BEMUSED BY BIAMPING OR BIWIRING?

 

BI-WIRING The simplest hook-up between amplifier and speakers involves using a two-core cable, one side of which is designated positive, marked with a '+' symbol and/or red plugs, carrying the signal from the power source to the speakers' crossover: an electrical circuit that splits the signal between the drive units. So in a two-way speaker, bass and midrange signals go to the woofer, while higher frequencies go to the tweeter.

One of the problems with a standard crossover and a single-wire connection is that low frequency signals tend to swamp the more delicate treble stuff, especially in the return (or negative) connection back to the amp. By separating the signal all the way back to the amp's output stage, using two runs of cable or a purpose made four-core biwire cable, these effects can be reduced. 

But the speakers need to be designed to be biwired. In a biwirable speaker, the two halves of the crossover - the circuitboard that takes bass frequencies out of the feed to the treble drive unit, and vice versa - is physically split into two sections. One filters out low frequencies from the feed to the tweeter, the other loses the squeaky stuff from the terminals connected to the mid/bass woofer unit. Only when the link bars are in place for single-wired operation is there any electrical connection between the two halves of the crossover. As an aside, if you're single-wiring a biwirable speaker with the link bars in place, experiment with using the upper or lower terminals - there's often a subtle change in the sound. If there are no multiple terminals, then biwiring is not possible.

To allow them to be used with a normal two-core cable, a jumper bar will usually be found connecting the terminals of a biwirable speaker - the loudspeaker instructions will tell you how to remove these to prepare the loudspeaker for biwiring. Having done that, you will need four conductors (two positive and two negative) connected to the loudspeakers terminals, whether you use two separate two-core cables or a four-core cable is a matter of personal preference, but most users will find the four-core option much tidier and professional looking.

With the possible exception of amplifiers that are equipped spring-clip terminals, which have trouble accommodating even single wire cables, any amplifier can be used for biwiring. Some amplifiers provide twin sets of speaker terminals specifically designed for biwiring, while others have outlets marked A and B that you can use for the same effect, though in the latter case, you will need to have both sets of outputs switched on.

An amplifier with a single set of terminals, i.e. just left +/- and right +/- can also be used: the two positive conductors from the left speaker being connected into the left '+/red' terminal, and the two negatives into the '-/black'. Repeat this for the right speaker, and that's all there is to it. If you have an amplifier with 4mm Banana socket terminals, most cable manufacturers or dealers will supply biwire cable 'combined' into a single set of plugs to make this even easier. If, however, you are using bare wire connections or are soldering up your own cables, check and double check the polarity of each amp-to-speaker connection - it is all too easy to get loudspeakers connected out of phase. If you do happen to get your loudspeakers connected out phase, no damage will occur but it will sound pretty strange to say the least. Done correctly, Biwiring will reward you with better focus and clarity in the treble in addition to an improved soundstage

So what about cables? There used to be a belief that a thin wire was best for the treble leg of a biwire set-up, with a thicker cable used for the mid/bass feed. There's some logic in that, and you could tune your speakers' sound by using a treble-happy, or even softer-sounding cable on the bass, and something fat and lush, or bright and lean, on the treble. It can be done, but in general terms I'd say the best starting-point is the use of the same cable on both legs, or even a dedicated four-conductor biwire cable. The latter is the neatest solution, especially when it's an ultra-flat cable, but you might prefer the macho hawser-style wire.

Finally, should you biwire? In almost every case where biwiring is possible I've found it beneficial, but it's something worth investigating during the demonstrations before you buy. If you really can't hear the difference you've just saved yourself the cost of two runs of cable.

That has covered the basics of biwiring. But why not take it a few steps further?

 

BI-AMPING If a loudspeaker can be biwired, it can also be biamped. Biamping is involves using one amplifier channel for each of the drive units to give yet further improvements in sound, as a sudden demand on the power supply for a heavy bassline won't impinge on the subtle treble detail, as it can with an integrated amplifier. A stereo pair of two-way loudspeakers will thus need four channels of amplification and there are numerous ways of doing this.

One current fashion is to use an integrated amplifier along with a power amplifier. There are two provisos; firstly, the integrated amplifier must be fitted with a pair of pre-out sockets. If you are in any doubt, check with your amplifier's manufacturer; secondly, the power amplifier should have the same gain, though no necessarily power output, as the integrated amplifier. That means that for a given input voltage, both units give the same output voltage, in other words increase volume by the same factor. If they didn't, you would have a sound with a louder bass than treble, or vice versa. The best way to gain-match is by using amplifiers from the same manufacturer. But that does not necessarily mean that all of the amplifiers need the same output - for example, good results can be had using the 50watt per-channel Musical Fidelity X-A1 integrated to drive the treble, with a brace of X-A200 200watt monoblocks handling the bass.

To biamp, your loudspeakers' four conductor runs will require four connectors at the amplifier end. The integrated and the power amplifier are connected together with a stereo pair of interconnect cables, the pre-out on the integrated amplifier connected to the pre-in on the power amplifier. You then use the amplifier to the left and right treble, and the other to power the left and the right bass. In general terms, the integrated drives the treble and the power amp the bass, but it's worth experimenting to get the sound that you desire.

Be sure to make all these connections with the amps turned off, double-check all connections before switching on, and then, as your finger hovers over the buttons, go back and check it again. It is all too easy to get your crossed, and though you won't fry yourself, mistakes could prove costly in terms of repairs.

 

ABOVE TEXT ADAPTED FROM MAY 1999 EDITION of What HiFi

 

 

If like me, you want to take this a step further you can also setup your amplifiers in the way described below.

I have four 180w Monoblock amplifiers and a Pre-Amplifier. I have taken separate outputs from the Pre Amp to drive each of the Power Amps. Each of the Power Amps' then drives its own particular driver on the loudspeakers i.e. Left Woofer, Right Woofer, Left Tweeter and Right Tweeter.

The only problem with the above setup is that it can become costly in purchasing four power amps and a pre amp. There is also the additional cost of the speaker cable to consider. If you can afford it and have the space and the will to do it, the rewards are well worth the extra effort.

 

Mick Evans 1999-2001

  [email protected]

[email protected]