Whether you're brand new to HiFi, or have been perfecting your system for decades, you are bound to have wondered at some point why some speakers, like the outrageously good Fyne Audio F700s pictured above, have four terminals on the rear, when cables only have two plugs at each end?
This is a good question, and one that’s divided the HiFi community since bi-wireable speakers became an option in the 1980s, but do you actually know what the physics is behind those extra two terminals on the back of your speakers, or have you merely dismissed them as cable manufacturers and speaker manufactures working in cahoots to encourage you to spend extra money on cables? After all, the rather cynical term ‘buy-wiring’ is not wholly un-true; you do have to buy twice as much speaker cable!
Some manufacturers offer bi-wire specific cables, which essentially combine two cables into one. Van Den Hul's offering is called the TeaTrack, and Chord Cables offer Leyline4x, pictured below, which you can see has four terminals at each end.
First off, if you are a cable sceptic then you’ll probably be a bi-wiring sceptic too; if you don’t believe that upgrading two cables can make a difference to your system, why would upgrading four? But stick with me, and I’ll try to explain how it works.
Let’s begin with exploring how single wiring works, as this is key to understanding the effect bi-wiring will have on the signal path of the music, which is, after all, the cardiovascular system of your entire HiFi set up. On a single wired speaker, with just two terminals at the back, or indeed a bi-wired speaker where you are only using two of the four terminals, the signal path will look something like my hastily drawn diagram below:
The current for one channel (i.e the left or the right speaker) will leave the amplifier at the red terminal along a single cable, and enter the rear of the speaker where it will meet the filtering circuit. Here the signal is divided so that the high-frequency goes only to the tweeter, and the low frequency goes to the bass driver, illustrated by the two squares marked HF and LF. Having passed through the coil behind each driver and produced beautiful music, the current then returns via the same cable to the black (negative) terminal on the amplifier. There is a small range of frequencies in the middle, unique to each driver design, where both tweeter and bass driver can output the same frequency with equal power, but as the two types of driver are each designed to handle a particular frequency range, the best sound is produced by each driver outputting its best suited frequencies. If designed well, the two drivers working in tandem will produce the same sound as if it was a single driver working across the whole audible frequency range.
However, the key thing to note here is that both the high frequency and low frequency signals have to travel along the same wire until they reach the filtering circuit.
Now let’s look at a bi-wired system, again using a diagram that illustrates the basic signal path from amplifier to speaker:
Here you will notice that you end up with two cables per channel, so two cables going from the amp to the left speaker and two cables going from the amp to the right speaker. The diagram only shows one channel of course. The same theory applies to this bi-wiring as to the single wiring, in as much as electrical current flows out of the positive amplifier terminal, into a filtering circuit to separate high and low frequencies, then through either the tweeter or bass driver, and finally back to the negative amplifier terminal. The difference here, however, is that there are separate cables for the high and low frequencies to travel along from amp to either tweeter or bass driver.
This does one crucial thing: eliminating any chance of interference between the differing frequencies to, in theory, produce a clearer and more rhythmically accurate sound.
Now you may raise your digital hand and point out that there is still the same signal being sent from amplifier to speaker along both cables, regardless of whether it ends up at the tweeter or bass driver, because the terminals on the amplifier haven’t been changed, so how has this actually separated the high and low frequencies from the same cable? Well, a curious electrical effect comes into play here that can be hard to wrap one’s head around to begin with, but is relatively simple once you understand it…or have just accepted it!
Despite the fact that the circuit which splits up the high and low frequencies to guide the correct frequency range into either tweeter or bass driver is at the speaker end of the system rather than the amplifier end, in blocking the low frequencies at the tweeter, for example, it prevents any low frequency current flowing along any point of the wire between amp and tweeter. The same goes for the bass driver; the circuit that blocks high frequency current at the speaker end essentially blocks the entire cable from carrying high frequency current. Therefore it makes sense that now the tweeter cable only carries high frequency current, and the bass driver cable only carries low frequency current, isolating the differing frequencies into completely separate wires.
Concurrently, one of the main reasons that higher quality speaker cables make such a difference to overall system performance is that, aside from more expensive metals being used in the actual wiring and termination, companies like Chord invest heavily in using materials carefully engineered to insulate the cables from any exterior or interior interference. Therefore it goes without saying that completely separating the different frequencies is going to further improve sound quality. And if you can afford to use expensively insulated cables as well as bi-wiring, for double the insulation-y goodness, then you are well on your way to audio nirvana...though we would suggest your money is better spent upgrading your single wired cables, or bi-amping (more on that in a later article) rather than doubling a lower quality set!
So you may remain sceptical, but now you know the theory behind why your amplifier may have two left pairs and two right pairs of terminals, or why your speakers have four terminals at the back, and you can see that physics dictates that utilising these extra terminals will result in better sound reproduction. I am afraid it is up to you, however, to decide whether the increase in sound quality is significant enough to be worth spending twice as much on cables…
If you already have an amplifier and a pair of speakers that support bi-wiring, my advice would be to visit your local HiFi retailer (preferably us!) and either arrange a demo where you can compare a system with and without bi-wiring, or borrow two pairs of good quality cables to experiment with on your own system at home. I suspect you will find, however, that the difference between a bi-wired system and a single wired system is not as great as a single wired system with a cheap cable vs another single wired system with a twice as expensive cable.
So, our personal opinion is that you are much better off spending twice as much money on a single wire speaker cable than you are on spending on a bi-wire cable, quality over quantity, as it were, but do come and borrow some cables from us a try it for yourselves if you are still curious!