i think you are missing the point here, bi-amping is only worthwhile for non-passive speakers. are yours capable of not utilizing your internal crossovers? if they must use them, THEN YOU ARE WASTING YOUR TIME.

I'd really like to know if you have ever implemented or even heard an active bi-amping system - let alone one that used tubes for the high frequencies? Have you ever even heard a well thought out and implemented tube system at all?

If you could cite some specific expamples and the perceived deficiencies you heard in such a system, I think it would be a bit easier to take what you are saying seriously.

That article is all well and good, however the damping factor of the power amplifier is what deals with back EMF - not the cables. If the cables are large enough and have a resistance that is significantly lower than the internal impedance of the power amplifier (fairly easy to do), their contribution is insignifcant.

In any event, active bi-amping makes the cable issue a moot point. Direct connection to the speaker drivers with no intervening passive components presents the power amplifier with a more benign load. Additionally, it is the inductor that exists in all passive crossover networks, and which is in series with the woofer, that is by far the largest contributor to the deterioration of effective damping factor, and which makes the effects of back EMF from the woofer more serious. The elimination of this inductor allows the damping of the amplifier to do it's work.

distortion is the enemy of audiophiles, tube amps distort. i am sure not every single one does horribly. but, in college we tested several different types of amplifiers (different brands) and anything with a tube in it typically showed more distortion. we found this by using an oscilliscope (sp?), controlling the input wave forms and measuring the output wave forms, then used some computer program to calculate the differences. after our testing, it was clear tube based amps had much higher distortions on average compared to others. i know that some people love tube amps, and they do so because of their sound, but that doesnt mean that they sound accurate, merely "good" to the user. i dont settle for good, i want it the way it was intended to be or as close as i can afford to get it. :-)

Oh brother

also tube amps need maintenance, and more and more maintenance means more and more potential for errors/damage to be done.

So do cars, trucks, boats.....that doesn't stop people from using them.

I believe that the engineers/scientists at B&W have a legitimate purpose for including the bi-wire/bi-amp option (other than sales). Since they design and build all the drivers in their speaker lines, they have detailed analysis of how the voltage/impedance characteristics at the speaker terminals can result in a form of "harmonic crosstalk" between the drivers themselves. Because advanced driver design (and analysis) has been a cornerstone of the B&W mark, their I believe their claims are based on sound science.

Of course, the active crossover that SH promotes would solve this problem also. The B&W crossovers are also designed to flatten the response of each driver, which might be difficult to achieve with an active crossover network. For those who have the analysis tools, EE skill set, and highly advanced knowledge of drivers and their acoustic performance characteristics; "go for it." While I DO EQ, active crossovers are out of my league.

Allan

From the B&W website:

Bi-wiring and bi-amping:
Most B&W speakers are provided with two pairs of speaker terminals; this allows you to either bi-wire or bi-amplify them. The aim of both these techniques is not to simply get the customer to spend more on cables and electronics (although no manufacturer objects to this spin off) but to improve the resolution of the speakers.
A multi-way speaker contains a crossover network that not only divides the incoming signal into different frequency ranges, appropriate to the working range of each drive unit, but also equalizes each driver’s response to be flat (raw driver responses are usually anything but flat).
There are two different basic types of crossover – series and parallel. Series crossovers have each filter section wired in series between the positive and negative input terminals. It is impossible to treat each filter section individually – each interacts with the others – and such crossovers are not suitable for bi-wiring or bi-amping. But 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 optimized 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 system 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.
Many people ask us whether the load on the amplifier is different if you bi-wire. It is not. As far as the amplifier is concerned, it matters not one jot whether you parallel the inputs to the filter sections at the speaker end or the amplifier end of the speaker cable.
Bi-amping takes advantage of all this and adds some benefits of its own. Like with cable, you can choose different amplifiers that excel in different frequency bands. You may, for example, be keen on valve (tube) amplifiers. But even the most die-hard of aficionados would be hard pushed to claim that they are any good at keeping good control of the bass. Bi-amping enables you to combine a valve amplifier for mid and high frequencies with the control of a solid-state device at low frequencies.
Unlike bi-wiring, the load to each amplifier is different from that using a single amplifier full range. The voltage demands on each amplifier remain the same (each is still fed a full-range input and gives a full-range output), but the current demands are reduced. This of itself can improve the amplifier’s ability to deliver the signal to the speaker.
Be careful when bi-amping that the gain and polarity of each amplifier are the same, otherwise you will compromise the frequency response of the system.

I am familiar with B&W's argument, and I just don't buy it. I have found in my own experience, and also while conducting experiments while working at Altec Lansing, that given sufficient gauge wiring, it does not matter at all audibly whether the junction of the two (or more) sections of the crossover are joined at the back of the speaker or several feet away at the power amplifier's terminals. I have always used good amplifiers with sufficient damping factors when experimenting: lacking this, and large enough gauge wire, of course alteration of the signal is possible and all bets are off.

Consider the source too. B&W is after all a speaker company, and they are in business to make money. The way they voice their speakers is a very significant part of their market identity. If this were to be eliminated, they would be basically marketing "drivers in a box".

The audio world is very heavily marketing driven. Aligning themselves with popular audiophile ideas is almost required from a marketing perspective. Saying that things like bi-wiring and passive bi-amping are not important would be as suicidal as a CD player manufacturer saying that "16 bits is enough".

B&O has just introduced a very expensive speaker system for consumer use that uses active bi-amplificaiton in addition to other DSP functions which are only possible with such a design. I believe as more speakers incorporate things like self-equalization to compensate for room interaction and various forms of DSP, active technology will become more the norm. Speakers like the Mackie HR 824 simply could not exist were it not for the flexibility afforded by active crossovers which in addition to the basic frequency division function, contour the frequency response with more precision and detail than any passive crossover could ever manage.

By the way, don't sell yourself short! Implementing an active system is not nearly difficult as you seem to think it is - no EE required! The crossover networks and equalizers can be bought off the shelf from firms like Rane and Behringer. Software based RTAs like TrueRTA are extremely powerful. Behringer makes a calibrated microphone suitable for measurement for around $80. With an inexpensive USB audio interface, a laptop, TrueRTA and the microphone, you have an extremely powerful sound analysis system.

[This message has been edited by soundhound (edited May 13, 2004).]

Actually, I was thinking about that. I have never heard a tube power amp in an audio sound system, only in my recording studio and my guitar amps. I notice that if I applied too much voltage or "tube sound" on my microphone preamp tubes, it was distorted and the solid state stuff sounded just the same and could be run at much higher levels throught the gain spectrum w/o the "tube sound"..ie distortion. And as for the guitar amps I have (my Marshall uses EL34's and my Mesa/Boogie uses 6L6/5881's), those have incredible overdrive characteristics. Ultra clean (more precise, but way less organic), is done with solid state stuff. I just don't know how this all applies to stereo systems or HT... I think we may be on the right track of thinking...? 'Cause wailin' on the guitar = distortion & organic cleans!