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post #61 of 86 Old 10-04-2012, 03:01 PM
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Originally Posted by kiwi2 View Post

Current generates magnetic fields. Separating current reduces magnetic field interaction.

But all of the current of all frequencies travels on the single wire from the amp circuit to the amp terminals.

And do you use speaker wire with magnetic shielding to prevent magnetic interaction between the two wires?

And to my other question, what about the current at 4kHz and 8kHz travelling on the same wire?
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Also as a driver is a coil inside a magnet, when a driver moves backwards it creates its own current that travels back down the cabels. Removing the post jumpers and bi-wiring back to the amp terminals reduces the chance of the backwards current to interfere with the other driver, as the amp itself is more capable to dampen the return current.

Removing the post jumpers just moves the point of electrical connectivity between the paths to the LF and HF crossovers to be at the terminals of the amp instead of the terminals of the speaker.

Any capability that an amp may (emphasis on may) have to dampen a return current would be moot because the return current would just happily head down the other wire from the electrical connection at the amp terminals.

Assuming you have used sufficient gauge wires on both sides of your bi-wire then the amount of return current arriving at the input of the LF crossover that the tweeter generated and sent back down its wire will be exactly the same whether the point of electrical connectivity is the speaker terminals or the amp terminals.
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You have just made the same logic error again by ignoring the current difference and focusing on signal. You say there is no difference because there is no difference in signal. But that is ignoring the difference in current.

But there is no science to explain how the amount of current at any frequency between the crossover and the driver would be any different in either situation.

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post #62 of 86 Old 10-04-2012, 03:07 PM
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Originally Posted by rick240 View Post

But there is no science to explain how the amount of current at any frequency between the crossover and the driver would be any different in either situation.

Why do you think we crossover low frequencies to powered subs?
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post #63 of 86 Old 10-04-2012, 03:19 PM
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Originally Posted by kiwi2 View Post

Why do you think we crossover low frequencies to powered subs?

Because subwoofers reproduce low frequencies better than mid-woofers...

Because low frequencies are generally best reproduced from a location other than where the mains speakers are...


And what does a discussion of the active crossover in a receiver to separate low frequencies from "main" frequencies have to do with a discussion of current getting from:
- an amp...
- through a single wire to its connectors
- then through either one wire to a speaker's terminal and then two wires to the two parts of a passive crossover; or through two wire further back to the same two parts of that same passive crossover
- then from that crossovers parts to the respective LF and HF drivers

In all situations, single amp/single wire, or single amp/bi-wire, or passive bi-amp the current getting from the passive crossover parts to its repsective driver is always the same.

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post #64 of 86 Old 10-04-2012, 03:28 PM
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Originally Posted by kiwi2 View Post

Current generates magnetic fields. Separating current reduces magnetic field interaction. ...

Please elaborate. Explain how the magnetic field generated by current flowing in a wire affects, uhm, the current flowing in that same wire.
As I've stated before, a wire is linear, at least at audio frequencies. The signal going through it is not affected by the...signal going through it.

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post #65 of 86 Old 10-04-2012, 03:36 PM
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Originally Posted by rick240 View Post

Because subwoofers reproduce low frequencies better than mid-woofers...
Because low frequencies are generally best reproduced from a location other than where the mains speakers are....

And also it takes a lot more power to drive a lower frequency driver that it does the higher frequencies drivers. Diverging 60hz or even 40hz and below takes a lot of load off the speaker's amp and frees up headroom.
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post #66 of 86 Old 10-04-2012, 03:40 PM
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Originally Posted by beaveav View Post

Please elaborate. Explain how the magnetic field generated by current flowing in a wire affects, uhm, the current flowing in that same wire.

A low frequency driver is using a hang of a lot more current than a high-frequency driver. Magnetic fields do interact with each other. Coils inside a crossover are usually arranged at 90° to each other in order to avoid magnetic field interaction, for example.

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As I've stated before, a wire is linear, at least at audio frequencies. The signal going through it is not affected by the...signal going through it.

And once again, you confuse signal with current.
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post #67 of 86 Old 10-04-2012, 03:51 PM
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Quote:
Originally Posted by kiwi2 View Post

A low frequency driver is using a hang of a lot more current than a high-frequency driver. Magnetic fields do interact with each other. Coils inside a crossover are usually arranged at 90° to each other in order to avoid magnetic field interaction, for example.

The coils inside a crossover are arranged that way to reduce mutual inductance, and to reduce the possibility of coupling. But that's an entirely separate issue from bi-wiring outside the speaker. before the crossover. This has been explained to you before by AJ. Do you still not understand? Of course you don't want low-frequency current going to the tweeter. That is why the crossover is there, and why it should be layed out to minimize coupling. That has nothing to do with bi-wiring.
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And once again, you confuse signal with current.

I did? And "once again?" I used the term signal to generically refer to either the voltage or the current...because it doesn't matter. Don't underestimate the educational and professional background of people on here.

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post #68 of 86 Old 10-04-2012, 04:03 PM
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Originally Posted by beaveav View Post

That is why the crossover is there, and why it should be layed out to minimize coupling. That has nothing to do with bi-wiring.

Except that bi-wiring maintains that separation back to the amp terminals. For $10 more worth of wire, it is an a advantage I would like to have.
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post #69 of 86 Old 10-04-2012, 04:14 PM
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Originally Posted by kiwi2 View Post

Except that bi-wiring maintains that separation back to the amp terminals.

Again, I won't try to argue the science or engineering here, I am perfectly happy to resign, "sure, bi-wiring impacts the current flowing to each of the speaker terminals", whether it is in fact true or not.
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For $10 more worth of wire, it is an a advantage I would like to have.

But that's the point - there is NO advantage.

Whether the current flow between the amp terminals to the parts of the crossover is different is irrelevant.

The current flow between the parts of the crossover and the drivers is identical - hence there is NO audible difference, there is NO advantage.

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post #70 of 86 Old 10-04-2012, 05:17 PM
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Originally Posted by rick240 View Post

Again, I won't try to argue the science or engineering here, I am perfectly happy to resign, "sure, bi-wiring impacts the current flowing to each of the speaker terminals", whether it is in fact true or not...

...But that's the point - there is NO advantage.
Whether the current flow between the amp terminals to the parts of the crossover is different is irrelevant.
The current flow between the parts of the crossover and the drivers is identical - hence there is NO audible difference, there is NO advantage.

So you don't even know if it is true or not if current flow separation occurs... yet you want to state it as an absolute fact that there is "NO" advantage? How can you be so certain if you don't even understand it?

Again, this is only your opinion.
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post #71 of 86 Old 10-04-2012, 05:33 PM
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Originally Posted by kiwi2 View Post

So you don't even know if it is true or not if current flow separation occurs... yet you want to state it as an absolute fact that there is "NO" advantage? How can you be so certain if you don't even understand it?

I can not state whether there is a difference in current flow is some segments of the amp to crossover path. I've never tried to measure it, and have no desire or intention to do so.

I can state that whether there is one wire between the amp to the speaker terminals and separate wire from there to the HPF and LPF parts of the crossover,

of one wire to the amp connector and then the two wires from there to the parts of the crossover will make absolutely NO difference in the current arriving at the crossover filter parts.

So yes, I feel confident in stating NO advantage.

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Again, this is only your opinion.

Yes, but it is based on science, not placebo and the "hope" that moving the one wire to two wire connection point in the path from the speakers connector to the amp's connector "may" make some kind of improvement.

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post #72 of 86 Old 10-04-2012, 06:00 PM
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All frequencies go to both speaker inputs, high and low. However, in the ideal case only LF current flows to the low terminals and vice-versa. If the signal had only LF then the only current flow would be in the LF wires and there would be no current and thus no voltage drop along the wire to the HF section.

The amplifier driving the high side "sees" only HF current, and the amp driving the low side "sees" only LF current. So, the HF amp delivers HF power, and the LF amp delivers LF power. Note there is no net power gain; two 100 W amps in a bi-amp configuration is the same as a single 100 W amp (you don't somehow get the same effect as if you had a 200 W amp). The HF amp is also isolated from LF kickback energy from the woofer, and the LF amp is isolated from HF kickback from the tweeter. Again assuming imperfect amplifiers this could reduce distortion caused by the lows modulating the highs and vice-versa. It does little for “normal” distortion since the amps are still delivering voltage and current (power). Finally, while voltage headroom is unchanged (since both have the same voltage output), current headroom could be improved depending on how the frequencies are split. So, this can provide theoretical benefits assuming imperfect amplifiers since power is delivered in only part of the frequency band.

As for the wires, their impedance is usually in the mud compared to the amp and speakers, and any distortion added by nonlinear wire changes is vanishingly small for any practical case. Maybe if you used fuse wire for speakers, but realistically wire “distortion” is insignificant.

In practice benefits are likely to be quite small and almost certainly inaudible. It would have to be a pretty bad amp to benefit from a passive bi-amping approach as it means the output impedance of the amp has to be high enough and current capability low enough that the amps benefit from doing this. It also means the power supply must not be the limitation, probably not a good assumption where most AVRs are concerned since the power supply limits the total output judging by virtually all the specs I have seen.

Bottom line: There are theoretical benefits, but they are (very!) unlikely to be audible in practice. I personally cannot imagine hearing any benefit, but obviously opinions vary.

FWIWFM - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #73 of 86 Old 10-04-2012, 06:03 PM
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Originally Posted by DonH50 View Post

All frequencies go to both speaker inputs, high and low. However, in the ideal case only LF current flows to the low terminals and vice-versa. If the signal had only LF then the only current flow would be in the LF wires and there would be no current and thus no voltage drop along the wire to the HF section.
The amplifier driving the high side "sees" only HF current, and the amp driving the low side "sees" only LF current. So, the HF amp delivers HF power, and the LF amp delivers LF power. Note there is no net power gain; two 100 W amps in a bi-amp configuration is the same as a single 100 W amp (you don't somehow get the same effect as if you had a 200 W amp). The HF amp is also isolated from LF kickback energy from the woofer, and the LF amp is isolated from HF kickback from the tweeter. Again assuming imperfect amplifiers this could reduce distortion caused by the lows modulating the highs and vice-versa. It does little for “normal” distortion since the amps are still delivering voltage and current (power). Finally, while voltage headroom is unchanged (since both have the same voltage output), current headroom could be improved depending on how the frequencies are split. So, this can provide theoretical benefits assuming imperfect amplifiers since power is delivered in only part of the frequency band.
As for the wires, their impedance is usually in the mud compared to the amp and speakers, and any distortion added by nonlinear wire changes is vanishingly small for any practical case. Maybe if you used fuse wire for speakers, but realistically wire “distortion” is insignificant.
In practice benefits are likely to be quite small and almost certainly inaudible. It would have to be a pretty bad amp to benefit from a passive bi-amping approach as it means the output impedance of the amp has to be high enough and current capability low enough that the amps benefit from doing this. It also means the power supply must not be the limitation, probably not a good assumption where most AVRs are concerned since the power supply limits the total output judging by virtually all the specs I have seen.
Bottom line: There are theoretical benefits, but they are (very!) unlikely to be audible in practice. I personally cannot imagine hearing any benefit, but obviously opinions vary.
FWIWFM - Don

Don - great discussion of passive bi-amping...

...but this discussion is about single amp and bi-wire vs single wire.

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post #74 of 86 Old 10-04-2012, 06:26 PM
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Oops, rats. tongue.gif What I get for trying to post while I practice.

The amp sees the same load no matter how many wires are used so there is no benefit as far as the amp is concerned. I can only see bi-wiring making a difference if the wire is so small that doubling up helps, and even there it's unlikely since the LF driver is usually seeing the largest signal -- you'd be better off doubling up the wire and connecting them together at both ends. Technically the wires have different current in them, true, but wires are not the problem, and wire nonlinearity is certainly not. Unless you are using fuse wire, as I said above.

Distortion in the speakers will usually swamp everything else by orders of magnitude.

Back to the horn - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #75 of 86 Old 10-04-2012, 08:09 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

If you had ever attended even a class is acoustical engineering one of the first things you would have learned is that the statement 'I know what I'm hearing' is usually not true. Obviously you have not. Here's a start for you:
http://www.youtube.com/watch?v=BYTlN6wjcvQ

Same is true for vision - not sure about the other senses. My point was that some people here have an agenda, and if what they hear serves it, then hearing rules, if not, then measurement rules. Seems to me, if you can't trust your hearing, then there's no point to DB listening tests?

At least get it right. I design speakers, both for the DIYer and for manufacturers. I don't sell speakers. What's misleading about that statement?

Confused here, maybe you didn't read it right - you sell speaker plans, I said, you sell speaker plans. Seems pretty clear.

The poster said you sell speakers, which is incorrect, but a secondary, and essentially irrelevant point to his main point. That is, you are commercially involved in the speaker world, and could easily have a bias because of it. The conflict of interest is baked in. Your reply simply stated that you don't sell speakers. Period. This might not go so far as to imply that you have no commercial interests in the speaker world, but it certainly invites an uniformed reader to infer it. That is misleading.


And never forget that the techno-fetishists you disdain are responsible for inventing what you listen to. Without them the world would be a very silent place.

You're putting words in my mouth by redefining the term. The TFs are here at AVS (and other places on the www.) Broadly defined, my audio heroes are recording engineers. They didn't "invent" music, but they did a remarkably good job of recording it with antique technology (thinking here of original Elvis to Simon and Garfunkel to Layton and the Living Stereo glories etc.) From articles and interviews I've read with the old timers, they were just as into their tech of the day as modern guys are. And part of their process was listening.

Most speakers I've delved into enough to get to the design phase involve a "voicing" stage. This inevitably involves listening to it. Plenty of engineering before you get to that point, but I'd hesitate to ever buy a speaker from someone who bragged that he didn't have to listen to it before release. Generic x-over bits from some lookup table do not a great speaker make.

After all, this hobby is about listening, so, really, how do you eliminate it from discussion? I'm all for educating the uniformed, but bullyism in the guise of teaching doesn't get anyone anywhere, except the bullies.

Eve: I thought I was through getting involved with men who were trouble. Falling in love on a look. I can't look at you.

Mickey: You have perfection about you. Your eyes have music. Your heart's the best part of your body. And when you move, every man, woman and child is forced to watch.
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post #76 of 86 Old 10-04-2012, 08:33 PM
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Originally Posted by rick240 View Post

I can not state whether there is a difference in current flow is some segments of the amp to crossover path. I've never tried to measure it, and have no desire or intention to do so.

No need to even measure it. You can calculate it. A circuit is a direct relationship between voltage, current, and resistance. It is basic stuff.





One side of a crossover shows a different resistance to the other side. That is how a passive crossover works. If voltage (the amp) sees a different resistance, then you will get a different current flow in the wiring to that side.

The links I posted earlier tried to explain this basic printable of electrical circuits.
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post #77 of 86 Old 10-04-2012, 08:58 PM
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So what? You might be able to calculate it but you cannot hear the difference!

Dumb enough to spend lots of cash on this junk!
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post #78 of 86 Old 10-04-2012, 09:11 PM
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Can you hear the difference between 320k Mp3 and WAV? Or the difference between WAV and FLAC? Or the difference between compressed FLAC and uncompressed FLAC?

Just let people know the facts on the matter and let them decide for themselves if it is worth it or not.
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post #79 of 86 Old 10-04-2012, 09:32 PM
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Originally Posted by kiwi2 View Post

No need to even measure it. You can calculate it. A circuit is a direct relationship between voltage, current, and resistance. It is basic stuff.

One side of a crossover shows a different resistance to the other side. That is how a passive crossover works. If voltage (the amp) sees a different resistance, then you will get a different current flow in the wiring to that side.
The links I posted earlier tried to explain this basic printable of electrical circuits.

Yes, but we aren't talking about different sides of a crossover.

Whether there is one wire from the amp to its connector, then to the speakers connector, and then two wires to the crossover, or

one wire to the amps, connector then two wires from there to the crossover,

is all on one side of the crossover

there were always two wires from the speakers connector to the crossover

you are merely moving the junction point of those two wires by a few feet

NO ELECTRICAL DIFFERENCE

NO CHANGE IN CURRENT ARRIVING AT THE CROSSOVER

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post #80 of 86 Old 10-04-2012, 09:35 PM
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Originally Posted by kiwi2 View Post

Just let people know the facts on the matter and let them decide for themselves if it is worth it or not.

Yes, the facts are:

- one wire leaves an amp,

- at some point it splits into two before reaching a crossover

Some people "believe" that if you change the ratio of the lengths of the single wire vs the double wire you will impact the electrical signal arriving at the crossover rolleyes.gif

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post #81 of 86 Old 10-04-2012, 09:43 PM
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Originally Posted by kiwi2 View Post

Can you hear the difference between 320k Mp3 and WAV? Or the difference between WAV and FLAC? Or the difference between compressed FLAC and uncompressed FLAC?
Just let people know the facts on the matter and let them decide for themselves if it is worth it or not.
The problem is that you are letting your "facts" get in the way of reality. Fact is the current is affected. Another fact is that you cannot perceive it using your ears.

Dumb enough to spend lots of cash on this junk!
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post #82 of 86 Old 10-05-2012, 07:39 PM
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Originally Posted by rick240 View Post

Yes, the facts are:
- one wire leaves an amp,
- at some point it splits into two before reaching a crossover
Some people "believe" that if you change the ratio of the lengths of the single wire vs the double wire you will impact the electrical signal arriving at the crossover.



Electronically amp terminals aren't considered as a length of the wire. They are terminals, just like battery terminals. There is a particular word that describes this electronically which I can't quite remember for now.

At least some of you are beginning to grasp the concept that the current in the speaker cables will be different even though the crossover is upstream. You don't need the crossover downstream to create the difference. That was the error most people were making when arguing against bi-wiring.

Possible advantages? The reverse current created by the driver's coil moving inside a magnetic field can be better damped by the amp rather than being more free to cross effect the other driver.
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post #83 of 86 Old 10-05-2012, 09:11 PM
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There is no change at the amp; if the amp cannot dampen the reverse charge from the speaker bi-wiring won't help. EXCEPT if the wire impedance is high enough that it reduces the energy fed back to the amp. This will reduce the amp's ability to control that same speaker, and reduce the energy into the speaker as well as the amp, generally a step in the wrong direction. The whole premise is that the amp is as close to perfect as possible and the wire's impedance high enough that high and low current does not "mix" in the wire. The technical basis for bi-wiring stretches the imagination, but I am a simple engineer, not a golden-eared audiophile.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #84 of 86 Old 10-05-2012, 09:28 PM
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Originally Posted by DonH50 View Post

There is no change at the amp; if the amp cannot dampen the reverse charge from the speaker bi-wiring won't help. EXCEPT if the wire impedance is high enough that it reduces the energy fed back to the amp. This will reduce the amp's ability to control that same speaker, and reduce the energy into the speaker as well as the amp, generally a step in the wrong direction. The whole premise is that the amp is as close to perfect as possible and the wire's impedance high enough that high and low current does not "mix" in the wire. The technical basis for bi-wiring stretches the imagination, but I am a simple engineer, not a golden-eared audiophile.
Doh!

Dumb enough to spend lots of cash on this junk!
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post #85 of 86 Old 10-05-2012, 09:42 PM
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That's "Don". biggrin.gif

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #86 of 86 Old 10-06-2012, 09:38 AM
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Quote:
Originally Posted by kiwi2 View Post

Electronically amp terminals aren't considered as a length of the wire. They are terminals, just like battery terminals. There is a particular word that describes this electronically which I can't quite remember for now.

Yes, the terminals on the speakers and the terminals on the receiver are just terminals. Everything connected to them, is completely connected to each other.

In the receiver, on it's circuit board is the actual amp. There is a wire, or a trace on the board (electrically the same as a wire) which connects the amp to the connector.

In the speaker, there is a wire from each of the connectors (typically jumpered to make them electrically one), or a trace on a board (again the same as a wire), to the HPF and LPF parts of the crossover.
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At least some of you are beginning to grasp the concept that the current in the speaker cables will be different even though the crossover is upstream. You don't need the crossover downstream to create the difference. That was the error most people were making when arguing against bi-wiring.

Again, I am willing to accept this from you.

But this difference in current would have always existed on the two wires from the speakers connector to the two parts of the crossover.

All bi-wiring does is change the point in the circuit where it goes from one wire to two. It does not in anyway electrically change the circuit, merely the amount of wire to achieve exactly the same thing.
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Possible advantages? The reverse current created by the driver's coil moving inside a magnetic field can be better damped by the amp rather than being more free to cross effect the other driver.

If an amp was better able to dampen such reflections, the amp would need to have two outputs for each channel, with separate paths to separate connectors for bi-wiring to take advantage of this capability. Whether the point of electrical connection is at the speaker terminals or the amp terminals is irrelevant to anything travelling on the wires - they are all connected without any magic dampening capabilities being applied.

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