bi-wire config question
 

Glenn Richards wrote:
APR wrote:

All you are doing with bi-wiring is placing the terminal that joins
the the LF and HF driver circuit inputs at the amp terminals instead
of the speaker terminals. If the speaker wire is so inadequate that
you are able to measure any significant changes in HF linearity due
to the effect of speaker wire resistance then the wire run is too
long or the wire is too light.

Ok, for those people that still don't "get it", here's an experiment
that will demonstrate visually what's going on:

Take a 12V DC power supply (one of those bench PSUs capable of supplying
several amps will suffice) and a 12V 1W bulb (any type will do, it's
easier to perform the experiment using a MES bulb and batten holder with
screw terminals though).

Connect the bulb to the power supply using 5 metres of 13-strand zip
wire and power up. Observe the brightness of the bulb.

Now take a second bulb and holder, and attach a few inches of the same
wire to the second holder. Connect the second bulb in parallel with the
first so that it is "chained" from the first bulb, ie you've got 5m of
cable from PSU to first bulb, then a few inches from the first bulb to
the second bulb. Make this connection with the power turned on.

As you connect the second bulb, you'll see the first bulb's brightness
decrease. This is caused by a voltage drop in the cable. Disconnect the
second bulb and the brightness of the first will increase again.

Now replace the short piece of wire on the second bulb with another 5
metre length, and connect the two bulbs in parallel by attaching two
sets of wire to the power supply. This time when you connect the second
bulb the first one won't dim, and the second will light up at full
brightness.

This is exactly what is happening with your speaker cables. The cable
run acts like a series resistor, and the load (in this case the driver
voice coil) causes a voltage drop across that series resistor. By
bi-wiring you are avoiding the load from the LF driver causing a voltage
drop to the HF driver. (Again this is a greatly simplified description
of what's going on.)

No it isn't! Your experiment is being done with dc. Repeat the
experiment with 50Hz to one bulb and 10kHz to the second bulb, both
bulbs being fed through a single amplifier and fed through a simple
capacitor or inductor "crossover". You will now see that the bulbs don't
change their brightness.

S

bi-wire config question
 

In article , Howard Haigh
wrote:

"Jim Lesurf" wrote in message
...

[snip]

These show that bi wiring can change the frequency response -
but by only a small amount even when using cables of exceptionally
high series resistance. Hence changes in measured behaviour are
possible. But are they audible in any sensible arrangement?... My
reaction tends to be that if I wanted a change in frequency response
of a few tenths of a dB I'd move my head slightly whilst listening.
:-)


Ah yes - the issue of listening position! Something I've noticed is that
when listening to music if I happen to tilt my head so that I'm either
looking upwards or downwards then there is a discernable change in the
sound - I hear more or less treble. I suspect that the actual shape of
my ears influences how well certain frequencies are heard. So (assuming
that I'm not the only one that this affects) unless we're going to
restrain our heads in some sort of clamp then any comparitive test of
speaker connectivity is more likely than not going to have to deal with
'is my head in exactly the right position to make it a fair trial'


This issue can be tackled. However it tends to require some mix of:

1) The listener(s) trying to put their head in the same position(s) as best
they can when comparing. Thus trying to reduce the effect of head movements.

2) *repeated* listening to the 'different arrangements' being compared, in
'randomised' order with the listener not being told which one is being used
at any time, so only having the sounds to go on. Then doing a statistical
analysis of the results.

Protocols//methods like the above can help to 'randomise' the effects of
differences in head location, changes in hearing physiology during the
tests, etc.

The key point here is that experimental physical scientists have for a
long time devised and used methods to 'randomise' uncorrelated effects
and then use test protocols which can be analysed to show the systematic
effect of the 'target' properties. The snag is that people have to
understand and use these methods, which can be time consuming and require
care and atention.

Alas, many of the reports are along the lines of, "I tried arrangement A,
then I tried arrangement B and they sounded different to me. Thus they do
sound different." For reasons like those above, such reports can be simply
wrong. They may also easily assign as the 'reason' for an 'audible
difference' to entirely the wrong cause. Thus as 'evidence' such reports
are of little use.


and indeed if moving one's head slightly can affect the sound heard then
is there any point in worrying about minor changes that might be
imparted via the speaker cable arrangement?

Indeed. :-) Personally, I stopped trying to chase 'differences' that were
this small some years ago - particularly when the 'evidence' seemed to
consist of unreliable reports of poorly-conducted 'tests'. Simpler to use
the time on enjoying the music. Take such reports in magazine reviews, etc
with a pinch of salt. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

bi-wire config question
 

In article , Glenn
Richards wrote:
Serge Auckland wrote:

You've obviously convinced yourself that it makes a difference. I've
never managed to hear any myself, and when I do the sums, I'm not a
bit surprised. By the way, if you are indeed sure it does make a
difference, have you tried to analyse why and how? What mechanism can
be acting to make the sound better (or even different)?

[snip]

Once you take the bridging straps off however, something else is
occurring. And what happens makes an audible difference. Too tired to do
the maths atm, but I'm sure a few ASCII art diagrams will help.

Actually, if people visit the webpages I've been mentioning they can see
the relevant diagrams displayed as gif images on the pages. Also the
relevant equiations modelling the arrangements, and the results for a
simple example. :-)

[snip]


Treat the run of cable between the amp and speaker as if it were a
resistor and it makes it easier to understand what's happening. And
remember that the LF driver can take a hefty current when you're trying
to move a lot of air - and that current is effectively being drawn
through a series resistor (ie the run of speaker cable). By bi-wiring,
you're no longer drawing that high current required by the LF driver
through the same series resistor as the HF driver.

That is correct. but you are drawing through another series resistor.

If the bi-wire cables are similar to the one used for conventional
wiring, then the HF signal will pass through the same series resistance
as before, and endure a similar Ohmic drop.

The result - much more linearity from the HF driver, as it's no longer
suffering from current drain via a series resistor when the LF driver
draws current.

That does not seem to follow from the above, and seem either incorrect or
confused. You gave changed one resistor (linear device) with another.
None of the above gives any reason for the result to be "much more linear".

If you change from using a common cable of series resistance, R, to one of
R feeding the HF driver, it will see a cable resistance of R in both cases.

The resistance of the cable will essentially be a linear element in both
cases.

Thus there is no need to assume any significant result in terms of "much
more linearity from the HF driver".

Therefore no current sag to the HF driver, resulting in a cleaner and
more dynamic HF response.

Not clear what 'current sag' you are assuming, nor why...

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

bi-wire config question
 

In article , Glenn Richards
wrote:
Eiron wrote:

Glenn said recently: "(HF needs less current so a thinner cable will
suffice)." Which shows that there is no point in discussing technical
stuff with him, unless it is to give the rest of us a laugh.

It's called "speaking in layman's terms". Some people aren't technically
minded, and don't really care about the how and the why, just the what.

But since you're being pedantic, let's put it another way. A loudspeaker
voice coil is basically a linear motor. The LF driver is going to draw
more current than the HF driver


Experience on usenet is that being pedantic can be unwise as someone
else will then nit-pick the 'pedantry'...

In this case I can point out that the LF and HF currents will vary
according to the signal patterns, as well as depending on the details
of the speaker units. Hence the above "is going to" would be better
expressed as "often tends to..."


- which should be blindingly obvious as it has to move in and out much
more (a throw of anything up to an inch or so). The HF driver only moves
by a few microns, as the frequencies it is reproducing are far higher.


Well, the powers/currents are required to *accellerate* the drivers.
Hence simply quoting the displacements is misleading in the above context.

The coil current (in the magnetic field) produces a force which then
accellerates the driver. The important point here is that the HF driver
tends to have a smaller mass than an LF driver, so lower forces are
required for a given accelleration.

The reduction in amplitude of movement simply comes from the higher
frequency, meaning that the acceleration in a given direction is 'reversed'
after a shorter time period.

Therefore the HF driver is going to draw far less current than the LF
driver - and therefore is less likely to be affected by a slightly
higher series resistance (eg a thinner cable) than the LF driver.

Alas, the above is misleading. The effect of high cable resistance is in
terms of the *impedance* interactions, altering the frequency response.
This will include the presence of any crossover/correction networks.

The HF and LF speakers may well also have different masses, coil details,
loss resistances, etc, etc. Hence we can't use the above to draw the
conclusion drawn above.


Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

bi-wire config question
 

In article , Glenn Richards
wrote:
APR wrote:

All you are doing with bi-wiring is placing the terminal that joins
the the LF and HF driver circuit inputs at the amp terminals instead
of the speaker terminals. If the speaker wire is so inadequate that
you are able to measure any significant changes in HF linearity due to
the effect of speaker wire resistance then the wire run is too long
or the wire is too light.

Ok, for those people that still don't "get it", here's an experiment
that will demonstrate visually what's going on:

Take a 12V DC power supply (one of those bench PSUs capable of supplying
several amps will suffice) and a 12V 1W bulb (any type will do, it's
easier to perform the experiment using a MES bulb and batten holder with
screw terminals though).

[snip details]

This is exactly what is happening with your speaker cables. The cable
run acts like a series resistor, and the load (in this case the driver
voice coil) causes a voltage drop across that series resistor.

The point to bear in mind, though, is that the cable resistance for any
sensible speaker cables should be tiny. Hence any effect should
be negligably small. If it isn't simply use thicker/shorter loudspeaker
cables. The following URL may help assess this.

http://www.st-and.demon.co.uk/AudioM.../lscables.html

For cable lengths of a few metres, the cables which cost the order of
50p per foot are likely to be fine, but the choice is up to you. :-)


Bybi-wiring you are avoiding the load from the LF driver causing a
voltage drop to the HF driver. (Again this is a greatly simplified
description of what's going on.)

To assess this, have a look at the other webpages I have been mentioning.
If you look at the simple example it should be clear that this implies that
any such effect in practice should tend to be so small as to be either
inaudible or smaller than moving your head slightly. If it isn't then
simply using a lower resistance cable should deal with the issue - unless
of course you *want* to alter the frequency response by the deliberate
introduction of 'high' cable resistance.

However if you do want this, then it would be easier and more controllable
to use a single cable, but feed the speaker units via some series resistors
at the speaker end of the cable. This method is familiar to speaker
designers. It is called "modifying the crossover/correction networks". :-)

You may find that a couple of low-value resistors are cheaper and more
convenient that more runs of cable. You can also change their values easily
if you want to fiddle about with the frequency response of your loudspeaker
system.

I've specified 13-strand zip wire in the experiment above as it makes
the results more obvious, but the effect will still stand with thicker
cable, it'll just be harder to see. And eventually you'll get to a
thickness of cable that will have a low enough series resistance that
the effect will no longer occur - but in the case of speakers that cable
will either be so expensive or so unwieldy that it makes more sense to
use two thinner runs of cable.

FWIW I tend to prefer the Maplin cables as they give low series resistance
for just a few quid per cable. The above URL uses them for example, so
people can decide for themselves what might suit for the lengths they need.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

bi-wire config question
 

Serge Auckland wrote:

No it isn't! Your experiment is being done with dc. Repeat the
experiment with 50Hz to one bulb and 10kHz to the second bulb, both
bulbs being fed through a single amplifier and fed through a simple
capacitor or inductor "crossover". You will now see that the bulbs
don't change their brightness.

Makes no difference, AC or DC. Series resistance is still the same,
regardless of line frequency. That experiment was to illustrate a
concept, not specifics. The principle is exactly the same.

--
Glenn Richards Tel: (01453) 845735
Squirrel Solutions http://www.squirrelsolutions.co.uk/

IT consultancy, hardware and software support, broadband installation

bi-wire config question
 

Don Pearce wrote:

Glenn, as I said in another post, please stop this. You have a
minuscule technical knowledge which ends far short of an ability to
understand and apply Ohm's law, but you persist in airing your
howlers. I know we are all amused when we have nothing better to do,
but you really are doing yourself no favours.

As opposed to you, who has already proved in a previous post that you
have no idea how an earth loop works, interpreted "two signals" to mean
combining a stereo signal onto a single core and couldn't understand the
correlation between "unwanted signal" and "noise" (hint - "noise" is any
"unwanted signal") etc etc.

You've proved your own ineptitude, now please stop foisting your
inadequacies onto me. This is Usenet, not work, and I don't get paid for
doing this. Therefore I'm not going to write a highly detailed analysis
of why bi-wiring does make a difference (and I can assure you it does)
which you've already demonstrated that you won't understand anyway.

Now please go back to your £39.99 micro system purchased from Currys
with speakers linked up with bell wire, and stop pretending you know
anything about hi-fi.

--
Glenn Richards Tel: (01453) 845735
Squirrel Solutions http://www.squirrelsolutions.co.uk/

IT consultancy, hardware and software support, broadband installation

bi-wire config question
 

On Sun, 18 Jun 2006 11:13:57 +0100, Glenn Richards
wrote:

Don Pearce wrote:

Glenn, as I said in another post, please stop this. You have a
minuscule technical knowledge which ends far short of an ability to
understand and apply Ohm's law, but you persist in airing your
howlers. I know we are all amused when we have nothing better to do,
but you really are doing yourself no favours.

As opposed to you, who has already proved in a previous post that you
have no idea how an earth loop works, interpreted "two signals" to mean
combining a stereo signal onto a single core and couldn't understand the
correlation between "unwanted signal" and "noise" (hint - "noise" is any
"unwanted signal") etc etc.

Glenn, I said no such thing - as that is complete nonsense. If that is
what you interpreted from what I said, it only illustrates your lack
of understanding.

You've proved your own ineptitude, now please stop foisting your
inadequacies onto me. This is Usenet, not work, and I don't get paid for
doing this. Therefore I'm not going to write a highly detailed analysis
of why bi-wiring does make a difference (and I can assure you it does)
which you've already demonstrated that you won't understand anyway.

No, there is actually another reason why you won't do this. I assure
you that the rest of us know what it is.

Now please go back to your £39.99 micro system purchased from Currys
with speakers linked up with bell wire, and stop pretending you know
anything about hi-fi.

If that pleases you.

d

--
Pearce Consulting
http://www.pearce.uk.com

bi-wire config question
 

On Sun, 18 Jun 2006 11:13:57 +0100, Glenn Richards
wrote:

Don Pearce wrote:

Glenn, as I said in another post, please stop this. You have a
minuscule technical knowledge which ends far short of an ability to
understand and apply Ohm's law, but you persist in airing your
howlers. I know we are all amused when we have nothing better to do,
but you really are doing yourself no favours.

As opposed to you, who has already proved in a previous post that you
have no idea how an earth loop works, interpreted "two signals" to mean
combining a stereo signal onto a single core and couldn't understand the
correlation between "unwanted signal" and "noise" (hint - "noise" is any
"unwanted signal") etc etc.

You've proved your own ineptitude, now please stop foisting your
inadequacies onto me. This is Usenet, not work, and I don't get paid for
doing this. Therefore I'm not going to write a highly detailed analysis
of why bi-wiring does make a difference (and I can assure you it does)
which you've already demonstrated that you won't understand anyway.

Now please go back to your £39.99 micro system purchased from Currys
with speakers linked up with bell wire, and stop pretending you know
anything about hi-fi.

OK - you snipped the substance, as you had no way of dealing with it.
So I will repeat it again:

First lets assume that your experiment is applicable.
Now complete it. Use you second case - with the two wires
run separately right back to the source ( for maximum brightness). Now
take your short piece of wire and join the two bulbs together. If
biwiring made a difference, there should be a change in brightness as
you do this. There is no change. All you have shown is that it is
usually better to have thicker wire.

The second point is that the tweeter and woofer are not in parallel.
Does that surprise you? This because we are dealing with signals in
defined frequency bands, and we have a crossover, which presents a
high impedance to the cable in the stopband of each driver. This means
that low frequency signals - no matter how big - do not suck voltage
away from the tweeter. In fact the tweeter doesn't even know there is
a woofer there. There are of course electrical devices that have the
effect you describe; they are called modulators and rely on controlled
non-linearity to achieve a multiplying function. If you can show that
cables act as modulators, you will have saved the broadcasting
industry a fortune overnight and your fame will be assured.

Now, answer both of those - if you are able. (breath not being held, I
promise).

d

--
Pearce Consulting
http://www.pearce.uk.com

bi-wire config question
 

Don Pearce wrote:

As opposed to you, who has already proved in a previous post that
you have no idea how an earth loop works, interpreted "two signals"
to mean combining a stereo signal onto a single core and couldn't
understand the correlation between "unwanted signal" and "noise"
(hint - "noise" is any "unwanted signal") etc etc.
Glenn, I said no such thing - as that is complete nonsense. If that
is what you interpreted from what I said, it only illustrates your
lack of understanding.

No, that was exactly what you said. You were harping on about "why would
you send two signals down one cable", completely missing the point that
noise is a signal, just one that isn't wanted.

It isn't me that is suffering from a lack of understanding here. I
suggest you go and take a look in the mirror.

--
Glenn Richards Tel: (01453) 845735
Squirrel Solutions http://www.squirrelsolutions.co.uk/

IT consultancy, hardware and software support, broadband installation