Science of biwiring

Particularly enjoyed the following:

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The impression after a week or month, however, is that all recordings sound very much alike, and the "airiness" appears on all records. It does not even sound like air anymore, instead more like a slime that pollutes every record you play.

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Interesting article! Maybe this makes sense of my past failure to get on with biwiring. I tried it with B&W 601s and Mission 771s, and yes the sound was markedly different, but not better. A superficial sense of increased detail was in the end replaced by a feeling that the treble had become rather 'detached', that there was less overall bottom-to-top integrity. Soundstaging seemed to suffer. Just one of the good things about Intros is that one need not worry about such things!

Audio engineer Jon Risch, a name familiar to regular visitors to The Audio Asylum, has a different opinion of biwiring. He writes:

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In point of fact, properly implemented bi-wiring has benefits that can not be achieved by a single unsophisticated cable or even a single exotic cable.

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Mr. Risch's web site has a long multi - page article on biwiring complete with measurement graphs.

If I recall my ancient studies correctly, biwiring doubles the amount of capacitance seen by the amplifier. I believe most speaker wire is pretty low capacitance, so that shouldn't matter (should it?).

Also, naim amps require that the speaker wire have a minimum amount of inductance as the amps themselves do not have output inductors; naim consider the speaker wire as part of the amplifier's components. With that in mind, does biwiring double the inductance or cut it in half?

Cheers

Keith.

Biwiring halves the inductance and doubles the capacitance.

Paul

It cuts it in half.
One of the reasons why bi-wiring in not good ( I should even say " not safe") with Naim amps.

Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.

You could make a set of links with a short length of NACA5. Keeping direction/polarity of course.

Howard

The only thing he explains clearly is that when you biwire, the different cables carry different signals. Then he graphically demonstrates it.

The question is what does the amp do with it. OK, so the two wires carry different signal. But contra Risch, when a bass impulse calls for a lot of current, the amplifier still has to deliver it, and that still affects what the amp will do with the rest of the signal. And doesn't the amp LIKE seeing a flat impedance with single wiring?

Maybe everything is explained coherently, but I certainly didn't follow it.

--Eri

Your Epos 11's are fine with the Naim amps. You just make an "F" connection with your cable - do a search on this forum, I know there is a picture somewhere that'll explain it pretty clearly (I don't think Linn K400 will be harmful to your amp, however most people here will recommend NACA5).

Best
Thom

Right, here's my chance to demonstrate once and for all that I know absolutely 'jack' about electronics engineering (I just love music...)

I've never understood the whole bi-wiring thing. My general perspective is this:

An amplifier 'boosts' the signal from a source device. That amplified signal is then 'fed' to a pair (usually) of loudspeakers. On the back of your typical amplifier there are two sets of two loudspeaker outputs - one set for the left channel and one for the right. Both sets have one 'positive' output and one 'negative'. But... the signal from each of these outputs is the same (except for the split channel, i.e. 'stereo' information) Right?

The sound is not sorted out into frequency ranges at this stage. Right?

The sound gets 'sorted out' when it reaches the loudspeaker crossover. This splits the signal and feeds it to the appropriate drivers. I think...

So, how can bi-wiring 'work'? The amplifier doesn't 'know' to send the higher frequencies down one set of cable and the lower ones down the other. Surely the full frequency range will simply be sent down both cables at the same time (or very nearly the same time, depending on the physical properties of each cable)?

Doesn't this simply mean the need for a more complicated crossover at the other end?

I just don't get it. Never have.

Thank you and goodnight

There is no problem biwiring with Naim amps,just make sure you use half the maximum length or less as recommended by Naim.

Imagine a signal mixed up from a 200Hz wave and a 5kHz wave. This gets amplified and passed down a single cable to a two way loudspeaker. The crossover in the loudspeaker separates the two waves and passes them to the woofer and tweeter as appropriate.

The speaker cable has a resistance. This means that the wave form at the speaker isn't the same as that at the output of the amplifier, it's attenuated according to the resistance of the cable, the impedance of the loudspeaker and the size of the signal.

If we look at the waveform presented to the input to the tweeter section of the crossover it will not be the same as the waveform at the amplifier output since the voltage drops caused by the interaction of the current required by the bass unit and the speaker cable resistance will be super-imposed on it.

If we biwire then the signal at the tweeter crossover input will be independent of the current drawn by the bass. It would look different on an oscilloscope. No magic would be required to demonstrate a difference.

The question is whether the difference matters to the operation of the tweeter. Whether a change in the part of the signal that the tweeter crossover is going to discard is relevant.

I suspect it needn't be. However it's probably quite dependent on the characteristics of the crossovers and where the crossover points are, what happens in the region where both drive units are working etc.

Paul

Sorry Quikie, your statement is false on all points.
Re-read the previous posts.

You should have said:
There can be problems biwiring with Naim amps, just make sure you use twice the minimum lenght or more, but it is not recommended by Naim.


Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.

[This message was edited by Manu on FRIDAY 01 November 2002 at 16:35.]

Tim:

I think you've got it pretty much right. It is much easier to see the point of *bi-amping* with an active crossover. There, the signal from the pre-amp is split into low- and high-frequency components by an electronic crossover. The LF signal goes to one power amp driving the woofer, the HF signal to an amp driving the tweeter. Each power amp handles just a portion of the full frequency range, and the speaker's passive crossover components are by-passed altogether (i.e. the drive units are driven directly). The LF and HF gains can be independently controlled to achieve a linear response.

I've seen some good articles on the web on why active systems are theoretically preferable. In part I think due to the energy-sapping and phase-monkeying characteristics of passive crossovers. Keeps life simple for each power amp too. I'll try to relocate the articles...

Dan

It looks exactly the same as if you biwired a single amp. Assuming the single amp isn't running out of puff.

Active rules, FWIW.

Paul

Well, I would say that it's this simple:

If the loudspeaker is designed to be bi wired, and you want it sound like the designer intended it to, you should bi wire it. And the opposite with a loudspeaker that is designed to be single wired.

JohanR

Through the years I have had a Nait 2 , 90 ,140 and now a 250 with different Naim preamps bi wired to my monitor audio studio 20's. I have two 11 foot naim wires to each speaker. I have had no problems with any amp ever. I do prefer the sound biwired, the studio 20's are made to be biwired. Just a thought, Ted.

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Originally posted by ted:
Through the years I have had a Nait 2 , 90 ,140 and now a 250 with different Naim preamps bi wired to my monitor audio studio 20's.

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Ted,

dunno about bi-wiring, but I found that Studio 60's were worse when bi-amped with 4x135s, and better with 2x135s.

The 60's appear to be a very easy load.

cheers, Martin

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Originally posted by Manu:
Sorry Quikie, your statement is false on all points.
Re-read the previous posts.

You should have said:
There can be problems biwiring with Naim amps, just make sure you use twice the minimum lenght or more, but it is not recommended by Naim.


Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.

[This message was edited by Manu on FRIDAY 01 November 2002 at 16:35.]

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My statement is not false,but yours is.If naim recommend say 15m per channel maximum(30m total)then the maximum you can biwire with is 4 lengths of 7.5m(30m total)
I thought the whole problem is if you hang too much cable on the end,you get to much capacitance which may make the amps unstable.
I had this problem with my NVA amps,they used to say do not biwire unless you keep the lengths short(I think under 5 meters)
From what you are saying,as long as you use the minimum length(3.5m per channel I think)you will be OK which is not the case.I realise that Naim amps should not be bi-wired at all,but at the end of the day people will,and by keeping the cables at sensible lengths,you should not run into trouble.

Cheers,
Paul.

Paul let us do some maths:
Naim amps likes inducance but not capacitance in a speaker wire. That's a fact, agree here?
If you bi-wire, the inductance is half, the capacitance is double, as seen by the amp. You go in the wrong direction here.
If you want to use the minimum recommanded length, to have the same inductance and same capacitance, you must double each run length.
If you want to use the maximum recommanded length, it is the same you must double each run. But here, the resistance can become a problem, you will have loss in each cable.

So, my statement is right:
Naim does not recommand bi-wiring, if you still want to do it, be sure you double the minimum recommanded length for each run. So, for a bi-wire stereo amp, you need 4*7m of naca5. That's the least risky option, if you want to bi-wire.

Things are reversed for your NVA amp, you are right, you must keep the length short, they don't like inductance.

Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.

I agree on the 2x 3.5m minimum length needed if you biwire so you can retain the minimum inductance needed as you rightly say it is half when you biwire.
But what about the maximum.Naim say up 20m should work ok single wired,but biwired that would be 40m on each channel,double the capacitance of the recommended length,which you say the naim amps don't like,agree.
So as I said before half this,maximum 4x10 metre lengths if you biwire and you will be fine.

Cheers,
Paul.

Ok, we end with almost the same result.
IMO, we don't need to worry about the maximum length, nobody will use more than 40m of cable.
But we have to warn bi-wire user of the minimum length: They should not use 3.5m runs, but at least 7m.
Anyway, bi-wiring is not safe with Naim amps.
And, all speakers i have tried with Naim amps sound better with the F-ended NACA5 than bi-wired.

Emmanuel

All opinions are my own, and reflect those of the organisation i work for, even if not stipulated.