Chuck Hawks - Bi-Amping and Bi-Wiring

[Loop 7]

A really great read on the subject. Being a skeptical person by nature, this piece made sense to me.

Anyway, if you have a few minutes, check it out:

Bi-Wiring and Bi-Amping Loudspeakers by Chuck Hawks

[vneal]

My fronts are bi-wired. Can't say I can tell the difference but if there is I won't be missing it

[Soup]

My front Totem's Model 1 Signatures are Bi-amped/Bi-wired

[copperpipe]

I mostly agree with him, but I do what he calls "fools bi-amping"; which in my opinion is unfair. It's obviously not as good as active bi-amping, but he seems to minimize the effect of doubling the watts/power supply, and does not mention (at all) the advantage of complete channel separation.

I do agree though, that I would not purposely set out to passively bi-amp. But (long story) I ended up with 2 identical mini's in my possession so I'm definitely going to use them.

[repeetavx]

The Chuck Hawks article has been around awhile and is greatly respected. There are other views though. Here's what the engineers at Vandersteen have to say about Bi-Wiring and "Passive" Bi-Amping. (About half way down the page).

We began experimenting with bi-wiring back in the early '80s, an era when horizontal bi-amplification was considered the ultimate way to drive quality loudspeakers. (Horizontal bi-amplification used one amplifier to drive the low-frequency section of a speaker and a second amplifier to drive the high-frequency section.) We noted that speakers sounded better when bi-amplified by two amplifiers than when driven by a single amplifier. Surprisingly, this superior performance was evident even when the speakers were bi-amplified by two identical amplifiers at a low volume level and the amplifiers were each driven full-range without an electronic crossover. We initially believed that the double power supplies and other components of two amplifiers were responsible for the improvement, however building amplifiers with twice the power supply and doubling-up on other critical components failed to provide the bi-amplification benefit.

So we looked at the speaker wires. With two amplifiers, bi-amplification used two sets of speaker cables so we experimented with doubling-up the speaker wires and with larger wire. Neither duplicated the bi-amplification improvements. Then we considered that in a bi-amplified system, one set of wires carries the low-frequencies and the other set of wires carries the high-frequencies. We modified a speaker's crossovers to accept two sets of cables and present different load characteristics to each set so that the low-frequencies would be carried by one set of wires and the high-frequencies by the other set of wires. Finally we heard the sonic improvements of bi-amplification with a single amplifier.

[405x5]

"Recent".....??
Where has this guy been?
Best advice for biamping/biwiring:
Follow your loudspeaker manufacturer's reccomendations
For amplifier connections.
Along with advisement on power requirements to achieve desired db. Levels.

Bill

[Loop 7]

Dec 10, 2016 11:07:57 GMT -5 repeetavx said:

The Chuck Hawks article has been around awhile and is greatly respected. There are other views though. Here's what the engineers at Vandersteen have to say about Bi-Wiring and "Passive" Bi-Amping. (About half way down the page).

We began experimenting with bi-wiring back in the early '80s....

Yes, I have Vandersteen speakers and bi-wire them but the crossovers in Vandersteen speakers are specifically designed for this configuration, correct? Whereas, most speakers are not.

[Dan Laufman]

I like Bi-Wiring loudspeakers! And not to sell more speaker cables!!

The improvements are audible. I'm gong to dig around and find an interesting experiment that was shown to me in the old days that graphically showed the benefits of Bi-Wiring.

The longer the speaker run and the less efficient the speaker, the more it helps... I'll explain in detail but I've got to dig up the test setup I was shown... It has to do with the voltage drop on the copper modulating the mid and hi frequencies... when you Bi-Wire, you are returning the large woofer currents to the zero impedance point, (the amplifier) separately from the mid-high currents. There is a modulated voltage drop on the speaker wire and this voltage drop causes audible artifacts in the highs, in particular. It's real and it's cool.

I'll get back to you on this soon. I've got stuff to do today.

Stand by for a future update...

[mgbpuff]

One must be careful in labeling others audiophools. The proof is in the listening. There is a technical reason why bi-wiring can make a difference - intermodulation within the single wire between differing frequencies which run at differing depths but in close parallel proximity with respect to the conductor center. Separating the higher frequencies from the lower ones via bi-wiring with separation between the two sets of wires may give improvements more or less depending upon the wire length and gauge and the speakers cross over design.

[copperpipe]

My definition of audiophoole is one who repeatedly makes a claim but refuses (or is unable) to back it up with a properly controlled test. If the difference in sound is audible, and worth talking about (beyond theory), then one should be able to prove, significantly, that they can hear a difference.

I'm willing to accept the science behind bi-wiring, as a theory, but whether one can hear a difference in a controlled test... that's a different issue. There are probably far more significant factors controlling what you hear, such as humidity/temperature of the room, the amount of people sitting in it, or the size of your trashcan. Nobody seems to worry about all that stuff.

[LCSeminole]

Given the length and gauge of wire, (from a given sample of speaker wire), are equal, I personally can not get past the physics. The bi-wire, as opposed to the one wire to the jumper on the speaker terminal, is electrically equivalent. While I've not heard any difference with my speakers in trying out bi-wiring, I don't discount what Charles Hawkes refers to as the "placebo effect in medicine" either. Some believe they hear a difference and believe this strongly, personally I don't hear a difference. I believe in exploring the world of audio and finding out for one's self, which is part of the fun of this. I'll also add that while I don't hear any differences in bi-wiring, I highly doubt I would hear a difference in blind testing. To each their own.

[RichGuy]

I prefer my speakers bi-wired and have found it to be a slight improvement in sound quality, I have been bi-wiring my system for over 20 years, my current wires I made using Mogami 2921 quad wire are the best I have ever had in my system and were quite a noticeable improvement in sound quality.

Here is one of the best explanations I have found on why bi-wiring works by Jon Risch.


"How Bi-wiring Works
Bi-wiring is accomplished via separate pairs of terminals on the loudspeaker system, typically one pair for the woofer, and one pair for the tweeter or midrange and tweeter. They are completely separated electrically from one another. The normal function of a loudspeaker crossover is to guide the proper frequency's to the proper driver. Lows to the woofer, and highs to the tweeter. This is done in part for protection from the division of labor that has occured with two disparate speakers: tweeters will be damaged or destroyed if exposed to low frequency's and woofers just heat up when exposed to the higher frequency's, as they are too massive to respond at all. The other function that a crossover provides is in allowing the two speakers to blend together, to mesh with one another to become a single apparent sound source. They can also provide some passive EQ of the drive units, as long as there is excess energy to throw away.

The fundamental way a loudspeaker crossover works is to vary the impedance seen by the speaker and by the power amplifier. In the case of the woofer, the crossover network for it has a very low series impedance at low frequency's that gets gradually higher and higher in impedance between the amp and the speaker at higher frequency's. For very low frequency's, there is lots of current flow to the woofer, and for higher frequency's, there is little current flow due to the much higher impedance. In the case of the tweeter, at low frequency's the series impedance is very high and very little current flows, and as the frequency goes higher, the impedance of the crossover network gets lower and lets through more current.

The situation is such that when the full range musical signal is applied to the terminals of a full-range speaker system, the woofer only gets sent low frequency signals, and the tweeter only gets sent high frequency signals. Once the crossover networks have been electrically separated, they still continue to function in the same manner, having a low impedance in their passband of application. This means that if separate speaker cables are hooked up for the woofer and it's portion of the network, and the tweeter, and it's portion of the network, not only have the speakers and the frequency's directed and divided for them, but the two separate speaker cables will now also carry different signals, the woofer cable mostly the lows, and the tweeter cable mostly the highs.

Once the highs and lows have been separated in this fashion, the strong current pulses and surges that a woofer demands when reproducing bass or drums will not interact with the delicate sounds of a flute or cymbal. The magnetic field of the low frequency signals cannot modulate or interfere with the highs, and to a lesser extent, the reverse is true.

Now that the low and high frequency signals have been divided among not only the speaker drivers, but the speaker cables, these cables can be more specialized for their intended purpose. The woofer cable can concentrate on low DCR, and not have any big concern for extremely low inductance, the tweeter cable can be designed for very low inductance, and not as concerned about total DCR.

Using one much larger unsophisticated cable to achieve the same thing as bi-wiring is just not possible, the separation of work has not occured, and the ability to optimize each separate run is not available. Additionally, as the gauge of a wire decreases (wire gets fatter) and the spacing between the pair of wires that constitute a speaker cable gets greater, the inductance tends to go up. Using one larger unsophisticated cable actually makes things worse for the tweeter, as even though the DCR has gone down and the woofer gets more energy compared to the thinner single cable, the tweeter now gets less energy in the extreme highs. The net result is a shift in the tonal balance that can even exceed the criteria held dear by the ABXers.

The current path's I describe can easily be plotted, measured and verified by any speaker or cable engineer. There is absolutely no doubt whatsoever about their existence or validity. 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.

Jon Risch


Bi-Wiring 101

In order to explain how bi-wiring works, it is necessary to explain a bit about how crossovers work. It will also be necessary to contemplate more than the usual voltage output of the crossover sections, so do not assume that if you know the basics for crossovers, that you will know what this will be all about.

Let's look at a simple two-way system with a first order crossover, the simplest crossover and system we can examine. It will be relevant to other more complex systems, so once you understand this one, the others will fall into place. We will not address the issues of tweeter level padding, response EQ, etc., just the basic crossover function itself.

In a simple first order crossover, there is an inductor in series with the woofer, and a capacitor in series with the tweeter. These two components comprise the crossover system. Normally, these two components are connected to the same input terminals on the speaker, in parallel. Hence this type of crossover topology is called a parallel type crossover.

A full range voltage signal is sent down a speaker cable, and appears at the single pair of input terminals. A current is drawn based on the input impedance of the speaker system as a whole, which in most cases, will have a relatively flat impedance curve once we get above the bass resonance region, where the impedance will be dominated by the cabinet design resonance's. If we say that (for purposes of this discussion) the overall impedance of the speaker in the midrange and on up is relatively flat, then a consistent amount of current will flow through the single speaker cable all across the audio band.

So there are several elements to the total circuit formed by the amp output terminals, the speaker cable, and the speaker system and crossover network. A signal appears at the amp terminals, represented by a voltage, the impedance of the speaker system causes it to draw an amount of current proportional to it's impedance for a given drive voltage, and this current flows through the speaker cable.

Now in order to examine what happens when we bi-wire, it will be necessary to go into some of the detail as to how a crossover "crosses over". If we look at just the woofer, and it's series inductor, the inductor provides little impediment to low frequencies traveling through the inductor, and a high amount of impediment to the higher frequencies. Looked at another way, the inductor impedes the highs but not the lows. If we examine an impedance curve of just the woofer with its series inductor, we would see that the impedance was pretty much just that of the woofer in the low frequencies, and would rise with frequency as the inductor impeded more and more of the highs. For this situation with just the woofer, for a given voltage drive level, a certain amount of current would be drawn at low frequencies, and this amount would decrease as the frequency went up, due to the rising impedance.

If all that was hooked up to the amp was the woofer and it's associated inductor, then the current flow in the single speaker cable would follow the impedance curve, a certain amount of current flow at low frequencies, tapering off at higher frequencies. Perhaps a glimmer of the true situation with bi-wiring is beginning to appear.

Now let's just look at the tweeter, and it's associated capacitor in series. At low frequencies, a capacitor tends to impede the flow of current, and at high frequencies, it provides little impediment. Hence, when we hook up just the tweeter and it's capacitor to the amp terminals through the single speaker cable, there is little current flow at low frequencies, and an increasing amount as the frequency goes up. At some higher frequency, the current draw is determined by the impedance of the tweeter alone.

Now just to make sure that it is understood, it is the current flow through a dynamic driver (one with a magnet and a voice coil) that causes it to move. A voltage applied that had no current capability would not cause any movement. This means that in order for the voltage at the amp terminals to cause a speaker to move, it must have a relatively low source impedance, so that when a given voltage appears at the amp output terminals, a given amount of current can flow into the load's impedance. That is why when the crossover components impede the current flow, they cause the output of the driver to drop off, hence the crossover function is achieved.

Note that the woofer and it's associated inductor, and the tweeter and it's associated capacitor will function independently, they roll-off the frequencies out of the driver's operating band without regard to whether or not the other half of the crossover is present or not. When both sections of the crossover are present, and connected in parallel, the overall impedance curve looks relatively flat, as when the tweeter section has it's impedance going up in the low frequencies, the woofer has it's impedance going down. At the crossover point they are more or less equal, and this is the point in frequency at which the impedance's of the two sections in parallel equal approximately half that of either section alone. This is how two 8 ohm drivers can be connected together through a crossover, and not equal a total load of 4 ohms.

By now, you should be getting the idea about bi-wiring. Instead of one speaker cable, or just one of the drivers and it's associated crossover component being connected to the amp's output terminals, two separate speaker cables are connected to the same amp output terminals and run to the now separated crossover sections. With different impedance's being presented across the audio band, each cable carries a different signal than a single speaker cable. The separate cable for the woofer carries mostly the LF currents, and the separate cable for the tweeter carries mostly the HF currents. This is due to the differing impedance's we discussed above.

Now if all you think of is the voltage at the amp terminals, and how the two cables are carrying the same voltage to the woofer and the tweeter sections, then it still may seem that the same signal is being delivered to the drivers as through one speaker cable. IF the speaker cables were perfect, and had zero impedance, infinite mass, and no digressions from ideal LCR behavior (DA, DF, hysterisis, etc.), then it may be that this would be the case. Since the cables we have available to us are not perfect, there are losses in the cables.

The $64,000,000 question is, how much does the real world speaker cable compromise the performance of a speaker compared to bi-wiring?

To make this easy to figure out, we will ignore the effects of inductance and secondary effects, and focus strictly on DCR effects. Let us assume that a cable sufficiently large enough to keep speaker system impedance variations from affecting the amplitude response by more than 0.1 dB was used, meeting the Krueger criteria. In many cases, this is a very large cable, usually at least a 14 gauge, and often 12 gauge OR LARGER.
For a copy of the Krueger criteria see: x42.deja.com/[ST_rn=ps]/getdoc.xp?AN=450322078&CONTEXT=927059192.1901920287&hitnum=6
(I should warn that I do not agree entirely with Arny's criteria, it completely ignores inductance, which typically gets worse as a ratio of DCR to HF impedance of the cable as the gauge gets smaller, or larger zip cords)

How quick do the gauge requirements add up? If you have only 10 foot cables, and a speaker with a minimum Z of 6 ohms, then a 14 gauge wire is necessary to prevent any more than a 0.1 dB amplitude variation due to the cable DCR. If the speaker Z minimum hits 3.7 ohms, you are now up to 12 gauge. Anything longer in terms of the speaker cable, or lower in terms of the Z, will require larger than 12 gauge to reduce the amplitude variations due to voltage drops to less than 0.1 dB.

For a single speaker cable, lets look at a simple signal containing only two frequencies: 100 Hz, and 6 kHz. (As a point of information, let's say that the crossover point is 3 kHz, a common crossover point for a 2-way system) In the single speaker cable that meets the 0.1 dB criteria, a lot of current will be drawn at 100 Hz to feed the woofers demands. This will cause a voltage drop due to the finite amount of resistance in the cable. While the loss of 0.1 dB of woofer output may not seem to be a problem, the current draw at 100 Hz will tend to modulate the 6 kHz signal. How much distortion will this generate? To cause a 0.1 dB change, the signal is being affected at levels of approximately -40 dB down from nominal. If the 6 kHz signal is modulated by the 100 Hz signal by that amount, the IM distortion would be on the order of 1%. These are ball park numbers, not intended to be absolute.

This is a distortion that would be reduced by the amount of LF current reduction in the tweeter cable, typically 26 to 36 dB lower in level. This would reduce the distortion from borderline audibility to very likely not audible.

If we were to look at the simple change in DCR from merely doubling up on the cable, then distortion would only go down 6 dB, from halving the DCR and nothing more.

Of course, once we start using real music, with more than just two frequencies, and real world cable situations that might have even more DCR, and the inductance differences between a single zip cord and two high performance speaker cables, the amount of distortions in a single speaker cable go up considerably, and the amount of reduction in distortion is increased for the bi-wire comparison. This means that we might be into 2% IM or more, and with multiple frequencies, which make it even worse sounding.

All of the above totally ignores any potential magnetic field interactions, many of which would be time delayed and would smear out transients and large signals. The magnetic field distortion reduction would come from the separation of the LF currents and the HF currents.
The time delayed and resonance associated signature would tend to make these distortions even more noticeable than the self-IM of the cable due to voltage drop.

I think it is easy to see that a multidriver system with higher order crossovers will react similarly to this very simple first order two-way system that has been analyzed.

It is interesting to note that higher order crossovers tend to have a similar input impedance for each section as a first order, and it is the output signal of the various sections of the crossover that are made to roll off steeper. In essence, the reductions in current for each cable in a bi-wire pair will be at a 6 dB/octave slope almost regardless of the crossover order.

Jon Risch"

[Boomzilla]

The purpose of bi-wiring isn't to deliver more power. The purpose is to prevent the woofer's back-EMF from interfering with that of the midrange/treble drivers. Since they're both going to the same amplifier outputs, the efficacy of the bi-wire technique is questionable. Some speaker manufacturers embrace the idea, others (equally prestigious) reject it completely.

The wire/speaker impedance is not changed by bi-wiring. Each driver or set of drivers still sees the same length of wire (and, assuming equivalent wire gauge) the same wire resistance whether bi-wiring or not.

The bottom line is that whether or not bi-wiring provides benefits (audible or theoretical), it does no harm. Therefore, bi-wire if you want to, don't if you don't. I doubt that most could tell any difference in the mythical "double-blind test."

Cheers - Boom

[Loop 7]

Why are some very high end speakers NOT bi-wire nor bi-amp capable?

[RichGuy]

Dec 10, 2016 14:18:53 GMT -5 Boomzilla said:

I doubt that most could tell any difference in the mythical "double-blind test."

Most people in general will have a hard time or not even be able to determine what speakers are being played in the mythical "double-blind test", however that doesn't mean all speakers sound the same, peoples hearing ability and their amount of interest in the performance change also have effects.

As many of you know if it were up to most of your wives interest in performance we'd all be listening to original TV speakers and have music systems that sound only as good as our phones, as it would all sound the same and just as good.

[novisnick]

Dec 10, 2016 15:30:45 GMT -5 RichGuy said:

Dec 10, 2016 14:18:53 GMT -5 Boomzilla said:

I doubt that most could tell any difference in the mythical "double-blind test."

Most people in general will have a hard time or not even be able to determine what speakers are being played in the mythical "double-blind test", however that doesn't mean all speakers sound the same, peoples hearing ability and their amount of interest in the performance change also have effects.

As many of you know if it were up to most of your wives interest in performance we'd all be listening to original TV speakers and have music systems that sound only as good as our phones, as it would all sound the same and just as good.

Im super blessed! My Mrs is fully involved in what audio gear we listen to and purchase! Gotta have it has come frm her more then once! 

[RichGuy]

Dec 10, 2016 15:52:32 GMT -5 novisnick said:

Dec 10, 2016 15:30:45 GMT -5 RichGuy said:

Most people in general will have a hard time or not even be able to determine what speakers are being played in the mythical "double-blind test", however that doesn't mean all speakers sound the same, peoples hearing ability and their amount of interest in the performance change also have effects.

As many of you know if it were up to most of your wives interest in performance we'd all be listening to original TV speakers and have music systems that sound only as good as our phones, as it would all sound the same and just as good.

Im super blessed! My Mrs is fully involved in what audio gear we listen to and purchase! Gotta have it has come frm her more then once! 

Yeah there are a few of em out there, not many but a few.

[Wideawake]

This topic seems to come up with some regularity on the forum. I shall refrain from posting the usual links to support the many observations that state that bi-wiring and passive multi-amping have no benefits and only add expense to the system.

IMO, only active multi-amping has sonic benefits that are clearly evident. That is, no passive xo is used, an active xo separates the audio bands and feeds the amplifier channels which are consequently band limited to the appropriate drivers.

I've tried bi-wiring and found no change in SQ. I have not tried passive multi-amping since that would require 2 sets of the same speaker so that a comparison can be made by removing the passive xo in one set and actively multi-amping it. An additional challenge in this scenario is that the active xo should emulate the passive xo as closely as it is possible to do so, in order to make a reasonable comparison. This is only truly possible if you have the exact specs for the passive xo or if you have built the passive xo yourself.

As others here have suggested, try it for yourself. If you like it use it; if not, use the savings for some other enhancement in your system. Above all, enjoy the journey! And the music!

[Boomzilla]

There is no doubt that electronic crossovers upstream of the individual amplifiers driving the transducers directly is a superior method (in theory). Note that Emotiva's Stealth speakers use exactly such an arrangement, if I understand correctly.

HOWEVER - multi-amping (or "vertical bi-amping") DOES completely separate the back-EMF from any common connector. No, the amplifier does not have as direct control of the coils as does the method mentioned above, but it is still (theoretically) superior to having a single amplifier drive all the transducers.

And it must be said - DESPITE the theoretical advantages mentioned, the majority of speaker manufacturers (and, indeed, the VAST majority) feel that the actual audible benefits of such designs are not worth pursuing.

Draw your own conclusions.

[405x5]

Dec 10, 2016 13:13:02 GMT -5 LCSeminole said:

Given the length and gauge of wire, (from a given sample of speaker wire), are equal, I personally can not get past the physics. The bi-wire, as opposed to the one wire to the jumper on the speaker terminal, is electrically equivalent. While I've not heard any difference with my speakers in trying out bi-wiring, I don't discount what Charles Hawkes refers to as the "placebo effect in medicine" either. Some believe they hear a difference and believe this strongly, personally I don't hear a difference. I believe in exploring the world of audio and finding out for one's self, which is part of the fun of this. I'll also add that while I don't hear any differences in bi-wiring, I highly doubt I would hear a difference in blind testing. To each their own.

Absolutely and certainly where passive crossovers are concerned.
 
My own main speakers came bi amp equipped with a toggle switch for bridging. Its purely a marketing ploy that was necessary at the time when more manufacturers were on the competitive bridging bandwagon. In fact, on my IC20's there was even a tri amp. Option. (Custom order).

I went out of my way to bypass the bi amp option and also the toggle by making jumper wires from 12 gauge.

Bill