Bi-amping Bi-wiring research material

[jomari]

*edit 05/31/09 - This post has been modified and approved to give informative detail regarding bi-amping and bi-wiring, and its benefits. by all means, we (BD and 'the other guy') have been tackling this topic to give the proper information regarding the said topics. By all means, contact either Big Daddy or yours truly, if you have any further informative detail we can addon here.*

A lot of questions arises when it comes to both these topics, thus here is a compilation of articles i have used in the past to clarify these quandaries

Bottom line?
The benefits of bi-amping or bi-wiring a certain system comes only when you have the appropriate equipment to fully maximize the experience.

GCaudio link

Rod Elliot article 2006

axiom audio by Alan Lofft (bio)
Former editor of Sound & Vision and Audio Magazines

I also have to credit my colleague on this article he wrote many years back regarding the said questions as well, COF/IG for this...

COF Article - Bi-wire, Bi-amp et al

For those who want a summation of the said article by IG

Bi-Wiring Pros:
Easy; Inexpensive; choice of ideal cable for use (high frequency = low capacitance / low frequency = low resistance); lowered resistance in total cable solution; some perceived improvement in sound in non-scientific tests.

Bi-Wiring Cons:
Questionable effect of one cable on the other since they are connected in parallel (capacitance and inductance of one cable will affect the capacitance of the whole system); not always perceived improvement.

Passive Bi-Amping Pros:
All the same pros as Bi-wiring pros; dedicated power supplies for each driver for improved dynamics and maximum sustained output; improved damping; greater isolation between low and high signals; amplifier technology could be matched to usage (Class-A for treble, High Current/Power for bass); more perceived improvement in sound in non-scientific tests.

Passive Bi-Amping Cons:
Added cost; more difficult as amps must be matched in gain ratio; no improvement in amplifier efficiency; still not 100% perceived improvment sound.

Active/Passive Bi-Amping Pros:
All the pros mentioned above; slight increase amp power supply efficiency; reduction in amp noise; easier to calibrate output levels (assuming crossover has level controls); yet more perceived improvement in sound.

Active/Passive Bi-Amping Cons:
Some passive crossovers designed for shallow slopes requiring crossover to be several octaves outside of crossover point; Few active crossovers have settings for unique crossover points for high pass and low pass (in this design the high pass must be an octave or two high than the passive crossover and the low pass crossover must be an octave or two below the passive crossover); more complicated setup; significant added cost (especially as active crossover must be custom designed for unique crossover points for each output); perceived improvement may not be improvement but perceived difference as setup is quite complex.

Active Bi-Amping Pros:
Most efficient use of amplifier power; maximum damping from amp due to elimination of all passive components; improved phase response (with proper crossover design); faster sound/greater "negative" dynamics (no discharging of fields in capacitors and inductors that cause ringing); nearly 100% perceived improvement of sound.

Active Bi-Amping Cons:
Most commercial loudspeakers are not design nor are easy to actively bi-amp; commercial speakers often have tuning circuits in passive crossovers that are not easily replicated with active crossovers requiring EQs; Very complex to tune; Fixed matching high pass and low pass slopes cannot take into account acoustical slopes inherent in drivers; Expensive.

You can sticky this hard earned posting if needed.

Edit 10/08

For a more advanced amount of learning, here is a very technical posting regarding series vs parallel crossover networks by Rod Elliot series vs parallel networks

CONCLUDING REMARKS AND COMMENTS BY BIG DADDY

If you disagree with any of the comments or have any questions, feel free to ask me. Don't blame Jomari (AKA "The Other Guy" ). I take full responsibility for my comments and/or any errors.

TYPICAL SPEAKER CONNECTIONS

Standard.jpg
Standard


Bi-Wiring.jpg
Bi-Wiring


Bi-Amping.jpg
Bi-Amping

BI-WIRING & BIAMPING

Unfortunately, many people tend to exaggerate about the benefits of tweaks and completely ignore the law of diminishing returns. In addition, certain things are pure science and not subject to personal interpretations.

The majority of people use passive bi-wiring and bi-amping without the use of external crossovers. Therefore, I limit my discussion to passive setups.

Passive bi-wiring requires that you run two wires from the same power source to the low frequency and high frequency drivers. The benefit of bi-wiring is minimal or non-existent.

Passive bi-amping requires that you run wires from two separate power sources to the high frequency and low frequency drivers. There are three different types of passive bi-amping. The diagram below demonstrates Passive Standard Bi-Amping with two separate external amplifiers. Please note that the wiring for the low input of the right speaker is accidentally drawn out of phase. Make sure you don't make this mistake.

The following diagram demonstrates Passive Vertical Bi-Amping with two external amplifiers:

The following diagram exhibits Active Bi-Amping with an external powered crossover:

Active Bi-Amping

The third type of passive bi-amping is with an AV receiver. Some of the older AV receivers such as the NAD 773 in the following diagram had pre-outs and main-ins for all the channels. They were connected with removable jumpers.

This allowed a great deal of flexibility as you could use the built-in amplifiers for other applications such as bi-amping. For example, you could use Y adapters (1 male, 2 female) and run one set of RCA cables from pre-outs for fronts to the main-ins for fronts and another set of RCA cables from pre-outs for fronts to the main-ins for back channels. With this modification, it would be possible to use the front speaker terminals for high frequency drivers and back channel speaker terminals for low frequency drivers.

Most new A/V receivers do not have main-ins for all the channels. A few of the high-end models such as the Denon 5308CI receiver have this option. Other receivers such as my Denon 4308CI allow to use the surround back channels for bi-amping.

The label for the pre-outs back channels is Surround Back/Bi-amp Assign. To take advantage of this option, you need to go to the receiver's menu and change the surround back channels for bi-amping. If you do this, your system will be reduced to 5.1. Although I am not familiar with other receivers, I am certain that other high-end A/V receivers from Pioneer, Onkyo, Sony, Marantz, Yamaha, etc. can do the same.

Bi-amping will enhance the sound much more than bi-wiring. However, the best way to bi-amp a speaker is with external amplifiers. Some speakers such as Definitive Technology Super Towers allow for tri-amping. They already have a built-in powered subwoofer. I have tried tri-amping on my Def. Tech super towers and it improved the sound slightly.

BI-AMPING AND ITS BENEFITS

If you bi-amp or tri-amp your speakers, you will hear some benefit, but don't expect miracles. The benefits of active bi-amping are summarized below.

Benefits of Active Bi-Amping:

1. Effectively (up to) twice the 'real' power of the amplifiers themselves.
2. Reduced intermodulation distortion.
3. Elimination of the low frequency passive crossover, its inherent losses, potentially poor linearity and crossover point inaccuracy.
4. Reduction of the difficulty of the load presented to the power amplifier.
5. No padding is required to align the driver sensitivities, so we are not simply wasting power.
6. The damping factor is greatly improved for both the low and midrange loudspeakers.
7. Complete freedom from any interaction between the loudspeaker driver (and its environment) and the crossover network.
8. Cost savings, since complex passive crossover networks are not needed
9. Bi-wiring is included free!
10. The flexibility to choose amplifiers which are at their best within a defined frequency range.
11. Ability to match amplifier power to the exact requirements of the drivers for maximum overall efficiency.

http://www.audioholics.com/education...g-vs-biwiring/

There also appears to be a benefit in passive biamping of amplifiers with finite output impedance such as those found in receivers. Having a dedicated amp to drive the woofer portion and another to drive the mid/tweeters can offer a better degree of system control and linearity assuming the power supply is capable of delivering the rated power into all four channels. In most cases however, very little power is consumed in the HP portion of the speaker since music above 8 kHz in harmonic in nature with very little energy.

However, if your amp is already beefy and accommodates your speakers and room and listening environment, then stay with what you have. Most audible differences are subtle if at all noticeable. The true benefits of bi-amping cannot be realized with passive crossover networks of a speaker system. Bi-amping truly shines when parts of the passive network of the speaker system is replaced by active networks where each amplifier is bandwith limited at the input.

Read this article on active bi-amping:
http://forums.klipsch.com/blogs/andy...bi-amping.aspx

Active Bi-Amplification
Source: Elliot Sound Products (ESP)

BI-WIRING

Theoretically, bi-wiring can change the frequency response of a speaker if the impedance of the speaker wires are high. In practice, the wire impedances are much lower than 0.1 Ohm. This indicates that while there are some minor differences in a speaker's performance, if reasonably sized cables are used, the difference is not audible unless the crossover network has serious design problems.

Bi-Wiring
Source: Elliot Sound Products (ESP)

People sometimes confuse bi-amping with bi-wiring. Bi-wiring is in direct contradiction with the Superposition Principle in science.

Superposition Principle:
Mathematically, for all linear systems F(x), where x is some sort of input, the superposition (i.e., sum) of the inputs yields a superposition of the individual responses:

F(X1 + X2 ...) = F(X1) + F(x2) + ...

A linear circuit is an electric circuit in which, for a sinusoidal input voltage of a given frequency, any output of the circuit is also sinusoidal with the same frequency.

The law of superposition states that any two voltages applied to a linear network (your crossover) will have the same voltage transfer as if they were applied separately.

To restate the superposition principle: For all linear systems, the net response at a given place caused by two or more stimuli is the sum of the responses which would have been caused by each stimulus individually. So that if input A produces response X and input B produces response Y then input (A + B) produces response (X + Y).

http://www.audioholics.com/education...o-loudspeaker/

The above results imply that bi-wiring may alter the frequency response and that, when using a very simple speaker system with an impedance of around 8 Ohms, this variation may be of the order of 0·1 dB when using cables whose series resistance is around 0·1 Ohms.

In general many loudspeaker cables will have a series resistance value well below 0·1 Ohms. Indeed, a low value is advisable to avoid other types of interaction with the loudspeaker input impedance. Thus in practice the actual variations may well be much smaller than those plotted in Figure 9. As a result, it is debatable if any variations in practice will normally be large enough to be audible or to be regarded as being of any real consequence. Moving your head a few centimetres when listening may have a larger effect in many rooms.

Thus we can conclude that there may be a small effect due to bi-wiring, but the above tends to imply it may normally be so small as to have little significance.

http://www.audioholics.com/education...g-vs-biwiring/

There are mixed opinions about biwiring. I for one biwire my mains simply because I have the means to do so as I own a pair of specific biwire cables given to me as a gift. The sonic differences are subtle, if any. Many times people think they hear a difference because they expect to. In actuality, 12 gauge wiring should suffice for most applications. If you feel the urge to biwire and have the money for the added expense, go for it. Worst case, you can use the wire elsewhere if you don't notice any sonic improvements. Some people argue that biwiring eliminates backwave EMF when electrically separating the crossover and using separate cables. In actuality, these cables are hooked in parallel to one common amp and thus still electrically combine at the amp.

http://audiokarma.org/forums/showpos...9&postcount=83

The late Peter Snell was an early bi-wire fan, and later recanted saying it was ‘baloney’. Many TOP speaker companies now either don’t offer the ‘dual’ terminals at all or do so only for bi-amping purposes. Many speak openly about its detrimental effects.

Bi-amping is not to be confused with bi-wiring - they are totally different animals. Bi-amping can lower IM distortion in the critical mid range frequencies and to which the ear is most sensitive, as Paul Klipsch and others have demonstrated over many years. You also get about 4dB more headroom, which can subjectively increase the perceived dynamic range.]

The law of superposition (the basis for why your speaker can reproduce a complex series of wavelengths simultaneously) states that any two voltages applied to a linear network (in this case, your crossover) will have the same voltage transfer as if they were applied separately. Simply stated, it says that any two currents applied simultaneously to a linear network result in the same current as when applied individually. If the crossover is poorly isolated (bass to Mid/treble) no manner of cable TWEAKING will correct it. Regarding the cable theorists (suppliers?) claim that running bass and treble frequencies protects the delicate trebles from the mean bass currents is sheer nonsense, and shows a complete lack of knowledge of the principles of electro-magnetism that govern signal transfer of audio frequencies over short distances.

It is invented for you to buy- wire and not based in science / engineering.

As I have said repeatedly here previously there have been some situations where bi-wring may have compensated for a poorly designed crossover network, but that does not make the principle valid. Poor crossover design is quite common unfortunately.

M&K Doesn't Believe in Bi-Wiring:

The Pro Market, especially those in post production, love M&K speakers and subs. But take a look at the back of any M&K speaker. There is one set of binding posts. M&K does not believe in bi-wiring, the benefits of which were dubious to me anyway. If you break it down into simple electronic theory, the only "benefit" possible with bi-wiring is theoretically more output at the crossover region (between the posts) if you've got long runs of high resistance cable, but I don't think that could be considered a benefit. As for passive bi-amplification, the benefits, with some amplifiers, can be substantial, although only due to shortcomings of those amplifiers. Passive bi-amping can do little to increase the total voltage applied to the speaker, though it will relieve each individual amp of some current draw.

http://www.answers.com/topic/superposition-theorem-1

Essentially, that it is permissible, if there are two or more sources of electromotive force in a linear electrical network, to compute at any element of the network the response of voltage or of current that results from one source alone, and then the response resulting from another source alone, and so on for all sources, and finally to compute the total response to all sources acting together by adding these individual responses.

Thus, if a load of constant resistance is supplied with electrical energy from a linear network containing two batteries, two generators, or one battery and one generator, it would be correct to find the current that would be supplied to the load by one source (the other being reduced to zero), then to find the current that would be supplied to the load by the second source (the first source now being reduced to zero), and finally to add the two currents so computed to find the total current that would be produced in the load by the two sources acting simultaneously.

CONCLUSIONS

1. You cannot use bi-amping and bi-wiring on all speakers. The speakers must have separate terminals for the high frequency and low frequency drivers.
2. Not all receivers offer the option of using the rear channel amplifiers for bi-amping. Some do and some don’t.
3. The improvement in sound quality with bi-wiring is minimal or non-existent.
4. The improvement in sound quality with bi-amping is more than bi-wiring, but don’t expect miracles.
5. When you use the rear channel amplifiers of a receiver for bi-amping, your setup will be reduced from 7.1 to 5.1.
6. The proper way of bi-amping is with external amplifiers. Amplifiers have their own separate power supplies and offer better sound quality than receivers.

http://www.padrick.net/LiveSound/Biwiring/Biwiring.htm