Why bi-wiring has no benefits
When a properly designed and constructed speaker cables are used in standard configuration there are no benefits of bi-wiring. Rather bi-wiring has great potential to cause timing differences, incoherence in the audio signal and unnecessary cable cost. |
Why bi-wiring has won unjustified recognition
It should be noted that the sound can be improve by bi-wiring in some specific situations. The sad part though is that those "improvements" all depend on insufficient equipment and can be better rectified with other solutions than bi-wiring.- First reason – The original speaker cables used in standard configured have been wrongly constructed (often with too high impedance). The cable impedance is composed of 3 components: Resistance (Rdc), Inductance (L), Capacitance (C). Rdc being the dominating parameter for speaker cables. By Ohms law we know that the Rdc will reduce by half when using double cable runs, which is the most common way to bi-wire. This will in many cases lead to a distinct audible increase in overall loudness level. While this can be seen as an improvement it should be noted that this is not due to the bi-wiring as such but solely due to the double cable runs. So this result could easily have been obtained by using a properly designed speaker cable of thicker gauge in the first place.
- Second reason - Speakers with bi-wire optionally have been used with the standard jumper- links or poor jumper-cables attached. When bi-wiring these are removed. This will in many cases lead to an audible improvement in the speaker section that was connected only with the jumper-links (not connected directly with the speaker cable). However, this improvement again is not due to the bi-wiring but rather due to the inadequate jumpers. Unfortunately most speakers with bi-wire optionally come mounted with jumper-links of poorest construction and material. This is due to cost concerns and the thought that the user will opt for bi-wire configuration and remove the jumper-links soonest.
The proposed benefits of Bi-wiring
While in recent years there have been a great buzz to bi-wire, more and more initiated high-end speaker manufacturers have for good reasons returned to or stuck with standard configurations terminals. We will now show why standard configuration is the better option for high-end sound reproduction.The advocates of bi-wiring most often use any or several of the following reasons to justify a bi-wiring (bi-amping), several originating from sources such as www.soundstage.com and supported by speaker manufactures such as Bowers & Wilkins:
- When the audio signal to the woofer (low-frequency unit) ceases, such as when a loud bass note is finished, the woofer tries to stop moving. Because of its size and mass it does not stop instantaneously instead it actually goes through a process of "settling". As it settles, it moves forward and backward repeatedly until it can completely come to rest. During this movement, as the voice coil is moving through the field of the magnet, it generates its own signal. That generated signal is sent backward up the woofer wires and into the crossover, where it corrupts the rest of the music signal.
- Bi-wiring works to reduce the tendency for strong bass signals (in general) to overwhelm the rest of the audio signal.
- Bi-wire configuration will improve the sound since it improves/bypasses the crossover
- When bi-wiring you can choose different cables optimised for the different frequency ranges, which will improve the overall reproduced sound.
Bi-wiring: what science show
Unfortunately a lot of what has been written about bi-wiring has lacked in-depth science and been based partly on invalid assumptions. In initial research we where open to the possibility that bi-wiring could potentially lead to better sound, since our multi-conductor cable design easily facilitates such configuration. However, further and more in-depth research made us rethink since we were able to falsify all the arguments that were brought forward by the bi-wire advocates.Lets take a closer look at the bi-wire advocates statement.
"High-frequency corruption by EMI/signal from settling woofer"
When a (low frequency) signal is played it makes the woofer move and this woofer movement through the magnetic field could by itself indeed generate a new unwanted electric signal. The woofer element will in fact act as a microphone, inducing a current. However, a certain understanding of how a microphone works will reveal that this unwanted signal is a mirror of the original signal, and with the same frequency. But since the woofer element is not a very "efficient" microphone, we know that the new unwanted signal will be of much lower strength and magnitude than the original signal. This unwanted signal will therefore be cancelled out by the original signal, and will only be seen as a slight resistance to the original signal.If we now look at the specific case where the original low frequency signal stops, we will in fact be stuck with a residual unwanted signal generated while the woofer element is breaking/settling in. However, from above we already know that this residual backward travelling "distortion" signal is of low frequency nature and consequently will be blocked from the high frequency section by the cross-over, just as the original signal was.
Conclusion
A woofer can induce an unwanted mirror of the original signal by its movement which theoretically can interfere with the original low frequency signal in an audible way. However, due to the inherent low frequency nature of the unwanted signal it can never interfere with the rest of the frequency spectra. In practice it will at worst make the low frequency a bit "woolly".
The misuse of this phenomenon by bi-wire advocates is due to their negligence or misunderstanding of the characteristics of the new unwanted signal that is generated by the woofer movement.
"Bi-wiring works by reducing the tendency for strong bass signals to overwhelm the rest of the audio signal"
This statement seems to be based on an idée that the signals of different frequency propagates alone along the cable and then the strong bass signals interferes with the rest of the audio signal. This is of cause not the reality even in its most liberal interpretation.If we assume that we are using “regular” speaker cables (which implies they are of sufficient gauge, say 12 AWG or thicker, made of copper or silver and have no active elements) then this statement is completely unfounded even in its broadest sense. In reality signals of different frequencies travel in one merged signal (Superposition) when propagating through a linear elements, such as copper and silver. The speaker crossover will upon arrival, as appropriate, sort out respective frequency without any alteration to the original signal.
If we instead assume that we have managed to create a non-linear cable against all odds, say:
- used a heavily corroded wire
- or used wire of magnetic material (e.g. iron),
- or used a excessively thin cable (single 20 AWG wire) on a power hungry system
- or added some not thought trough active device in a little box on the cable
Then we potentially would be able to create some interference as propose, by what is called Intermodulation Distortion (IMD).
When Intermodulation Distortion occurs two or more signals will mix and create new signals (distortion), which are the sum and the difference of the original signal.
Example of Intermodulation Distortion |
|
| Input signal |
Output signal |
| 10 000Hz | 10
500Hz (IMD component) |
| 10 000Hz | |
| 500Hz | 9 500Hz (IMD component) |
| 500Hz | |
Conclusion:
- The cables themselves will not create any IMD. Any potential IMD created by the amplifier or the speakers are beyond the cables, independent of configuration.
- In the event that the cables should cause any IMD (highly unlikely!), then bi-wiring would not rectify it since bi-wiring would make the same distorted signal propagate down two cable runs instead of one without doing anything about the distortion as such.
- The best way to avoid intermodulation distortion is to buy high quality hi-fi components with low measured distortion levels and avoid cables with active devices of dubious origin.
"Bi-wire configuration will improve the sound since it improves/bypasses the crossover "
Independent of if you use standard configuration or bi-wiring the signal will pass through the same crossover with a signal that need to be properly split for the different speaker elements. There is no way to improve or bypass the crossover without performing physical changes inside the speaker (crossover section) of the speaker itself.So a poorly designed speaker crossover will continue to be poor whether or not you bi-wire.
"When bi-wiring you can choose different cables optimised for the different frequency ranges, which will improve the overall reproduced sound"
It is true that signals of different frequencies will behave differently in cables of dependant geometry and construction.However, if the aim is to reproduce the sound as close as possible to the original sound which is the case in most, if not all, hi-end hi-fi we also need to consider the related trade-offs.
Assume that we chose to have cables of different construction and design for the different signal ranges, as proposed above. Then this also implies that the different frequency ranges will be exposed to different impedance (Resistance, Inductance and Capacitance).
This impedance difference will unfortunately lead to incoherent signal losses. This is particularly undesirable since the ear is much more sensitive to that some frequencies are altered differently then the rest than that all frequencies are altered similarly. While much has already been written in this area, for the interested reader, some simple experiment suite to exemplify for the common public.
Consider the following example:
- Have your mother, boyfriend, girlfriend (or who ever you find suitable for the experiment) talk to you when you are both outside, in the living room and e.g. in the restroom. You will notice that the voice sounds quite identical to you. Although the acoustic environment is drastically altered the ear will compensate for this since the sound is treated coherently, evenly good or bad.
- If you redo the same experiment with an instrument of yours or play a piece of music you will come to basically the same conclusion, although you might come to the conclusion that the restroom is not you optimal long-time listening room.
- However, if you now consider the same person as mentioned above with a cold (or after his/hers late night out) you will hear a clearly audible difference in the voice. This is due to alteration to part of the frequency range which occur when e.g. part of the sinuses is blocked.
This experiment suit to show that the your ears are much more sensitive to changes in part of the frequency range than a even alteration of the complete frequency range.