Bi-amping
In entertainment electronics , bi-amping (from Latin bi "two, double" and English amplify "amplify") describes the technology of operating a loudspeaker box with two or more external amplifiers - output stages . Several loudspeaker chassis or groups of loudspeaker chassis, which work together in one box, are each controlled with a separate power amplifier.
Number of power amplifiers per channel and terms
As a rule, two power amplifiers are used per channel, which is the reason for the "bi" in bi-amping. However, you can split the signal into three or more branches. These variants are also often covered by the term "bi-amping", although the somewhat more precise terms tri-amping for three power amplifiers per channel and multi-amping are used as a generic term for all path numbers.
As a counterpart to bi-amping, the operation of the loudspeaker box with only one output stage per box is referred to as single-amping or mono-amping .
variants
Basically, the loudspeaker box used must be prepared for bi-amping, i.e. it must have separate connections for each amplifier output to be fed in. Any metal bridges or pieces of cable that connect the two connections for the mono amping must be removed.
There are two types of bi-amping:
- Passive bi-amping: Since most loudspeaker boxes have a permanently installed passive crossover network , the most common form of bi-amping is passive bi-amping, in which the full frequency spectrum is fed to both branches of the amplifier, and the passive crossover in the low-frequency branch by means of one The low-pass filter filters the high frequencies from the signal, in the mid-high range it uses a high-pass filter to filter the low frequencies.
- Active bi-amping: The second variant is bi-amping with an active crossover that divides the signal into its respective paths before the output stages. These signals are then amplified separately. In addition to the active crossover, this method requires that there is no longer a passive crossover in the signal path in the loudspeaker box. Since this requires the box to be opened and modified not by the manufacturer for standard loudspeakers for home use, active bi-amping is almost only used in the PA area and in many finished active boxes .
Interconnection of the amplifiers
With AV receivers it is often possible to use power amplifiers that are not required for the front speakers in bi-amping mode. There are no variations regarding the interconnection.
When using two or more stereo amplifiers , there are two different options for stereo applications:
- Horizontal bi-amping: Here, one channel of the same stereo amplifier is used for the bass branch of both channels, as well as for each further branch. In this way, output stages with different output power can be used for each route, e.g. a particularly powerful amplifier for the mostly power-hungry bass branch and a less powerful amplifier for the mid-high range.
- Vertical bi-amping: Each loudspeaker has its own stereo amplifier, in which the high-frequency branch is amplified by one channel and the low-frequency branch is amplified by the other channel. If possible, two identical amplifiers should be used for the right and left channels.
Advantages and disadvantages
The advantages and disadvantages of bi-amping are controversial. Scientifically sound publications are not known. Manufacturers and consumer audio magazines describe bi-amping mainly as improving the sound; In contrast, the topic is discussed very controversially in internet forums. Many users report of sometimes enormous sound improvements, others of unchanged sound. Many hi-fi fans at least classify passive bi-amping as "Voodoo" with no added sound; the perceived sound improvements are either imagination or frequency response changes due to poor implementation and therefore, before the objective of linear reproduction, in truth sound deterioration.
Active bi-amping
There is broad consensus that active bi-amping can in certain cases have tonal advantages, which arise primarily from the possibilities of an active crossover. Depending on the type of active crossover network, it is possible to adapt to the loudspeaker box, the loudspeaker setup and the room in which the loudspeakers play. This has great potential for improvement (see also active box - this is practically an active box with external amplifiers). A sufficiently large change in the frequency response can therefore lead to a better assessment of the sound. Such a change can also be clearly demonstrated in hearing tests.
Another advantage can arise from the lack of a passive crossover, which causes distortions in certain application scenarios and often has relatively high component tolerances. These two causes can lead to measurable and possibly also audible improvements / changes in bi-amping.
However, the implementation requires specialist knowledge and suitable measurement technology and cannot be implemented by a layperson without extensive training in the subject. In the event of a mismatch, active bi-amping can quickly lead to objectively poorer results.
The significantly increased hardware expenditure and the associated additional costs of this configuration are also disadvantageous.
Passive bi-amping
The potential increase in performance is mentioned as an advantage of passive bi-amping. However, what is being compared with is questionable here. By bridging two amplifiers used for bi-amping and operating them in mono-amping, a significant, potentially even greater, increase in performance could be achieved. In addition, more power only leads to sound advantages if the power in mono amping is insufficient, i.e. usually only at very high volumes in the limit range of the amplifier. In this case, the desired improvement can also be achieved by using a more powerful amplifier in mono amping. In the case of the bi-amping function of AV receivers, it is also argued that the power would usually be limited by the common power supply of all power amplifiers and not by the power amplifier itself, so that a distribution to more power amplifiers would not lead to an increase in output.
Proponents also see the reduction in intermodulation distortion between the branches as a further advantage. However, it is controversial whether such distortion occurs at all and, if so, whether it is audible.
An undisputed advantage is that the volume ratio between the separated paths can be set individually with the appropriate amplifiers. This enables the frequency response to be adjusted . However, if the setting is incorrect, this adaptability can also lead to undesired changes.
Disadvantages of passive bi-amping are the higher costs due to the second amplifier (for acquisition and power consumption) and the need for double cabling.
Günther Nubert also states that phase shifts between the amplifiers can often occur, which would have significant disadvantages in terms of sound. His conclusion is "Bi-Amping ... can cause some problems and therefore requires the experience of professionals."
Individual evidence
- ↑ Audio knowledge: About bi-amping, bi-wiring and cable bridges. Heck, accessed December 1, 2018 .
- ↑ Steve Munz, Gene DellaSala: Bi-amping vs Bi-wiring: What's the Difference and is it Audible? In: Audioholics. March 23, 2015, accessed December 1, 2018 .
- ↑ Chuck Hawks, Bi-Wiring and Bi-Amping Loudspeakers
- ↑ a b Günther Nubert: Technology fed up. August 2016, p. 20 , accessed December 2, 2018 .
- ^ Günther Nubert: Technology fed up. August 2016, p. 21 , accessed December 2, 2018 .