Question On Biamping

[JKnPA]

Passive filters.........

Most speakers employ 'passive filters' to smooth-out' the frequency response of their drivers! If you have 'jumpers' on your speaker cabinet, it is probably a 2way or 3way system.
Most quality speakers have good(rigid) jumpers connecting the woofer/mid/tweeter in the cabinet, if you have thin flimsy wire jumpers, that could be a problem.
What speaker/s are you using?
See link below........ namely par. 1.8,1.13, and figure 5.
* I think the entire website is great, but that's just my opinion!

http://sound.westhost.com/bi-amp.htm
JK

 

[rmongiovi]

The speakers are B&W 803Ds. But regardless of the speaker, the jumper is still just a piece of metal and switching to bi-wiring isn't going to remove it. All it will do is remove the jumper from the current path and give a direct amp to speaker connection.

 

[PENG]

It doesn't matter where you split the wires. Having separate speaker cables from the amp's binding posts outward won't prevent one current path from stealing amperage from the other once you get to a single current path inside the single amp. Unless there are separate amplification circuits inside the amplifier that lead to the separate binding posts, it's all the same to the electrons.

Yes, the wire inside the single amp is a single path hence subject to that IM stuff but that piece of wire would typically be very short compared to the external wire.

No it is not the same to the electrons. As you know, from the amp terminals (where it splits) to the speaker terminals, the electrons will have two paths to choose, each with frequency dependent impedance with the speaker's crossovers split when the links are removed. Whether it is the same to the ears is what matters but I won't argue that point other than the fact that I cannot tell the difference.

 

[PENG]

The speakers are B&W 803Ds. But regardless of the speaker, the jumper is still just a piece of metal and switching to bi-wiring isn't going to remove it. All it will do is remove the jumper from the current path and give a direct amp to speaker connection.

I hope you don't mind taking a couple minutes to read the following explanation by B&W.

Link:
http://www.bwspeakers.com/index.cfm/fuseaction/local.faq/ObjectID/F5CA2E9F-3D20-11D4-A67F00D0B7473B37 (in case you want to read the whole thinig).

"by far the most common type is parallel. Here, each driver has its own filter wired between it and the input terminals. If there is only one pair of input terminals, the inputs to all the filters are connected in parallel to that one pair of terminals. If, however, you have more than one pair of terminals, you can completely separate the inputs to each filter. Why on earth would you want to do such a thing?

In the case of bi-wiring, the answer lies in the cable connecting the speaker to the amplifier and the fact that the amplifier is a voltage source but the speaker is a current driven device (force on voice coil = magnet flux density x length of conductor in the magnet gap x current).

Firstly, all cables are a compromise. Some types of construction work better at low frequencies and others at higher frequencies. Providing separate inputs to the speaker allows you to use different cable types, each optimised for the frequency range of use.

Secondly, consider that the cable has an impedance that causes a voltage drop along its length. Now consider the current flowing along the cable. Assume for the argument that the amplifier delivers a perfect voltage waveform to the cable and the cable itself adds no distortion. However, each driver has a non-linear impedance (for example, the inductance of the voice coil alters depending on its position in the magnet gap) that causes the current to be non-linear. This non-linear current through the impedance of the cable causes the voltage drop along the cable to be non-linear and thus the voltage across the speaker terminals is also non-linear, even though it is linear at the amplifier end.

If we were just concerned with one driver, things would not be too bad. But that non-linear voltage at the speaker terminals may contain harmonics within the frequency range of one of the other drivers and that driver will reproduce them, albeit at low level. If, however, you separate the inputs to each driver filter, each driver’s distortion is kept to itself and the total syI stem distortion goes down. We are talking small changes here, but the resolution of some modern drivers is now so good that small improvements like this are readily detectable by keen listeners."

I hope mtrycrafts would read it too. It is consistent with Axiom's, but in more depth. Note that B&W probably considers the resolution of some of their own drivers are "good".

Thank you guys.

 

[JKnPA]

Good post........... Peng

I gave him that link, which explains what you have said.
It gives you the option to bi-wire or bi-amp speakers, if you choose to do that.
I'll look at the link you provided him, too.
John

 

[rmongiovi]

I think the argument I'm trying to make, as far as IM prevention by bi-wiring is that we're talking about splitting the current from the amplifier either at the speaker terminals or at the amplifier terminals. Since the speed of electricity in copper is about 2.3 x 10^8 meters/second, unless you've got REALLY long speaker cable I fail to see how that difference in distance makes a bit of difference to the signal.

Bi-amping can make a difference because an amplifier can only deliver a certain amount of current. If the lower impedence drivers need power, they'll take it and nothing will be available for the higher impedence drivers. By separating the two sets of drivers onto two amplifiers, each set has the full output of its amp available at all times; the other set of drivers can't steal from it. This is, of course, also assuming well designed amps that store a reasonable amount of power and don't expect to be able to pull all they need instantaneously from the wall socket.

With bi-wiring that isn't the case. Any effect that driver impedence might have is going to have an instantaneous effect (essentially) on the point where the wires diverge whether at the speaker or at the amplifier. While Cray might have thought the speed of light to be too slow, it's still pretty fast. As far as "cables work better at different frequencies" I agree in theory, but you've got to have a truly pathological speaker wire to demontrate that difference at auditory frequencies. Again, the speed of propagation of electricity makes your speaker cable essentially zero length even at 20 kilohertz. Certainly one could build a speaker cable with enough impedence to cause a frequency dependent rolloff, but given a reasonably sensible design I don't see how bi-wiring can make a difference (except, as I argued above, in minimizing the number of points of failure in the signal path).

In case you haven't figured this out yet, I'm really a pragmatist, not an audiophile.

 

[JKnPA]

Nice speakers........

Rm,
I read your manual........... briefly.
They do recommend bi-wiring or bi-amping. They said the unit comes with the jumpers off, and they do explain the connection process.
So if you have the jumpers off, you have removed that particular issue, in your case.
Good luck.
Jk

 

[PENG]

Again, the speed of propagation of electricity makes your speaker cable essentially zero length even at 20 kilohertz. Certainly one could build a speaker cable with enough impedence to cause a frequency dependent rolloff, but given a reasonably sensible design I don't see how bi-wiring can make a difference (except, as I argued above, in minimizing the number of points of failure in the signal path).

In case you haven't figured this out yet, I'm really a pragmatist, not an audiophile.

No one would argue about how fast electrons travel but impedance and electromagnetic interference are part of the reasons why the length of cable matter. Again, that single path inside the amp you talked about is relatively short. Anyway, at least we are talking about physics here, not about the audible or not thing, what a relieve for a change!

 

[PENG]

I gave him that link, which explains what you have said.
It gives you the option to bi-wire or bi-amp speakers, if you choose to do that.
I'll look at the link you provided him, too.
John

Thank you John, I really appreciate it. Finally someone understands I was not talking about audibility (hope there is such a word) but only talking about physics/electrical theory. People says then it does not matter, and I would agree with that but it is hard not to defend the theory part......

 

[mtrycrafts]

I hope you don't mind taking a couple minutes to read the following explanation by B&W.

Link:
http://www.bwspeakers.com/index.cfm/fuseaction/local.faq/ObjectID/F5CA2E9F-3D20-11D4-A67F00D0B7473B37 (in case you want to read the whole thinig).

"by far the most common type is parallel. Here, each driver has its own filter wired between it and the input terminals. If there is only one pair of input terminals, the inputs to all the filters are connected in parallel to that one pair of terminals. If, however, you have more than one pair of terminals, you can completely separate the inputs to each filter. Why on earth would you want to do such a thing?

In the case of bi-wiring, the answer lies in the cable connecting the speaker to the amplifier and the fact that the amplifier is a voltage source but the speaker is a current driven device (force on voice coil = magnet flux density x length of conductor in the magnet gap x current).

Firstly, all cables are a compromise. Some types of construction work better at low frequencies and others at higher frequencies. Providing separate inputs to the speaker allows you to use different cable types, each optimised for the frequency range of use.

Secondly, consider that the cable has an impedance that causes a voltage drop along its length. Now consider the current flowing along the cable. Assume for the argument that the amplifier delivers a perfect voltage waveform to the cable and the cable itself adds no distortion. However, each driver has a non-linear impedance (for example, the inductance of the voice coil alters depending on its position in the magnet gap) that causes the current to be non-linear. This non-linear current through the impedance of the cable causes the voltage drop along the cable to be non-linear and thus the voltage across the speaker terminals is also non-linear, even though it is linear at the amplifier end.

If we were just concerned with one driver, things would not be too bad. But that non-linear voltage at the speaker terminals may contain harmonics within the frequency range of one of the other drivers and that driver will reproduce them, albeit at low level. If, however, you separate the inputs to each driver filter, each driver’s distortion is kept to itself and the total syI stem distortion goes down. We are talking small changes here, but the resolution of some modern drivers is now so good that small improvements like this are readily detectable by keen listeners."

I hope mtrycrafts would read it too. It is consistent with Axiom's, but in more depth. Note that B&W probably considers the resolution of some of their own drivers are "good".

Thank you guys.

Well, since you posted it here so kindly, how could I not read it.
But, their
We are talking small changes here, but the resolution of some modern drivers is now so good that small improvements like this are readily detectable by keen listeners."

Is counter to Axioms DBT tests, unless Axiom didn't find the right keen listeners

I am also unsure of this in their paper
But that non-linear voltage at the speaker terminals may contain harmonics within the frequency range of one of the other drivers

The more I am reading their passage above, I am unclear how the voltage varies due to an impedance variation in the driver? The voltage varies with music, hope that is not what they mean.
The voltage source is constant as long as the power supply is not sagging due to current demand beyond a point. Sure, the power cube tests by David rich tests the rail voltage sag with decreasing impedance and phase change, but that is at full power, if I am not mistaken, which certainly can happen

What about the signal fluctuations of the music causing voltage nonlinearity? Why would that not cause those harmonics?

And,
non-linear voltage at the speaker terminals may contain harmonics within the frequency range of one of the other drivers

why is it 'may' and not confirmed by measured results to become 'will'?
Just more questions.

ps. I wonder what they mean by resolution? Reproducing small voltage changes? Accuracy? Both? Other parameters?

 

[mtrycrafts]

Well, I don't believe in skin effect at auditory frequencies. Unless my hearing extended into the megahertz I wouldn't want to worry too much about that.

But each connector is a place where oxidation, loose connection, etc. has a chance to cause measurable signal loss and/or noise introduction. Especially in a speaker, where vibration is a desired goal, I think avoiding extra connections is a sensible precaution.

As with all things involving human senses, your mileage may vary....

Are you implying that you hear the junction resistances???

Oh, skin effect can be measured at audio frequencies, that is why I asked you the question. Or, you just pick and choose what you will ignore or not?

 

[mtrycrafts]

If the lower impedence drivers need power, they'll take it and nothing will be available for the higher impedence drivers.

How so? After all, amps are rated 20Hz-20kHz at full power to the full band. So, that power is available to all the frequencies at the same time to full power. No?

Again, the speed of propagation of electricity makes your speaker cable essentially zero length even at 20 kilohertz.

While that may be the case, it is certainly not the same impedance at 20Hz and at 20kHz, hence the non flat nature of that wire FR response.


Certainly one could build a speaker cable with enough impedence to cause a frequency dependent rolloff,

Actually, cables roll of no matter what as frequency increases. The issue is the amount of roll off and audibility of this roll off compared to a better cable with very low inductance and resistance would.

Davis, Fred E., 'Effects of cable, Loudspeaker and Amplifier Interactions,' JAES, vol. 39, no. 6 Jun 91, pg.
Used to be on line

After all, 24ga cable is audibly different from 12ga and 16 ga wire:

Greenhill, Larry 'Speaker Cables: Can you Hear the Difference?' Stereo Review, Aug 83, pg 46-51.

In case you haven't figured this out yet, I'm really a pragmatist, not an audiophile.

Or, you just choose to be an audiophile on junction resistances?

 

[rmongiovi]

Well, I've certainly heard loose connections, and all I originally said was that I planned to bi-wire not because I thought it would sound better but because it removes one connection, which is one fewer points of failure. One fewer place where things can come loose is a win in my book. I'm quite acquainted enough with that Murphy fellow.

A previous post had said that bi-wiring reduces IM distortion, and I said I doubted that. My point was that all bi-wiring does is move the point where the wire splits from the speaker (with single wiring) to the amp (with bi-wiring) and I find it hard to believe that that amount of distance (5 feet in my case) makes a bit of difference as far as signal path goes. Why would splitting a current source 5 feet earlier make a difference unless my speaker cable had a ridiculously high impedence?

As far as skin effect at auditory frequencies, I can't argue it. I'm a computer geek. The EEs I went to school with showed me equations that indicated it couldn't be audible until you got up into the megahertz frequencies. Were they lying to me? I have no idea. I can't see why they would, though. Maybe it's a EE kind of joke and they all went off laughing about the wool they were able to pull over my eyes. Can't say I care, though. Speaker cable with reasonably low resistence and capacitance and I'm happy. You want to buy Cardas hex link with the stranded copper with diameters related by the golden ratio, knock yourself out.

Oh yeah, as far as frequency rolloff, you're right, I should have said "noticible frequency rolloff." My bad. I thought that was understood. In fact, maybe I should point out that my speakers roll off frequencies, both high and low. I guess I should just hire the band....

 

[JKnPA]

Biwiring...... Filters...... IM distortion

A previous post had said that bi-wiring reduces IM distortion, and I said I doubted that. My point was that all bi-wiring does is move the point where the wire splits from the speaker (with single wiring) to the amp (with bi-wiring) and I find it hard to believe that that amount of distance (5 feet in my case) makes a bit of difference as far as signal path goes. Why would splitting a current source 5 feet earlier make a difference unless my speaker cable had a ridiculously high impedence?

The IM distortion is reduced because you removed the 'jumpers' that connect the ' low pass & high pass filters' not because of the wiring itself. The wire is now necessary because you seperated the filters/drivers.
Poorly designed 'Xover filters' can have their 'Xover freq' shifted when employed in 2or 3way speaker systems, but that is probably not the case with your 'high quality' speakers.
Here is another article(part).... different source..... that cites "IM distortion' between the bass & tweeter drivers, when the jumpers are connected.
**************************************************
Biwiring works by reducing of the tendency for strong bass signals to overwhelm the rest of the audio signal. The larger, more powerful bass signal can greatly affect the integrity of the much lower-energy components of both the midrange and fragile treble information. Running separate wires from the amplifier can have a profound impact on relieving the tweeter circuit from the back flush of EMF (elector-motive force) generated by the woofer. When the audio signal to the woofer ceases, such as when a loud bass note is finished, the woofer tries to stop moving. In trying to stop, it actually goes through a process of "settling" because it is too massive to just stop instantly. As it settles, it moves forward and backward repeatedly until it can completely come to rest. During this movement, as the voice coil is moving through the field of the magnet, it generates its own signal. That generated signal is sent backward up the woofer wires and into the crossover, where it corrupts the rest of the music signal.

http://www.soundstage.com/synergize/synergize031998.htm

* Just 'food for thought'................
Best wishes.....
Jk

 

[rmongiovi]

Ok, let's assume this back EMF does exist, and that it's of an audible magnitude.

What you're saying is that the back EMF can travel outward from the woofer to the binding posts at the back of the speaker, across the jumper to the midrange/tweeter binding posts and impact those drivers, but it *can't* travel back up 5 or so feet of speaker cable to the common amplifier binding posts and then back up the other speaker cable to those same midrange/tweeters.

Why not?

 

[JKnPA]

Maybe................

Maybe it does to some extent........ both authors stated the 'IM' is reduced, they didn't say it was totally eliminated.
I would think the 'physical layout' of the filters/drivers is the main factor, if the jumper is connected.
I'm not an audio engineer, so I can't argue the case. I'm just citing two men (design eng.) from two seperate articles.
If I were you, I would email B&W, and ask why they recommend bi-wiring or bi-amping those speakers.

Just curious......
JK

 

[Nick250]

When Klipsch first came out with dual binding posts the scuttle butt on the Klipsch forum was that it was a marketing decision not engineering one. I could be wrong, but my guess is that if true, they were not the only ones.

Nick

 

[PENG]

Maybe it does to some extent........ both authors stated the 'IM' is reduced, they didn't say it was totally eliminated.

Mr. rmongiovi is right but as you said, no one said the back emf could be eliminated, just reduced. That few inches of wire in the amp would not have much back emf induced in them. Another point, if I remember correctly, like me, you have not said the effect was audible.

 

[mtrycrafts]

When Klipsch first came out with dual binding posts the scuttle butt on the Klipsch forum was that it was a marketing decision not engineering one. I could be wrong, but my guess is that if true, they were not the only ones.

Nick

Well, it is more than scuttle butt. I had an email passed on to me from another poster, another board, don't have it anymore or would have posted it, that he recently at that time received from their engineering department. The 4 post wasn't their idea but a marketing one.

You remember Dunlavy? Same with him, from his mouth in print way back then.
Paradigm has it. I called their engineering department to support their manual supporting it since they have DBT facility as that is how they test theirs as well. No can do, no such evidence.

 

[mtrycrafts]

Well, I've certainly heard loose connections,

Ah, a bit of difference from having connections in the first place.

it removes one connection, which is one fewer points of failure.


No, you still have the same number of connections on the right side, 6. and you have 6 on the left side, 2 at the amp, no matter buy-wiring or not, and 4 connections at the speaker, no matter you buy-wire or not.
If you use banana plugs so you have no connections coming loose, replace that shorting strip with a 6" jumper with bananas on them.
If one is so worried about connections coming loose, active speakers should be bought.
I don't give it another though about the connections, it happens, or it doesn't.
I don't worry about my chances of dying in a car accident, pretty high compared to other things. I still drive.



A previous post had said that bi-wiring reduces IM distortion, and I said I doubted that.

This is from the Axiom site:
by eliminating potential intermodulation distortion between the low- and high-frequency portions of the audio signal.
And
This could prevent intermodulation distortion that may occur using one big “fire hose” or single speaker cable.

Well, I see 'potential' and may occur.' I have not seen evidence that IM in wire would be caused from current differentials at different frequencies. So, I would think you may be right since there is none to eliminate? But, I could be wrong on that too.

My point was that all bi-wiring does is move the point where the wire splits from the speaker (with single wiring) to the amp (with bi-wiring) and I find it hard to believe that that amount of distance (5 feet in my case) makes a bit of difference as far as signal path goes.

Pretty much agree


As far as skin effect at auditory frequencies, I can't argue it. I'm a computer geek. The EEs I went to school with showed me equations that indicated it couldn't be audible until you got up into the megahertz frequencies.


Well, we agree here too. But, you implied skin effect was non-existent at audio frequency? You can calculate skin depth for any frequency above DC.
I am only talking about its effects, not audibility of the effects
It is not audible. Perhaps a Vulcan will hear it?


Speaker cable with reasonably low resistence and capacitance and I'm happy.


Actually, you should be happier with low resistance and low inductance and minimizing capacitance if you have a sensitive amp to capacitance like a Naim amp that needs special speaker cables.



Oh yeah, as far as frequency rolloff, you're right, I should have said "noticible frequency rolloff." My bad.


No biggie. Now we know.


I thought that was understood.

Not always