The discussion of active systems in The General Audio forum has quickly evolved into a standard audiophile argument -- "everything matters." Of course it does, it's a matter of how, how much, and to what effect, it matters in context. In the context of that discussion, the position is being taken that active systems multiply the amplifier investment by the number of drivers in the system, making active systems much more expensive. This ignores what I think may be the core active advantage - individual amplifiers tasked to individual drivers, based on the requirements of the drivers in question, rather than the unknown of whatever passive speakers the amplifier buyer may choose, and the need for that amplifier to drive all the drivers in the box, through its nest of lossy, passive components, at once.
From this link, posted in the other thread by ESLdude:
The truth will, of course, be variable, and probably lies somewhere between the blanket statement and the utmost extreme above, but the point is that applying passive, audiophile principles to active designs is overkill, at best. It's like changing from Wilsons to Klispchorns and insisting that you still need 1000 watt Krells because they're "the best." I'm not engineer, but the fallacy in this argument is clear to me. From another article about the advantages of active:
From the same article, on amplifier choices:
Maybe over here we can discuss this without veering off into arguments that ignore the basic principles and advantages of active systems. I don't expect anyone to provide any measurements; I certainly don't have the wherewithal to do that, but hopefully some of our smartest engineering-oriented audiophiles can explore the subject without being interrupted by the standard, irrelevant audiophile arguments. This is one of the audio subjects that interests me most, because I have experienced these advantages, even on the small scale of my monitors. I'd love to get the educated perspectives of some of the members who frequent this sub forum.
Tim
From this link, posted in the other thread by ESLdude:
If we were to make a blind, blanket statement about active vs. passive system efficiency differences, we could say that active systems are roughly twice as efficient with their amplifier power than passive ones. If you were to take the utmost extreme (and dishonest) scenario, you could set up a test case that would show an active system as four times as effective with a given amplifier rating as a passive loudspeaker system, based entirely on how loud you could play that particular signal before the amplifiers clipped. It's not really an accurate example outside of the lab, but some of that example would be applicable as a matter of illustration.
The truth will, of course, be variable, and probably lies somewhere between the blanket statement and the utmost extreme above, but the point is that applying passive, audiophile principles to active designs is overkill, at best. It's like changing from Wilsons to Klispchorns and insisting that you still need 1000 watt Krells because they're "the best." I'm not engineer, but the fallacy in this argument is clear to me. From another article about the advantages of active:
The magnitude of the frequency response of both active and passive loudspeakers can be controlled, with good design, to be within 1dB of one another. However, the phase component of the frequency response will always be better in an active system. The active filters produce better filter roll-off characteristics at crossover. Combine this with the inclusion of a variable all-pass filter at each crossover point to correct the phase response of the drive units through the crossover regions and the result is a loudspeaker with much better group delay characteristics. The benefit to the listener will be improved polar response and therefore radiated power response. Such an active loudspeaker will have a large stable sound field with stable imaging and source location. Very difficult and costly to achieve with a passive loudspeaker system.
A passive crossover will only operate correctly into the load impedance of a particular loudspeaker drive unit. However, the impedance of a loudspeaker drive unit will change with the amount of power input. This is because loudspeakers are very inefficient and most of the input power is dissipated as heat in the voice coil. As a result the temperature of the voice coil will rise and because copper has a positive temperature coefficient of resistance the impedance of the loudspeaker drive unit will rise. The result will be frequency response errors as the filters move from their designed response with increased input power. This effect does not occur in active loudspeakers where the filter response is maintained independent of input power to the loudspeaker.
From the same article, on amplifier choices:
The Separates amplifier manufacturer, has no idea what is going to be hung on the end of his product. Hence the need (as would be the case in the car analogy), to massively over-build to ensure that the amplifier will sound good with almost any speaker impedance and cable. It is not surprising that the massive amplifiers that typify the high end today are both costly and power consuming.
These problems of efficiency, size and cost are much reduced in the case of amplifiers designed for Active loudspeakers. Here the designer has the luxury of designing an amplifier pack containing separate mono amplifiers that only have to power one drive unit, whose every performance characteristic, bandwidth, frequency range, power handling, and shortcomings, are known to the designer.
Because the amplifiers in an active loudspeaker system are only required to operate over reduced frequency bands the intermodulation distortion products present in a passive system will be dramatically reduced, by typically 20dB, in an active system.
For a given amount of amplifier power, an active loudspeaker can be expected to produce approximately 6dB more level (twice as much) than the equivalent passive system. Furthermore, power for each drive unit may be more optimally specified in an active system. A tweeter, for example, requires much less power than a woofer to produce a balanced system performance.
A power amplifier designed specifically for the limited frequency range of an individual drive unit gains further benefits in efficiency, due to the fact that the wider the amplifier bandwidth, the less efficient it is. A well designed two or three way mono active power amp, for a given input and power rating, will always be capable of safely reaching higher peak SPL levels with less distortion than the equivalent single wide band power amp. This additional safety margin is now essential for coping with the wider dynamic range of DVD-Audio, SACD, DTS and Dolby Digital film soundtracks. In an active system the absence of both passive crossovers and long cable runs, together with a known amplifier damping factor, prevents the modification of the loudspeaker drive unit "Q" ensuring better controlled low frequency performance.
Maybe over here we can discuss this without veering off into arguments that ignore the basic principles and advantages of active systems. I don't expect anyone to provide any measurements; I certainly don't have the wherewithal to do that, but hopefully some of our smartest engineering-oriented audiophiles can explore the subject without being interrupted by the standard, irrelevant audiophile arguments. This is one of the audio subjects that interests me most, because I have experienced these advantages, even on the small scale of my monitors. I'd love to get the educated perspectives of some of the members who frequent this sub forum.
Tim