Bi-wiring with two cables or one bi-wire cable?

[K.K.]

My Musical Fidelity kW500 amp has two speaker outputs per channel, presumably set parallel internally. I currently bi-wire my 803s the normal way i.e. 2 connectors at amp end and 4 connectors at speakers end.

My question is whether it is better to leave it this way or to get TWO mono-wire cables to connect each channel i.e. 4 connectors at amp end and 4 connectors at speakers end?

Thanks.

[DrJRapp]

I don't think ANYONE could hear a difference either way, assuming all things equal.

[K.K.]

I was at the B&W showroom yesterday to pay for my HTM3S and noticed that they are using two mono-wire cables to connect their Classe amp to the 803Ds. The sales guy claimed that this sounded better although I could not verify this without an A/B comparison available.

[dyazdani]

I had my 802s biwired in that way to my Levinson amp. My dad has his that way also, with two different types of cable. He has the top of the line Straightwire to the HF posts and the 2nd to top to the LF posts.

The B&W dealer where I went to college always had the high end B&Ws wired that way. I'm not sure that there is a striking difference. I would say that if you do not choose to biwire (single or double) then at least get a high quality set of jumpers.

[SRT-10 Viper]

Can you use dual sets of wires with an amp that has single posts (i.e put both wires on single amp posts)... Why would I do this??? I have my center bi-wired today with wires going though the wall. I will be changing my current amp (with bi-wire posts) to an amp with single posts and want to know if I can use it the way it is currently wired.

[dyazdani]

Viper,

I am currently set up as you describe - I went from a Levinson amp with dual posts to one without. There are several options. Both runs of my cable have spade connections. I have Goertz cable so the spades are flat and can basically fit on top of one another.

I used to have double runs of some AQ Argent+ with spades, but the part where the wire connects the spade is thick (1/4" or so). In that case, I had to put one spade at an angle - looked like a "V".

I suppose you could have one run spade and one with banana terminations as well.

[Lex]

There is probably quite a bit smaller chance you'd hear a difference in methods of bi-wire, vs single vs bi-wire for example. Certainly, the more resolving a person's system, the greater chance even small differences could be heard in setup. However, in actual practice, this isn't as high a percentage change area as some others on your system you could worry about-

Lex

[K.K.]

I had my 802s biwired in that way to my Levinson amp. My dad has his that way also, with two different types of cable. He has the top of the line Straightwire to the HF posts and the 2nd to top to the LF posts.

Interesting thought regarding using different cables for LF and HF. I do not have any experience regarding cable characteristics to do this sort of tweak but I guess some people out there would have tried it and can share their experiences...

[grit]

I just switched from a single wired system to bi-wired (B&W 703s). I can certainly hear a difference, but that doesn't make it a huge one. Sound stage seems to have gotten wider and there is more detail in the sound. However, for all I know, i could have accomplished the same thing I replacing the factory brass jumpers with speaker wire jumpers (like the 800 series comes with).

Is there someone with 800s that can comment on bi-wiring vs using the factory 800 series "jumpers"?

[RobP]

I finally bi-wired my 803's and it does make a difference from the factory setup, it wasnt a huge difference but non the less it was an improvement.

here is what B&W says about Bi-Wiring as well as Bi-Amping.

Bi-wiring and bi-amping

Most B&W speakers are provided with two pairs of speaker terminals; this allows you to either bi-wire or bi-amplify them. The aim of both these techniques is not to simply get the customer to spend more on cables and electronics (although no manufacturer objects to this spin off) but to improve the resolution of the speakers.

A multi-way speaker contains a crossover network that not only divides the incoming signal into different frequency ranges, appropriate to the working range of each drive unit, but also equalises each driver’s response to be flat (raw driver responses are usually anything but flat).

There are two different basic types of crossover – series and parallel. Series crossovers have each filter section wired in series between the positive and negative input terminals. It is impossible to treat each filter section individually – each interacts with the others – and such crossovers are not suitable for bi-wiring or bi-amping. But by far the most common type is parallel. Here, each driver has its own filter wired between it and the input terminals. If there is only one pair of input terminals, the inputs to all the filters are connected in parallel to that one pair of terminals. If, however, you have more than one pair of terminals, you can completely separate the inputs to each filter. Why on earth would you want to do such a thing?

In the case of bi-wiring, the answer lies in the cable connecting the speaker to the amplifier and the fact that the amplifier is a voltage source but the speaker is a current driven device (force on voice coil = magnet flux density x length of conductor in the magnet gap x current).

Firstly, all cables are a compromise. Some types of construction work better at low frequencies and others at higher frequencies. Providing separate inputs to the speaker allows you to use different cable types, each optimised for the frequency range of use.

Secondly, consider that the cable has an impedance that causes a voltage drop along its length. Now consider the current flowing along the cable. Assume for the argument that the amplifier delivers a perfect voltage waveform to the cable and the cable itself adds no distortion. However, each driver has a non-linear impedance (for example, the inductance of the voice coil alters depending on its position in the magnet gap) that causes the current to be non-linear. This non-linear current through the impedance of the cable causes the voltage drop along the cable to be non-linear and thus the voltage across the speaker terminals is also non-linear, even though it is linear at the amplifier end.

If we were just concerned with one driver, things would not be too bad. But that non-linear voltage at the speaker terminals may contain harmonics within the frequency range of one of the other drivers and that driver will reproduce them, albeit at low level. If, however, you separate the inputs to each driver filter, each driver’s distortion is kept to itself and the total system distortion goes down. We are talking small changes here, but the resolution of some modern drivers is now so good that small improvements like this are readily detectable by keen listeners.

Many people ask us whether the load on the amplifier is different if you bi-wire. It is not. As far as the amplifier is concerned, it matters not one jot whether you parallel the inputs to the filter sections at the speaker end or the amplifier end of the speaker cable.

Bi-amping takes advantage of all this and adds some benefits of its own. Like with cable, you can choose different amplifiers that excel in different frequency bands. You may, for example, be keen on valve (tube) amplifiers. But even the most die-hard of aficionados would be hard pushed to claim that they are any good at keeping good control of the bass. Bi-amping enables you to combine a valve amplifier for mid and high frequencies with the control of a solid-state device at low frequencies.

Unlike bi-wiring, the load to each amplifier is different from that using a single amplifier full range. The voltage demands on each amplifier remain the same (each is still fed a full-range input and gives a full-range output), but the current demands are reduced. This of itself can improve the amplifier’s ability to deliver the signal to the speaker.

Be careful when bi-amping that the gain and polarity of each amplifier are the same, otherwise you will compromise the frequency response of the system.