I just upgraded my main speakers from B&W CDM 7NTs to B&W 803s and am currently driving them with a 7100 (using 4 channels to biamp each speaker). I have a 950 as the pre/pro. Nautilus speakers have a reputation of being power hungry and although I like the sound I'm getting now I'm wondering if I might get an improvement by getting a couple of M200s and using them to drive the 803s.

Any suggestions on whether I'd notice an appreciable difference? At just $299 each it would be a relatively cheap experiment.

The difference you will hear will be little, if anything at all. The power handling or output will be largely uneffected. This is a very umpopular viewpoint in audiophile circles though..

If you are bi-amping by using active crossovers ahead of each amplifier channel, I would not go back to using passive crossovers.

[This message has been edited by bestbang4thebuck (edited October 06, 2004).]

I use B&W N803's as my main front left and right channels. The B&W N803's have an internal (passive) crossover network that is optimized for the individual drivers, which are designed and built by B&W. I do not recommend bypassing your speaker's crossover in favor of an external (active) crossover network. B&W has a section on bi-wiring and bi-amping in the FAQ section of their website which advocated these configurations. While I am convinced that bi-amping my N803's is worth the trouble, I believe that I am in the minority in this forum.

While there are good arguments for active crossovers, your speakers are not good candidates. Passive crossovers utilize resistors and capacitors in the signal path; the significance (negative effect) of this passive design is a strongly debated subject. B&W favors the optimized design of their passive crossover, while others will argue that unless you use an active crossover, there is no benefit to bi-amp your speakers.

I bi-amp my passive crossover speakers (B&W N803's) because:

1) I process the bass frequency signal (under 400 Hz) coming from my 950 pre-amp with a parametric equalizer (PEQ). The room/speaker interaction has been analyzed with the True RTA program, a Real Time Analysis frequency measurement tool. The result of employing the PEQ is a leveling of the bass response without altering the tonality (or phase coherence) of the instruments. This has been the single most important improvement to the sound quality of my system. Many audiophiles will argue that using equalization in this way is a sin against the God of sound purity. So be it.

2) The amplifier serving the mid-high frequency speaker driver circuit is fed the full (non-EQ'd) signal, so the internal crossover of the B&W N803 does all the work. Since the midrange and tweeter transducers provide the most of the spatial and subtle tonal information, I have chosen not to include a processor in this signal path. The actual current demand for the mid-high circuit is relatively small.

I am not against active crossovers, as I have used them in live concert venues. Also, there are many who work in a studio environment who use purpose built monitor arrays with customized active crossovers.

There are, however, a very significant number of highly regarded professional studios that use the passive crossovers found in the monitors themselves. The studio space and audio systems are all professionally analyzed and balanced by the recording engineers to provide as "neutral" an environment as possible for the type of music (varies for classical, jazz, rock...). This list includes Tellarc, Deutsche Grammophon Gesellschaft, Abbey Road Studios, etc... There is no expense spared in these studios and control rooms.

Good Luck...

Allan

I would agree that if the passive crossover network is accomplishing something important for the driver/enclosure system that an active crossover would not do, then I wouldn’t want to ‘mess with success’ and bypass the passive crossover.

I did notice, however, that B&W uses an active crossover network on their five-figure Model Nautilus, requiring four amplifier channels between crossover and drivers for each individual Nautilus. Indirectly, this says to me: B&W knows the advantages direct amp-to-driver connection. They avoid capacitors, coils and resistors between amp and driver to help obtain their flagship system performance – and their active crossover may do more than just divide frequencies. In any case, a response of 25Hz – 25KHz with a variance of +/- 0.5 dB, at very low distortion, is quite an accomplishment.

My guess is that the decision to use passive crossovers in their loudspeaker models costing approximately five to fifty percent of the flagship Nautilus is marketing driven. Someone said, “You mean you want us to ask people to buy four-figure speakers and ask them to buy two, three or four amplifier channels per unit in addition to that?” When it came to the Model Nautilus, the remark was probably, “If someone is laying out $20K per speaker, they are seeking the ultimate in sound and would also have the money to buy four amplifier channels per speaker.”

I am not adamantly against things like bi-wiring (I’m offering a friendly opinion, not an argument), but coming more from an engineering background than an marketing background, I know there are demonstrable benefits to direct amplifier-to-driver connections, while I have never been shown anything, other than opinion, that demonstrates advantages of bi-wiring to passive crossovers – assuming that cables with good electrical properties are used (can be low $) in all cases.

Finding something that works well for you is the goal, correct?

I'm not using an active crossover (so am basically just connecting a separate 100W amplifier channel to each set of bindings before the speakers' internal crossover), and actually only biamped my 7NTs as an experiment because I have two spare channels - theoretically I didn't expect it to make any difference.

It turned out I could actually hear an improvement (mostly a less strained treble to my ear) so I kept it. I suppose my real question is whether going from 100W to 200W feeds into my N803s would make a noticeable difference, or whether to have a real improvement I'd need to move to a totally different amplifier line (e.g. Rotel, B&K, Musical Fidelity etc.).

BB4TB:

The newest true workhorse and flagship of the Nautilus line used in studios is the N800. It has a very sophisticated passive crossover located in the plinth of the speaker to separate it from the speaker enclosure. These monitors weigh almost 300 lbs. each, and are usually bi-amped. It might be informative to read the FAQ section on Bi-Wiring and Bi-Amping on the B&W website.

Having spoken to two of the engineers at B&W, I can say that they do not believe that the sonic penalty of their passive crossover is significant enough to outweigh the advantages of designing a crossover to complement the detailed characteristics of their drivers. The active crossover monitor, "Nautilus" is the experiment that generated the technological and philosophical approach to a new direction in R&D. The suggestion that their decision to include passive crossovers in monitors like the model N800 is market driven is not consistent with this philosophy. Practical would be a better description. Clearly the less expensive B&W lines have less sophisticated crossovers, and the market becomes a more significant factor in their design, but this is true of all marks.

I would guess that if B&W were to adopt an active (line level) crossover for the ultimate studio workhorse monitor, it would be a powered monitor design so that they would be able to control both the crossover and the amplification feeding the drivers.

If these guys were not designing sound transducers, they would be working for some Formula One racing team in England. They are perfectionists, with a practical side. Needless to say I am a big fan.

[This message has been edited by AGAssarsson (edited October 08, 2004).]

Allan:

Despite your obvious bias toward B&W, the fact remains: the best way to achieve the best performance from a loudspeaker system is through direct amplifier-to-driver connections, with nothing between them but the speaker wire.

This can only be achieved with an active crossover network. No passive crossover can do this.

Additionally, the quality and precision of the capacitors (Polystryene for example) is much higher for the small values used in active crossovers than for the large values needed for passive ones. Inductors are conpletely unnecessary in active crossovers. Additionally, the crossover slopes and whatever equalization needed can be implemented with much greater precision and with much less sonic degredation in a low-level active crossover network.

For home use, it is a moot point really since most people don't have the expertise to implement an active crossover, multiple amplifier setup. In some professional situations (live venue recording for instance) simplicity and ease of setup is desired becasue of time pressures - there is simply no time to fiddle with the multiple amplifier volume controls and real-time acoustic analysis needed for active crossover setups. In studio situations, the inclusion of an active crossover setup means the studio designer/installer must have the expertise and equipment necessary to properly design and implement such a system - not all studio design firms have this expetise, so turn-key passive systems are used.

The decisions on which technology to use more often has to do with practical matters than pure performance ones. This does not take away from the fact that ultimately, active crossovers are the best way to go when the absolute highest performance is desired.

It's really a shame the Hi-Fi industry didn't go in the active crossover direction from day one, but budget and complexity factors undoubtedly were more important for the average consumer.

I would challenge you to describe in full detail (no links to, or cut-and-paste from manufacturer's white sheets allowed!) exactly what technical advantages passive crossovers have over active ones beyond simplicity, cost and that so-and-so makes them and they are used by this-or-that studio.

[This message has been edited by soundhound (edited October 08, 2004).]

Thank you for taking the time to respond. Your contributions on this subject carry significant weight with me, and my understanding of this subject has been significantly enhanced.

First... I do believe that an active crossover, properly designed and implemented is a fundamentally superior approach. It makes sound sense that employing the crossover at line level would promote very precise control of the signal contours and simplify the circuit between the amplifier(s) and the driver(s). Assuming this is a simple demonstrable fact, any opinions to the contrary, no matter how well intentioned, would be ignorant, uniformed and otherwise false, period. Opinions are like #@$%&$#, everybody's got one.

I personally do not have the expertise or resources to perform a detailed comparison and evaluation of the advantages and/or disadvantages of an active (line level) crossover vs. a passive crossover. This comparison should be the subject of a very large number of research papers, authored by researchers in both the audio industry and academia. The quality and motivations of the research are sure to vary widely.

Even if we accept the simple truth that an active crossover design is fundamentally better, there are important questions that beg asking... How much better? What criteria do you use to evaluate sound quality? And, what weight to you place on each of these criteria? Is the sonic degradation you describe so severe and inevitable that no passive design can compare favorably? At this point, things start getting in to the subjective realm.

Please consider this experiment. To provide an "optimum" "performance benchmark, we expertly design a "spare-no-expense" active crossover network to complement a three-way speaker using the best drivers available. If we could demonstrate through careful measurement and analysis that SOME passive crossover designs were significantly inferior to this optimized active design, would that lead to the conclusion that ALL passive crossovers are significantly inferior to active ones? NO it would not. Furthermore, if you could demonstrate that an expertly designed passive crossover very closely approached the quality criteria of the "optimum" active design, would it be worth consideration as an alternative approach? Depending on the savings inherent in the passive design, it might well be a worthy alternative. This is the crucial issue I am attempting to resolve.

I promise you that I will pursue your comments regarding the superiority of active crossovers, and report any research and informed opinions that I discover. For my part, it is not about winning an argument, but in developing an better informed opinion that is worthy of consideration.

Respectfully,

Allan

Allan:

I base my findings on the performance of active vs passive crossover networks on over 30 years in the professional audio industry in designing, installing and using speaker systems of both types. Ten of these years was spent at Altec Lansing and JBL Professional, both premier speaker manufacturers with large R&D departments. At Altec in particular, I delved very deeply into this area.

In my experiments, active crossovers always sounded cleaner, with much better dynamic performance since the signal did not have to pass through highly reactive components (inductors and capacitors) which greatly increase the complexity of the load presented to the power amplifier. Additionally, any "voicing" (equalization implemented in the passive crossover to suit the traits of the drivers) involves complex combinations of capacitors, inductors and resistors - the presence of resistors especially wastes power - that's what resistors are for, to limit current. This equals wasted power that would otherwise be directed to the speaker drivers.

The effects of a passive crossover in the signal path can be seen and measured with ocilloscopes and distortion analyzers. Just passing a square wave through a passive crossover and viewing the output presented to the speaker drivers is in it's self an informative exercise.

The use of an active crossover allows direct amplifier to speaker driver connection - this makes the power amplifier's life much easier because it only has to deal with the back EMF from the speaker drivers, without the added burden of inductive and capacitive reactance from a passive crossover network's components. Depending on the amplifier design, this reduces distortion and allows the amplifier to simply sound better. One of the reasons for the popularity of "bi-wiring" and "passive bi-amping" is the fact that with passive crossovers, the signal from one section of the crossover can modulate the other, causing distortion. This band-aid approach is unnecessary in an active setup since the drivers are completely isolated.

Additionally, the inductors necessary to implement a low pass filter to feed the woofer present a significant series resistance. It's literally like placing a resistor in-line with your speaker wires or using a thin-gauge speaker cable! You would never think of doing this, yet this is exactly what is happening inside a speaker with a passive crossover by virtue of the series resistance presented by the inductor in the woofer circuit. This is the very place you don't want resistance since it destroys the damping factor!

Is an active crossover always the only way a speaker should be designed? Of course not!! In the vast majority of instances, active crossovers are simply impractical for complexity and cost reasons. It takes a serious amount of effort and the proper equipment to properly sort out and set up in an optimum way an active system. The expertise to do this properly is very rare in the audio field.

I'm still tweaking with my own system after 30 years!! Active crossover use allows the speaker system to sound just about any way you wish by changing the crossover frequencies, slopes, phase and amplitude. The variations are endless - and the possiblilties for screw-ups are also endless.

This is why for the vast majority of users, a turn-key system using passive crossovers is better from a practical standpoint, even though this approach trades ultimate performance for ease of setup and lower cost.

There has been a recent trend toward professional monitor speakers that use built-in power amplifiers and active crossovers that incorporate crossover duties with intricate equalization and phase compensation that optimises the overall design toward really unbelievable sonic quality. One such speaker that I am very impressed with is the Mackie HR 824, which is being used by quite a few professional studios and film post production houses here in Hollywood, CA.

Speakers like the Mackie HR 824 retain turn-key practicality, yet benefit from the sonic superiorities of active crossovers with optimum equalization for the speaker driver/cabinet combination.

You should really try to hear these speakers if you get a chance: they show very convincingly what an optimum implementation of active crossovers can do in a single package design.

The future trend of "digital input" speakers (speakers which accept direct digital inputs from a signal source and incorporate DSP functions such as automatic room equalization) will have to incorporate active crossover networks (the active crossover will simply be part of the DSP processing) since the equalization functions would be impossible to implement in a passive design. These speakers will benefit greatly from the fact that the active crossover and power amplifiers are incorporated into, and optimised for, the overall speaker design.

Thankfully, as DSP chips find their way into more speaker designs, we can begin to look forward to a future where the benefits of active crossovers will begin to trickle down to the average consumer level and inefficient passive crossovers will be relagated to the dust bin of Hi-Fi history.

[This message has been edited by soundhound (edited October 09, 2004).]