Why Bi-wiring Makes No Sense.

[jonnythan]

This is all wire loss, right? Beyond the fact that "bi-wiring" necessitates the first foot or so of the wire carrying the amplified signal is already monowire and then split into two wires, are you really trying to convince me that wire loss from a 100W signal on 20' of 12g wire is in any way significant compared to the actual signal??

 

[jonnythan]

Think of the instant in time when the woof has 1 ampere positive and the tweet has one ampere negative...at that instant, a monowire sees zero current, therefore zero power loss within the wire... But, a biwire setup has one ampere in the bass wire with it's dissipation, the tweet wire has negative one ampere and the exact same loss as the bass wire...

The result? In a monowire setup, the current of one signal will modulate the losses that are caused by the other..

That's absolutely true and it doesn't matter at all in the context of biwiring. No matter whether you monowire or biwire, that exact thing is already going on in the foot or so of wire inside the amplifier. You're completely ignoring the fact that the only difference between monowire and biwire is the length of the single-wire and dual-wire sections of the circuit.

 

[jneutron]

That's absolutely true and it doesn't matter at all in the context of biwiring. No matter whether you monowire or biwire, that exact thing is already going on in the foot or so of wire inside the amplifier. You're completely ignoring the fact that the only difference between monowire and biwire is the length of the single-wire and dual-wire sections of the circuit.

Not at all. Consider the amp as a voltage source. Also consider the fact that external to the amplifier, the normal recommendation is not to exceed 5% of the load resistance. So the instantaneous dissipation error in the monowire is not an insignificant portion of the overall power delivered to the load.

BTW, I ignore nothing. You are ignoring the cable dissipation aspect.

Please re-read my post. You have to understand what I have posted before you can engage a discussion about it. Gut reactions without proper consideration, such as your last post, serve nothing within the discussion.

Cheers, John

ps..Once you understand this, you should be able to figure out an audibility test to hear the effect.. I did, bout 6 years ago..

 

[jonnythan]

I understood your post. I think your conclusions are BS and that you are ignoring fundamentals of the setups.

Let's hear more about this audibility test.

 

[jneutron]

This is all wire loss, right? Beyond the fact that "bi-wiring" necessitates the first foot or so of the wire carrying the amplified signal is already monowire and then split into two wires, are you really trying to convince me that wire loss from a 100W signal on 20' of 12g wire is in any way significant compared to the actual signal??

Bingo. You are correct.

Consider your example..100 wrms into 8 ohms, 40 volt peak, 5 amp peak.

20 feet #12 is 1.71 milliohms times 40, 68 milliohms. Toss in 10 milliohms more for the connections, you get 78 milli..

5 amperes in 78 milliohms, I ²R, 25 times .078, 1.95 watts dissipative loss in the wire. Does anybody consider 1.95% to be below audibility? (this is just a calc of level of effect)

Now, lets add the tweet signal...100 watts..for a monowire, the peak current will be 10 amperes, the peak loss is 4 times previous, or 7.8 watts, out of 200 watts..

The peak loss using one wire is twice that of biwiring, yet the rms loss is the same..

Keep in mind, 20 feet of #12 is rather robust...I use #12 for 100 foot runs, as they meet my need..


Cheers, John

 

[jneutron]

I understood your post. I think your conclusions are BS and that you are ignoring fundamentals of the setups.

Let's hear more about this audibility test.

Take a day or two to understand what I have posted. To me it is quite clear what you are thinking, how you are thinking, and why you think it..I've had this discussion with many through the years.

Think in terms of instantaneous power loss, contrast mono vs biwire.

No amount of my verbage will be as good as you thinking about the problem correctly.

And some wonder why I do not present the inductive part.. that requires much more focus than the simple resistive problem.

Cheers, John

 

[gene]

Bingo. You are correct.

Consider your example..100 wrms into 8 ohms, 40 volt peak, 5 amp peak.

20 feet #12 is 1.71 milliohms times 40, 68 milliohms. Toss in 10 milliohms more for the connections, you get 78 milli..

5 amperes in 78 milliohms, I 2R, 25 times .078, 1.95 watts dissipative loss in the wire. Does anybody consider 1.95% to be below audibility? (this is just a calc of level of effect)

Now, lets add the tweet signal...100 watts..for a monowire, the peak current will be 10 amperes, the peak loss is 4 times previous, or 7.8 watts, out of 200 watts..

The peak loss using one wire is twice that of biwiring, yet the rms loss is the same..

Keep in mind, 20 feet of #12 is rather robust...I use #12 for 100 foot runs, as they meet my need..

John;

Rather than using a pair of 12AWG cables for biwiring, use a 9AWG single cable and call it a day

PS. Just to be clear, this isn't steady state power loss. As you know, music is peaky in nature, NOT continuous. You're lucky if you are dissipating more than 3-4 watts in a speaker at any given time on a continuous basis. Plus you seem to be mixing RMS power (which doesn't exist) with Peak power

If there is a calculatable difference (as you show) in instantaneous power loss, we are talking fractions of seconds which I have been waiting years for you to prove is audible.

:edit PS comments after I re-read jeutrons last post

 

[Audioholics]

jneutron,

Have you ever measured the audible/mechanical effects of high levels of dust buildup on the woofers of loudspeakers? Or the effects of oxidation over time on the wire connecting to the leads? Or the effects of instantaneous barometric pressure on SPl and loudspeaker wave propogation?

These are all things that I feel are of equal importance to the complex, yet important issues of bi-wiring.

 

[jneutron]

John;

Rather than using a pair of 12AWG cables for biwiring, use a 9AWG single cable and call it a day .

You forget who you are talking to. I'd rather use some G-2 (from american superconductor) in liquid nitrogen. Plenty of scraps lying around.. Or some 500 mcm..but it would topple the woofers..

PS. You also assume a steady state power loss which is far from reality. Music is peaky in nature, NOT continuous. You're lucky if you are dissipating more than 3-4 watts in a speaker at any given time on a continuous basis.

No, the calcs were to demonstrate the peak losses, and the intermodulation of the lossed as a result of a monowire feeding a branch circuit. As such, the calculations are indicative of ABSOLUTE worst case monowire error. That occurs when both signals are of the same value, which typically occurs several milliseconds prior to tweeter failure.. been there, done that..

And btw, the calc percentage of the delivered power doesn't change, if I used 1 watt the numbers still work out the same percentage wise..100 watts is just easier on the mind when it comes to values..

Cheers, John

 

[gene]

John;

you respond quicker than I can make edits after I post. I went back and read your post and then edited mine accordingly. Please re-read my prior post and discuss audibility. thanks.

 

[jneutron]

jneutron,

Have you ever measured the audible/mechanical effects of high levels of dust buildup on the woofers of loudspeakers? Or the effects of oxidation over time on the wire connecting to the leads? Or the effects of instantaneous barometric pressure on SPl and loudspeaker wave propogation?

These are all things that I feel are of equal importance to the complex, yet important issues of bi-wiring.

I've considered all those, but worry not about them..

Who said I consider biwiring to be of importance to me? I monowire everything I own, up to 300 wrms and 100 foot with #12.. Biwiring my rigs would just be a pita, and will provide zero gain in a 450 seat venue..

I present the real, measureable, audible aspects of the problem...nothing more, nothing less.

The fact that under certain conditions it can be audible, and simple tests can be devised to hear it, is of no real concern to me. I have no intent to listen to contrived test scenarios while listening to music..and I have no desire to try to hear it given recording technology as it exists today..why bother? I have better things to do with my free time, and prefer to enjoy the music I listen to..

Like surviving double black diamond glade slopes with my kids..sheesh, they're bulletproof..Luckily, I didn't pull a "Sonny".

Cheers, John

 

[jneutron]

If there is a calculatable difference (as you show) in instantaneous power loss, we are talking fractions of seconds which I have been waiting years for you to prove is audible.

Waiting for <i>me</i> to prove it's audible??

Why?

Cheers, John

 

[jonnythan]

You're not looking at the difference between "monowire" and bi-wire.

Using your numbers, and ignoring the wire in the amp:

An amp putting 100W into an 8 ohm speaker sees a total resistance of 8.078 ohms with a single wire.

An amp putting 100W into two parallel 16.078 ohm speakers sees a total resistance of 8.039 ohms, assuming *worst case scenario* of each speaker getting an equal amount of power (which is unlikely).

The difference in ohms? 0.48%. Assuming power stays constant, the difference in current is about 0.24%. I'm obviously not very well versed on how an amplifier works, and how much current and power will change with respect to each other, but it's abundantly clear to me that the *difference* between monowire and biwire is totally insignificant. Best case, where one driver is using all of the power, the difference is 0%.

 

[jonnythan]

John;

Rather than using a pair of 12AWG cables for biwiring, use a 9AWG single cable and call it a day

Exactly. The difference is even smaller than simply moving up to 11AWG from 12AWG.

 

[jonnythan]

No, the calcs were to demonstrate the peak losses, and the intermodulation of the lossed as a result of a monowire feeding a branch circuit.

Whether you biwire or not, you're still using a single wire to feed two circuits. The two wires are wired in parallel to a single amplifier terminal either way, and that terminal is fed by a single wire inside the amp.

 

[jneutron]

You're not looking at the difference between "monowire" and bi-wire.

Using your numbers, and ignoring the wire in the amp:

An amp putting 100W into an 8 ohm speaker sees a total resistance of 8.078 ohms with a single wire.

An amp putting 100W into two parallel 16.078 ohm speakers sees a total resistance of 8.039 ohms, assuming *worst case scenario* of each speaker getting an equal amount of power (which is unlikely)..

Why did you swap the speaker impedances?? If you wish to discuss it accurately, you must stick to the same numbers.

Use two 8 ohm drivers. And parallel them correctly with their crossover elements..

Would a diagram help you?

I'm obviously not very well versed on how an amplifier works, and how much current and power will change with respect to each other, but it's abundantly clear to me...

I have been aware throughout this discussion that you are not well versed in how amplifiers work (but that is irrelevant to this discussion)...it also seems you are not clear on biwiring either, based on your last post. Biwiring is an extension from the crossover node to the drivers, as opposed to all the dissipation occuring in front of the node as monowire does.

Best case, where one driver is using all of the power, the difference is 0%.

That is correct, but you did not arrive at that conclusion based on facts, nor by understanding the graph I posted..

Worst case is when both drives see the same power. That is the upper limit which my calcs show.

Cheers, John

 

[jneutron]

Whether you biwire or not, you're still using a single wire to feed two circuits. The two wires are wired in parallel to a single amplifier terminal either way, and that terminal is fed by a single wire inside the amp.

Where are you getting this??? When you biwire, you separate the currents at the amp node, when you don't the separation occurs at the speaker, which can be a significant resistive length away from the voltage node of the output terminals.

Sigh. Can you find a schematic somewhere showing biwire?? It would help you understand a little better..

Cheers,John

 

[jonnythan]

Where are you getting this??? When you biwire, you separate the currents at the amp node, when you don't the separation occurs at the speaker, which can be a significant resistive length away from the voltage node of the output terminals.

Sigh. Can you find a schematic somewhere showing biwire?? It would help you understand a little better..

Cheers,John

Open up an amplifier and you will see one wire connected to the red post of the output and one wire connected to the black post of the output.

Bi-wiring is taking this single-wire output and splitting it into two wires at the amp instead of at the speaker via a jumper.

 

[MDS]

It would help you understand a little better..

From reading your posts on anything that has to do with wire and calculations I gather that you believe you are the only competent engineer on the whole planet as you *always* say 'you don't understand', 'where do these guys come up with this rubbish', etc.

While I cannot follow all of your equations I do see that in the best case they 'prove' a MINISCULE difference. Is it audible? You always side-step that question because you have better things to do with your time.

 

[jonnythan]

I was using 8 and 16 to represent the speaker, whether or not those are real world numbers. Let me break it down for you.

Two 16 ohm loads in parallel gives you 8 ohms. Add the resistance in the single speaker wire running from the amp to the speaker terminal and you get 8.078 ohms.

Now, if you biwire, each of those 16 ohm loads instead of feeding them with a single wire, then you're dealing with two 16.078 ohm loads wired in parallel, giving you 8.039 ohms total.