Bi-Wiring A Loudspeaker: Does it Make a Difference?
Originally published at: University of St. Andrews, St Andrews, Fife KY16 9SS, Scotland.
“Bi-wiring” is a controversial topic. Some people are quite certain it
makes an audible difference. Some others are convinced that it can’t
actually make any difference at all. The purpose of this analysis is to
try and decide whether it is at least theoretically feasible that
bi-wiring can make any difference.
To define what is meant by “bi-wiring”, and understand what effects it
may (or may not) have, we can start by considering the situation
illustrated in Figure 1.
This shows an amplifier connected to a loudspeaker by a
standard cable made from a pair of connecting wires. For clarity, only
one channel of a stereo pair is shown. The loudspeaker consists of two
drive units. – a high-frequency (HF) unit often called a “tweeter”, and
a low frequency (LF) unit often called a “woofer”. Loudspeakers
generally employ a “cross-over network” to direct low signal
frequencies to the woofer, and high frequencies to the tweeter. In the
example shown here this network is split into distinct HF and LF
sections. This split permits the loudspeaker to be bi-wired. (Not all
loudspeaker cross-over arrangements will permit this without
modification.) In practice, as shown here, loudspeakers designed to
permit bi-wiring have extra sets of input terminals which may be joined
together when bi-wiring is not employed.
In the conventional wiring arrangement shown in Figure 1, the
HF and LF input terminals are wired together in parallel at the
speaker, and just one pair of connecting wires are employed to link
both speaker units to the amplifier. In most cases “bi-wiring” means
using an extra pair of connecting wires (i.e. another cable) so that
the signals for the tweeter and woofer are sent from the amplifier to
the speaker by separate routes. This bi-wiring arrangement is
illustrated in Figure 2. In this new arrangement, Cable 1 carries the
signals destined for the tweeter, and Cable 2 carries the signals
destined for the woofer.
Various arguments have been presented for this bi-wiring arrangement by adherents who feel it alters the sound. For example, it may be claimed that each of the two cables may now be optimised in some way for the limited range of signal frequencies it now carries, and hence act more effectively. Alternatively, it is sometimes claimed that separating the signals for the tweeter and woofer means they do not now ‘interfere’ in some manner which may arise when they share the same cable. Unfortunately, these claims are generally unclear in technical terms, and there is a general lack of any reliable analysis or measured data to support the claims. This makes it questionable whether the claims are justified. It is also unclear whether the alternative arrangement in Figure 3 might also be “better” than the conventional arrangement. The arrangement in Figure 3 is also bi-wired, but the pairs of wires are now joined at both ends of the signal connection from amplifier to loudspeaker.
In the modified arrangement shown in Figure 3 both
cables are used “in parallel” to connect signals to both speaker units.
The question now becomes, “Are the arrangements shown in Figures 1, 2,
and 3, all going to produce exactly the same results in use?”
Detailed analysis of the three arrangements is made difficult
by two factors. Firstly, the electrical properties of the items
involved can be quite complicated. The networks used in loudspeaker
crossovers may contain a number of components and have a complex
behaviour. Similarly for the actual speaker units. As we have seen on
the webpages on cables, even the behaviour of simple twin-feed
connecting cable can be more complicated that we might expect.
The second problem for a precise analysis is that the actual
details of the loudspeaker crossover, etc, will vary a great deal from
one model of loudspeaker to another. Hence we can expect any results to
depend upon the choice of loudspeaker, cable, etc.
To make understanding these questions easier we can address a
simpler question – i.e. we can ask, “Is is possible for the changes
between the arrangements in Figures 1 - 3 to make any difference, or
not?” To answer this question we need only look at a simplified
example. If, in that example, a difference can be show to be possible,
then it implies that a difference may appear even in more complicated
arrangements. If no such difference is shown, this does not necessarily
resolve the real issue, but at least we have progressed part of the way
to a better understanding. With the above in mind we can now form a
electronic models of the above arrangements, simplify them as far as
seems reasonable, then compare their computed behaviours.
Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!