Bi-Wiring speakers - confused?

[zcacogp]

Chaps,

A theoretical question.

I've been looking at some bi-wired speakers recently, and am a little confused about how they work.

I understand that each pair of speaker posts connect to either the main driver or the tweeter. However, you can run them in either of two ways; either feeding the same signal to both sets of posts (usually done by connecting the pairs together with the bars), or by feeding seperate, pre-filtered signals to them.

Presumably there is a filter (crossover) inside the speakers to ensure that the right frequencies go to the right driver if you run a single signal to the speaker, but why is there not a switch to remove the crossover from the circuit if you decide to run it bi-wired?

(Did the question make sense?)


Oli.

[Mr_Yogi]

In Bi-wired operation signals are not pre-filtered, the crossovers in the speakers are used to filter the signals (remove high freqs from the woofer and low freqs from the tweeter in the case of a 2-way speaker).

The advantage of b-wiring is questionable as both driver units are connected to the same amp channel, but each driver just has it's own cables (some argue this reduces back emf amongst other things), as opposed to a single run of cable with the bridging bars or cable in signle wired mode.

The advantage of bi-wirable speakers is that you can bi-amp them (running separate amp channels to each drive unit). In this instance the drive units are totally separate as there is no internal connection between the crossovers of each driveunit.

Edited by Mr_Yogi on Thursday 17th June 12:28

[zcacogp]

Mr Yogi,

Thanks. I hadn't appreciated that bi-wiring involved both wires being connected to the same amp channel.

So I am confusing bi-wiring with bi-amping, by the sounds of it. Are bi-amped speakers sold specifically as bi-amp speakers, or are they bi-wired speakers which have been re-wired (i.e. with the crossovers removed)?


Oli.

[LeeME3]

All you need to know here: http://www.oregondv.com/Audio_FAQ_Bi-Wire_Bi-amp%2...

With pics for the hard of thinking (i.e. me!)

[zcacogp]

Lee,

Thanks - that's helpful.

I'm surprised that bi-wiring (as opposed to bi-amping) can make any difference. To me, it should make no difference at all, as everything is connected to the same teminals which means they are therefore recieving the samwe signal.

But then, HiFi is something I know little about ...


Oli.

[theboss]

There are some circumstances (depending on manufacturer) where you can remove or bypass the internal crossovers in the speaker and use external 'active' crossovers either in a standalone powered unit or in the power amps. Linn offer this with most of their speakers and I believe Naim do or have done in the past. So in the case of a two-way speaker that gives the following configurations:

1) single amp channel (per speaker), single pair of wires, using internal (passive) crossovers
2) single amp channel (per speaker, two pairs of wires (bi-wired), using internal (passive) crossovers
3) two amp channels (per speaker), two pairs of wires (bi-amped), using internal (passive) crossovers
4) two amp channels (per speaker), two pairs of wires (bi-amped), using external (active) crossovers

In the case of the active configuration each power amp channel is 'fed' a filtered signal consisting of either the treble or mid/bass frequencies, and is then wired directly to the corresponding driver without anything else in the signal path.

Generally the sound improves as you move down the list (in that order) assuming like-for-like components, however its also possible that you could start with the most basic configuration no.1, upgrade your single cable pair for much better wires, and have something that sounds superior to no.2 based on inferior wires. Likewise a single-amped single-wired system with a *very good* power amp and cables may well sound better (in some ways) than a bi-amped, active configuration with inferior amps and cables. It's all down to the relative cost of these upgrades and personal preference, I personally like the 'weight' and 'presence' of sound provided by a decent power amp even though a bi-amped configuration on weaker amps may sound more detailed. So generally I try to start with the most basic configuration and improve it in any way possible before adding to it.

[zcacogp]

I don't understand number 3 in that list. Two amp channels, bi-amped, but using internal crossovers?


Oli.

[theboss]

zcacogp said:

I don't understand number 3 in that list. Two amp channels, bi-amped, but using internal crossovers?


Oli.

Thats right... you are taking two identical amp channels (unfiltered - full bandwidth) and feeding the treble binding posts with one and the mid/bass binding posts with the other. Any plates or wires on the back of the speaker linking the two sets of posts gets removed. The internal crossovers then filter the signal so each driver only receives the appropriate frequency range. You end up giving each driver its own dedicated amp channel, but with a passive filtering circuit between each amp and driver. Does that make sense?

[Mr_Yogi]

theboss said:

zcacogp said:

I don't understand number 3 in that list. Two amp channels, bi-amped, but using internal crossovers?


Oli.

Thats right... you are taking two identical amp channels (unfiltered - full bandwidth) and feeding the treble binding posts with one and the mid/bass binding posts with the other. Any plates or wires on the back of the speaker linking the two sets of posts gets removed. The internal crossovers then filter the signal so each driver only receives the appropriate frequency range. You end up giving each driver its own dedicated amp channel, but with a passive filtering circuit between each amp and driver. Does that make sense?

In fact that is the most common type of bi-amping (passive bi-amping) as most can't afford active crossovers

[zcacogp]

Yes, but in that case then why are you providing it with two amp channels? And how are those amp channels wired - series or parallel?

I think my problem comes from the notion of connecting the outputs of two amps together. The speaker end of things is fine (same as in 1 and 2 from your list.)


Oli.

[zcacogp]

Actually, I've just understood it. It's clicked. Thanks.

The crossovers in the speakers aren't crossovers per se, they are just filters. Therefore you aren't connecting the amp output stages together, as they are going to non-connected speaker drivers.

Makes sense. Thanks. And sorry for being slow on the uptake.


Oli.

[cjs]

Bi-Wiring is a waste of time & money in most circumstances, you will not hear any difference.

[Le TVR]

cjs said:

Bi-Wiring is a waste of time & money in most circumstances, you will not hear any difference.

^^^^

Bi-amping will only benefit IF the LF/HF intermodulation performance of the amplifier is doubtful. This will require the use of active filters between preamp and power amps as in the link. However, most active filter units I have ever measured had quite unusable phase shift at the turnover frequencies.

Also some manufacturers let you bypass the passive crossover network for bi-wiring. Please remember that (in a competent crossover design) half the components are for impedance and resonance damping and the last thing you should ever do is switch them out of the circuit!

[theboss]

Le TVR said:

cjs said:

Bi-Wiring is a waste of time & money in most circumstances, you will not hear any difference.

^^^^

Bi-amping will only benefit IF the LF/HF intermodulation performance of the amplifier is doubtful. This will require the use of active filters between preamp and power amps as in the link. However, most active filter units I have ever measured had quite unusable phase shift at the turnover frequencies.

Also some manufacturers let you bypass the passive crossover network for bi-wiring. Please remember that (in a competent crossover design) half the components are for impedance and resonance damping and the last thing you should ever do is switch them out of the circuit!

I agree with the above about bi-wiring but every time I have bi-amped (or tri-amped) a speaker it has made a considerable positive difference. Just to emphasise my previous point that, that I would rather have a single-amped system with a very good power amp than a bi-amped system with mediocre power amps. I have never heard a difference in sound just by bi-wiring though.

Edited by theboss on Friday 18th June 14:37