.

For bridging (bridges):

In general, an output stage must be designed for bridging. The prerequisite for this is a push-pull circuit with a symmetrical structure of the output stage: the same operating voltage (+ and -), iron-free and electrolytic-free coupling of the loudspeaker. The signal is fed to the input of one of the two amplifiers and via a phase inverter to the second amplifier.

How are the loudspeakers connected: The two ground connections of the amplifier are connected to each other and the loudspeaker is connected to the signal-carrying connection. The phase rotation ensures that the loudspeaker does not work against ground, but between the wave crest and wave trough of the two amplifiers. The output AC voltage is thus doubled, i.e. a power increase of almost four times is achieved P = ( Us - 2Uv)² / 2R. Uv stands for the residual voltage of an output stage combination and is around 3V.

When do you do bridging: On the one hand, you do this when there is not enough operating voltage available (e.g. in a car), on the other hand, for cost reasons by saving on expensive power supplies and high-voltage semiconductors. the speaker must double impedance of a normally operated loudspeaker because the peak collector current also increases. Imax = ( Us – 2 Uv ) / R
In practice, the power is often only doubled instead of quadrupled because the same loudspeakers are used as before the bridging and the power supply units cannot deliver the higher current.

Im Hifi-area, there are only a few amplifiers that are designed for bridge operation. Here are a few examples where it works because a phase inverter is also built in: Marantz PM17/SM17
McIntosch: Many stereo amplifiers can be bridged here: e.g. B. the MC202 Stereo Power Amplifier.

In the PA area, almost every power amplifier can be bridged. To avoid bridging, you can also buy a stronger power amp right away, which is usually less of a problem.

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